import SharedModels
import SwiftUI

public protocol FlaggedViewStyle {
  associatedtype Body: View
  typealias Configuration = FlaggedViewStyleConfiguration

  @ViewBuilder
  func makeBody(configuration: Self.Configuration) -> Self.Body
}

public struct FlaggedViewStyleConfiguration {
  public let flagged: Flagged
  public let label: Label

  /// A type erased label for a flagged view.
  public struct Label: View {
    public let body: AnyView

    public init<Content: View>(_ content: Content) {
      self.body = AnyView(content)
    }
  }
}

public struct AnyFlaggedViewStyle: FlaggedViewStyle {
  private var _makeBody: (Configuration) -> AnyView

  internal init(makeBody: @escaping (Configuration) -> AnyView) {
    self._makeBody = makeBody
  }

  public init<S: FlaggedViewStyle>(style: S) {
    self.init { configuration in
      AnyView(style.makeBody(configuration: configuration))
    }
  }

  public func makeBody(configuration: Configuration) -> some View {
    _makeBody(configuration)
  }
}

public struct DefaultFlagViewStyle: FlaggedViewStyle {

  let alignment: HorizontalAlignment
  let fractionLength: Int
  let spacing: CGFloat

  init(
    alignment: HorizontalAlignment = .leading,
    fractionLength: Int = 2,
    spacing: CGFloat = 8
  ) {
    self.alignment = alignment
    self.fractionLength = fractionLength
    self.spacing = spacing
  }

  public func makeBody(configuration: Configuration) -> some View {
    VStack(alignment: alignment, spacing: spacing) {
      HStack {
        configuration.label
        Spacer()
        Text(
          configuration.flagged.wrappedValue,
          format: .number.precision(.fractionLength(fractionLength))
        )
        configuration.flagged.flagImage
      }
      FlaggedMessageView(flagged: configuration.flagged)
    }
  }
}

public struct FlagAndMessageOnlyStyle: FlaggedViewStyle {

  public enum StackStyle {
    case horizontal
    case vertical
  }

  let stackStyle: StackStyle

  @ViewBuilder
  public func makeBody(configuration: Configuration) -> some View {
    switch stackStyle {
    case .horizontal:
      HStack {
        FlaggedMessageView(flagged: configuration.flagged)
        configuration.flagged.flagImage
      }
    case .vertical:
      VStack {
        configuration.flagged.flagImage
        FlaggedMessageView(flagged: configuration.flagged)
      }
    }
  }
}

extension FlaggedViewStyle where Self == FlagAndMessageOnlyStyle {
  public static func flagAndMessageOnly(_ stackStyle: FlagAndMessageOnlyStyle.StackStyle = .vertical) -> Self {
    .init(stackStyle: stackStyle)
  }
}

public struct FlaggedGridRowStyle: FlaggedViewStyle {

  let fractionLength: Int

  public func makeBody(configuration: Configuration) -> some View {
    GridRow {
      VStack(alignment: .leading, spacing: 8) {
        configuration.label
          .foregroundStyle(Color.secondary)
        FlaggedMessageView(flagged: configuration.flagged)
      }
      Text(
        configuration.flagged.wrappedValue,
        format: .number.precision(.fractionLength(fractionLength))
      )
      configuration.flagged.flagImage
        .gridCellAnchor(.trailing)
    }
  }
}

extension FlaggedViewStyle where Self == FlaggedGridRowStyle {
  public static func gridRow(fractionLength: Int = 2) -> Self {
    .init(fractionLength: fractionLength)
  }
}

private struct FlaggedViewStyleKey: EnvironmentKey {
  static let defaultValue = AnyFlaggedViewStyle(style: DefaultFlagViewStyle())
}

extension EnvironmentValues {
  public var flaggedViewStyle: AnyFlaggedViewStyle {
    get { self[FlaggedViewStyleKey.self] }
    set { self[FlaggedViewStyleKey.self] = newValue }
  }
}

extension FlaggedViewStyle where Self == DefaultFlagViewStyle {
  public static func `default`(alignment: HorizontalAlignment = .leading, fractionLength: Int = 2, spacing: CGFloat = 8) -> Self {
    .init(alignment: alignment, fractionLength: fractionLength, spacing: spacing)
  }
}


extension Flagged {
  var flagColor: Color { self.status.flagColor }

  public var flagImage: some View {
    Image(systemName: "flag.fill")
      .foregroundStyle(flagColor)
  }

  public var messageView: some View {
    FlaggedMessageView(flagged: self)
  }
}

extension View {
  public func flaggedViewStyle(_ style: AnyFlaggedViewStyle) -> some View {
    environment(\.flaggedViewStyle, style)
  }

  public func flaggedViewStyle<S: FlaggedViewStyle>(
    _ style: S
  ) -> some View {
    flaggedViewStyle(AnyFlaggedViewStyle(style: style))
  }
}