import SwiftUI
import AppKit

struct DJLoopDrag {
    enum Mode { case seek, start, end, move, create }
    let mode: Mode
    let viewport: Double
    let secondsPerPixel: Double
    let anchor: Double
    let original: ClosedRange<Double>?
    init(x: Double,viewport: Double,span: Double,width: Double,loop: ClosedRange<Double>?,create: Bool) {
        self.viewport = viewport;secondsPerPixel = span/max(1,width);anchor = viewport+x*secondsPerPixel;original = loop
        if create { mode = .create }
        else if let loop {
            let left = abs(anchor-loop.lowerBound),right = abs(anchor-loop.upperBound),tolerance = min(8*secondsPerPixel,(loop.upperBound-loop.lowerBound)/4)
            if min(left,right) <= tolerance { mode = left <= right ? .start : .end }
            else if loop.contains(anchor) { mode = .move }
            else { mode = .seek }
        } else { mode = .seek }
    }
    func range(x: Double,duration: Double) -> ClosedRange<Double>? {
        guard duration >= 0.1,secondsPerPixel > 0 else { return nil }
        let point = min(duration,max(0,viewport+x*secondsPerPixel))
        switch mode {
        case .seek: return nil
        case .create:
            let first = min(duration,max(0,anchor)),start = min(duration-0.1,min(first,point))
            return start...min(duration,max(start+0.1,max(first,point)))
        case .start:
            guard let original else { return nil };return min(point,original.upperBound-0.1)...original.upperBound
        case .end:
            guard let original else { return nil };return original.lowerBound...max(original.lowerBound+0.1,point)
        case .move:
            guard let original else { return nil }
            let length = original.upperBound-original.lowerBound
            let start = min(duration-length,max(0,original.lowerBound+(viewport+x*secondsPerPixel-anchor)))
            return start...(start+length)
        }
    }
}

struct DJLoopWaveInteraction: ViewModifier {
    @ObservedObject var player: Player
    let start: Double
    let span: Double
    let width: Double
    @Binding var frozenStart: Double?
    @State private var drag: DJLoopDrag?
    func body(content: Content) -> some View {
        content.contentShape(Rectangle())
            .gesture(DragGesture(minimumDistance:0).onChanged { value in
                guard player.canJog,span > 0 else { return }
                if drag == nil {
                    let loop = player.loopEnabled ? player.loopIn.flatMap { a in player.loopOut.map { a...$0 } } : nil
                    drag = DJLoopDrag(x:value.startLocation.x,viewport:start,span:span,width:width,loop:loop,create:NSEvent.modifierFlags.contains(.shift))
                    frozenStart = start
                }
                guard let drag else { return }
                if let range = drag.range(x:value.location.x,duration:player.duration) { player.defineLoop(start:range.lowerBound,end:range.upperBound) }
                else if drag.mode == .seek { player.seek(drag.viewport+value.location.x*drag.secondsPerPixel) }
            }.onEnded { _ in drag = nil;frozenStart = nil })
            .onChange(of:player.currentSongID) { _ in drag = nil;frozenStart = nil }
            .onContinuousHover { phase in
                switch phase {
                case .active(let point):
                    let loop = player.loopEnabled ? player.loopIn.flatMap { a in player.loopOut.map { a...$0 } } : nil
                    let mode = DJLoopDrag(x:point.x,viewport:frozenStart ?? start,span:span,width:width,loop:loop,create:NSEvent.modifierFlags.contains(.shift)).mode
                    switch mode {
                    case .start,.end: NSCursor.resizeLeftRight.set()
                    case .move: NSCursor.openHand.set()
                    case .create: NSCursor.crosshair.set()
                    case .seek: NSCursor.arrow.set()
                    }
                case .ended: NSCursor.arrow.set()
                }
            }
            .help("Drag green IN/OUT edges to resize; drag inside the loop to move it. Shift-drag to define a new loop. Drag outside it to seek.")
    }
}

struct DJLoopEditor: View {
    @ObservedObject var player: Player
    let letter: String
    @State private var start: Double
    @State private var end: Double
    @Environment(\.dismiss) private var dismiss
    init(player: Player,letter: String) {
        self.player = player;self.letter = letter
        let first = player.loopIn ?? min(max(0,player.time),max(0,player.duration-0.1))
        _start = State(initialValue:first);_end = State(initialValue:player.loopOut ?? min(player.duration,first+4))
    }
    private var valid: Bool { start.isFinite && end.isFinite && start >= 0 && end <= player.duration && end-start >= 0.1-1e-9 }
    var body: some View {
        VStack(alignment:.leading,spacing:18) {
            Text("Deck \(letter) · Loop Points").font(.title2.bold())
            HStack { Text("Start (seconds)").frame(width:120,alignment:.leading);TextField("Start",value:$start,format:.number.precision(.fractionLength(3))).textFieldStyle(.roundedBorder);Button("Use Playhead") { start = player.time } }
            HStack { Text("End (seconds)").frame(width:120,alignment:.leading);TextField("End",value:$end,format:.number.precision(.fractionLength(3))).textFieldStyle(.roundedBorder);Button("Use Playhead") { end = player.time } }
            Text(valid ? String(format:"Loop length: %.3f seconds",end-start) : "End must be at least 0.1 seconds after start, within the track.").font(.caption).foregroundStyle(valid ? Color.secondary : Color.orange)
            Text("On either waveform, drag the green edges to resize or the loop region to move. Shift-drag defines a new loop. Playback continues while editing.").font(.callout).foregroundStyle(.secondary)
            HStack { Button("Cancel") { dismiss() };Spacer();Button("Activate Loop") { player.defineLoop(start:start,end:end);dismiss() }.disabled(!valid || !player.canJog).keyboardShortcut(.defaultAction) }
        }.padding(24).frame(width:540)
    }
}