//
//  ChatThinkingIndicatorView.swift
//  App for Indeed
//

import Cocoa
import QuartzCore

/// Single sparkle with a soft brand-blue glow and three dots whose opacity animates in a staggered wave (typing-style “thinking” affordance).
final class ChatThinkingIndicatorView: NSView {
    private enum AnimationKey {
        static let dotOpacity = "thinkingDotOpacity"
        static let sparklePulse = "thinkingSparklePulse"
    }

    /// Matches `DashboardView.Theme.brandBlue` — Indeed-style `#2557a7`.
    private static let accentBlue = NSColor(srgbRed: 37 / 255, green: 87 / 255, blue: 167 / 255, alpha: 1)
    /// Slightly lighter blue for the sparkle glow (reads clearly on light banner/chat surfaces).
    private static let accentBlueGlow = NSColor(srgbRed: 54 / 255, green: 130 / 255, blue: 220 / 255, alpha: 1)

    private let sparkleView = NSImageView()
    private let dotStack = NSStackView()
    private var dotViews: [NSView] = []

    init(compact: Bool, accessibilityLabel: String = "Assistant is searching") {
        super.init(frame: .zero)
        translatesAutoresizingMaskIntoConstraints = false

        let sparklePoint: CGFloat = compact ? 11 : 14
        let dotSize: CGFloat = compact ? 4 : 5
        let sparkleDotGap: CGFloat = compact ? 7 : 10
        let dotSpacing: CGFloat = compact ? 4 : 5

        sparkleView.translatesAutoresizingMaskIntoConstraints = false
        sparkleView.image = NSImage(systemSymbolName: "sparkle", accessibilityDescription: nil)
        sparkleView.symbolConfiguration = NSImage.SymbolConfiguration(pointSize: sparklePoint, weight: .medium)
        sparkleView.contentTintColor = Self.accentBlue
        sparkleView.wantsLayer = true
        sparkleView.layer?.masksToBounds = false
        sparkleView.layer?.shadowColor = Self.accentBlueGlow.cgColor
        sparkleView.layer?.shadowRadius = compact ? 5 : 9
        sparkleView.layer?.shadowOpacity = 0.55
        sparkleView.layer?.shadowOffset = .zero

        NSLayoutConstraint.activate([
            sparkleView.widthAnchor.constraint(equalToConstant: sparklePoint + 6),
            sparkleView.heightAnchor.constraint(equalToConstant: sparklePoint + 6)
        ])

        dotStack.orientation = .horizontal
        dotStack.spacing = dotSpacing
        dotStack.alignment = .centerY
        dotStack.translatesAutoresizingMaskIntoConstraints = false

        let dotFill = Self.accentBlue
        for _ in 0..<3 {
            let dot = NSView()
            dot.translatesAutoresizingMaskIntoConstraints = false
            dot.wantsLayer = true
            dot.layer?.cornerRadius = dotSize / 2
            dot.layer?.backgroundColor = dotFill.cgColor
            NSLayoutConstraint.activate([
                dot.widthAnchor.constraint(equalToConstant: dotSize),
                dot.heightAnchor.constraint(equalToConstant: dotSize)
            ])
            dotStack.addArrangedSubview(dot)
            dotViews.append(dot)
        }

        let row = NSStackView(views: [sparkleView, dotStack])
        row.orientation = .horizontal
        row.spacing = sparkleDotGap
        row.alignment = .centerY
        row.translatesAutoresizingMaskIntoConstraints = false

        addSubview(row)
        NSLayoutConstraint.activate([
            row.leadingAnchor.constraint(equalTo: leadingAnchor),
            row.trailingAnchor.constraint(equalTo: trailingAnchor),
            row.topAnchor.constraint(equalTo: topAnchor),
            row.bottomAnchor.constraint(equalTo: bottomAnchor)
        ])

        setAccessibilityElement(true)
        setAccessibilityRole(.group)
        setAccessibilityLabel(accessibilityLabel)
    }

    @available(*, unavailable)
    required init?(coder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }

    private static var reducedMotion: Bool {
        NSWorkspace.shared.accessibilityDisplayShouldReduceMotion
    }

    func startAnimatingIfNeeded() {
        stopAnimating()
        guard !Self.reducedMotion else {
            dotViews.forEach { $0.layer?.opacity = 0.78 }
            return
        }
        guard let sparkleLayer = sparkleView.layer else { return }
        let waveDuration: CFTimeInterval = 0.52
        let n = max(1, dotViews.count)
        for (i, dot) in dotViews.enumerated() {
            guard let layer = dot.layer else { continue }
            layer.opacity = 1
            let pulse = CABasicAnimation(keyPath: "opacity")
            pulse.fromValue = 0.2
            pulse.toValue = 1.0
            pulse.duration = waveDuration
            pulse.autoreverses = true
            pulse.repeatCount = .greatestFiniteMagnitude
            pulse.timingFunction = CAMediaTimingFunction(name: .easeInEaseOut)
            pulse.timeOffset = waveDuration * Double(i) / Double(n)
            layer.add(pulse, forKey: AnimationKey.dotOpacity)
        }

        let scale = CABasicAnimation(keyPath: "transform.scale")
        scale.fromValue = 1.0
        scale.toValue = 1.07
        scale.duration = 1.15
        scale.autoreverses = true
        scale.repeatCount = .greatestFiniteMagnitude
        scale.timingFunction = CAMediaTimingFunction(name: .easeInEaseOut)
        sparkleLayer.add(scale, forKey: AnimationKey.sparklePulse)
    }

    func stopAnimating() {
        sparkleView.layer?.removeAnimation(forKey: AnimationKey.sparklePulse)
        sparkleView.layer?.transform = CATransform3DIdentity
        for dot in dotViews {
            dot.layer?.removeAnimation(forKey: AnimationKey.dotOpacity)
            dot.layer?.opacity = 1
        }
    }
}