import SwiftUI
import AppKit

// MARK: - Classic Workbench Colours

private enum WB {
    static let toolbar = Color(nsColor: NSColor(
        calibratedWhite: 0.88, alpha: 1
    ))
    static let sidebar = Color(nsColor: NSColor(
        calibratedWhite: 0.94, alpha: 1
    ))
    static let border = Color(nsColor: NSColor(
        calibratedWhite: 0.76, alpha: 1
    ))
    static let header = Color(nsColor: NSColor(
        calibratedWhite: 0.91, alpha: 1
    ))
}

// MARK: - Main Window

struct MainView: View {
    @EnvironmentObject private var model: DatabaseModel

    @State private var showingEditor = false
    @State private var showingDatabaseTransfer = false

    @State private var editing = ConnectionProfile()
    @State private var editingPassword = ""

    @State private var expandedSchemas: Set<String> = []
    @State private var expandedTableFolders: Set<String> = []
    @State private var selectedTableName: String? = nil
    @State private var outputExpanded = true

    @State private var navigatorMode = 1
    @State private var administrationPage: WorkbenchAdminPage? = nil


    var body: some View {
        VStack(spacing: 0) {
            mainToolbar

            Rectangle()
                .fill(WB.border)
                .frame(height: 1)

            HSplitView {
                navigator
                    .frame(
                        minWidth: 180,
                        idealWidth: 250,
                        maxWidth: 420
                    )

                workspace
                    .frame(minWidth: 480)
            }

            statusBar
        }
        .frame(minWidth: 800, minHeight: 520)
        .preferredColorScheme(
            UserDefaults.standard.string(
                forKey: "preferences.appearance"
            ) == "dark" ? .dark : .light
        )
        .background(Color(nsColor: .windowBackgroundColor))
        .task {
            if model.databases.isEmpty, model.selected != nil {
                model.loadDatabases()
            }
        }
        .sheet(isPresented: $showingDatabaseTransfer) {
            WorkbenchDatabaseTransferView(model: model)
        }
        .sheet(isPresented: $showingEditor) {
            ConnectionEditor(
                profile: $editing,
                password: $editingPassword
            ) {
                model.save(editing, password: editingPassword)
                showingEditor = false
            }
        }
    }

    // MARK: - Main Toolbar

    private var mainToolbar: some View {
        HStack(spacing: 16) {
            Image(systemName: "externaldrive.connected.to.line.below")
                .font(.system(size: 23))
                .foregroundStyle(.blue)

            Text("MySQL Workbench")
                .font(.system(size: 15, weight: .semibold))
                .foregroundStyle(.primary)

            Rectangle()
                .fill(WB.border)
                .frame(width: 1, height: 30)

            toolbarButton(
                "New Connection",
                icon: "plus.rectangle.on.rectangle"
            ) {
                editing = ConnectionProfile(name: "New Connection")
                editingPassword = ""
                showingEditor = true
            }

            toolbarButton(
                "Import / Export",
                icon: "arrow.up.arrow.down.square"
            ) {
                showingDatabaseTransfer = true
            }

            toolbarButton(
                "Refresh",
                icon: "arrow.clockwise"
            ) {
                model.loadDatabases()
            }

            toolbarButton(
                "Execute",
                icon: "bolt.fill"
            ) {
                model.runSQL()
            }
            .keyboardShortcut(.return, modifiers: [.command])

            toolbarButton(
                "Format SQL",
                icon: "text.alignleft"
            ) {
                model.formatSQL()
            }

            Spacer()

            VStack(alignment: .trailing, spacing: 2) {
                Text(model.selected?.name ?? "No Connection")
                    .font(.system(size: 12, weight: .semibold))

                Text(model.selectedDatabase.isEmpty
                     ? "No default schema"
                     : model.selectedDatabase)
                    .font(.system(size: 11))
                    .foregroundStyle(.secondary)
            }
        }
        .padding(.horizontal, 10)
        .frame(height: 46)
        .background(WB.toolbar)
    }

    private func toolbarButton(
        _ title: String,
        icon: String,
        action: @escaping () -> Void
    ) -> some View {
        Button(action: action) {
            VStack(spacing: 3) {
                Image(systemName: icon)
                    .font(.system(size: 19))
                    .frame(height: 23)

                Text(title)
                    .font(.system(size: 10))
            }
            .foregroundStyle(.primary)
            .frame(minWidth: 65)
        }
        .buttonStyle(.plain)
        .help(title)
    }

    // MARK: - Navigator

    private var navigator: some View {
        VStack(spacing: 0) {
            Picker("Navigator", selection: $navigatorMode) {
                Text("Administration").tag(0)
                Text("Schemas").tag(1)
            }
            .pickerStyle(.segmented)
            .labelsHidden()
            .padding(8)

            if navigatorMode == 0 {
                administrationNavigator
            } else {
                schemasNavigator
            }


        }
        .background(WB.sidebar)
    }

    private var schemasNavigator: some View {
        VStack(spacing: 0) {
            HStack {
                Text("SCHEMAS")
                    .font(.system(size: 11, weight: .bold))

                Spacer()

                Button {
                    model.loadDatabases()
                } label: {
                    Image(systemName: "arrow.clockwise")
                }
                .buttonStyle(.borderless)
            }
            .padding(.horizontal, 12)
            .frame(height: 34)

            Divider()

            ScrollView {
                LazyVStack(alignment: .leading, spacing: 2) {
                    ForEach(model.databases, id: \.self) { db in
                        schemaNode(db)
                    }
                }
                .padding(.vertical, 8)
            }

            Divider()

            sectionHeader("MYSQL CONNECTIONS")

            ScrollView {
                VStack(alignment: .leading, spacing: 4) {
                    ForEach(model.profiles) { profile in
                        Button {
                            model.selectedID = profile.id
                            model.loadDatabases()
                        } label: {
                            Label(
                                profile.name,
                                systemImage: "server.rack"
                            )
                            .frame(
                                maxWidth: .infinity,
                                alignment: .leading
                            )
                            .padding(6)
                            .background(
                                model.selectedID == profile.id
                                    ? Color.blue.opacity(0.14)
                                    : Color.clear
                            )
                        }
                        .buttonStyle(.plain)
                        .contextMenu {
                            Button("Edit Connection") {
                                edit(profile)
                            }
                        }
                    }
                }
                .padding(8)
            }
            .frame(height: 125)
        }
    }

    private var administrationNavigator: some View {
        ScrollView {
            VStack(alignment: .leading, spacing: 4) {
                administrationSection(
                    "MANAGEMENT",
                    pages: [
                        .serverStatus,
                        .clientConnections,
                        .users,
                        .variables
                    ]
                )

                administrationSection(
                    "PERFORMANCE",
                    pages: [
                        .dashboard,
                        .performanceReports,
                        .performanceSchema
                    ]
                )
            }
            .padding(8)
        }
        .frame(maxWidth: .infinity, maxHeight: .infinity)
    }

    private func administrationSection(
        _ title: String,
        pages: [WorkbenchAdminPage]
    ) -> some View {
        VStack(alignment: .leading, spacing: 4) {
            Text(title)
                .font(.system(size: 11, weight: .bold))
                .foregroundStyle(.secondary)
                .padding(.top, 12)
                .padding(.bottom, 4)

            ForEach(pages) { page in
                Button {
                    administrationPage = page
                } label: {
                    Label(page.rawValue, systemImage: page.icon)
                        .frame(
                            maxWidth: .infinity,
                            alignment: .leading
                        )
                        .padding(.horizontal, 8)
                        .padding(.vertical, 7)
                        .background(
                            administrationPage == page
                                ? Color.accentColor.opacity(0.18)
                                : Color.clear
                        )
                        .clipShape(RoundedRectangle(cornerRadius: 5))
                }
                .buttonStyle(.plain)
            }
        }
    }


    // MARK: - Compact Schema Tree

    private func schemaNode(_ db: String) -> some View {
        VStack(alignment: .leading, spacing: 0) {

            HStack(spacing: 5) {
                Image(systemName:
                    expandedSchemas.contains(db)
                        ? "chevron.down"
                        : "chevron.right"
                )
                .font(.system(size: 10))
                .foregroundStyle(.secondary)
                .frame(width: 13)

                Image(systemName: "cylinder.split.1x2")
                    .foregroundStyle(.blue)
                    .frame(width: 17)

                Text(db)
                    .font(.system(size: 12, weight:
                        model.selectedDatabase == db
                            ? .semibold : .regular))
                    .lineLimit(1)

                Spacer(minLength: 0)
            }
            .frame(height: 25)
            .padding(.leading, 10)
            .contentShape(Rectangle())
            .onTapGesture {
                toggleSchema(db)
            }
            .onTapGesture(count: 2) {
                model.selectedDatabase = db
                expandedSchemas.insert(db)
                expandedTableFolders.insert(db)

                if model.schemaTables[db] == nil {
                    model.loadTables(database: db)
                }
            }
            .contextMenu {
                Button("Set as Default Schema") {
                    model.selectedDatabase = db
                }

                Button("Refresh Tables") {
                    model.loadTables(database: db)
                }
            }

            if expandedSchemas.contains(db) {
                schemaChildren(db)
            }
        }
        .frame(maxWidth: .infinity, alignment: .leading)
    }

    private func toggleSchema(_ db: String) {
        if expandedSchemas.contains(db) {
            expandedSchemas.remove(db)
        } else {
            expandedSchemas.insert(db)
            expandedTableFolders.insert(db)

            if model.schemaTables[db] == nil {
                model.loadTables(database: db)
            }
        }
    }

    private func schemaChildren(_ db: String) -> some View {
        VStack(alignment: .leading, spacing: 0) {

            // Tables folder
            HStack(spacing: 5) {
                Image(systemName:
                    expandedTableFolders.contains(db)
                        ? "chevron.down"
                        : "chevron.right"
                )
                .font(.system(size: 10))
                .foregroundStyle(.secondary)
                .frame(width: 13)

                Image(systemName: "folder")
                    .foregroundStyle(.secondary)
                    .frame(width: 17)

                Text("Tables")
                    .font(.system(size: 12))

                Spacer(minLength: 0)
            }
            .frame(height: 24)
            .padding(.leading, 28)
            .contentShape(Rectangle())
            .onTapGesture {
                if expandedTableFolders.contains(db) {
                    expandedTableFolders.remove(db)
                } else {
                    expandedTableFolders.insert(db)

                    if model.schemaTables[db] == nil {
                        model.loadTables(database: db)
                    }
                }
            }

            // Tables
            if expandedTableFolders.contains(db) {
                if let tables = model.schemaTables[db] {
                    ForEach(tables, id: \.self) { table in
                        tableNode(database: db, table: table)
                    }
                } else {
                    Button("Load Tables") {
                        model.loadTables(database: db)
                    }
                    .font(.system(size: 11))
                    .buttonStyle(.borderless)
                    .padding(.leading, 66)
                    .frame(height: 24)
                }
            }

            folderNode("Views", indent: 28)
            folderNode("Stored Procedures", indent: 28)
            folderNode("Functions", indent: 28)
        }
        .frame(maxWidth: .infinity, alignment: .leading)
    }

    private func tableNode(database: String, table: String) -> some View {
        let identifier = database + "." + table
        let isSelected = selectedTableName == identifier

        return HStack(spacing: 5) {
            Image(systemName: "tablecells")
                .font(.system(size: 11))
                .foregroundStyle(
                    isSelected ? Color.blue : Color.gray
                )
                .frame(width: 17)

            Text(table)
                .font(.system(size: 12))
                .lineLimit(1)
                .truncationMode(.middle)

            Spacer(minLength: 0)
        }
        .frame(height: 23)
        .padding(.leading, 49)
        .frame(maxWidth: .infinity, alignment: .leading)
        .background(
            isSelected
                ? Color.blue.opacity(0.14)
                : Color.clear
        )
        .contentShape(Rectangle())
        .onTapGesture {
            selectedTableName = identifier
        }
        .onTapGesture(count: 2) {
            selectedTableName = identifier
            model.selectTable(
                database: database,
                table: table
            )
        }
        .contextMenu {
            Button("Select First 100 Rows") {
                selectedTableName = identifier
                model.selectTable(
                    database: database,
                    table: table
                )
            }
        }
    }

    private func folderNode(
        _ title: String,
        indent: CGFloat
    ) -> some View {
        HStack(spacing: 5) {
            Image(systemName: "chevron.right")
                .font(.system(size: 10))
                .foregroundStyle(.secondary)
                .frame(width: 13)

            Image(systemName: "folder")
                .foregroundStyle(.secondary)
                .frame(width: 17)

            Text(title)
                .font(.system(size: 12))

            Spacer(minLength: 0)
        }
        .frame(height: 24)
        .padding(.leading, indent)
        .frame(maxWidth: .infinity, alignment: .leading)
    }

    // MARK: - Workspace

    private var workspace: some View {
        Group {
            if let page = administrationPage {
                WorkbenchAdministrationView(
                    page: page,
                    profile: model.selected
                ) {
                    administrationPage = nil
                    navigatorMode = 1
                }
            } else {
                sqlWorkspace
            }
        }
    }

    private var sqlWorkspace: some View {
        VStack(spacing: 0) {
            queryTabBar

            Divider()

            queryToolbar

            Divider()

            VSplitView {
                sqlEditor
                    .frame(minHeight: 150)

                bottomWorkspace
                    .frame(minHeight: 150)
            }
        }
    }


    private var queryTabBar: some View {
        HStack(spacing: 0) {
            ScrollView(.horizontal) {
                HStack(spacing: 2) {
                    ForEach(model.queryTabs) { tab in
                        HStack(spacing: 8) {
                            Button {
                                model.activateQuery(tab.id)
                            } label: {
                                Label(tab.title, systemImage: "doc.text")
                                    .lineLimit(1)
                            }
                            .buttonStyle(.plain)

                            Button {
                                model.closeQuery(tab.id)
                            } label: {
                                Image(systemName: "xmark")
                                    .font(.system(size: 9))
                            }
                            .buttonStyle(.plain)
                        }
                        .font(.system(size: 12))
                        .padding(.horizontal, 10)
                        .frame(height: 30)
                        .background(
                            model.activeQueryID == tab.id
                                ? Color(nsColor: .textBackgroundColor)
                                : Color.clear
                        )
                        .clipShape(
                            UnevenRoundedRectangle(
                                topLeadingRadius: 5,
                                topTrailingRadius: 5
                            )
                        )
                    }
                }
            }
            .scrollIndicators(.hidden)

            Button {
                model.newQueryTab()
            } label: {
                Image(systemName: "plus")
            }
            .buttonStyle(.borderless)
            .padding(.horizontal, 10)
            .help("New Query Tab")
        }
        .background(WB.header)
    }

    private var queryToolbar: some View {
        HStack(spacing: 14) {
            Button {
                model.runSQL()
            } label: {
                Image(systemName: "bolt.fill")
                    .foregroundStyle(.orange)
            }
            .help("Execute SQL")

            Button {
                model.formatSQL()
            } label: {
                Image(systemName: "text.alignleft")
            }
            .help("Format SQL")

            Divider()
                .frame(height: 17)

            Text("Default Schema:")
                .font(.system(size: 11))

            Text(model.selectedDatabase.isEmpty
                 ? "None"
                 : model.selectedDatabase)
                .font(.system(size: 11, weight: .semibold))

            Spacer()

            Text("SQL Editor")
                .font(.system(size: 11))
                .foregroundStyle(.secondary)
        }
        .buttonStyle(.borderless)
        .padding(.horizontal, 12)
        .frame(height: 30)
        .background(WB.header)
    }

    private var sqlEditor: some View {
        HStack(spacing: 0) {
            if UserDefaults.standard.object(
                forKey: "preferences.showLineNumbers"
            ) as? Bool ?? true {
                lineNumbers

                Rectangle()
                    .fill(WB.border)
                    .frame(width: 1)
            }

            Rectangle()
                .fill(WB.border)
                .frame(width: 1)

            SQLTextView(text: $model.sql)
        }
        .background(Color(nsColor: .textBackgroundColor))
    }

    private var lineNumbers: some View {
        ScrollView {
            VStack(alignment: .trailing, spacing: 0) {
                ForEach(
                    1...max(1, model.sql.components(
                        separatedBy: "\n"
                    ).count),
                    id: \.self
                ) { number in
                    Text("\(number)")
                        .frame(height: 19)
                }
            }
            .padding(.horizontal, 9)
            .padding(.top, 8)
        }
        .font(.system(size: 12, design: .monospaced))
        .foregroundStyle(.secondary)
        .frame(width: 48)
        .background(WB.header)
        .allowsHitTesting(false)
    }

    // MARK: - Results and Action Output

    private var bottomWorkspace: some View {
        VSplitView {
            resultsPanel
                .frame(minHeight: 230)

            if outputExpanded {
                actionOutput
                    .frame(minHeight: 90)
            }
        }
    }

    private var resultsPanel: some View {
        VStack(spacing: 0) {
            HStack {
                Image(systemName: "tablecells")
                Text("Result Grid")
                    .fontWeight(.semibold)

                Spacer()

                Text(model.result.message)
                    .foregroundStyle(.secondary)
            }
            .font(.system(size: 12))
            .padding(.horizontal, 12)
            .frame(height: 28)
            .background(WB.header)

            Divider()

            if model.result.columns.isEmpty {
                VStack {
                    Spacer()
                    Text("No query results")
                        .foregroundStyle(.secondary)
                    Spacer()
                }
            } else {
                resultGrid
            }
        }
    }


    private var resultGrid: some View {
        NativeResultGrid(
            columns: model.result.columns,
            rows: model.result.rows
        )
    }

    private var actionOutput: some View {
        VStack(spacing: 0) {
            HStack {
                Image(systemName: "list.bullet.rectangle")
                Text("Action Output")
                    .fontWeight(.semibold)

                Spacer()

                Button {
                    outputExpanded = false
                } label: {
                    Image(systemName: "chevron.down")
                }
                .buttonStyle(.borderless)
            }
            .font(.system(size: 12))
            .padding(.horizontal, 12)
            .frame(height: 26)
            .background(WB.header)

            Divider()

            HStack(alignment: .top, spacing: 12) {
                Image(systemName:
                    model.status == "Error"
                        ? "xmark.circle.fill"
                        : "checkmark.circle.fill"
                )
                .foregroundStyle(
                    model.status == "Error"
                        ? .red : .green
                )

                VStack(alignment: .leading, spacing: 5) {
                    Text(model.status)
                        .fontWeight(.semibold)

                    Text(model.result.message)
                        .foregroundStyle(.secondary)
                }

                Spacer()
            }
            .font(.system(size: 12))
            .padding(12)

            Spacer()
        }
    }

    // MARK: - Status Bar

    private var statusBar: some View {
        HStack(spacing: 10) {
            Circle()
                .fill(
                    model.status == "Error"
                        ? Color.red : Color.green
                )
                .frame(width: 8, height: 8)

            Text(model.status)
                .lineLimit(1)

            Spacer()

            Text(model.selected?.name ?? "Disconnected")

            Divider()
                .frame(height: 13)

            Text(model.selectedDatabase.isEmpty
                 ? "No Schema"
                 : model.selectedDatabase)

            Divider()
                .frame(height: 13)

            Text("UTF-8")
        }
        .font(.system(size: 11))
        .padding(.horizontal, 12)
        .frame(height: 22)
        .background(WB.header)
    }

    private func sectionHeader(_ title: String) -> some View {
        HStack {
            Text(title)
                .font(.system(size: 11, weight: .bold))
                .foregroundStyle(.secondary)

            Spacer()
        }
        .padding(.horizontal, 12)
        .frame(height: 30)
        .background(WB.header)
    }

    private func edit(_ profile: ConnectionProfile) {
        editing = profile
        editingPassword = PasswordStore.read(profile.id)
        showingEditor = true
    }
}

// MARK: - Native SQL Text Editor

struct SQLTextView: NSViewRepresentable {
    @Binding var text: String

    func makeCoordinator() -> Coordinator {
        Coordinator(self)
    }

    func makeNSView(context: Context) -> NSScrollView {
        let scroll = NSTextView.scrollableTextView()
        let editor = scroll.documentView as! NSTextView

        scroll.appearance = NSAppearance(named: .aqua)
        editor.appearance = NSAppearance(named: .aqua)
        editor.backgroundColor = .white
        editor.textColor = .black
        scroll.backgroundColor = .white

        editor.isEditable = true
        editor.isRichText = false
        editor.allowsUndo = true
        editor.isAutomaticQuoteSubstitutionEnabled = false
        editor.isAutomaticDashSubstitutionEnabled = false
        editor.font = NSFont.monospacedSystemFont(
            ofSize: CGFloat(
                UserDefaults.standard.object(
                    forKey: "preferences.editorFontSize"
                ) as? Double ?? 13
            ),
            weight: .regular
        )
        editor.textContainerInset = NSSize(
            width: 10,
            height: 8
        )
        editor.delegate = context.coordinator
        editor.string = text

        context.coordinator.highlight(editor)

        return scroll
    }

    func updateNSView(
        _ scroll: NSScrollView,
        context: Context
    ) {
        guard let editor = scroll.documentView as? NSTextView else {
            return
        }

        if editor.string != text {
            let selection = editor.selectedRange()
            editor.string = text

            let safeLocation = min(
                selection.location,
                (text as NSString).length
            )

            editor.setSelectedRange(
                NSRange(location: safeLocation, length: 0)
            )

            context.coordinator.highlight(editor)
        }
    }

    final class Coordinator: NSObject, NSTextViewDelegate {
        var parent: SQLTextView

        init(_ parent: SQLTextView) {
            self.parent = parent
        }

        func textDidChange(_ notification: Notification) {
            guard let editor = notification.object as? NSTextView else {
                return
            }

            parent.text = editor.string
            highlight(editor)
        }

        func highlight(_ editor: NSTextView) {
            guard let storage = editor.textStorage else {
                return
            }

            let text = editor.string as NSString
            let range = NSRange(
                location: 0,
                length: text.length
            )

            storage.beginEditing()

            storage.setAttributes([
                .foregroundColor: NSColor.textColor,
                .font: NSFont.monospacedSystemFont(
                    ofSize: CGFloat(
                        UserDefaults.standard.object(
                            forKey: "preferences.editorFontSize"
                        ) as? Double ?? 13
                    ),
                    weight: .regular
                )
            ], range: range)

            let pattern = """
            \\b(SELECT|FROM|WHERE|INSERT|UPDATE|DELETE|CREATE|TABLE|DATABASE|SHOW|USE|JOIN|LEFT|RIGHT|INNER|OUTER|ON|AS|AND|OR|ORDER|GROUP|BY|LIMIT|VALUES|SET|NULL|NOT|IN|LIKE|DISTINCT|ALTER|DROP|DESCRIBE|EXPLAIN)\\b
            """

            if let regex = try? NSRegularExpression(
                pattern: pattern,
                options: [.caseInsensitive]
            ) {
                for match in regex.matches(
                    in: editor.string,
                    range: range
                ) {
                    storage.addAttribute(
                        .foregroundColor,
                        value: NSColor.systemBlue,
                        range: match.range
                    )
                }
            }

            storage.endEditing()
        }
    }
}

// MARK: - Connection Editor

struct ConnectionEditor: View {
    @Binding var profile: ConnectionProfile
    @Binding var password: String

    let save: () -> Void

    @Environment(\.dismiss) private var dismiss

    var body: some View {
        VStack(alignment: .leading, spacing: 14) {
            Text("Connection Settings")
                .font(.title2.bold())

            Form {
                TextField(
                    "Connection Name",
                    text: $profile.name
                )

                TextField(
                    "Hostname",
                    text: $profile.host
                )

                TextField(
                    "Port",
                    value: $profile.port,
                    format: .number
                )

                TextField(
                    "Username",
                    text: $profile.username
                )

                SecureField(
                    "Password (macOS Keychain)",
                    text: $password
                )

                TextField(
                    "Default Schema",
                    text: $profile.database
                )
            }

            HStack {
                Spacer()

                Button("Cancel") {
                    dismiss()
                }

                Button("Save") {
                    save()
                }
                .buttonStyle(.borderedProminent)
            }
        }
        .padding(24)
        .frame(width: 520)
    }
}



// MARK: - High Performance Native Result Grid

struct NativeResultGrid: NSViewRepresentable {

    let columns: [String]
    let rows: [[String]]

    func makeCoordinator() -> Coordinator {
        Coordinator()
    }

    func makeNSView(context: Context) -> NSScrollView {
        let scroll = NSScrollView()
        scroll.hasVerticalScroller = true
        scroll.hasHorizontalScroller = true
        scroll.autohidesScrollers = true
        scroll.drawsBackground = true
        scroll.backgroundColor = .white

        let table = NSTableView()
        table.headerView = NSTableHeaderView()
        table.usesAlternatingRowBackgroundColors =
            UserDefaults.standard.object(
                forKey: "preferences.alternatingRows"
            ) as? Bool ?? true
        table.rowHeight = CGFloat(
            UserDefaults.standard.object(
                forKey: "preferences.resultRowHeight"
            ) as? Double ?? 24
        )
        table.intercellSpacing = NSSize(width: 1, height: 1)
        table.allowsMultipleSelection = true
        table.allowsColumnResizing = true
        table.allowsColumnReordering = true
        table.columnAutoresizingStyle = .noColumnAutoresizing
        table.backgroundColor = .white

        context.coordinator.columns = columns
        context.coordinator.rows = rows

        table.delegate = context.coordinator
        table.dataSource = context.coordinator

        configureColumns(table)

        scroll.documentView = table
        table.reloadData()

        return scroll
    }

    func updateNSView(
        _ scroll: NSScrollView,
        context: Context
    ) {
        guard let table = scroll.documentView as? NSTableView else {
            return
        }

        let oldColumns = context.coordinator.columns

        context.coordinator.columns = columns
        context.coordinator.rows = rows

        if oldColumns != columns {
            configureColumns(table)
        }

        table.reloadData()
    }

    private func configureColumns(_ table: NSTableView) {
        for column in Array(table.tableColumns) {
            table.removeTableColumn(column)
        }

        for (index, name) in columns.enumerated() {
            let identifier = NSUserInterfaceItemIdentifier(
                "column_\(index)"
            )

            let column = NSTableColumn(identifier: identifier)
            column.title = name
            column.width = CGFloat(
                UserDefaults.standard.object(
                    forKey: "preferences.resultColumnWidth"
                ) as? Double ?? 170
            )
            column.minWidth = 70
            column.maxWidth = 700
            column.resizingMask = .userResizingMask

            table.addTableColumn(column)
        }
    }

    final class Coordinator: NSObject,
                             NSTableViewDataSource,
                             NSTableViewDelegate {

        var columns: [String] = []
        var rows: [[String]] = []

        func numberOfRows(in tableView: NSTableView) -> Int {
            rows.count
        }

        func tableView(
            _ tableView: NSTableView,
            viewFor tableColumn: NSTableColumn?,
            row: Int
        ) -> NSView? {

            guard let tableColumn,
                  row >= 0,
                  row < rows.count else {
                return nil
            }

            let identifier = tableColumn.identifier.rawValue

            guard identifier.hasPrefix("column_"),
                  let columnIndex = Int(identifier.dropFirst(7)),
                  columnIndex < columns.count else {
                return nil
            }

            let cellIdentifier =
                NSUserInterfaceItemIdentifier("ResultCell")

            let cell: NSTableCellView

            if let reused = tableView.makeView(
                withIdentifier: cellIdentifier,
                owner: nil
            ) as? NSTableCellView {
                cell = reused
            } else {
                cell = NSTableCellView()
                cell.identifier = cellIdentifier

                let field = NSTextField(labelWithString: "")
                field.font = NSFont.monospacedSystemFont(
                    ofSize: 12,
                    weight: .regular
                )
                field.lineBreakMode = .byTruncatingTail
                field.translatesAutoresizingMaskIntoConstraints = false

                cell.addSubview(field)
                cell.textField = field

                NSLayoutConstraint.activate([
                    field.leadingAnchor.constraint(
                        equalTo: cell.leadingAnchor,
                        constant: 7
                    ),
                    field.trailingAnchor.constraint(
                        equalTo: cell.trailingAnchor,
                        constant: -7
                    ),
                    field.centerYAnchor.constraint(
                        equalTo: cell.centerYAnchor
                    )
                ])
            }

            let values = rows[row]

            cell.textField?.stringValue =
                columnIndex < values.count
                    ? values[columnIndex]
                    : ""

            return cell
        }
    }
}


// MARK: - MySQL Administration

enum WorkbenchAdminPage: String, CaseIterable, Identifiable {
    case serverStatus = "Server Status"
    case clientConnections = "Client Connections"
    case users = "Users and Privileges"
    case variables = "Status and System Variables"
    case dashboard = "Dashboard"
    case performanceReports = "Performance Reports"
    case performanceSchema = "Performance Schema Setup"

    var id: String { rawValue }

    var icon: String {
        switch self {
        case .serverStatus: return "server.rack"
        case .clientConnections: return "person.2"
        case .users: return "person.crop.circle.badge.checkmark"
        case .variables: return "slider.horizontal.3"
        case .dashboard: return "chart.xyaxis.line"
        case .performanceReports: return "chart.bar.xaxis"
        case .performanceSchema: return "gauge.with.dots.needle.67percent"
        }
    }

    var statement: String {
        switch self {
        case .serverStatus:
            return """
            SHOW GLOBAL STATUS WHERE Variable_name IN (
                'Uptime',
                'Threads_connected',
                'Threads_running',
                'Questions',
                'Queries',
                'Connections',
                'Bytes_received',
                'Bytes_sent'
            )
            """

        case .clientConnections:
            return "SHOW FULL PROCESSLIST"

        case .users:
            return """
            SELECT User, Host, plugin, account_locked
            FROM mysql.user
            ORDER BY User, Host
            """

        case .variables:
            return "SHOW GLOBAL VARIABLES"

        case .dashboard:
            return """
            SHOW GLOBAL STATUS WHERE Variable_name IN (
                'Uptime',
                'Connections',
                'Threads_connected',
                'Threads_running',
                'Questions',
                'Queries',
                'Bytes_received',
                'Bytes_sent',
                'Innodb_buffer_pool_reads',
                'Innodb_buffer_pool_read_requests',
                'Slow_queries'
            )
            """

        case .performanceReports:
            return """
            SELECT *
            FROM sys.statement_analysis
            LIMIT 100
            """

        case .performanceSchema:
            return """
            SELECT NAME, ENABLED, TIMED
            FROM performance_schema.setup_instruments
            LIMIT 250
            """
        }
    }
}

struct WorkbenchAdministrationView: View {
    let page: WorkbenchAdminPage
    let profile: ConnectionProfile?
    let close: () -> Void

    @State private var result = QueryResult()
    @State private var loading = false
    @State private var errorMessage: String?
    @State private var lastUpdated: Date?

    var body: some View {
        VStack(spacing: 0) {
            header

            Divider()

            if loading && result.columns.isEmpty {
                Spacer()

                ProgressView("Loading \(page.rawValue)…")

                Spacer()
            } else if let errorMessage {
                ContentUnavailableView {
                    Label(
                        "Unable to Load \(page.rawValue)",
                        systemImage: "exclamationmark.triangle"
                    )
                } description: {
                    Text(errorMessage)
                } actions: {
                    Button("Retry") {
                        Task { await refresh() }
                    }
                }
                .frame(maxWidth: .infinity, maxHeight: .infinity)
            } else if result.columns.isEmpty {
                ContentUnavailableView(
                    "No Data",
                    systemImage: "tablecells",
                    description: Text(
                        "The server did not return any columns."
                    )
                )
                .frame(maxWidth: .infinity, maxHeight: .infinity)
            } else {
                resultContent
            }

            Divider()

            footer
        }
        .frame(maxWidth: .infinity, maxHeight: .infinity)
        .task(id: "\(page.id)-\(profile?.id.uuidString ?? "")") {
            await refresh()
        }
    }

    private var header: some View {
        HStack(spacing: 14) {
            Image(systemName: page.icon)
                .font(.system(size: 27))
                .foregroundStyle(.blue)
                .frame(width: 40)

            VStack(alignment: .leading, spacing: 3) {
                Text(profile?.name ?? "No Connection")
                    .font(.caption)
                    .foregroundStyle(.secondary)

                Text(page.rawValue)
                    .font(.system(size: 22, weight: .semibold))
            }

            Spacer()

            Button {
                Task { await refresh() }
            } label: {
                Label("Refresh", systemImage: "arrow.clockwise")
            }
            .disabled(loading)

            Button {
                close()
            } label: {
                Label("SQL Editor", systemImage: "chevron.left.forwardslash.chevron.right")
            }
        }
        .padding(18)
    }

    @ViewBuilder
    private var resultContent: some View {
        if page == .dashboard || page == .serverStatus {
            ScrollView {
                LazyVGrid(
                    columns: [
                        GridItem(.adaptive(minimum: 180), spacing: 12)
                    ],
                    spacing: 12
                ) {
                    ForEach(result.rows.indices, id: \.self) { index in
                        let row = result.rows[index]

                        if row.count >= 2 {
                            VStack(alignment: .leading, spacing: 10) {
                                Text(
                                    row[0]
                                        .replacingOccurrences(
                                            of: "_",
                                            with: " "
                                        )
                                )
                                .font(.caption)
                                .foregroundStyle(.secondary)

                                Text(row[1])
                                    .font(
                                        .system(
                                            size: 23,
                                            weight: .semibold,
                                            design: .rounded
                                        )
                                    )
                                    .lineLimit(1)
                                    .minimumScaleFactor(0.65)
                            }
                            .frame(
                                maxWidth: .infinity,
                                minHeight: 90,
                                alignment: .leading
                            )
                            .padding(14)
                            .background(
                                Color(nsColor: .controlBackgroundColor)
                            )
                            .clipShape(
                                RoundedRectangle(cornerRadius: 10)
                            )
                        }
                    }
                }
                .padding(18)
            }
        } else {
            NativeResultGrid(
                columns: result.columns,
                rows: result.rows
            )
            .frame(
                maxWidth: .infinity,
                maxHeight: .infinity
            )
        }
    }

    private var footer: some View {
        HStack {
            if let lastUpdated {
                Text(
                    "Updated \(lastUpdated.formatted(date: .omitted, time: .standard))"
                )
            } else {
                Text("Not loaded")
            }

            Spacer()

            Text("\(result.rows.count) rows")
        }
        .font(.caption)
        .foregroundStyle(.secondary)
        .padding(.horizontal, 16)
        .frame(height: 30)
    }

    @MainActor
    private func refresh() async {
        guard let profile else {
            errorMessage = "Select a MySQL connection first."
            return
        }

        loading = true
        errorMessage = nil

        defer {
            loading = false
        }

        do {
            let response = try await NativeMySQLRunner.run(
                profile: profile,
                database: "",
                password: PasswordStore.read(profile.id),
                sql: page.statement
            )

            result = response
            lastUpdated = Date()
        } catch {
            errorMessage = error.localizedDescription
        }
    }
}


// MARK: - Built-in Database Import / Export

struct WorkbenchDatabaseTransferView: View {
    @ObservedObject var model: DatabaseModel
    @Environment(\.dismiss) private var dismiss

    @State private var selectedMode = 0
    @State private var database = ""
    @State private var isWorking = false
    @State private var progress = 0.0
    @State private var status = "Ready"
    @State private var operationTask: Task<Void, Never>?
    @State private var showingImportConfirmation = false
    @State private var pendingImportURL: URL?
    @State private var availableTables: [String] = []
    @State private var selectedTables: Set<String> = []
    @State private var exportStructure = true
    @State private var exportData = true
    @State private var includeDrop = false
    @State private var includeViews = true
    @State private var availableViews: [String] = []
    @State private var selectedViews: Set<String> = []
    @State private var loadingTables = false
    @State private var availableDatabases: [String] = []
    @State private var loadingDatabases = false

    private var selectedProfile: ConnectionProfile? {
        model.selected
    }

    var body: some View {
        VStack(spacing: 0) {
            header

            Divider()

            Picker("Operation", selection: $selectedMode) {
                Text("Data Export").tag(0)
                Text("Data Import / Restore").tag(1)
            }
            .pickerStyle(.segmented)
            .padding(20)

            ScrollView {
                VStack(alignment: .leading, spacing: 16) {
                GroupBox("MySQL Connection") {
                    VStack(alignment: .leading, spacing: 10) {
                    LabeledContent("Connection") {
                        Text(selectedProfile?.name ?? "Not selected")
                    }

                    Picker("Database", selection: $database) {
                        Text("Select Database").tag("")

                        ForEach(availableDatabases, id: \.self) { name in
                            Text(name).tag(name)
                        }
                    }
                    HStack {
                        if loadingDatabases { ProgressView().controlSize(.small) }
                        Button("Refresh Databases") {
                            Task { await loadTransferDatabases() }
                        }
                        .disabled(loadingDatabases || selectedProfile == nil)
                    }
                    }
                }

                if selectedMode == 0 {
                    GroupBox("Export Options") {
                    VStack(alignment: .leading, spacing: 10) {
                        Toggle("Table structure", isOn: $exportStructure)
                        Toggle("Table data", isOn: $exportData)
                        Toggle("Add DROP TABLE IF EXISTS", isOn: $includeDrop)
                            .disabled(!exportStructure)
                        Toggle("Include views (definitions)", isOn: $includeViews)
                            .disabled(!exportStructure)
                        HStack {
                            Text("Tables (\(selectedTables.count) selected)")
                            Spacer()
                            Button("All") { selectedTables = Set(availableTables) }
                            Button("None") { selectedTables.removeAll() }
                            Button("Refresh") { Task { await loadTables() } }
                                .disabled(loadingTables)
                        }
                        if loadingTables { ProgressView("Loading tables…") }
                        if availableTables.isEmpty && !loadingTables {
                            Text("No tables found. Select a database or refresh the list.")
                                .foregroundStyle(.secondary)
                        }
                        ForEach(availableTables, id: \.self) { table in
                            Toggle(table, isOn: Binding(
                                get: { selectedTables.contains(table) },
                                set: { checked in
                                    if checked { selectedTables.insert(table) }
                                    else { selectedTables.remove(table) }
                                }
                            ))
                        }
                        if includeViews && exportStructure {
                            HStack {
                                Text("Views (\(selectedViews.count) selected)")
                                Spacer()
                                Button("All") { selectedViews = Set(availableViews) }
                                Button("None") { selectedViews.removeAll() }
                            }
                            ForEach(availableViews, id: \.self) { view in
                                Toggle(view, isOn: Binding(
                                    get: { selectedViews.contains(view) },
                                    set: { checked in
                                        if checked { selectedViews.insert(view) }
                                        else { selectedViews.remove(view) }
                                    }
                                ))
                            }
                        }
                        Text("Exports base tables and selected views. Triggers, routines, consistent snapshots and guaranteed row ordering are not yet supported.")
                            .font(.caption).foregroundStyle(.secondary)
                    }
                    }
                } else {
                    GroupBox("Import Options") {
                    VStack(alignment: .leading, spacing: 10) {
                        Text("Import SQL statements into the selected database.")
                            .foregroundStyle(.secondary)

                        Text("Supports MySQL DELIMITER directives, triggers and stored routines. Import is not transactional; use a verified backup before restoring.")
                            .font(.caption)
                            .foregroundStyle(.secondary)
                    }
                    }
                }

                GroupBox("Progress") {
                    VStack(alignment: .leading, spacing: 10) {
                    ProgressView(value: progress)
                        .frame(maxWidth: .infinity)

                    Text(status)
                        .font(.caption)
                        .foregroundStyle(.secondary)
                        .textSelection(.enabled)
                    }
                }
                }
            }
            .frame(maxWidth: .infinity, alignment: .leading)
            .padding(20)

            Divider()

            HStack {
                Button("Close") {
                    operationTask?.cancel()
                    dismiss()
                }

                Spacer()

                if isWorking {
                    Button("Cancel") {
                        operationTask?.cancel()
                        status = "Cancelling after current statement…"
                    }
                } else {
                    Button(
                        selectedMode == 0
                            ? "Export SQL…"
                            : "Import SQL…"
                    ) {
                        if selectedMode == 0 {
                            chooseExportDestination()
                        } else {
                            chooseImportSource()
                        }
                    }
                    .buttonStyle(.borderedProminent)
                    .disabled(
                        selectedProfile == nil ||
                        database.isEmpty ||
                        (selectedMode == 0 && ((!exportStructure && !exportData) || (selectedTables.isEmpty && !(exportStructure && includeViews && !selectedViews.isEmpty))))
                    )
                }
            }
            .padding(16)
        }
        .frame(minWidth: 650, idealWidth: 780, minHeight: 500)
        .onAppear {
            if database.isEmpty {
                database = model.selectedDatabase.isEmpty
                    ? (model.databases.first ?? "")
                    : model.selectedDatabase
            }
        }
        .task(id: selectedProfile?.id) {
            await loadTransferDatabases()
        }
        .task(id: database) {
            availableTables = []
            selectedTables = []
            availableViews = []
            selectedViews = []
            if !database.isEmpty { await loadTables() }
        }
        .confirmationDialog(
            "Import SQL into \(database)?",
            isPresented: $showingImportConfirmation
        ) {
            Button("Import SQL") {
                guard let url = pendingImportURL else { return }

                operationTask = Task {
                    await importSQL(from: url)
                }
            }

            Button("Cancel", role: .cancel) {
                pendingImportURL = nil
            }
        } message: {
            Text(
                "SQL files can modify or delete existing database objects and data. Ensure you have a backup before continuing."
            )
        }
    }

    private var header: some View {
        HStack(spacing: 12) {
            Image(systemName: "externaldrive.badge.timemachine")
                .font(.system(size: 28))
                .foregroundStyle(.blue)

            VStack(alignment: .leading, spacing: 4) {
                Text("Database Import / Export")
                    .font(.system(size: 22, weight: .semibold))

                Text("Built-in native MySQL database tools")
                    .font(.caption)
                    .foregroundStyle(.secondary)
            }

            Spacer()
        }
        .padding(20)
    }

    private func chooseExportDestination() {
        let panel = NSSavePanel()
        panel.title = "Export MySQL Database"
        panel.nameFieldStringValue = "\(database).sql"
        panel.canCreateDirectories = true

        guard panel.runModal() == .OK,
              let url = panel.url
        else { return }

        operationTask = Task {
            await exportSQL(to: url)
        }
    }

    private func chooseImportSource() {
        let panel = NSOpenPanel()
        panel.title = "Import MySQL SQL File"
        panel.allowedContentTypes = [.plainText]
        panel.allowsOtherFileTypes = true
        panel.canChooseDirectories = false
        panel.canChooseFiles = true

        guard panel.runModal() == .OK,
              let url = panel.url
        else { return }

        pendingImportURL = url
        showingImportConfirmation = true
    }

    @MainActor
    private func execute(_ statement: String) async throws -> QueryResult {
        guard let profile = selectedProfile else {
            throw WorkbenchTransferError.message(
                "No MySQL connection selected"
            )
        }

        return try await NativeMySQLRunner.run(
            profile: profile,
            database: statement == "SHOW DATABASES" ? "" : database,
            password: PasswordStore.read(profile.id),
            sql: statement
        )
    }

    private func quoteIdentifier(_ identifier: String) -> String {
        "`" + identifier.replacingOccurrences(
            of: "`",
            with: "``"
        ) + "`"
    }

    @MainActor
    private func loadTransferDatabases() async {
        guard selectedProfile != nil else {
            availableDatabases = []
            database = ""
            status = "Select a MySQL connection first"
            return
        }
        loadingDatabases = true
        defer { loadingDatabases = false }
        do {
            // Do not depend on the schema navigator having been opened first.
            let response = try await execute("SHOW DATABASES")
            let names = response.rows.compactMap { $0.first }
            availableDatabases = names
            if !names.contains(database) {
                let preferred = model.selectedDatabase
                database = names.contains(preferred) ? preferred : (names.first ?? "")
            }
            status = names.isEmpty ? "No accessible databases" : "Ready"
        } catch {
            availableDatabases = []
            database = ""
            status = "Cannot load databases: \(error.localizedDescription)"
        }
    }

    @MainActor
    private func loadTables() async {
        guard !database.isEmpty else {
            availableTables = []; selectedTables = []
            availableViews = []; selectedViews = []
            return
        }
        loadingTables = true
        defer { loadingTables = false }
        do {
            let rows = try await execute("SHOW FULL TABLES FROM \(quoteIdentifier(database))")
            availableTables = rows.rows.compactMap { row in
                row.count > 1 && row[1].uppercased() == "BASE TABLE" ? row[0] : nil
            }
            selectedTables = Set(availableTables)
            availableViews = rows.rows.compactMap { row in
                row.count > 1 && row[1].uppercased() == "VIEW" ? row[0] : nil
            }
            selectedViews = Set(availableViews)
        } catch {
            status = "Cannot list tables: \(error.localizedDescription)"
            availableTables = []
            selectedTables = []
            availableViews = []
            selectedViews = []
        }
    }

    // The server constructs SQL literals, so NULL, quotes and binary data are
    // preserved rather than reconstructed from QueryResult's String values.
    @MainActor
    private func exportSQL(to url: URL) async {
        guard exportStructure || exportData else { return }
        let views = exportStructure && includeViews
            ? availableViews.filter { selectedViews.contains($0) }
            : []
        guard !selectedTables.isEmpty || !views.isEmpty else { return }
        isWorking = true
        progress = 0
        let tables = availableTables.filter { selectedTables.contains($0) }
        let tempURL = url.deletingLastPathComponent().appendingPathComponent(".\(UUID().uuidString).sql.tmp")
        var handle: FileHandle?
        defer {
            try? handle?.close()
            try? FileManager.default.removeItem(at: tempURL)
            isWorking = false
            operationTask = nil
        }
        do {
            guard FileManager.default.createFile(atPath: tempURL.path, contents: nil) else {
                throw WorkbenchTransferError.message("Cannot create temporary export file")
            }
            handle = try FileHandle(forWritingTo: tempURL)
            func write(_ value: String) throws {
                try handle?.write(contentsOf: Data(value.utf8))
            }
            try write("-- WorkbenchReplacement native export\n-- Database: \(database)\n-- Generated: \(Date())\nSET NAMES utf8mb4;\n\n")
            let db = quoteIdentifier(database)
            for (index, table) in tables.enumerated() {
                try Task.checkCancellation()
                let qualified = "\(db).\(quoteIdentifier(table))"
                status = "Exporting \(table) (\(index + 1)/\(tables.count))"
                try write("\n-- Table \(qualified)\n")
                if exportStructure {
                    let definition = try await execute("SHOW CREATE TABLE \(qualified)")
                    guard let row = definition.rows.first, row.count > 1 else {
                        throw WorkbenchTransferError.message("Missing CREATE TABLE for \(table)")
                    }
                    if includeDrop { try write("DROP TABLE IF EXISTS \(qualified);\n") }
                    try write(row[1] + ";\n")
                }
                if exportData {
                    // Column metadata drives binary-safe SQL literal formatting.
                    let metadata = try await execute("""
                        SELECT COLUMN_NAME, DATA_TYPE
                        FROM information_schema.COLUMNS
                        WHERE TABLE_SCHEMA = \(sqlLiteral(database)) AND TABLE_NAME = \(sqlLiteral(table))
                        ORDER BY ORDINAL_POSITION
                        """)
                    guard !metadata.rows.isEmpty else {
                        throw WorkbenchTransferError.message("No column metadata for \(table)")
                    }
                    let names = metadata.rows.map { quoteIdentifier($0[0]) }.joined(separator: ", ")
                    let expressions = metadata.rows.map { row -> String in
                        let col = quoteIdentifier(row[0])
                        let kind = row[1].lowercased()
                        // HEX avoids decoding arbitrary bytes as UTF-8.
                        if ["binary", "varbinary", "tinyblob", "blob", "mediumblob", "longblob", "bit"].contains(kind) {
                            return "IF(\(col) IS NULL, 'NULL', CONCAT('0x', HEX(\(col))))"
                        }
                        return "IF(\(col) IS NULL, 'NULL', QUOTE(\(col)))"
                    }.joined(separator: ", ")
                    let statement = "SELECT CONCAT('(', CONCAT_WS(',', \(expressions)), ')') FROM \(qualified) LIMIT 250 OFFSET "
                    var offset = 0
                    while true {
                        try Task.checkCancellation()
                        let batch = try await execute(statement + String(offset))
                        if batch.rows.isEmpty { break }
                        for row in batch.rows {
                            guard let literalRow = row.first else { continue }
                            try write("INSERT INTO \(qualified) (\(names)) VALUES \(literalRow);\n")
                        }
                        offset += batch.rows.count
                        status = "Exporting \(table): \(offset) rows"
                        if batch.rows.count < 250 { break }
                    }
                }
                progress = Double(index + 1) / Double(max(tables.count + views.count, 1))
            }
            // Views are exported after base tables so dependencies exist on restore.
            // The server's SHOW CREATE VIEW response may contain a DEFINER clause;
            // importing under a different MySQL account can require extra privileges.
            for (index, view) in views.enumerated() {
                try Task.checkCancellation()
                let qualified = "\(db).\(quoteIdentifier(view))"
                status = "Exporting view \(view)"
                let definition = try await execute("SHOW CREATE VIEW \(qualified)")
                guard let row = definition.rows.first, row.count > 1 else {
                    throw WorkbenchTransferError.message("Missing CREATE VIEW for \(view)")
                }
                try write("\n-- View \(qualified)\n")
                if includeDrop { try write("DROP VIEW IF EXISTS \(qualified);\n") }
                try write(row[1] + ";\n")
                progress = Double(tables.count + index + 1) / Double(max(tables.count + views.count, 1))
            }
            try Task.checkCancellation()
            try handle?.close()
            handle = nil
            if FileManager.default.fileExists(atPath: url.path) {
                _ = try FileManager.default.replaceItemAt(url, withItemAt: tempURL)
            } else {
                try FileManager.default.moveItem(at: tempURL, to: url)
            }
            progress = 1
            status = "Export complete: \(tables.count) tables, \(views.count) views"
        } catch is CancellationError {
            status = "Export cancelled; no final backup was written"
        } catch {
            status = "Export failed: \(error.localizedDescription)"
        }
    }

    private func sqlLiteral(_ value: String) -> String {
        "'" + value.replacingOccurrences(of: "\\", with: "\\\\")
                   .replacingOccurrences(of: "'", with: "''") + "'"
    }

    @MainActor
    private func importSQL(from url: URL) async {
        isWorking = true
        progress = 0
        status = "Reading SQL file…"

        defer {
            isWorking = false
            operationTask = nil
        }

        do {
            let sql = try String(
                contentsOf: url,
                encoding: .utf8
            )

            let statements = try WorkbenchSQLImportParser.parse(sql)

            guard !statements.isEmpty else {
                status = "No SQL statements found"
                return
            }

            for (index, statement) in statements.enumerated() {
                try Task.checkCancellation()

                status = "Executing statement \(index + 1) of \(statements.count)"

                _ = try await execute(statement)

                progress = Double(index + 1) /
                    Double(statements.count)
            }

            status = "Import complete: \(statements.count) statements"

            model.loadDatabases()

        } catch is CancellationError {
            status = "Import cancelled; previously executed statements may remain applied"
        } catch {
            status = "Import failed: \(error.localizedDescription)"
        }
    }
}

enum WorkbenchTransferError: LocalizedError {
    case message(String)

    var errorDescription: String? {
        switch self {
        case .message(let message):
            return message
        }
    }
}

// MARK: - SQL Import Parser
// Supports MySQL DELIMITER directives, quoted text, executable /*! */
// comments, and routine bodies. Parsing does not execute SQL.

enum WorkbenchSQLImportParser {
    static func parse(_ sql: String) throws -> [String] {
        let chars = Array(sql)
        var statements: [String] = []
        var current = ""
        var delimiter = ";"
        var quote: Character? = nil
        var lineComment = false
        var blockComment = false
        var escaped = false
        var lineStart = true
        var i = 0

        func matches(_ value: String, at index: Int) -> Bool {
            let pattern = Array(value)
            guard index + pattern.count <= chars.count else { return false }
            return Array(chars[index..<(index + pattern.count)]) == pattern
        }

        func emit() {
            let value = current.trimmingCharacters(in: .whitespacesAndNewlines)
            if !value.isEmpty { statements.append(value) }
            current = ""
        }

        while i < chars.count {
            let ch = chars[i]
            let next: Character? = i + 1 < chars.count ? chars[i + 1] : nil

            // DELIMITER is a client-side directive, never sent to MySQL.
            if lineStart && quote == nil && !lineComment && !blockComment {
                var j = i
                while j < chars.count && (chars[j] == " " || chars[j] == "\t") { j += 1 }
                if j + 9 <= chars.count && String(chars[j..<min(j + 9, chars.count)]).uppercased() == "DELIMITER" &&
                    (j + 9 == chars.count || chars[j + 9].isWhitespace) {
                    let pending = current.trimmingCharacters(in: .whitespacesAndNewlines)
                    if !pending.isEmpty {
                        throw WorkbenchTransferError.message("DELIMITER directive encountered inside an unfinished statement")
                    }
                    var k = j + 9
                    while k < chars.count && chars[k] != "\n" && chars[k] != "\r" { k += 1 }
                    let token = String(chars[(j + 9)..<k]).trimmingCharacters(in: .whitespacesAndNewlines)
                    guard !token.isEmpty && !token.contains(where: { $0.isWhitespace }) else {
                        throw WorkbenchTransferError.message("Invalid DELIMITER directive")
                    }
                    delimiter = token
                    i = k
                    lineStart = true
                    continue
                }
            }

            if lineComment {
                if ch == "\n" || ch == "\r" {
                    lineComment = false
                    current.append("\n")
                    lineStart = true
                }
                i += 1
                continue
            }
            if blockComment {
                // Preserve MySQL executable and optimizer-hint comments in SQL.
                if ch == "*" && next == "/" {
                    if current.hasSuffix("*") { /* no-op */ }
                    current.append("*/")
                    blockComment = false
                    i += 2
                } else {
                    current.append(ch)
                    i += 1
                }
                continue
            }
            if let active = quote {
                current.append(ch)
                if escaped { escaped = false }
                else if ch == "\\" && active != "`" { escaped = true }
                else if ch == active {
                    if next == active {
                        current.append(next!)
                        i += 1
                    } else { quote = nil }
                }
                i += 1
                continue
            }
            if ch == "'" || ch == "\"" || ch == "`" {
                quote = ch
                current.append(ch)
                lineStart = false
                i += 1
                continue
            }
            if ch == "#" || (ch == "-" && next == "-" &&
                (i + 2 == chars.count || chars[i + 2].isWhitespace)) {
                lineComment = true
                i += ch == "#" ? 1 : 2
                continue
            }
            if ch == "/" && next == "*" {
                // Keep executable comments; ordinary comments may also contain
                // SQL hints, so preserve all block comments verbatim.
                current.append("/*")
                blockComment = true
                i += 2
                continue
            }
            if matches(delimiter, at: i) {
                emit()
                i += delimiter.count
                lineStart = false
                continue
            }
            current.append(ch)
            if ch == "\n" || ch == "\r" { lineStart = true }
            else if !ch.isWhitespace { lineStart = false }
            i += 1
        }
        guard quote == nil && !blockComment else {
            throw WorkbenchTransferError.message("SQL file ends inside a quoted string or block comment")
        }
        guard delimiter == ";" else {
            throw WorkbenchTransferError.message("SQL file ends without resetting DELIMITER to ;")
        }
        emit()
        return statements
    }
}