import SessionCore
import SwiftUI

/// T-iOS-15 · Terminal destination view: TerminalScreen (T-iOS-11) plus the
/// gate/digest surfaces (T-iOS-14) wired to the controller's GateViewModel —
/// the "接入 TerminalScreen 的 wiring 归 T-iOS-15" hand-off.
///
/// Layout decisions (documented):
/// - `.id(controller.generation)`: a rebuild (background→foreground) swaps the
///   ViewModels; without a new identity SwiftUI would keep the old UIView and
///   `makeUIView` (where the output sink attaches) would never run again.
/// - Digest + tool-gate banner live in a TOP overlay stack: the bottom edge
///   belongs to the keyboard + key bar. TerminalScreen's own ReconnectBanner
///   is also top-aligned, but it hides on `.connected` while gates/digests
///   only arrive connected — practical overlap is nil.
/// - Plan gate presents as a medium-detent sheet; swiping it away is allowed
///   (the user may need to scroll the terminal to read the plan), and a
///   "计划待批" re-entry chip appears until the gate resolves. Deciding
///   removes the gate server-side → `planGate` goes nil → sheet dismisses.
struct TerminalContainerView: View {
    let controller: TerminalSessionController
    /// Epoch of a plan gate the user swiped away — suppresses re-present for
    /// THAT gate only; a new epoch re-presents automatically.
    @State private var dismissedPlanGateEpoch: Int?

    private enum Metrics {
        static let overlaySpacing: CGFloat = 8
        static let overlayHorizontalPadding: CGFloat = 12
        /// Clears TerminalScreen's own top-aligned ReconnectBanner zone.
        static let overlayTopPadding: CGFloat = 52
    }

    private enum Copy {
        static let planGatePending = "⚠ 计划待批准"
    }

    var body: some View {
        TerminalScreen(viewModel: controller.terminalViewModel)
            .id(controller.generation)
            .navigationBarTitleDisplayMode(.inline)
            .overlay(alignment: .top) { topOverlays }
            .sheet(isPresented: planGateBinding) { planGateSheet }
    }

    // MARK: - Digest + tool gate (top stack)

    @ViewBuilder private var topOverlays: some View {
        let gateViewModel = controller.gateViewModel
        VStack(spacing: Metrics.overlaySpacing) {
            if let digest = gateViewModel.digest {
                AwayDigestView(
                    digest: digest,
                    isExpanded: gateViewModel.isDigestExpanded,
                    onExpand: { gateViewModel.expandDigest() },
                    onDismiss: { gateViewModel.dismissDigest() }
                )
            }
            if let gate = gateViewModel.toolGate {
                GateBanner(gate: gate) { affordance, epoch in
                    gateViewModel.decide(affordance, epoch: epoch)
                }
            }
            if hasDismissedPendingPlanGate {
                Button(Copy.planGatePending) { dismissedPlanGateEpoch = nil }
                    .buttonStyle(.borderedProminent)
                    .tint(.orange)
                    .controlSize(.small)
            }
        }
        .padding(.horizontal, Metrics.overlayHorizontalPadding)
        .padding(.top, Metrics.overlayTopPadding)
        .animation(.default, value: gateViewModel.toolGate)
        .animation(.default, value: gateViewModel.digest)
    }

    // MARK: - Plan gate sheet

    private var hasDismissedPendingPlanGate: Bool {
        guard let gate = controller.gateViewModel.planGate else { return false }
        return gate.epoch == dismissedPlanGateEpoch
    }

    private var planGateBinding: Binding<Bool> {
        Binding(
            get: {
                guard let gate = controller.gateViewModel.planGate else { return false }
                return gate.epoch != dismissedPlanGateEpoch
            },
            set: { presented in
                guard !presented else { return }
                dismissedPlanGateEpoch = controller.gateViewModel.planGate?.epoch
            }
        )
    }

    @ViewBuilder private var planGateSheet: some View {
        if let gate = controller.gateViewModel.planGate {
            PlanGateSheet(gate: gate) { affordance, epoch in
                controller.gateViewModel.decide(affordance, epoch: epoch)
            }
        }
    }
}