import SwiftUI
import NucleicProtocol

/// One session: a segmented Transcript/Diff read view over a status-driven action area
/// (UX_IOS §4). Subscribes on appear, unsubscribes on disappear.
struct SessionDetailView: View {
    @EnvironmentObject var store: RemoteStore
    let sessionID: SessionID
    // Initial tab (0 = Transcript, 1 = Diff); overridable via NUCLEIC_DETAIL_TAB for
    // offline UI previews, matching NUCLEIC_TAB / NUCLEIC_DEMO_SESSION.
    @State private var tab = Int(ProcessInfo.processInfo.environment["NUCLEIC_DETAIL_TAB"] ?? "") ?? 0
    @State private var draft = ""
    @State private var showRename = false
    @State private var renameDraft = ""
    @State private var showIntegrate = false
    @State private var showDiscard = false

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

    var body: some View {
        Group {
            if tab == 0 {
                TranscriptList(events: store.openEvents)
            } else 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)
            }
        }
        // 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)
        .toolbar {
            // Transcript/Diff lives in the navigation bar (icon segments) rather than a
            // dedicated row — it's a mode flip, not content, and shouldn't cost chat height.
            ToolbarItem(placement: .topBarTrailing) {
                Picker("View", selection: $tab) {
                    Image(systemName: "text.bubble").tag(0)
                        .accessibilityLabel("Transcript")
                    Image(systemName: "plus.forwardslash.minus").tag(1)
                        .accessibilityLabel("Diff")
                }
                .pickerStyle(.segmented)
                .fixedSize()
            }
            if let summary, store.canControl {
                ToolbarItem(placement: .topBarTrailing) { sessionMenu(summary) }
            }
        }
        .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 {
                Label("\(percent)%", systemImage: "gauge.with.dots.needle.33percent")
                    .font(.caption2).foregroundStyle(.secondary)
                    .help("Context window used")
            }
            Toggle(isOn: Binding(get: { summary.auto }, set: { store.setSessionAuto(sessionID, $0) })) {
                Label("Auto", systemImage: summary.auto ? "bolt.fill" : "bolt.slash")
            }
            .toggleStyle(.button).tint(Palette.accent).font(.caption2)
        }
        .padding(.horizontal)
        .padding(.bottom, 6)
    }

    @ViewBuilder
    private func sessionMenu(_ summary: WireSessionSummary) -> some View {
        Menu {
            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")
            }
        } label: {
            Image(systemName: "ellipsis.circle")
        }
    }

    @ViewBuilder
    private var actionArea: some View {
        Divider()
        if let approval = store.openApprovals.first {
            ApprovalCardView(approval: approval)
                .padding()
        } else if let status = summary?.status {
            let running = status == .running
            let canCompose = running || status == .awaitingInput || status.isTerminal
            VStack(spacing: 8) {
                // 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 let queued = summary?.queuedMessages, !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(.secondary)
                        Spacer()
                    }
                    .frame(maxWidth: .infinity, alignment: .leading)
                }
                if canCompose {
                    HStack(spacing: 8) {
                        TextField(running ? "Queue a follow-up…" : "Send a follow-up…",
                                  text: $draft, axis: .vertical)
                            .textFieldStyle(.roundedBorder)
                            .lineLimit(1...4)
                            .keyboardDismissable()
                        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()
        }
    }

    /// 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]
    @AppStorage("nucleic.showRawEvents") private var showRaw = false
    @AppStorage("nucleic.showLockEvents") private var showLockEvents = true

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

    var body: some View {
        ScrollViewReader { proxy in
            ScrollView {
                LazyVStack(alignment: .leading, spacing: 10) {
                    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)
            // 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.
            .onChange(of: events.count) {
                if let last = items.last { withAnimation { proxy.scrollTo(last.id, anchor: .bottom) } }
            }
        }
    }
}

/// The Diff tab, 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()
    }
}