nucleic-remote-ios/NucleicRemote/NucleicRemote/Views/SessionDetailView.swift

import SwiftUI
import NucleicProtocol

/// One session: a full-height transcript with a status-driven action bar floating over it on
/// Liquid Glass; the diff viewer sits behind the ⋯ menu as a sheet (UX_IOS §4). Subscribes on
/// appear, unsubscribes on disappear.
struct SessionDetailView: View {
    @EnvironmentObject var store: RemoteStore
    let sessionID: SessionID
    // Diff sheet visibility; NUCLEIC_DETAIL_TAB=1 opens it for offline UI previews,
    // matching NUCLEIC_TAB / NUCLEIC_DEMO_SESSION.
    @State private var showDiff = ProcessInfo.processInfo.environment["NUCLEIC_DETAIL_TAB"] == "1"
    @State private var draft = ""
    @State private var showRename = false
    @State private var renameDraft = ""
    @State private var showIntegrate = false
    @State private var showDiscard = false
    // Bumped on send to jump the transcript to the bottom, even if the user had scrolled up to
    // read history — sending is a deliberate "show me what happens next" (mirrors the Mac).
    @State private var scrollToBottomRequest = 0

    private var summary: WireSessionSummary? {
        store.sessions.first { $0.sessionID == sessionID }
    }

    var body: some View {
        TranscriptList(events: store.openEvents, scrollToBottomRequest: scrollToBottomRequest)
            // The chat bar floats over the scrolling content on Liquid Glass instead of sitting
            // in a boxed strip below it, so the transcript runs the full height of the screen.
            .safeAreaInset(edge: .bottom) { actionArea }
            .navigationTitle(summary?.title ?? "Session")
            .navigationBarTitleDisplayMode(.inline)
            // With a session open the floating chat bar owns the bottom edge, so the compact
            // shell's `NucleicTabBar` slides away while this detail is pushed — driven by the
            // `open`/`closeOpen` below toggling `store.openSessionID`, not a per-navigation tab-bar
            // toolbar hide (which restored the system bar late and made the "+" jump). A no-op in
            // the iPad split, which has no tab bar.
            .toolbar {
                ToolbarItem(placement: .topBarTrailing) { sessionMenu }
            }
            .sheet(isPresented: $showDiff) { diffSheet }
        .alert("Rename chat", isPresented: $showRename) {
            TextField("Title", text: $renameDraft)
            Button("Cancel", role: .cancel) {}
            Button("Rename") { store.renameSession(sessionID, to: renameDraft) }
        }
        .confirmationDialog("Integrate this branch", isPresented: $showIntegrate, titleVisibility: .visible) {
            Button("Merge") { store.integrate(sessionID, .merge) }
            Button("Squash & merge") { store.integrate(sessionID, .squash) }
            Button("Rebase") { store.integrate(sessionID, .rebase) }
            Button("Cancel", role: .cancel) {}
        }
        .confirmationDialog(
            "Discard this session's branch and worktree? Unmerged work is lost.",
            isPresented: $showDiscard, titleVisibility: .visible
        ) {
            Button("Discard", role: .destructive) { store.discard(sessionID) }
            Button("Cancel", role: .cancel) {}
        }
        .onAppear { store.open(sessionID) }
        // Pass our own id so an iPad split-view A→B switch (which may mount B before A
        // disappears) unsubscribes A without tearing down B's just-opened state.
        .onDisappear { store.closeOpen(sessionID) }
        .background { interruptShortcut }
    }

    /// ⌘. interrupts a running session (the Mac's "stop" convention) — the action is otherwise
    /// only in the ⋯ menu. A hidden button carries the shortcut; present only when it applies.
    @ViewBuilder
    private var interruptShortcut: some View {
        if store.canControl, summary?.status == .running {
            Button("Interrupt") { store.interrupt(sessionID) }
                .keyboardShortcut(".", modifiers: .command)
                .opacity(0)
                .accessibilityHidden(true)
        }
    }

    /// Whether this session's project is under Nucleic Control (gates Orchestra + autoship).
    private var controlled: Bool {
        store.dashboard.projects.first { $0.id.rawValue == summary?.projectID }?.isNucleicControlled ?? false
    }

    private var modelBinding: Binding<String?> {
        Binding(get: { summary?.model }, set: { store.setSessionModel(sessionID, $0) })
    }
    private var effortBinding: Binding<String> {
        Binding(
            get: {
                let fallback = store.modelCatalog.fallbackEffort.isEmpty
                    ? MobileEfforts.fallback : store.modelCatalog.fallbackEffort
                return summary?.effort ?? fallback
            },
            set: { store.setSessionEffort(sessionID, $0) })
    }

    /// Live context-window occupancy (newest turn's input tokens ÷ the model's window), read
    /// from the transcript exactly as the Mac header does.
    private var contextPercent: Int? {
        let used = store.openEvents.reversed().lazy.compactMap { event -> Int? in
            switch event.kind {
            case .turnCompleted(let turn): return turn.usage?.contextInputTokens
            case .usage(let usage): return usage.contextInputTokens
            default: return nil
            }
        }.first { $0 > 0 }
        guard let used else { return nil }
        let window = store.modelCatalog.contextWindow(summary?.model)
        guard window > 0 else { return nil }
        return min(100, Int((Double(used) / Double(window)) * 100))
    }

    /// The model / effort / auto controls for the open session — the mobile echo of the Mac's
    /// session header, folded into the glass chat bar so they don't cost a strip of transcript
    /// height. Reads current state from the summary; each change is a control intent.
    @ViewBuilder
    private func controlRow(_ summary: WireSessionSummary) -> some View {
        HStack(spacing: 10) {
            // A session's backend is fixed at creation, so only same-backend models are offered.
            ModelMenu(model: modelBinding, catalog: store.modelCatalog, backend: summary.backend)
            EffortMenu(effort: effortBinding, catalog: store.modelCatalog,
                       // No explicit model yet → use the session backend's default, so the menu
                       // shows that backend's effort range rather than collapsing to one level.
                       modelSKU: summary.model ?? store.modelCatalog.models(for: summary.backend).first?.sku,
                       controlled: controlled,
                       // Orchestra is a one-way latch for an existing chat — the host won't turn it
                       // off, so disable the other levels here to match.
                       lockWhenOrchestra: true)
            Spacer(minLength: 4)
            if let percent = contextPercent {
                // Weight and primary ink (not `.secondary`) so the metric stays legible over
                // whatever the Liquid Glass bar is blurring through.
                Label("\(percent)%", systemImage: "gauge.with.dots.needle.33percent")
                    .font(.caption2.weight(.semibold)).foregroundStyle(.primary)
                    .help("Context window used")
            }
            // Locked on for a Nucleic Control project — those chats always run autonomously, and
            // the host keeps Auto on regardless of what the phone sends, so show it locked on to
            // match rather than offering a toggle that wouldn't take.
            Toggle(isOn: Binding(get: { controlled || summary.auto },
                                 set: { store.setSessionAuto(sessionID, $0) })) {
                Label("Auto", systemImage: (controlled || summary.auto) ? "bolt.fill" : "bolt.slash")
            }
            .toggleStyle(.button).tint(Palette.accent).font(.caption2.weight(.semibold))
            .disabled(controlled)
            .help(controlled
                ? "Auto-approve is always on for Nucleic Control chats — they run autonomously."
                : "Auto-approve safe actions; destructive ones still ask.")
        }
    }

    /// The ⋯ menu: the diff viewer for everyone, then the control-scope session actions.
    @ViewBuilder
    private var sessionMenu: some View {
        Menu {
            Button { showDiff = true } label: {
                Label(diffLabel, systemImage: "plus.forwardslash.minus")
            }
            if let summary, store.canControl {
                Divider()
                sessionActions(summary)
            }
        } label: {
            Image(systemName: "ellipsis.circle")
        }
    }

    /// "View changes" with the live +/− counts when the host projects them, so the menu hints
    /// whether there's anything to look at before opening the sheet.
    private var diffLabel: String {
        guard let stat = summary?.diffStat, stat.filesChanged > 0 else { return "View changes" }
        return "View changes · +\(stat.added) −\(stat.removed)"
    }

    /// The diff, presented as a sheet from the ⋯ menu — a viewer you visit, not a mode the
    /// chat lives in.
    private var diffSheet: some View {
        NavigationStack {
            Group {
                if store.capabilities.canFetchDiff || store.openDiff != nil {
                    SessionDiffView(diff: store.openDiff, loading: store.diffLoading)
                        .onAppear { store.fetchDiff(sessionID) }
                } else {
                    // Older host with no on-demand diff — the stat summary is all it projects.
                    DiffSummaryView(diffStat: summary?.diffStat)
                }
            }
            .navigationTitle("Changes")
            .navigationBarTitleDisplayMode(.inline)
            .toolbar {
                ToolbarItem(placement: .topBarTrailing) {
                    Button("Done") { showDiff = false }
                }
            }
        }
    }

    @ViewBuilder
    private func sessionActions(_ summary: WireSessionSummary) -> some View {
        Button { renameDraft = summary.title; showRename = true } label: {
            Label("Rename", systemImage: "pencil")
        }
        Button { store.setFavorite(sessionID, !summary.favorite) } label: {
            Label(summary.favorite ? "Unfavorite" : "Favorite",
                  systemImage: summary.favorite ? "star.slash" : "star")
        }
        // Autoship is a Nucleic Control capability — offered only for Control projects, and
        // the host couples it with auto-approval (enabling it turns Auto on).
        if controlled {
            Button { store.setSessionAutoShip(sessionID, !summary.autoShip) } label: {
                Label(summary.autoShip ? "Turn off Autoship" : "Turn on Autoship",
                      systemImage: summary.autoShip ? "shippingbox.fill" : "shippingbox")
            }
        }
        if summary.status == .running {
            Button { store.interrupt(sessionID) } label: { Label("Interrupt", systemImage: "stop.circle") }
        }
        Section {
            Button { showIntegrate = true } label: { Label("Integrate…", systemImage: "arrow.triangle.merge") }
            Button(role: .destructive) { showDiscard = true } label: {
                Label("Discard…", systemImage: "xmark.bin")
            }
            Button { store.setArchived(sessionID, !summary.archived) } label: {
                Label(summary.archived ? "Unarchive" : "Archive",
                      systemImage: summary.archived ? "tray.and.arrow.up" : "archivebox")
            }
        }
        Button(role: .destructive) { store.deleteSession(sessionID) } label: {
            Label("Delete", systemImage: "trash")
        }
    }

    /// The floating action layer: one Liquid Glass bar carrying the queued pills, the working
    /// indicator, the session controls, and the composer — or the approval card when a gate is
    /// pending. Content scrolls beneath it; nothing renders when there's nothing to act on.
    private var actionArea: some View {
        VStack(spacing: 8) {
            // Interacting with a chat while the owning Mac is unreachable surfaces this first, so a
            // disabled composer reads as "offline / read-only history" rather than broken.
            if !store.connectivity.isLive { disconnectedBanner }
            actionContent
        }
        .padding(.horizontal, 12)
        .padding(.bottom, 8)
    }

    /// The offline notice over the transcript: the chat's history is cached and readable, but the
    /// composer + controls below stay disabled until the Mac that owns it is reachable again.
    private var disconnectedBanner: some View {
        HStack(spacing: 10) {
            Image(systemName: "wifi.slash").foregroundStyle(.secondary)
            VStack(alignment: .leading, spacing: 1) {
                Text("Disconnected").font(.footnote.weight(.semibold))
                Text("Showing saved history · reconnect to send")
                    .font(.caption2).foregroundStyle(.secondary)
            }
            Spacer(minLength: 8)
            Button("Reconnect") { store.reconnect() }
                .font(.caption.weight(.semibold))
                .buttonStyle(.borderless)
                .disabled(!store.isPaired)
        }
        .frame(maxWidth: .infinity, alignment: .leading)
        .padding(.horizontal, 14).padding(.vertical, 10)
        .glassSurface(cornerRadius: 20)
    }

    @ViewBuilder
    private var actionContent: some View {
        Group {
            if let approval = store.openApprovals.first {
                // AskUserQuestion isn't a permission gate — it collects the user's answers and
                // needs them folded back into `updatedInput`. Render the picker (matching the
                // Mac's `AskUserQuestionBar`) instead of a plain allow/deny card, which would
                // reply with no selection and make the CLI report the question went unanswered.
                if approval.toolName == AskUserQuestion.toolName,
                    let questions = AskUserQuestion.questions(from: approval.input)
                {
                    AskUserQuestionCardView(approval: approval, questions: questions)
                } else {
                    ApprovalCardView(approval: approval)
                }
            } else if let status = summary?.status {
                let running = status == .running
                let canCompose = running || status == .awaitingInput || status.isTerminal
                let queued = summary?.queuedMessages ?? []
                if canCompose || store.canControl || !queued.isEmpty {
                    VStack(spacing: 10) {
                        // Follow-ups submitted mid-turn, held by the host to send when the current
                        // turn finishes. Each is shown as its own pill (with its attachments) and —
                        // at control scope — can be cancelled individually, matching the Mac
                        // composer. (They still send as one combined turn.)
                        if !queued.isEmpty {
                            VStack(spacing: 6) {
                                ForEach(queued) { message in
                                    queuedMessageRow(message)
                                }
                            }
                        }
                        if running {
                            HStack(spacing: 8) {
                                ProgressView().controlSize(.small)
                                Text("Agent is working…").font(.footnote).foregroundStyle(.primary)
                                Spacer()
                            }
                            .frame(maxWidth: .infinity, alignment: .leading)
                        }
                        if store.canControl, let summary { controlRow(summary) }
                        if canCompose {
                            HStack(alignment: .bottom, spacing: 8) {
                                // No keyboard-accessory Done button here (it floats awkwardly
                                // over the glass bar on iOS 26) — a drag on the transcript
                                // dismisses the keyboard instead (`scrollDismissesKeyboard`).
                                TextField(running ? "Queue a follow-up…" : "Send a follow-up…",
                                          text: $draft, axis: .vertical)
                                    .textFieldStyle(.plain)
                                    .lineLimit(1...4)
                                    .padding(.vertical, 3)
                                Button {
                                    store.sendInput(draft, to: sessionID)
                                    draft = ""
                                } label: {
                                    Image(systemName: running ? "clock.arrow.circlepath" : "arrow.up.circle.fill")
                                        .font(.title2)
                                }
                                .disabled(draft.trimmingCharacters(in: .whitespaces).isEmpty || !store.connectivity.isLive)
                                // Hardware-keyboard send (Magic Keyboard on iPad), mirroring the
                                // Mac — plain Return stays newline in the multiline field.
                                .keyboardShortcut(.return, modifiers: .command)
                            }
                        }
                    }
                    .padding(.horizontal, 14)
                    .padding(.vertical, 12)
                    .glassSurface(cornerRadius: 26)
                }
            }
        }
    }

    /// A queued follow-up shown above the composer: its text (or attachment names) with the
    /// attachments as chips, and — at control scope — a ✕ that cancels just this message.
    @ViewBuilder
    private func queuedMessageRow(_ message: QueuedMessage) -> some View {
        VStack(alignment: .leading, spacing: 4) {
            HStack(spacing: 6) {
                Image(systemName: "clock").foregroundStyle(.secondary)
                Text(queuedRowText(message)).lineLimit(1).truncationMode(.tail)
                    .foregroundStyle(.secondary)
                Spacer(minLength: 8)
                if store.canControl {
                    Button {
                        // Refill the composer for editing (text only — the phone can't stage the
                        // host's files) unless the user has already started typing; then drop it.
                        if draft.trimmingCharacters(in: .whitespaces).isEmpty { draft = message.text }
                        store.cancelQueuedMessage(sessionID, message.id)
                    } label: {
                        Image(systemName: "xmark.circle.fill").foregroundStyle(.secondary)
                    }
                    .buttonStyle(.plain)
                    .disabled(!store.connectivity.isLive)
                }
            }
            .font(.footnote)
            if !message.attachments.isEmpty {
                ScrollView(.horizontal, showsIndicators: false) {
                    HStack(spacing: 6) {
                        ForEach(message.attachments) { attachment in
                            Label(attachment.filename, systemImage: "doc")
                                .font(.caption2)
                                .lineLimit(1)
                                .padding(.horizontal, 7).padding(.vertical, 3)
                                .background(.quaternary, in: .capsule)
                        }
                    }
                }
            }
        }
        .frame(maxWidth: .infinity, alignment: .leading)
        .padding(.horizontal, 8).padding(.vertical, 6)
        .background(.quaternary.opacity(0.4), in: .rect(cornerRadius: 10))
    }

    /// The one-line label for a queued pill: the message text, or — for an attachment-only
    /// message — the attachment names (the chips below repeat them), so it's never blank.
    private func queuedRowText(_ message: QueuedMessage) -> String {
        if !message.text.isEmpty { return message.text }
        return message.attachments.map(\.filename).joined(separator: ", ")
    }
}

struct TranscriptList: View {
    let events: [AgentEvent]
    /// Bumped by the parent when the user sends a message — a deliberate "show me what happens
    /// next" that jumps to the bottom even if they'd scrolled up to read history.
    var scrollToBottomRequest: Int = 0
    @AppStorage("nucleic.showRawEvents") private var showRaw = false
    @AppStorage("nucleic.showLockEvents") private var showLockEvents = true

    /// True while the user is parked at (within a hair of) the bottom, so live output keeps
    /// following; once they scroll up it flips false, following stops, and the jump-to-bottom
    /// chevron appears. Starts true — a freshly opened chat is anchored at the bottom.
    @State private var isScrolledToBottom = true

    /// True for a short window right after the transcript appears, while it runs its first
    /// layout passes and its events fill in. During it we accept only "at bottom" scroll
    /// readings, so the settling layout can't strand the chat above its true bottom or flash the
    /// chevron; live scrolls are honored once it clears. Mirrors the Mac's `transcriptSettling`.
    @State private var transcriptSettling = true

    /// Total scroll-content height, tracked live from the scroll view's geometry, but only while
    /// settling — a `.task(id:)` debounces it to detect when the opening layout has come to rest.
    @State private var transcriptContentHeight: CGFloat = 0

    private var items: [TranscriptItem] {
        TranscriptProjection.build(events, showRaw: showRaw, showLockEvents: showLockEvents)
    }

    /// How much content may still sit below the viewport's bottom edge and still count as "at
    /// the bottom" — a little slack so streaming deltas and rounding never flip the gate. Mirrors
    /// the Mac's `bottomFollowThreshold`.
    private let bottomFollowThreshold: CGFloat = 24

    var body: some View {
        ScrollViewReader { proxy in
            ScrollView {
                LazyVStack(alignment: .leading, spacing: 14) {
                    ForEach(items) { item in
                        TranscriptRow(item: item).id(item.id)
                    }
                }
                .padding()
                // Cap the transcript to a readable measure on a wide iPad so lines don't run
                // edge-to-edge on a 13-inch screen; a no-op at phone width.
                .readableColumn()
            }
            // A drag on the transcript dismisses the keyboard, so a tall multiline composer can
            // be put away without leaving the session.
            .scrollDismissesKeyboard(.interactively)
            // The single-argument `defaultScrollAnchor(.bottom)` governs both the initial offset
            // and how the scroll view re-pins on content-size changes — it sticks the bottom edge
            // in view as the transcript grows. That native stickiness is what we want while the
            // user is parked at the bottom (the chat opens at the end and follows live output),
            // but it's also what yanked them back down whenever anything changed while they'd
            // scrolled up to read history. So gate the anchor itself: drop it to `nil` the moment
            // they scroll away, which lets new content land off-screen below instead of dragging
            // the viewport, and restore `.bottom` once they're back at the end.
            .defaultScrollAnchor(isScrolledToBottom ? .bottom : nil)
            // Track the live scroll position straight from the scroll view's geometry: how much
            // content still sits below the viewport bottom. Within the slack threshold means the
            // user is parked at the end (live output keeps following); scrolling up flips this
            // false, which drops the anchor (above) and reveals the jump-to-bottom chevron.
            .onScrollGeometryChange(for: Bool.self) { geo in
                geo.contentSize.height - geo.containerSize.height - geo.contentOffset.y
                    <= bottomFollowThreshold
            } action: { _, atBottom in
                // While the chat is opening the layout grows over a few passes and the scroll
                // offset lags each growth by a frame — sampling that frame reads "not at bottom"
                // even though `.defaultScrollAnchor(.bottom)` is about to re-pin. So during the
                // open window accept only "at bottom" readings; honor real scroll-ups after.
                if transcriptSettling {
                    if atBottom { isScrolledToBottom = true }
                } else {
                    isScrolledToBottom = atBottom
                }
            }
            // Detect when the opening layout has come to rest: track the content height while
            // settling and let `.task(id:)` debounce it — the task restarts on every change and
            // only reaches its body once the height has held steady. Freezing the tracker after
            // settling keeps live streaming (which changes the height every frame) from re-arming.
            .onScrollGeometryChange(for: CGFloat.self) { $0.contentSize.height.rounded() } action: { _, height in
                if transcriptSettling { transcriptContentHeight = height }
            }
            .task(id: transcriptContentHeight) {
                guard transcriptSettling, transcriptContentHeight > 0 else { return }
                try? await Task.sleep(for: .milliseconds(80))
                if Task.isCancelled { return }
                transcriptSettling = false
            }
            // Coalescing means item count lags event count; key the autoscroll on the raw stream
            // so every streamed delta keeps the view pinned to the bottom — but only while the
            // user is already parked there. Scrolling up to read history is never yanked down.
            .onChange(of: events.count) {
                if isScrolledToBottom { scrollToLast(proxy, animated: !transcriptSettling) }
            }
            // An explicit jump — the chevron or sending a message — always wins.
            .onChange(of: scrollToBottomRequest) { scrollToLast(proxy) }
            // Floating chevron above the chat bar, shown only while scrolled up; tap to jump back
            // to the latest output. Mirrors the Mac's `JumpToBottomButton`.
            .overlay(alignment: .bottom) {
                ZStack {
                    if !isScrolledToBottom {
                        JumpToBottomButton { scrollToLast(proxy) }
                            .padding(.bottom, 12)
                            .transition(.move(edge: .bottom).combined(with: .opacity))
                    }
                }
                .animation(.easeInOut(duration: 0.15), value: isScrolledToBottom)
            }
        }
    }

    /// Scroll the last message to the bottom edge; `animated: false` during the open-settle
    /// window so a chat that's still laying out snaps to the tail instead of easing into place.
    private func scrollToLast(_ proxy: ScrollViewProxy, animated: Bool = true) {
        guard let last = items.last else { return }
        if animated {
            withAnimation { proxy.scrollTo(last.id, anchor: .bottom) }
        } else {
            proxy.scrollTo(last.id, anchor: .bottom)
        }
    }
}

/// The floating "jump to the latest" chevron shown above the chat bar while the user has
/// scrolled up away from the bottom of the transcript. The mobile twin of the Mac's
/// `JumpToBottomButton`.
private struct JumpToBottomButton: View {
    let action: () -> Void

    var body: some View {
        Button(action: action) {
            Image(systemName: "chevron.down")
                .font(.system(size: 13, weight: .semibold))
                .foregroundStyle(Palette.accent)
                .frame(width: 30, height: 30)
                .background(.regularMaterial, in: .circle)
                .overlay(Circle().strokeBorder(.separator, lineWidth: 0.5))
                .shadow(color: .black.opacity(0.18), radius: 4, y: 1)
        }
        .buttonStyle(.plain)
        .accessibilityLabel("Jump to the latest message")
    }
}

/// The diff sheet's content, read-only over the on-demand `WireSessionDiff`. On a phone it's a per-file
/// summary over one scrolling unified patch; on a regular-width iPad it becomes the Mac's
/// two-pane diff — a selectable file list beside the selected file's patch — exploiting the
/// wide detail column. Same wire, no new protocol.
struct SessionDiffView: View {
    let diff: WireSessionDiff?
    let loading: Bool
    /// Below this available width the two-pane diff would leave the patch too cramped, so we
    /// keep the phone stack. Picks two-pane on a wide iPad (landscape, or a large iPad) and the
    /// stack on a phone or a narrow portrait split — based on real width, not just size class.
    private let twoPaneMinWidth: CGFloat = 700

    var body: some View {
        if let diff, diff.stat.filesChanged > 0 {
            GeometryReader { geo in
                if geo.size.width >= twoPaneMinWidth {
                    SplitDiffView(diff: diff)
                } else {
                    stacked(diff)
                }
            }
        } else if loading {
            ProgressView("Fetching diff…")
                .frame(maxWidth: .infinity, maxHeight: .infinity)
        } else {
            ContentUnavailableView("No changes yet", systemImage: "doc")
        }
    }

    /// Phone form: the file summary over one scrolling unified patch.
    private func stacked(_ diff: WireSessionDiff) -> some View {
        ScrollView {
            VStack(alignment: .leading, spacing: 14) {
                VStack(alignment: .leading, spacing: 6) {
                    DiffStatHeader(stat: diff.stat)
                    ForEach(diff.files) { DiffFileRow(file: $0) }
                }
                .card()
                PatchText(patch: diff.patch)
                if diff.truncated { TruncatedPatchNote() }
            }
            .padding()
            .readableColumn()
        }
    }
}

/// iPad form: the Mac's two-pane diff. A tappable file list on the left drives the selected
/// file's patch on the right. Row taps use a plain `Button` (not `List(selection:)`, whose
/// single-select tap handling is unreliable outside an edit-mode / split-view context).
private struct SplitDiffView: View {
    let diff: WireSessionDiff
    @State private var selected: String?

    /// The combined patch split into per-file sections, keyed by file path.
    private var sections: [String: String] { UnifiedPatch.sections(diff.patch, files: diff.files) }
    private var current: String? { selected ?? diff.files.first?.path }

    var body: some View {
        HStack(spacing: 0) {
            fileList
                .frame(width: 280)
                .background(Color(.secondarySystemBackground))
            Divider()
            patchPane
                .frame(maxWidth: .infinity, maxHeight: .infinity)
        }
        .onAppear { if selected == nil { selected = diff.files.first?.path } }
        // Keep the selection valid as the diff refetches (files can appear/vanish between turns).
        .onChange(of: diff.files) { _, files in
            if selected == nil || !files.contains(where: { $0.path == selected }) {
                selected = files.first?.path
            }
        }
    }

    private var fileList: some View {
        ScrollView {
            LazyVStack(alignment: .leading, spacing: 0) {
                DiffStatHeader(stat: diff.stat)
                    .padding(.horizontal, 12).padding(.vertical, 10)
                    .frame(maxWidth: .infinity, alignment: .leading)
                Divider()
                ForEach(diff.files) { file in
                    Button { selected = file.path } label: {
                        DiffFileRow(file: file)
                            .padding(.horizontal, 12).padding(.vertical, 9)
                            .frame(maxWidth: .infinity, alignment: .leading)
                            .background(current == file.path
                                ? Palette.accent.opacity(0.15) : Color.clear)
                            .contentShape(Rectangle())
                    }
                    .buttonStyle(.plain)
                    .hoverEffect(.highlight)
                }
                if diff.truncated { TruncatedPatchNote().padding(12) }
            }
        }
    }

    @ViewBuilder
    private var patchPane: some View {
        if let path = current, let patch = sections[path], !patch.isEmpty {
            ScrollView { PatchText(patch: patch).padding() }
        } else if current != nil {
            // A file with no textual hunk (binary, or a section dropped by patch truncation).
            ContentUnavailableView(
                "No preview", systemImage: "doc",
                description: Text("This file has no textual diff\(diff.truncated ? " in the fetched patch" : "").")
            )
        } else {
            ContentUnavailableView("Select a file", systemImage: "sidebar.left")
        }
    }
}

/// The "N files changed · +A −R" header shared by both diff forms.
private struct DiffStatHeader: View {
    let stat: DiffStat
    var body: some View {
        Text("\(stat.filesChanged) file\(stat.filesChanged == 1 ? "" : "s") changed · +\(stat.added) −\(stat.removed)")
            .font(.subheadline.weight(.semibold))
    }
}

/// One file's row: status glyph, path, and its +/− counts. Shared by the phone summary and the
/// iPad file list.
struct DiffFileRow: View {
    let file: WireFileDiff
    var body: some View {
        HStack(spacing: 8) {
            Image(systemName: DiffStatus.icon(file.status))
                .font(.caption)
                .foregroundStyle(DiffStatus.color(file.status))
            Text(file.path)
                .font(.caption.monospaced())
                .lineLimit(1).truncationMode(.middle)
            Spacer(minLength: 8)
            Text("+\(file.added)").font(.caption2.monospacedDigit()).foregroundStyle(Palette.success)
            Text("−\(file.removed)").font(.caption2.monospacedDigit()).foregroundStyle(Palette.danger)
        }
    }
}

enum DiffStatus {
    static func icon(_ status: String) -> String {
        switch status {
        case "added", "untracked": "plus.circle"
        case "deleted": "minus.circle"
        case "renamed": "arrow.right.circle"
        default: "pencil.circle"
        }
    }
    static func color(_ status: String) -> Color {
        switch status {
        case "added", "untracked": Palette.success
        case "deleted": Palette.danger
        default: .secondary
        }
    }
}

private struct TruncatedPatchNote: View {
    var body: some View {
        Label("Patch truncated — open the Mac for the rest.", systemImage: "scissors")
            .font(.caption).foregroundStyle(.secondary)
            .frame(maxWidth: .infinity, alignment: .leading)
    }
}

/// Splits a combined `git diff` patch into per-file sections for the iPad's two-pane view.
enum UnifiedPatch {
    /// Map from file path to that file's slice of the unified patch. Sections begin at a
    /// `diff --git a/… b/…` line. When the section count matches `files` we pair positionally
    /// (the host emits patch and files together, in order); otherwise we key each section by the
    /// new path parsed from its header. Callers fall back to a "no preview" state on a miss.
    static func sections(_ patch: String, files: [WireFileDiff]) -> [String: String] {
        guard patch.contains("diff --git ") else {
            // A single-file patch with no git header: attribute the whole thing to the sole file.
            return files.count == 1 ? [files[0].path: patch] : [:]
        }
        var chunks: [String] = []
        var current: [Substring] = []
        for line in patch.split(separator: "\n", omittingEmptySubsequences: false) {
            if line.hasPrefix("diff --git ") {
                if !current.isEmpty { chunks.append(current.joined(separator: "\n")) }
                current = [line]
            } else if !current.isEmpty {
                current.append(line)
            }
        }
        if !current.isEmpty { chunks.append(current.joined(separator: "\n")) }

        var result: [String: String] = [:]
        if chunks.count == files.count {
            for (file, chunk) in zip(files, chunks) { result[file.path] = chunk }
        } else {
            for chunk in chunks where newPath(chunk) != nil { result[newPath(chunk)!] = chunk }
        }
        return result
    }

    /// The new-side path from a section's `diff --git a/OLD b/NEW` header. Nil when the header is
    /// absent or the path is quoted/spaced in a way we don't split cleanly.
    private static func newPath(_ chunk: String) -> String? {
        guard let header = chunk.split(separator: "\n", maxSplits: 1).first,
              header.hasPrefix("diff --git "),
              let bRange = header.range(of: " b/") else { return nil }
        let path = header[bRange.upperBound...]
        return path.isEmpty ? nil : String(path)
    }
}

/// The unified patch, one `Text` per line with the classic +/− coloring. Lines scroll
/// horizontally as a block so long lines don't wrap into noise.
private struct PatchText: View {
    let patch: String

    var body: some View {
        ScrollView(.horizontal, showsIndicators: false) {
            VStack(alignment: .leading, spacing: 0) {
                ForEach(Array(patch.components(separatedBy: "\n").enumerated()), id: \.offset) { _, line in
                    Text(line.isEmpty ? " " : line)
                        .font(.caption.monospaced())
                        .foregroundStyle(lineColor(line))
                        .frame(maxWidth: .infinity, alignment: .leading)
                        .background(lineBackground(line))
                }
            }
            .textSelection(.enabled)
            .padding(8)
        }
        .background(Color(.secondarySystemBackground), in: RoundedRectangle(cornerRadius: 10))
    }

    private func lineColor(_ line: String) -> Color {
        if line.hasPrefix("+++") || line.hasPrefix("---") { return .secondary }
        if line.hasPrefix("+") { return Palette.success }
        if line.hasPrefix("-") { return Palette.danger }
        if line.hasPrefix("@@") { return Palette.active }
        if line.hasPrefix("diff ") { return .secondary }
        return Palette.primaryText
    }

    private func lineBackground(_ line: String) -> Color {
        if line.hasPrefix("+++") || line.hasPrefix("---") { return .clear }
        if line.hasPrefix("+") { return Palette.success.opacity(0.10) }
        if line.hasPrefix("-") { return Palette.danger.opacity(0.10) }
        return .clear
    }
}

struct DiffSummaryView: View {
    let diffStat: DiffStat?

    var body: some View {
        VStack(spacing: 12) {
            if let diff = diffStat, diff.filesChanged > 0 {
                Label("\(diff.filesChanged) file\(diff.filesChanged == 1 ? "" : "s") changed", systemImage: "doc.text")
                    .font(.headline)
                HStack(spacing: 16) {
                    Text("+\(diff.added)").foregroundStyle(.green)
                    Text("−\(diff.removed)").foregroundStyle(.red)
                }
                .font(.title3.monospacedDigit())
                Text("Open the Mac for the full patch.")
                    .font(.footnote).foregroundStyle(.secondary)
            } else {
                ContentUnavailableView("No changes yet", systemImage: "doc")
            }
        }
        .frame(maxWidth: .infinity, maxHeight: .infinity)
        .padding()
    }
}