import SwiftUI

public struct AIButtonStyle: ButtonStyle {
  public static let pressedScale: CGFloat = 0.97

  public enum Kind: Hashable {
    case primary
    case secondary
    case danger

    var foregroundColor: Color { foregroundColor(isEnabled: true) }

    var backgroundColor: Color { backgroundColor(isEnabled: true) }

    func foregroundColor(isEnabled: Bool) -> Color {
      switch self {
      case .primary: return isEnabled ? AITheme.onPrimary : AITheme.muted
      case .danger: return isEnabled ? AITheme.onDanger : AITheme.muted
      case .secondary: return isEnabled ? AITheme.ink : AITheme.muted
      }
    }

    func backgroundColor(isEnabled: Bool) -> Color {
      switch self {
      case .primary, .secondary, .danger:
        return isEnabled ? kindBackground : AITheme.control
      }
    }

    private var kindBackground: Color {
      switch self {
      case .primary: return AITheme.primary
      case .secondary: return AITheme.control
      case .danger: return AITheme.danger
      }
    }
  }

  public enum Size: Hashable {
    case compact
    case regular
    case large
    case toolbar
    case toolbarInline
  }

  private let kind: Kind
  private let size: Size
  private let fixedWidthRequest: CGFloat?
  let fillsWidth: Bool
  @Environment(\.isEnabled) private var isEnabled

  public init(
    kind: Kind = .secondary,
    size: Size = .regular,
    fixedWidth: CGFloat? = nil,
    fillsWidth: Bool = false
  ) {
    self.kind = kind
    self.size = size
    self.fixedWidthRequest = fixedWidth
    self.fillsWidth = fillsWidth
  }

  public func makeBody(configuration: Configuration) -> some View {
    let height: CGFloat =
      switch size {
      case .compact: AITheme.compactButtonHeight
      case .large: AITheme.largeButtonHeight
    case .regular: AITheme.buttonHeight
    case .toolbar: AITheme.toolbarButtonHeight
    case .toolbarInline: AITheme.toolbarButtonHeight
      }

    configuration.label
      .labelStyle(.titleAndIcon)
      .font(
        .system(size: size == .compact || size == .toolbarInline ? 15 : 16, weight: .semibold)
      )
      .lineLimit(1)
      .foregroundStyle(kind.foregroundColor(isEnabled: isEnabled))
      .padding(.horizontal, fixedWidth == nil ? (kind == .secondary ? 12 : 14) : 0)
      .frame(
        minWidth: (!fillsWidth && fixedWidth == nil) ? minimumWidth : 0,
        minHeight: height
      )
      .frame(maxWidth: fillsWidth ? .infinity : nil)
      .frame(width: fixedWidth)
      .background(
        kind == .primary && isEnabled && size != .toolbarInline
          ? AnyShapeStyle(
            LinearGradient(
              colors: [AITheme.primaryTop, AITheme.primaryBottom],
              startPoint: .top,
              endPoint: .bottom
            )
          )
          : AnyShapeStyle(kind.backgroundColor(isEnabled: isEnabled))
      )
      .shadow(
        color: (kind == .secondary || !isEnabled) ? .clear : .black.opacity(0.10),
        radius: 12,
        x: 0,
        y: 5
      )
      .clipShape(
        RoundedRectangle(
          cornerRadius: size == .toolbarInline ? AITheme.toolbarButtonHeight / 2 : AITheme.buttonRadius,
          style: .continuous
        )
      )
      .overlay {
        RoundedRectangle(
          cornerRadius: size == .toolbarInline ? AITheme.toolbarButtonHeight / 2 : AITheme.buttonRadius,
          style: .continuous
        )
        .strokeBorder(
          size == .toolbarInline && kind == .primary
            ? AITheme.primary.opacity(0.28)
            : (kind == .secondary || !isEnabled ? AITheme.line : .clear)
        )
      }
      .scaleEffect(configuration.isPressed ? Self.pressedScale : 1)
      .opacity(configuration.isPressed ? 0.82 : 1)
  }

  private var minimumWidth: CGFloat {
    switch size {
    case .compact: return AITheme.compactButtonMinWidth
    case .regular: return AITheme.regularButtonMinWidth
    case .large: return 92
    case .toolbar, .toolbarInline: return AITheme.toolbarButtonMinWidth
    }
  }

  private var fixedWidth: CGFloat? {
    fixedWidthRequest ?? (size == .toolbar ? AITheme.toolbarButtonWidth : nil)
  }
}