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
    var relativeSeek = false
    @Binding var frozenStart: Double?
    func body(content: Content) -> some View {
        content.contentShape(Rectangle())
            .overlay {
                DJWaveMouseSurface(player:player,start:start,span:span,width:width,relativeSeek:relativeSeek,frozenStart:$frozenStart)
            }
            .onChange(of:player.currentSongID) { _ in 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: (relativeSeek ? NSCursor.openHand : 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. In the large spectrum, hold the left button and drag left to advance or right to rewind.")
    }
}

// Native tracking survives the nested hosting views used by the deck drop zones.
struct DJWaveMouseSurface: NSViewRepresentable {
    let player: Player
    let start: Double
    let span: Double
    let width: Double
    var relativeSeek = false
    @Binding var frozenStart: Double?
    func makeNSView(context: Context) -> DJWaveMouseView { DJWaveMouseView() }
    func updateNSView(_ view: DJWaveMouseView,context: Context) {
        view.player = player;view.viewport = start;view.span = span;view.waveWidth = width;view.relativeSeek = relativeSeek
        view.freeze = { frozenStart = $0 }
    }
}
class DJWaveMouseView: NSView {
    weak var player: Player?
    var viewport = 0.0,span = 0.0,waveWidth = 1.0
    var freeze: ((Double?) -> Void)?
    var relativeSeek = false
    private var drag: DJLoopDrag?
    private var initialTime = 0.0,initialX = 0.0
    override var isFlipped: Bool { true }
    override func acceptsFirstMouse(for event: NSEvent?) -> Bool { true }
    override func mouseDown(with event: NSEvent) {
        guard let player,player.canJog,span > 0 else { return }
        let point = convert(event.locationInWindow,from:nil)
        let loop = player.loopEnabled ? player.loopIn.flatMap { a in player.loopOut.map { a...$0 } } : nil
        drag = DJLoopDrag(x:point.x,viewport:viewport,span:span,width:waveWidth,loop:loop,create:event.modifierFlags.contains(.shift))
        initialTime = player.displayTime;initialX = point.x
        freeze?(viewport)
        if !relativeSeek || drag?.mode != .seek { updateDrag(point.x) }
    }
    override func mouseDragged(with event: NSEvent) { updateDrag(convert(event.locationInWindow,from:nil).x) }
    override func mouseUp(with event: NSEvent) {
        updateDrag(convert(event.locationInWindow,from:nil).x);drag = nil;freeze?(nil);NSCursor.openHand.set()
    }
    private func updateDrag(_ x: Double) {
        guard let player,let drag else { return }
        if let range = drag.range(x:x,duration:player.duration) { player.defineLoop(start:range.lowerBound,end:range.upperBound) }
        else if drag.mode == .seek {
            if relativeSeek {
                let target = min(player.duration,max(0,initialTime-(x-initialX)*drag.secondsPerPixel))
                if abs(player.time-target) > 0.0001 { player.seek(target) }
                freeze?(drag.viewport+target-initialTime)
                NSCursor.closedHand.set()
            } else { player.seek(drag.viewport+x*drag.secondsPerPixel) }
        }
    }
}

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)
    }
}

// Display-link-style redraws stay inside AppKit, keeping 60 Hz spectrum motion
// independent of SwiftUI layout, the karaoke library and lyric accessibility.
struct DJNativeSpectrum: NSViewRepresentable {
    let player: Player
    let bpm: Double?
    let color: NSColor
    let seconds: Double
    let label: String
    let showTimeGrid: Bool
    let spectralWaveforms: Bool
    func makeNSView(context: Context) -> DJNativeSpectrumView { DJNativeSpectrumView() }
    func updateNSView(_ view: DJNativeSpectrumView,context: Context) {
        view.player = player;view.bpm = bpm;view.color = color;view.span = seconds
        view.label = label;view.showTimeGrid = showTimeGrid;view.spectralWaveforms = spectralWaveforms
        view.setAccessibilityElement(true);view.setAccessibilityRole(.image)
        view.setAccessibilityLabel(label == "KARAOKE" ? "Karaoke scrolling waveform" : "Deck \(label) scrolling waveform")
        view.setAccessibilityValue(String(format:"%d:%02d",Int(max(0,player.time))/60,Int(max(0,player.time))%60))
        view.relativeSeek = true;view.waveWidth = view.bounds.width;view.needsDisplay = true
    }
}
final class DJNativeSpectrumView: DJWaveMouseView {
    var bpm: Double?
    var color = NSColor.systemCyan
    var label = ""
    var showTimeGrid = true,spectralWaveforms = true
    private var clock: Timer?
    private var frozenViewport: Double?
    private var hoverX: Double?
    private var tracking: NSTrackingArea?
    override init(frame: NSRect) {
        super.init(frame:frame)
        freeze = { [weak self] start in self?.frozenViewport = start;self?.needsDisplay = true }
    }
    required init?(coder: NSCoder) { fatalError("init(coder:) has not been implemented") }
    override func viewDidMoveToWindow() {
        super.viewDidMoveToWindow();clock?.invalidate();clock = nil
        if window != nil {
            let timer = Timer(timeInterval:1.0/60,repeats:true) { [weak self] _ in
                guard let self,self.player?.playing == true,!self.isHiddenOrHasHiddenAncestor else { return }
                self.needsDisplay = true
            }
            RunLoop.main.add(timer,forMode:.common);clock = timer
        }
    }
    deinit { clock?.invalidate() }
    override func updateTrackingAreas() {
        super.updateTrackingAreas();if let tracking { removeTrackingArea(tracking) }
        let area = NSTrackingArea(rect:.zero,options:[.activeInKeyWindow,.inVisibleRect,.mouseMoved,.mouseEnteredAndExited],owner:self)
        addTrackingArea(area);tracking = area
    }
    override func resetCursorRects() { addCursorRect(bounds,cursor:.openHand) }
    override func mouseMoved(with event: NSEvent) { hoverX = convert(event.locationInWindow,from:nil).x;needsDisplay = true }
    override func mouseExited(with event: NSEvent) { hoverX = nil;needsDisplay = true }
    override func mouseDown(with event: NSEvent) {
        viewport = (player?.displayTime ?? 0)-span/2;waveWidth = bounds.width
        super.mouseDown(with:event)
    }
    override func draw(_ dirtyRect: NSRect) {
        NSColor.black.setFill();bounds.fill()
        guard let player,player.duration > 0,span > 0,!player.waveform.isEmpty else { return }
        let time = player.displayTime,start = frozenViewport ?? (time-span/2),width = bounds.width,height = bounds.height
        guard width > 0,height > 0 else { return }
        if showTimeGrid {
            NSColor.white.withAlphaComponent(0.15).setFill()
            for tick in 0...8 { NSRect(x:Double(tick)/8*width,y:0,width:0.5,height:height).fill() }
        }
        let paths = (0..<32).map { _ in NSBezierPath() },count = max(1,Int(width/2))
        for i in 0..<count {
            let seconds = start+Double(i)/Double(count)*span
            guard seconds >= 0,seconds < player.duration else { continue }
            let sample = min(Double(player.waveform.count-1),seconds/player.duration*Double(player.waveform.count))
            let index = Int(sample),next = min(player.waveform.count-1,index+1),fraction = sample-Double(index)
            let amplitude = Double(player.waveform[index])*(1-fraction)+Double(player.waveform[next])*fraction
            let barHeight = max(1,amplitude*height*0.85)
            var bucket = 0
            if spectralWaveforms,player.waveformBands.indices.contains(index) {
                let band = player.waveformBands[index],sum = max(0.0001,band.low+band.mid+band.high)
                bucket = min(31,max(0,Int((Double(band.mid/sum)*0.38+Double(band.high/sum)*0.72)*31)))
            }
            paths[bucket].appendRect(NSRect(x:Double(i)*width/Double(count),y:(height-barHeight)/2,width:1.5,height:barHeight))
        }
        for bucket in paths.indices where !paths[bucket].isEmpty {
            (spectralWaveforms ? NSColor(calibratedHue:Double(bucket)/31,saturation:0.85,brightness:0.95,alpha:1) : color).setFill();paths[bucket].fill()
        }
        if let bpm {
            for beat in DJWaveMarkers.beats(start:start,span:span,bpm:bpm,width:width) {
                let x = (Double(beat)*60/bpm-start)/span*width,major = beat % 4 == 0
                (major ? NSColor.systemYellow.withAlphaComponent(0.85) : NSColor.white.withAlphaComponent(0.4)).setFill()
                NSRect(x:x,y:0,width:major ? 1.2 : 0.6,height:height).fill()
                if major,height >= 45 { text("\(beat/4+1)",at:NSPoint(x:x+5,y:2),color:.systemYellow) }
            }
        }
        if player.loopEnabled,let first = player.loopIn,let last = player.loopOut {
            let left = max(0,(first-start)/span*width),right = min(width,(last-start)/span*width)
            if right > left {
                let rect = NSRect(x:left,y:0,width:right-left,height:height)
                NSColor.systemGreen.withAlphaComponent(0.22).setFill();rect.fill()
                NSColor.systemGreen.setStroke();let border = NSBezierPath(rect:rect.insetBy(dx:0.8,dy:0.8));border.lineWidth = 1.5;border.stroke()
            }
            for (point,label) in [(first,"IN"),(last,"OUT")] {
                let x = (point-start)/span*width
                if x >= 0,x <= width {
                    NSColor.systemGreen.setFill();NSRect(x:x,y:0,width:2,height:height).fill();NSRect(x:x-3,y:height/2-7,width:7,height:14).fill()
                    text(label,at:NSPoint(x:min(width-24,max(0,x)),y:2),color:.systemGreen)
                }
            }
        }
        NSColor.systemRed.setFill();NSRect(x:(time-start)/span*width,y:0,width:1.5,height:height).fill()
        text(label+String(format:" · %.1f s",span),at:NSPoint(x:5,y:4),color:color)
        if let hoverX {
            let seconds = max(0,start+hoverX/width*span)
            text(String(format:"%d:%05.2f",Int(seconds)/60,seconds.truncatingRemainder(dividingBy:60)),at:NSPoint(x:max(0,width-65),y:max(0,height-14)),color:.white)
        }
    }
    private func text(_ value: String,at point: NSPoint,color: NSColor) {
        (value as NSString).draw(at:point,withAttributes:[.font:NSFont.monospacedSystemFont(ofSize:9,weight:.semibold),.foregroundColor:color])
    }
}