ghostty/macos/Sources/Features/Terminal/TerminalView.swift

import SwiftUI
import GhosttyKit

/// This delegate is notified of actions and property changes regarding the terminal view. This
/// delegate is optional and can be used by a TerminalView caller to react to changes such as
/// titles being set, cell sizes being changed, etc.
protocol TerminalViewDelegate: AnyObject {
    /// Called when the currently focused surface changed. This can be nil.
    func focusedSurfaceDidChange(to: Ghostty.SurfaceView?)

    /// The title of the terminal should change.
    func titleDidChange(to: String)

    /// The cell size changed.
    func cellSizeDidChange(to: NSSize)

    /// The surface tree did change in some way, i.e. a split was added, removed, etc. This is
    /// not called initially.
    func surfaceTreeDidChange()

    func zoomStateDidChange(to: Bool)
}

// Default all the functions so they're optional
extension TerminalViewDelegate {
    func focusedSurfaceDidChange(to: Ghostty.SurfaceView?) {}
    func titleDidChange(to: String) {}
    func cellSizeDidChange(to: NSSize) {}
    func zoomStateDidChange(to: Bool) {}
}

/// The view model is a required implementation for TerminalView callers. This contains
/// the main state between the TerminalView caller and SwiftUI. This abstraction is what
/// allows AppKit to own most of the data in SwiftUI.
protocol TerminalViewModel: ObservableObject {
    /// The tree of terminal surfaces (splits) within the view. This is mutated by TerminalView
    /// and children. This should be @Published.
    var surfaceTree: Ghostty.SplitNode? { get set }
}

/// The main terminal view. This terminal view supports splits.
struct TerminalView<ViewModel: TerminalViewModel>: View {
    @ObservedObject var ghostty: Ghostty.App

    // The required view model
    @ObservedObject var viewModel: ViewModel

    // An optional delegate to receive information about terminal changes.
    weak var delegate: (any TerminalViewDelegate)? = nil

    // This seems like a crutch after switching from SwiftUI to AppKit lifecycle.
    @FocusState private var focused: Bool

    // Various state values sent back up from the currently focused terminals.
    @FocusedValue(\.ghosttySurfaceView) private var focusedSurface
    @FocusedValue(\.ghosttySurfaceTitle) private var surfaceTitle
    @FocusedValue(\.ghosttySurfaceZoomed) private var zoomedSplit
    @FocusedValue(\.ghosttySurfaceCellSize) private var cellSize

    // The title for our window
    private var title: String {
        var title = "👻"

        if let surfaceTitle = surfaceTitle {
            if (surfaceTitle.count > 0) {
                title = surfaceTitle
            }
        }

        return title
    }

    var body: some View {
        switch ghostty.readiness {
        case .loading:
            Text("Loading")
        case .error:
            ErrorView()
        case .ready:
            VStack(spacing: 0) {
                // If we're running in debug mode we show a warning so that users
                // know that performance will be degraded.
                if (Ghostty.info.mode == GHOSTTY_BUILD_MODE_DEBUG) {
                    DebugBuildWarningView()
                }

                Ghostty.TerminalSplit(node: $viewModel.surfaceTree)
                    .environmentObject(ghostty)
                    .focused($focused)
                    .onAppear { self.focused = true }
                    .onChange(of: focusedSurface) { newValue in
                        self.delegate?.focusedSurfaceDidChange(to: newValue)
                    }
                    .onChange(of: title) { newValue in
                        self.delegate?.titleDidChange(to: newValue)
                    }
                    .onChange(of: cellSize) { newValue in
                        guard let size = newValue else { return }
                        self.delegate?.cellSizeDidChange(to: size)
                    }
                    .onChange(of: viewModel.surfaceTree?.hashValue) { _ in
                        // This is funky, but its the best way I could think of to detect
                        // ANY CHANGE within the deeply nested surface tree -- detecting a change
                        // in the hash value.
                        self.delegate?.surfaceTreeDidChange()
                    }
                    .onChange(of: zoomedSplit) { newValue in
                        self.delegate?.zoomStateDidChange(to: newValue ?? false)
                    }
            }
        }
    }
}

struct DebugBuildWarningView: View {
    @State private var isPopover = false

    var body: some View {
        HStack {
            Spacer()

            Image(systemName: "exclamationmark.triangle.fill")
                .foregroundColor(.yellow)

            Text("You're running a debug build of Ghostty! Performance will be degraded.")
                .padding(.all, 8)
                .popover(isPresented: $isPopover, arrowEdge: .bottom) {
                    Text("""
                    Debug builds of Ghostty are very slow and you may experience
                    performance problems. Debug builds are only recommended during
                    development.
                    """)
                    .padding(.all)
                }

            Spacer()
        }
        .background(Color(.windowBackgroundColor))
        .frame(maxWidth: .infinity)
        .onTapGesture {
            isPopover = true
        }
    }
}