import AppKit

/// Renders the capture overlay. All interaction state lives in
/// CaptureController (driven by the CGEventTap); this view only draws.
final class OverlayWindow: NSPanel {
    init(screen: NSScreen, controller: CaptureController) {
        let content = OverlayView()
        super.init(
            // Non-activating: the overlay must NOT steal focus, so the app
            // being captured keeps its active appearance (undimmed chrome).
            // Input comes from the CGEventTap, not panel events.
            contentRect: screen.frame,
            styleMask: [.borderless, .nonactivatingPanel],
            backing: .buffered,
            defer: false
        )
        contentView = content
        content.controller = controller
        level = .screenSaver
        collectionBehavior = [.canJoinAllSpaces, .fullScreenAuxiliary, .stationary]
        backgroundColor = .clear
        isOpaque = false
        hasShadow = false
        isReleasedWhenClosed = false
        acceptsMouseMovedEvents = true
    }

    override var canBecomeKey: Bool { true }
}

final class OverlayView: NSView {
    weak var controller: CaptureController?
    /// In frozen mode: the still image to display for this screen (already
    /// full resolution). Nil = live mode (dim the real screen).
    var frozenImage: CGImage?

    override var acceptsFirstResponder: Bool { true }

    override func acceptsFirstMouse(for event: NSEvent?) -> Bool { true }

    override func resetCursorRects() {
        addCursorRect(bounds, cursor: .crosshair)
    }

    /// The screen frame this overlay covers, in AppKit global space.
    private var screenFrame: NSRect {
        guard let window else { return .zero }
        return window.convertToScreen(NSRect(origin: .zero, size: bounds.size))
    }

    /// Convert an AppKit-global rect into this view's coordinates.
    private func viewRect(_ global: NSRect) -> NSRect {
        let sf = screenFrame
        return NSRect(
            x: global.origin.x - sf.origin.x,
            y: global.origin.y - sf.origin.y,
            width: global.width,
            height: global.height
        )
    }

    /// Draw the frozen snapshot filling the screen, then replace its centre
    /// hole with the live... no: the image IS the content, drawn opaque.
    private func drawFrozen(_ image: CGImage) {
        guard let ctx = NSGraphicsContext.current?.cgContext else { return }
        ctx.saveGState()
        ctx.interpolationQuality = .high
        // Image is in pixels, view in points — draw into the view bounds.
        ctx.draw(image, in: bounds)
        ctx.restoreGState()
    }

    private func drawSizeLabel(for sel: NSRect, in vf: NSRect) {
        let label = "\(Int(sel.width)) × \(Int(sel.height))"
        let attrs: [NSAttributedString.Key: Any] = [
            .font: NSFont.monospacedDigitSystemFont(ofSize: 12, weight: .medium),
            .foregroundColor: NSColor.white,
        ]
        let labelSize = label.size(withAttributes: attrs)
        let labelRect = NSRect(
            x: vf.maxX - labelSize.width - 8,
            y: vf.minY - labelSize.height - 10,
            width: labelSize.width + 8,
            height: labelSize.height + 6
        )
        NSColor.black.withAlphaComponent(0.6).setFill()
        NSBezierPath(roundedRect: labelRect, xRadius: 4, yRadius: 4).fill()
        label.draw(at: NSPoint(x: labelRect.minX + 4, y: labelRect.minY + 3), withAttributes: attrs)
    }

    override func draw(_ dirtyRect: NSRect) {
        if let frozenImage {
            drawFrozen(frozenImage)
        } else {
            NSColor.black.withAlphaComponent(0.35).setFill()
            NSBezierPath(rect: bounds).fill()
        }

        // Esc hint — the only way out once clicks are consumed by the tap.
        let hint: String
        if controller?.isRecordingMode == true {
            hint = "Drag to select · hover + click a window to record · Esc to cancel"
        } else if frozenImage != nil {
            hint = "Frozen screen · drag to select · Esc to cancel"
        } else {
            hint = "Drag to select · hover + click a window to capture it · Esc to cancel"
        }
        let hintAttrs: [NSAttributedString.Key: Any] = [
            .font: NSFont.monospacedSystemFont(ofSize: 12, weight: .medium),
            .foregroundColor: NSColor.white.withAlphaComponent(0.85),
        ]
        let hintSize = hint.size(withAttributes: hintAttrs)
        let hintRect = NSRect(
            x: (bounds.width - hintSize.width) / 2 - 10,
            y: bounds.height - 46,
            width: hintSize.width + 20,
            height: hintSize.height + 12
        )
        NSColor.black.withAlphaComponent(0.65).setFill()
        NSBezierPath(roundedRect: hintRect, xRadius: 8, yRadius: 8).fill()
        hint.draw(at: NSPoint(x: hintRect.minX + 10, y: hintRect.minY + 6), withAttributes: hintAttrs)

        guard let controller else { return }

        // Frozen mode: same look as live mode — a dark veil over everything,
        // with the selection showing the frozen pixels undimmed.
        if let frozenImage {
            NSColor.black.withAlphaComponent(0.35).setFill()
            NSBezierPath(rect: bounds).fill()

            if let sel = controller.marqueeRect, sel.width > 0, sel.height > 0 {
                let vf = viewRect(sel)
                NSGraphicsContext.current?.saveGraphicsState()
                NSBezierPath(rect: vf).addClip()
                drawFrozen(frozenImage)
                NSGraphicsContext.current?.restoreGraphicsState()

                let border = NSBezierPath(rect: vf)
                border.lineWidth = 1.5
                NSColor.controlAccentColor.setStroke()
                border.stroke()
                drawSizeLabel(for: sel, in: vf)
            }
            return
        }

        // Highlight the hovered window (rounded, like real window corners)
        if let frame = controller.hoverFrame {
            let vf = viewRect(frame)
            NSGraphicsContext.current?.saveGraphicsState()
            NSGraphicsContext.current?.compositingOperation = .clear
            NSColor.black.setFill()
            NSBezierPath(roundedRect: vf, xRadius: 10, yRadius: 10).fill()
            NSGraphicsContext.current?.restoreGraphicsState()

            let border = NSBezierPath(roundedRect: vf, xRadius: 10, yRadius: 10)
            border.lineWidth = 2
            NSColor.controlAccentColor.setStroke()
            border.stroke()
            return
        }

        // Marquee selection
        guard let sel = controller.marqueeRect, sel.width > 0, sel.height > 0 else { return }
        let vf = viewRect(sel)

        NSGraphicsContext.current?.saveGraphicsState()
        NSGraphicsContext.current?.compositingOperation = .clear
        NSColor.black.setFill()
        NSBezierPath(rect: vf).fill()
        NSGraphicsContext.current?.restoreGraphicsState()

        let border = NSBezierPath(rect: vf)
        border.lineWidth = 1.5
        NSColor.controlAccentColor.setStroke()
        border.stroke()

        let label = "\(Int(sel.width)) × \(Int(sel.height))"
        let attrs: [NSAttributedString.Key: Any] = [
            .font: NSFont.monospacedDigitSystemFont(ofSize: 12, weight: .medium),
            .foregroundColor: NSColor.white,
        ]
        let labelSize = label.size(withAttributes: attrs)
        let labelRect = NSRect(
            x: vf.maxX - labelSize.width - 8,
            y: vf.minY - labelSize.height - 10,
            width: labelSize.width + 8,
            height: labelSize.height + 6
        )
        NSColor.black.withAlphaComponent(0.6).setFill()
        NSBezierPath(roundedRect: labelRect, xRadius: 4, yRadius: 4).fill()
        label.draw(
            at: NSPoint(x: labelRect.minX + 4, y: labelRect.minY + 3),
            withAttributes: attrs
        )
    }
}