// LiquidGlassBackground.swift
// A SwiftUI wrapper around Apple’s private NSGlassEffectView.
// Provides easy access to every liquid‑glass variant (0–19).


import SwiftUI
import AppKit
import Defaults

/// All 20 available liquid‑glass variants.
/// Apple does not publicly describe how each value looks so experiment and pick the one you like!
public enum LiquidGlassVariant: Int, CaseIterable, Identifiable, Defaults.Serializable, Sendable {
    case v0  = 0,  v1  = 1,  v2  = 2,  v3  = 3,  v4  = 4
    case v5  = 5,  v6  = 6,  v7  = 7,  v8  = 8,  v9  = 9
    case v10 = 10, v11 = 11, v12 = 12, v13 = 13, v14 = 14
    case v15 = 15, v16 = 16, v17 = 17, v18 = 18, v19 = 19

    public var id: Int { rawValue }

    public static let supportedRange = 0...19

    public static var defaultVariant: LiquidGlassVariant { .v11 }

    public static func clamped(_ rawValue: Int) -> LiquidGlassVariant {
        let clamped = min(max(rawValue, supportedRange.lowerBound), supportedRange.upperBound)
        return LiquidGlassVariant(rawValue: clamped) ?? .defaultVariant
    }
}

/// A SwiftUI view that embeds its content inside Apple’s private liquid‑glass material.
///
/// ```swift
/// GlassBackground(variant: .v11, cornerRadius: 12) {
///     VStack(spacing: 12) {
///         Image(systemName: "sparkles")
///             .font(.largeTitle)
///         Text("Hello, glass!")
///             .font(.title2)
///     }
///     .padding()
/// }
/// ```
public struct LiquidGlassBackground<Content: View>: NSViewRepresentable {
    private let content: Content
    private let cornerRadius: CGFloat
    private let variant: LiquidGlassVariant
    private let trigger: Double
    /// Creates a new liquid‑glass container.
    /// - Parameters:
    ///   - variant: Any ``LiquidGlassVariant`` (0–19). Defaults to `.v11`, which is visually super pleasing
    ///   - cornerRadius: Corner radius in points. Defaults to `10`.
    ///   - content: Your SwiftUI hierarchy.
    public init(
        variant: LiquidGlassVariant = .defaultVariant,
        cornerRadius: CGFloat = 10,
        trigger: Double = 0,
        @ViewBuilder content: () -> Content
    ) {
        self.variant      = variant
        self.cornerRadius = cornerRadius
        self.trigger = trigger
        self.content      = content()
    }


    @inline(__always)
    private func setterSelector(for key: String, privateVariant: Bool = true) -> Selector? {
        guard !key.isEmpty else { return nil }
        let name: String
        if privateVariant {
            let cleaned = key.hasPrefix("_") ? key : "_" + key
            name = "set" + cleaned
        } else {
            let first = String(key.prefix(1)).uppercased()
            let rest  = String(key.dropFirst())
            name = "set" + first + rest
        }
        return NSSelectorFromString(name + ":")
    }

    private typealias VariantSetterIMP = @convention(c) (AnyObject, Selector, Int) -> Void

    private func callPrivateVariantSetter(on object: AnyObject, value: Int) {
        guard
            let sel   = setterSelector(for: "variant", privateVariant: true),
            let m     = class_getInstanceMethod(object_getClass(object), sel)
        else {
            #if DEBUG
            print("✗ LiquidGlassBackground: selector set_variant: not found. falling back to default")
            #endif
            return
        }
        let imp = method_getImplementation(m)
        let f   = unsafeBitCast(imp, to: VariantSetterIMP.self)
        f(object, sel, value)
    }



    public func makeNSView(context: Context) -> NSView {
        // `NSGlassEffectView` is private. Look it up dynamically to avoid compile‑time coupling.
        if let glassType = NSClassFromString("NSGlassEffectView") as? NSView.Type {
            let glass = glassType.init(frame: .zero)
            glass.setValue(cornerRadius, forKey: "cornerRadius")
            callPrivateVariantSetter(on: glass, value: variant.rawValue)

            let hosting = NSHostingView(rootView: content)
            hosting.translatesAutoresizingMaskIntoConstraints = false
            glass.setValue(hosting, forKey: "contentView")
            return glass
        }

        // Fallback for earlier macOS – use an ordinary blur.
        let fallback = NSVisualEffectView()
        fallback.material = .underWindowBackground

        let hosting = NSHostingView(rootView: content)
        hosting.translatesAutoresizingMaskIntoConstraints = false
        fallback.addSubview(hosting)
        NSLayoutConstraint.activate([
            hosting.leadingAnchor.constraint(equalTo: fallback.leadingAnchor),
            hosting.trailingAnchor.constraint(equalTo: fallback.trailingAnchor),
            hosting.topAnchor.constraint(equalTo: fallback.topAnchor),
            hosting.bottomAnchor.constraint(equalTo: fallback.bottomAnchor)
        ])
        return fallback
    }

    public func updateNSView(_ nsView: NSView, context: Context) {
        if let hosting = nsView.value(forKey: "contentView") as? NSHostingView<Content> {
            hosting.rootView = content
        }
        nsView.setValue(cornerRadius, forKey: "cornerRadius")
        callPrivateVariantSetter(on: nsView, value: variant.rawValue)

        // Micro-jitter: imperceptibly adjust opacity so WindowServer re-samples the wallpaper every frame.
        let jitter = sin(trigger * 100) * 0.000001
        nsView.alphaValue = 1.0 - CGFloat(abs(jitter))

        nsView.needsDisplay = true
    }
}