divkit/client/ios/DivKit/Extensions/DivContainer/DivContainerExtensions.swift

import CoreGraphics
import LayoutKit
import VGSL

extension DivContainer: DivBlockModeling {
  public func makeBlock(context: DivBlockModelingContext) throws -> Block {
    let context = modifiedContextParentPath(context)
    return try applyBaseProperties(
      to: { try makeBaseBlock(context: context) },
      context: context,
      actionsHolder: self,
      applyPaddings: false,
      clipToBounds: resolveClipToBounds(context.expressionResolver)
    )
  }

  var nonNilItems: [Div] {
    items ?? []
  }

  private func makeBaseBlock(context: DivBlockModelingContext) throws -> Block {
    let expressionResolver = context.expressionResolver
    let params = DivContainerParams(
      orientation: resolveOrientation(expressionResolver),
      paddings: paddings?.resolve(context) ?? .zero,
      aspectRatio: aspect.resolveAspectRatio(expressionResolver),
      clipToBounds: resolveClipToBounds(expressionResolver)
    )
    var block: Block = switch params.orientation {
    case .overlap:
      try makeOverlapBlock(context: context, params: params)
    case .horizontal, .vertical:
      try makeContainerBlock(
        context: context,
        params: params,
        layoutMode: resolveLayoutMode(expressionResolver)
      )
    }

    block = block.addingEdgeInsets(params.paddings, clipsToBounds: params.clipToBounds)

    if let aspectRatio = params.aspectRatio, block.calculateWidthFirst {
      block = block.aspectRatio(aspectRatio)
    }

    return block
  }

  private func makeOverlapBlock(
    context: DivBlockModelingContext,
    params: DivContainerParams
  ) throws -> Block {
    let expressionResolver = context.expressionResolver
    let defaultAlignment = BlockAlignment2D(
      horizontal: resolveContentAlignmentHorizontal(expressionResolver).alignment,
      vertical: resolveContentAlignmentVertical(expressionResolver).alignment
    )

    let children = makeChildren(
      context: context,
      mappedBy: { div, block, context in
        LayeredBlock.Child(
          content: block,
          alignment: div.value.resolveAlignment(context, defaultAlignment: defaultAlignment)
        )
      }
    )

    return LayeredBlock(
      widthTrait: resolveContentWidthTrait(context, paddings: params.paddings),
      heightTrait: resolveContentHeightTrait(context, params: params),
      children: children
    )
  }

  private func makeContainerBlock(
    context: DivBlockModelingContext,
    params: DivContainerParams,
    layoutMode: LayoutMode
  ) throws -> Block {
    let expressionResolver = context.expressionResolver
    let layoutDirection = params.orientation.layoutDirection

    let divContentAlignmentVertical = resolveContentAlignmentVertical(expressionResolver)
    let divContentAlignmentHorizontal = resolveContentAlignmentHorizontal(expressionResolver)

    let axialAlignment = makeAxialAlignment(
      layoutDirection,
      verticalAlignment: divContentAlignmentVertical,
      horizontalAlignment: divContentAlignmentHorizontal,
      uiLayoutDirection: context.layoutDirection
    )

    let crossAlignment = makeCrossAlignment(
      layoutDirection,
      verticalAlignment: divContentAlignmentVertical,
      horizontalAlignment: divContentAlignmentHorizontal,
      uiLayoutDirection: context.layoutDirection
    )

    let defaultCrossAlignment = switch layoutMode {
    case .noWrap:
      crossAlignment
    case .wrap:
      ContainerBlock.CrossAlignment.leading
    }
    let crossSizeIsWrapContent: Bool = switch layoutDirection {
    case .horizontal:
      getTransformedHeight(context).isIntrinsic && aspect == nil
    case .vertical:
      getTransformedWidth(context).isIntrinsic
    }
    let children: [ContainerBlock.Child] = makeChildren(
      context: context,
      mappedBy: { div, block, context in
        let childMatchesParentOnCrossAxis = layoutDirection == .horizontal
          ? div.isVerticallyMatchParent
          : div.isHorizontallyMatchParent
        return ContainerBlock.Child(
          content: block,
          crossAlignment: div.value.crossAlignment(
            for: layoutDirection,
            context: context
          ) ?? defaultCrossAlignment,
          fillsCrossAxis: crossSizeIsWrapContent && childMatchesParentOnCrossAxis
        )
      }
    )
    let separator = resolveSeparator(context, orientation: params.orientation)
    let lineSeparator = resolveLineSeparator(context, orientation: params.orientation)

    let paddings = params.paddings
    return try ContainerBlock(
      blockLayoutDirection: context.layoutDirection,
      layoutDirection: layoutDirection,
      layoutMode: layoutMode.system,
      widthTrait: resolveContentWidthTrait(context, paddings: paddings),
      heightTrait: resolveContentHeightTrait(context, params: params),
      axialAlignment: axialAlignment,
      crossAlignment: crossAlignment,
      children: children,
      separator: separator,
      lineSeparator: lineSeparator,
      clipContent: params.clipToBounds && paddings == .zero,
      path: context.path
    )
  }

  private func createSpacingSeparator(
    spacing: Int,
    orientation: DivContainer.Orientation,
    isLineSpacing: Bool
  ) -> ContainerBlock.Child? {
    guard spacing > 0 else { return nil }

    let direction: SeparatorBlock.Direction
    switch orientation {
    case .horizontal:
      direction = isLineSpacing ? .vertical : .horizontal
    case .vertical:
      direction = isLineSpacing ? .horizontal : .vertical
    case .overlap:
      return nil
    }

    let spacingBlock = SeparatorBlock(
      color: .clear,
      direction: direction,
      size: CGFloat(spacing)
    )

    return ContainerBlock.Child(content: spacingBlock)
  }

  private func resolveContentHeightTrait(
    _ context: DivBlockModelingContext,
    params: DivContainerParams
  ) -> LayoutTrait {
    if params.aspectRatio != nil {
      return .resizable
    }
    return resolveContentHeightTrait(context, paddings: params.paddings)
  }

  private func resolveSeparator(
    _ context: DivBlockModelingContext,
    orientation: DivContainer.Orientation
  ) -> ContainerBlock.Separator? {
    let expressionResolver = context.expressionResolver
    let itemSpacing = resolveItemSpacing(expressionResolver)

    let betweenSeparator = createSpacingSeparator(
      spacing: itemSpacing,
      orientation: orientation,
      isLineSpacing: false
    )

    guard let separator else {
      return betweenSeparator.flatMap {
        ContainerBlock.Separator(start: nil, end: nil, between: $0)
      }
    }

    let separatorBlock = separator.style.makeBlock(
      context: context, corners: .all
    ).addingEdgeInsets(separator.margins.resolve(context))
    let style = ContainerBlock.Child(
      content: separatorBlock,
      crossAlignment: .center
    )

    let showBetween = separator.resolveShowBetween(expressionResolver)
    if showBetween, betweenSeparator != nil {
      let error = DivBlockModelingWarning(
        "item_spacing will be ignored due to the 'separator' property.",
        path: context.path
      )
      context.errorsStorage.add(error)
    }

    return ContainerBlock.Separator(
      start: separator.resolveShowAtStart(expressionResolver) ? style : nil,
      end: separator.resolveShowAtEnd(expressionResolver) ? style : nil,
      between: showBetween ? style : betweenSeparator
    )
  }

  private func resolveLineSeparator(
    _ context: DivBlockModelingContext,
    orientation: DivContainer.Orientation
  ) -> ContainerBlock.Separator? {
    let expressionResolver = context.expressionResolver

    let lineSpacing = resolveLineSpacing(expressionResolver)
    let betweenSeparator = createSpacingSeparator(
      spacing: lineSpacing,
      orientation: orientation,
      isLineSpacing: true
    )

    guard let lineSeparator else {
      return betweenSeparator.flatMap {
        ContainerBlock.Separator(start: nil, end: nil, between: $0)
      }
    }

    let lineSeparatorBlock = lineSeparator.style.makeBlock(
      context: context, corners: .all
    ).addingEdgeInsets(lineSeparator.margins.resolve(context))
    let style = ContainerBlock.Child(
      content: lineSeparatorBlock,
      crossAlignment: .center
    )

    let showBetween = lineSeparator.resolveShowBetween(expressionResolver)
    if showBetween, betweenSeparator != nil {
      let error = DivBlockModelingWarning(
        "line_spacing will be ignored due to the 'line_separator' property.",
        path: context.path
      )
      context.errorsStorage.add(error)
    }

    return ContainerBlock.Separator(
      start: lineSeparator.resolveShowAtStart(expressionResolver) ? style : nil,
      end: lineSeparator.resolveShowAtEnd(expressionResolver) ? style : nil,
      between: lineSeparator.resolveShowBetween(expressionResolver) ? style : betweenSeparator
    )
  }
}

extension DivBase {
  fileprivate func crossAlignment(
    for direction: ContainerBlock.LayoutDirection,
    context: DivBlockModelingContext
  ) -> ContainerBlock.CrossAlignment? {
    let expressionResolver = context.expressionResolver
    switch direction {
    case .horizontal:
      return resolveAlignmentVertical(expressionResolver)?.crossAlignment
    case .vertical:
      return resolveAlignmentHorizontal(expressionResolver)?.makeCrossAlignment(
        layoutDirection: context.layoutDirection
      )
    }
  }
}

extension DivContainer.Orientation {
  fileprivate var layoutDirection: ContainerBlock.LayoutDirection {
    switch self {
    case .vertical:
      return .vertical
    case .horizontal:
      return .horizontal
    case .overlap:
      assertionFailure("layout direction for overlap")
      return .vertical
    }
  }
}

extension DivAlignmentHorizontal {
  func alignment(isRTLLayout: Bool) -> Alignment {
    switch self {
    case .left:
      isRTLLayout ? .trailing : .leading
    case .right:
      isRTLLayout ? .leading : .trailing
    case .start:
      .leading
    case .center:
      .center
    case .end:
      .trailing
    }
  }

  fileprivate func makeCrossAlignment(
    layoutDirection: UserInterfaceLayoutDirection
  ) -> ContainerBlock.CrossAlignment {
    switch self {
    case .left:
      .leading
    case .right:
      .trailing
    case .start:
      layoutDirection == .leftToRight ? .leading : .trailing
    case .center:
      .center
    case .end:
      layoutDirection == .rightToLeft ? .leading : .trailing
    }
  }
}

extension DivAlignmentVertical {
  var alignment: Alignment {
    switch self {
    case .top:
      return .leading
    case .center:
      return .center
    case .bottom:
      return .trailing
    case .baseline:
      DivKitLogger.warning("Baseline alignment not supported.")
      return .leading
    }
  }

  fileprivate var crossAlignment: ContainerBlock.CrossAlignment {
    switch self {
    case .top:
      .leading
    case .center:
      .center
    case .bottom:
      .trailing
    case .baseline:
      .baseline
    }
  }
}

extension DivContentAlignmentHorizontal {
  fileprivate var alignment: Alignment {
    switch self {
    case .left, .start:
      return .leading
    case .center:
      return .center
    case .right, .end:
      return .trailing
    case .spaceEvenly, .spaceAround, .spaceBetween:
      DivKitLogger.warning("Alignment \(rawValue) is not supported")
      return .leading
    }
  }
}

extension DivContentAlignmentVertical {
  fileprivate var alignment: Alignment {
    switch self {
    case .top:
      return .leading
    case .center:
      return .center
    case .bottom:
      return .trailing
    case .spaceEvenly, .spaceAround, .spaceBetween, .baseline:
      DivKitLogger.warning("Alignment \(rawValue) is not supported")
      return .leading
    }
  }
}

extension DivContainer.LayoutMode {
  fileprivate var system: ContainerBlock.LayoutMode {
    switch self {
    case .noWrap:
      .noWrap
    case .wrap:
      .wrap
    }
  }
}

fileprivate func makeCrossAlignment(
  _ direction: ContainerBlock.LayoutDirection,
  verticalAlignment: DivContentAlignmentVertical,
  horizontalAlignment: DivContentAlignmentHorizontal,
  uiLayoutDirection: UserInterfaceLayoutDirection = .leftToRight
) -> ContainerBlock.CrossAlignment {
  switch direction {
  case .horizontal:
    switch verticalAlignment {
    case .top:
      .leading
    case .center:
      .center
    case .bottom:
      .trailing
    case .baseline:
      .baseline
    case .spaceBetween, .spaceEvenly, .spaceAround:
      .leading
    }
  case .vertical:
    switch horizontalAlignment {
    case .left:
      uiLayoutDirection == .leftToRight ? .leading : .trailing
    case .right:
      uiLayoutDirection == .rightToLeft ? .leading : .trailing
    case .start:
      .leading
    case .center:
      .center
    case .end:
      .trailing
    case .spaceBetween, .spaceEvenly, .spaceAround:
      .center
    }
  }
}

fileprivate func makeAxialAlignment(
  _ direction: ContainerBlock.LayoutDirection,
  verticalAlignment: DivContentAlignmentVertical,
  horizontalAlignment: DivContentAlignmentHorizontal,
  uiLayoutDirection: UserInterfaceLayoutDirection = .leftToRight
) -> ContainerBlock.AxialAlignment {
  switch direction {
  case .horizontal:
    switch horizontalAlignment {
    case .left:
      return .leading
    case .right:
      return .trailing
    case .start:
      return uiLayoutDirection == .leftToRight ? .leading : .trailing
    case .center:
      return .center
    case .end:
      return uiLayoutDirection == .rightToLeft ? .leading : .trailing
    case .spaceBetween:
      return .spaceBetween
    case .spaceAround:
      return .spaceAround
    case .spaceEvenly:
      return .spaceEvenly
    }
  case .vertical:
    switch verticalAlignment {
    case .top:
      return .leading
    case .center:
      return .center
    case .bottom:
      return .trailing
    case .baseline:
      DivKitLogger.warning("Baseline alignment not supported.")
      return .leading
    case .spaceBetween:
      return .spaceBetween
    case .spaceAround:
      return .spaceAround
    case .spaceEvenly:
      return .spaceEvenly
    }
  }
}

private struct DivContainerParams {
  let orientation: DivContainer.Orientation
  let paddings: EdgeInsets
  let aspectRatio: CGFloat?
  let clipToBounds: Bool
}