import Foundation
import SwiftUI
import UserNotifications

enum HealthStatus: String, Codable {
    case ok, warn, fail

    var title: String {
        switch self {
        case .ok: "Healthy"
        case .warn: "Warning"
        case .fail: "Critical"
        }
    }

    var symbol: String {
        switch self {
        case .ok: "checkmark.circle.fill"
        case .warn: "exclamationmark.triangle.fill"
        case .fail: "xmark.circle.fill"
        }
    }

    var color: Color {
        switch self {
        case .ok: .green
        case .warn: .orange
        case .fail: .red
        }
    }
}

struct HealthCounts: Codable {
    let ok: Int
    let warn: Int
    let fail: Int
}

struct HealthGroup: Codable, Identifiable {
    let name: String
    let status: HealthStatus
    let missing: [String]
    var id: String { name }
}

struct HealthCheck: Codable, Identifiable {
    let name: String
    let status: HealthStatus
    let detail: String
    let section: String
    var id: String { "\(section)/\(name)" }
}

struct HealthReport: Codable {
    let schema: Int
    let host: String?
    let generatedAt: String?
    let overall: HealthStatus
    let counts: HealthCounts
    let groups: [HealthGroup]
    let checks: [HealthCheck]
    let diagnostics: String?
}

struct SSHSettings {
    @AppStorage("server.host") var host = "192.168.1.2"
    @AppStorage("server.user") var user = "mag"
    @AppStorage("server.port") var port = "22"
    @AppStorage("server.keyFile") var keyFile = ""
    @AppStorage("monitor.intervalMinutes") var intervalMinutes = 5
    @AppStorage("monitor.notifications") var notifications = true
}

@MainActor
final class ServerMonitor: ObservableObject {
    @Published private(set) var report: HealthReport?
    @Published private(set) var status: HealthStatus = .warn
    @Published private(set) var isRefreshing = false
    @Published private(set) var lastChecked: Date?
    @Published private(set) var lastError: String?
    @Published var showDiagnostics = false
    @Published var showSettings = false

    private var settings = SSHSettings()
    private var timer: Timer?
    private var everLoaded = false

    init() {
        configureTimer()
        Task { await refresh() }
    }

    func configureTimer() {
        timer?.invalidate()
        let minutes = max(1, settings.intervalMinutes)
        timer = Timer.scheduledTimer(withTimeInterval: TimeInterval(minutes * 60), repeats: true) { [weak self] _ in
            Task { @MainActor in await self?.refresh() }
        }
    }

    func refresh() async {
        guard !isRefreshing else { return }
        isRefreshing = true
        defer { isRefreshing = false; lastChecked = Date() }
        let previous = report?.overall
        do {
            let data = try await SSHRunner.run(host: settings.host, user: settings.user, port: settings.port, keyFile: settings.keyFile, remoteCommand: "sudo -n /usr/local/bin/pegasus-health-json")
            let value = try JSONDecoder().decode(HealthReport.self, from: data)
            guard value.schema == 1, value.groups.count == 14 else { throw SSHError.invalidResponse }
            report = value
            status = value.overall
            lastError = nil
            if settings.notifications && everLoaded && previous == .ok && value.overall != .ok {
                notify(title: "Pegasus \(value.overall.title)", message: "\(value.counts.fail) failures, \(value.counts.warn) warnings")
            }
            everLoaded = true
        } catch {
            lastError = error.localizedDescription
            status = .fail
            if settings.notifications && everLoaded && previous != .fail {
                notify(title: "Pegasus Unreachable", message: error.localizedDescription)
            }
        }
    }

    func showSystemSettings() {
        NSApp.sendAction(Selector(("showSettingsWindow:")), to: nil, from: nil)
    }

    private func notify(title: String, message: String) {
        let center = UNUserNotificationCenter.current()
        center.requestAuthorization(options: [.alert, .sound]) { allowed, _ in
            guard allowed else { return }
            let content = UNMutableNotificationContent()
            content.title = title
            content.body = message
            center.add(UNNotificationRequest(identifier: UUID().uuidString, content: content, trigger: nil))
        }
    }
}

enum SSHError: LocalizedError {
    case invalidSettings, timeout, invalidResponse, process(String)
    var errorDescription: String? {
        switch self {
        case .invalidSettings: "Invalid SSH settings. Check host, user and port."
        case .timeout: "SSH connection timed out."
        case .invalidResponse: "Server returned invalid health JSON. Install the server adapter."
        case .process(let text): text
        }
    }
}

enum SSHRunner {
    static func run(host: String, user: String, port: String, keyFile: String, remoteCommand: String) async throws -> Data {
        guard !host.isEmpty, !user.isEmpty, let number = Int(port), (1...65535).contains(number),
              host.range(of: #"^[A-Za-z0-9.:-]+$"#, options: .regularExpression) != nil,
              user.range(of: #"^[A-Za-z0-9_-]+$"#, options: .regularExpression) != nil else {
            throw SSHError.invalidSettings
        }
        return try await Task.detached(priority: .utility) {
            let process = Process()
            process.executableURL = URL(fileURLWithPath: "/usr/bin/ssh")
            var args = ["-T", "-o", "BatchMode=yes", "-o", "StrictHostKeyChecking=yes", "-o", "ConnectTimeout=8", "-o", "ServerAliveInterval=5", "-o", "ServerAliveCountMax=2", "-p", String(number)]
            if !keyFile.isEmpty { args += ["-i", (keyFile as NSString).expandingTildeInPath] }
            args += ["--", "\(user)@\(host)", remoteCommand]
            process.arguments = args
            let output = Pipe()
            let errors = Pipe()
            process.standardOutput = output
            process.standardError = errors
            try process.run()
            // Drain both pipes concurrently so verbose output cannot block the child.
            let stdout = Task.detached { output.fileHandleForReading.readDataToEndOfFile() }
            let stderr = Task.detached { errors.fileHandleForReading.readDataToEndOfFile() }
            let timeout = Task.detached {
                try? await Task.sleep(for: .seconds(90))
                if process.isRunning { process.terminate() }
            }
            let bytes = await stdout.value
            let errorBytes = await stderr.value
            process.waitUntilExit()
            timeout.cancel()
            // Health status exits 1/2 intentionally; JSON remains authoritative.
            if bytes.isEmpty {
                let errorMessage = String(data: errorBytes, encoding: .utf8) ?? "SSH returned no data"
                throw SSHError.process(errorMessage.isEmpty ? "SSH returned no data" : errorMessage)
            }
            return bytes
        }.value
    }
}