TUIkit/Sources/TUIkitView/Core/PrimitiveViews.swift

//  🖥️ TUIKit — Terminal UI Kit for Swift
//  PrimitiveViews.swift
//
//  Created by LAYERED.work
//  License: MIT

import TUIkitCore
// MARK: - EmptyView

/// A view that displays no content.
///
/// `EmptyView` is useful for placeholders or when a view
/// should display nothing under certain conditions.
///
/// ```swift
/// if showContent {
///     Text("Content")
/// } else {
///     EmptyView()
/// }
/// ```
public struct EmptyView: View, Equatable {
    /// Creates an empty view.
    public init() {}

    public var body: Never {
        fatalError("EmptyView has no body")
    }
}

// MARK: - ConditionalView

/// A view that represents either the true or false branch of a conditional.
///
/// This type is used internally by `ViewBuilder` for if-else statements.
///
/// - Important: This is framework infrastructure. Created automatically by
///   `@ViewBuilder` for `if`/`else` branches. Do not instantiate directly.
public enum ConditionalView<TrueContent: View, FalseContent: View>: View {
    /// The true branch was executed.
    case trueContent(TrueContent)

    /// The false branch was executed.
    case falseContent(FalseContent)

    public var body: Never {
        fatalError("ConditionalView renders its children directly")
    }
}

// MARK: - ViewArray

/// A view that contains an array of identical views.
///
/// This type is used internally by `ViewBuilder` for for-in loops.
///
/// ```swift
/// ForEach(items) { item in
///     Text(item.name)
/// }
/// ```
///
/// - Important: This is framework infrastructure. Created automatically by
///   `@ViewBuilder` for array content. Do not instantiate directly.
public struct ViewArray<Element: View>: View {
    /// The contained views.
    let elements: [Element]

    /// Creates a ViewArray from an array of views.
    ///
    /// - Parameter elements: The views this container holds.
    public init(_ elements: [Element]) {
        self.elements = elements
    }

    public var body: Never {
        fatalError("ViewArray renders its children directly")
    }
}

// MARK: - AnyView

/// A type-erased view for conditional returns.
///
/// Use `AnyView` when you need to return different view types
/// from a conditional expression.
///
/// ```swift
/// func content(showDetail: Bool) -> AnyView {
///     if showDetail {
///         return AnyView(DetailView())
///     } else {
///         return AnyView(SummaryView())
///     }
/// }
/// ```
public struct AnyView: View {
    private let _render: (RenderContext) -> FrameBuffer

    /// Creates an AnyView wrapping the given view.
    ///
    /// - Parameter view: The view to type-erase.
    public init<V: View>(_ view: V) {
        self._render = { context in
            TUIkitView.renderToBuffer(view, context: context)
        }
    }

    public var body: Never {
        fatalError("AnyView renders via Renderable")
    }
}

// MARK: - AnyView Rendering

extension AnyView: Renderable {
    public func renderToBuffer(context: RenderContext) -> FrameBuffer {
        _render(context)
    }
}

// MARK: - EmptyView Rendering

extension EmptyView: Renderable {
    public func renderToBuffer(context: RenderContext) -> FrameBuffer {
        FrameBuffer()
    }
}

// MARK: - ConditionalView Rendering

extension ConditionalView: Renderable {
    public func renderToBuffer(context: RenderContext) -> FrameBuffer {
        let stateStorage = context.environment.stateStorage!
        switch self {
        case .trueContent(let content):
            stateStorage.invalidateDescendants(of: context.identity.branch("false"))
            return TUIkitView.renderToBuffer(content, context: context.withBranchIdentity("true"))
        case .falseContent(let content):
            stateStorage.invalidateDescendants(of: context.identity.branch("true"))
            return TUIkitView.renderToBuffer(content, context: context.withBranchIdentity("false"))
        }
    }
}

// MARK: - ViewArray Rendering

extension ViewArray: Renderable, ChildInfoProvider {
    public func renderToBuffer(context: RenderContext) -> FrameBuffer {
        FrameBuffer(verticallyStacking: childInfos(context: context).compactMap(\.buffer))
    }

    public func childInfos(context: RenderContext) -> [ChildInfo] {
        elements.enumerated().map { index, element in
            makeChildInfo(
                for: element,
                context: context.withChildIdentity(type: type(of: element), index: index)
            )
        }
    }
}