import SwiftUI

/// **The board settings sheet** — "the setup home" (03-board-ui.md ▸ Board settings sheet, ruled
/// 2026-07-31: the popover/sheet split, 04-interactions.md's configuration carve-out).
///
/// ### Why there are two configuration surfaces and not one
///
/// The split's reasons are mechanical, not aesthetic (04 ▸ The map): setup flows fire confirmation
/// alerts, run inline network probes, and accept drag-in key import — "acts that need a surface a
/// stray click can't dismiss". So the **popover** keeps the daily face (rename, styling, the branch
/// display and its switch picker, the posture lines) and this sheet takes everything setup-shaped.
/// **Each control has exactly one home**: "the popover never duplicates a sheet control, the sheet
/// never hosts the daily surface."
///
/// ### What is here, and what joins it
///
/// Three sections ship with the sheet itself, and each of them *moved* here rather than being written
/// here: **add-git** (mode `none`), **branch creation** (mode `git`), and the **commit-identity**
/// fields (mode `git`). 03's inventory for this surface is longer — add/change remote with its inline
/// verify probe, the HTTPS credential fields, the whole SSH surface with its drag-in key import and
/// TOFU confirms, push-on-commit — and every one of those is a pro-m2 card that joins as **one more
/// section** (`BoardSettingsSection`), which is the only thing the shape here has to promise.
///
/// ### Undo routing needs nothing from this file
///
/// "The settings sheet's text fields own ⌘Z/⇧⌘Z as field-local text undo while focused"
/// (06-history-undo.md ▸ Undo routing). A SwiftUI sheet is hosted in its own `NSWindow`, so a focused
/// field's editor supplies its own undo manager through the responder chain exactly as the popover's
/// rename field does — the platform's first-responder rule, working by construction. Nothing here
/// wires it, and nothing here may quietly take it away: a board-level ⌘Z reaching a typo would be
/// 06's "reflexive undo over a typo must never become a tree checkout".

// MARK: - Presentation state

/// Whether **this window's** settings sheet is open, and the session posture that decides whether it
/// may open at all.
///
/// `BoardInfoPresentation`'s sibling in every respect (see it for why the flag is per *window* rather
/// than per board or per app): one per window, `@State` in `BoardWindowHost`, published through the
/// focus system so Board ▸ Board Settings… means "the board in front".
///
/// **It carries the session's tier and git state** where the popover flag carries nothing, and for a
/// reason the popover does not have: both of this sheet's doors have to *validate*, and one of them
/// is a menu row with no view around it to ask. The facts are adopted once, from the session, at the
/// same moment the titlebar widget adopts them (`BoardWindowHost.configureWindow`) and never
/// re-derived — 12-editions.md ▸ The entitlement, "a lapse never interrupts an open session". The
/// *mode* inside the git state is `@Observable` and does move, by add-git alone, which is exactly the
/// transition this sheet is where the user performs: the sections re-resolve under it live.
@MainActor
@Observable
final class BoardSettingsPresentation {

    var isPresented = false

    /// The tier this window's board composed under — the free tier's default until a session says
    /// otherwise, which is the harmless direction (an unreachable sheet).
    private(set) var tier: Tier = .free

    /// This window's board git state, `nil` under the free tier and on a window whose session has not
    /// been adopted yet.
    private(set) var git: HistoryStore?

    /// Called once per window, from the same place the titlebar widget is handed the same two facts.
    func adopt(tier: Tier, git: HistoryStore?) {
        self.tier = tier
        self.git = git
    }

    /// What the sheet would show right now — and therefore, when empty, that there is no sheet to
    /// show (`BoardSettingsAvailability`).
    var sections: [BoardSettingsSection] {
        BoardSettingsSection.resolve(
            tier: tier,
            mode: git?.mode ?? .none,
            isRepositoryUnreadable: git?.isRepositoryUnreadable ?? false
        )
    }

    /// Both doors' validation: the menu row's `disabled` state and whether the popover shows its row
    /// at all.
    var isReachable: Bool {
        BoardSettingsAvailability.resolve(
            tier: tier,
            mode: git?.mode ?? .none,
            isRepositoryUnreadable: git?.isRepositoryUnreadable ?? false
        )
    }

    /// **Opening, not toggling** — unlike ⌘I. A sheet is modal to its window and carries its own
    /// dismissal (Done, and Escape through it), so a command that could also *close* it would be a
    /// second exit for a surface that already has the platform's; and neither door is reachable while
    /// the sheet is up anyway (the menu is behind it, the popover is dismissed by it).
    ///
    /// The guard is not defensive dressing: both doors validate on `isReachable` already, and a
    /// third path that forgot to would present a sheet with no sections in it.
    func present() {
        guard isReachable else { return }
        isPresented = true
    }

    func dismiss() {
        isPresented = false
    }
}

/// The focused board window's settings sheet, beside `FocusedValues.boardInfo` — see
/// `FocusedBoardStoreKey` for why board-window menu items reach their window this way.
struct FocusedBoardSettingsKey: FocusedValueKey {
    typealias Value = BoardSettingsPresentation
}

extension FocusedValues {
    var boardSettings: BoardSettingsPresentation? {
        get { self[FocusedBoardSettingsKey.self] }
        set { self[FocusedBoardSettingsKey.self] = newValue }
    }
}

// MARK: - What the sheet holds

/// **The sheet's inventory for one board**, as a pure function of the tier and the mode — the shape
/// `BoardGitSection.resolve` has one surface over, and for the same reason: the *contents* are the
/// part worth pinning and the SwiftUI that renders them is not.
///
/// Ordered as the sheet lays them out, top to bottom. pro-m2's cards each add a case here and a
/// branch in `BoardSettingsSheet.section(_:)` — nothing else.
enum BoardSettingsSection: String, Equatable, CaseIterable, Identifiable {

    /// Pro, mode `none`: **add-git** (06-history-undo.md ▸ Rules ▸ Opt-in init).
    case git

    /// Pro, mode `git`: **branch creation**. Switching stays in the popover (03 ▸ Board popover);
    /// create-and-switch runs 06's identical settle sequence from here.
    case branch

    /// Pro, mode `git`: the **commit identity** name/email that repo-local `.git/config` carries
    /// (06 ▸ Interaction with external writers).
    case commitIdentity

    var id: String { rawValue }

    /// The section header — a heading VoiceOver navigates by (10-accessibility.md ▸ Board settings
    /// sheet: "titled and sectioned with headers VoiceOver can navigate by").
    var title: String {
        switch self {
        case .git: "Git"
        case .branch: "Branch"
        case .commitIdentity: "Commit Identity"
        }
    }

    /// - Parameter isRepositoryUnreadable: whether the board's `.git` exists and will not open
    ///   (`HistoryStore.isRepositoryUnreadable`). Defaulted, because it can only ever be true in mode
    ///   `git` — every other mode has no repository for the probe to have failed on, and a caller
    ///   that has no git state to ask is describing one of those boards.
    static func resolve(
        tier: Tier,
        mode: BoardGitMode,
        isRepositoryUnreadable: Bool = false
    ) -> [BoardSettingsSection] {
        // **The free tier has no setup to host** (12-editions.md ▸ The free tier and `.git`): git is
        // the Pro subscription's, "any `.git` is inert", and 03 gives the free tier's whole git story
        // as the popover's one-line pointer. There is nothing for a sheet to be about.
        guard tier == .pro else { return [] }
        switch mode {
        case .none:
            return [.git]
        case .git:
            // **An unreadable repository hosts no setup either** (06-history-undo.md ▸ Rules, the
            // corrupt-`.git` loud failure, ruled 2026-07-31: "the whole git surface paused …
            // Lanework leaves the repository untouched"), and it lands on repo-nested's emptiness by
            // repo-nested's own reasoning, one step further along: both sections here are *writes* to
            // a repository — a branch created in it, an identity written into its config — and there
            // is no repository the app can open to write either into. An empty sheet would be the
            // greyed-out button 06 rules out one level up, so the surface simply does not exist for
            // such a board and the popover's own prose carries the explanation
            // (`BoardGitBranchSurface.unreadableNote`).
            //
            // The mode stays `.git` throughout — this is emptiness *within* git mode, never a fall
            // to mode none, which is what would let add-git be offered against an existing `.git`.
            return isRepositoryUnreadable ? [] : [.branch, .commitIdentity]
        case .repoNested:
            // **Nothing setup-shaped can apply** (06 ▸ Rules): the board lives inside a repository
            // Lanework leaves alone, so there is no add-git (the design is insistent that the option
            // is *absent*, "prose, not a disabled button"), no branch of ours to create, and no
            // repo-local config of ours to write. An empty sheet would be the greyed-out button one
            // level up — so the popover's prose stands and this surface simply does not exist for
            // such a board.
            return []
        case .unverifiable:
            // **Structurally the same emptiness as `.repoNested`, for the same reason** (06 ▸ Rules ▸
            // Detection, "Denial is not absence"): a denied ancestor check can never be told apart
            // from a repository actually being there, so add-git stays unreachable and this surface
            // does not exist for such a board either. Only the popover's *prose* tells the two apart
            // — this inventory does not, because the sheet has nothing to set up on either.
            return []
        }
    }
}

/// **Whether the sheet is reachable at all**, for both of its doors — Board ▸ Board Settings…'s
/// `disabled` state and whether the popover renders its Board Settings… row.
///
/// Reachable **iff the sheet has something to show**, which is the rule rather than a shortcut: a
/// surface whose whole job is hosting setup controls has no honest empty state, and deriving the
/// answer from the inventory is what keeps the two from drifting when pro-m2's sections land. In
/// today's terms that reads: Pro, on a board whose mode is `none` or `git`.
///
/// The two unreachable postures are unreachable for *different* reasons, and both are the design's:
///
/// - **The free tier**: no setup exists there at all (03-board-ui.md ▸ Board popover;
///   12-editions.md). The popover's own postures are untouched by this card — an ordinary board
///   shows nothing, a board carrying an inert `.git` shows the one-line Pro pointer.
/// - **Pro, repo-nested**: `BoardSettingsSection.resolve`'s own comment carries this one — nothing
///   setup-shaped can apply, so the popover's prose stands and no door opens.
///
/// The menu **row stays visible and disabled** either way (standard menu validation — a command that
/// does not apply here is still a command this app has), while the **popover row appears only where
/// the sheet is reachable**: a menu is an inventory of the app, a popover section is a description of
/// this board.
enum BoardSettingsAvailability {

    static func resolve(
        tier: Tier,
        mode: BoardGitMode,
        isRepositoryUnreadable: Bool = false
    ) -> Bool {
        !BoardSettingsSection.resolve(
            tier: tier,
            mode: mode,
            isRepositoryUnreadable: isRepositoryUnreadable
        ).isEmpty
    }
}

// MARK: - The sheet

/// The sheet itself: a header naming it and the board, the sections, and one Done.
struct BoardSettingsSheet: View {

    let store: BoardStore
    let presentation: BoardSettingsPresentation

    private var bodyPointSize: CGFloat { BoardMetrics.bodyPointSize }

    private var width: CGFloat {
        BoardSettingsSheetLayout.width(bodyPointSize: bodyPointSize)
    }

    private var inset: CGFloat {
        BoardSettingsSheetLayout.inset(bodyPointSize: bodyPointSize)
    }

    var body: some View {
        VStack(alignment: .leading, spacing: 0) {
            header

            Divider()

            // No scroll container, deliberately: three sections fit any screen at any text size, and
            // a `ScrollView` inside a content-sized sheet has to be given a height — a decision worth
            // making when pro-m2's credential and SSH sections make it real, not before.
            VStack(alignment: .leading, spacing: inset) {
                ForEach(presentation.sections) { section in
                    self.section(section)
                }
            }
            .padding(inset)
            .frame(maxWidth: .infinity, alignment: .leading)

            Divider()

            footer
        }
        .frame(width: width)
    }

    // MARK: The chrome

    /// **Titled** (10-accessibility.md ▸ Board settings sheet) — the surface's own name, plus the
    /// board's so a user with two boards open knows which one this is about.
    ///
    /// The board's name is `AppModel.displayName(of:)` — the title-falls-back-to-the-folder-name rule
    /// (01-storage-format.md ▸ Board naming), called rather than restated: `BoardInfoTitlebarSummary`
    /// restates it only because it must answer without a `BoardStore`, and this sheet has one.
    private var header: some View {
        VStack(alignment: .leading, spacing: 2) {
            Text("Board Settings")
                .font(.headline)
                .accessibilityAddTraits(.isHeader)
            Text(AppModel.displayName(of: store))
                .font(.subheadline)
                .foregroundStyle(.secondary)
                .lineLimit(1)
                .truncationMode(.tail)
        }
        .frame(maxWidth: .infinity, alignment: .leading)
        .padding(inset)
    }

    /// **The one exit, twice** — the button and Escape.
    ///
    /// `.cancelAction` is what wires Escape to it, and the naming is deliberate rather than sloppy:
    /// nothing on this sheet is staged, so there is nothing a Cancel could roll back — every control
    /// writes when it is used, and the button says Done because that is what dismissing means here.
    /// Not `.defaultAction`, so Return stays the focused field's (the branch name field submits with
    /// it).
    private var footer: some View {
        HStack {
            Spacer()
            Button("Done") {
                presentation.dismiss()
            }
            .keyboardShortcut(.cancelAction)
        }
        .padding(inset)
    }

    // MARK: The sections

    @ViewBuilder
    private func section(_ section: BoardSettingsSection) -> some View {
        VStack(alignment: .leading, spacing: 6) {
            Text(section.title)
                .font(.subheadline.weight(.semibold))
                // What "sectioned" buys a VoiceOver user: headings the rotor jumps between, rather
                // than one flat run of controls (10 ▸ Board settings sheet — "the sheet exists partly
                // *because* Tab-walking two dozen controls in an untitled popover failed this bar").
                .accessibilityAddTraits(.isHeader)

            if let git = presentation.git {
                switch section {
                case .git:
                    BoardGitAddAction(git: git, isEnabled: store.acceptsBoardMutations)
                case .branch:
                    BoardSettingsBranchSection(git: git, isEnabled: store.acceptsBoardMutations)
                case .commitIdentity:
                    BoardGitIdentityFields(git: git, isEnabled: store.acceptsBoardMutations)
                }
            }
        }
        .frame(maxWidth: .infinity, alignment: .leading)
    }
}

// MARK: - Geometry

/// The sheet's two figures, **derived from the body font** like every other surface's
/// (10-accessibility.md ▸ Text scaling: "relative text styles everywhere, no fixed point sizes"), and
/// stated here rather than inline so they are one decision.
///
/// A sheet is a window the app sizes, so a width it does not choose is a width AppKit derives from
/// whatever the widest control happened to be — which would move every time a section joined. The
/// figure is wide enough for a labeled two-column form (the identity fields) and narrower than the
/// board window's own floor, so the sheet reads as a card on the window rather than as a second one.
enum BoardSettingsSheetLayout {

    /// 30 em: 390pt at the standard 13pt body.
    static func width(bodyPointSize: CGFloat) -> CGFloat {
        BoardMetrics.em(30, bodyPointSize: bodyPointSize)
    }

    /// The sheet's inset **and** the gap between two sections — one figure, because a section's
    /// distance from its neighbour and from the sheet's edge are the same rhythm. 1.55 em: 20pt at
    /// the standard body.
    static func inset(bodyPointSize: CGFloat) -> CGFloat {
        BoardMetrics.em(1.55, bodyPointSize: bodyPointSize)
    }

    /// The identity form's label column. 3.4 em: 44pt at the standard body, which is what those
    /// fields have always drawn.
    static func labelColumn(bodyPointSize: CGFloat) -> CGFloat {
        BoardMetrics.em(3.4, bodyPointSize: bodyPointSize)
    }
}

// MARK: - Add git

/// **The add-git action** (06-history-undo.md ▸ Rules ▸ Opt-in init) — the one place in the app that
/// creates a repository, and the reason "no silent auto-init, ever" is a checkable claim rather than
/// a promise: there is no other caller of `HistoryStore.addGit`.
///
/// The caption states what pressing it does, in the order it happens, because it is not undoable in
/// the ordinary sense: a repository appears in the board's folder and its current state becomes the
/// first commit.
///
/// **It moved here from the popover with the 2026-07-31 split** (03-board-ui.md ▸ Board settings
/// sheet: the sheet hosts "add-git (mode none; opt-in init — 06)"), carrying the two lines below with
/// it.
private struct BoardGitAddAction: View {

    let git: HistoryStore
    /// The read-only lock's reach (02-architecture.md ▸ The lock's scope): a board that refuses
    /// writes refuses this one too — initializing a repository is a write, and a commit is several.
    /// The sheet **stays open** under the lock and disables in place, which is the style popover's
    /// settled precedent (03 ▸ Board settings sheet).
    let isEnabled: Bool

    var body: some View {
        VStack(alignment: .leading, spacing: 6) {
            Button("Add Git") {
                Task { await git.addGit() }
            }
            .disabled(!isEnabled || git.isAddingGit)

            Text("Creates a git repository in this board's folder and commits its current state.")
                .font(.caption)
                .foregroundStyle(.secondary)
                .fixedSize(horizontal: false, vertical: true)

            if let failure = git.lastFailure {
                Text(failure.message)
                    .font(.caption)
                    .foregroundStyle(.red)
                    .fixedSize(horizontal: false, vertical: true)
            }
        }
        // **The form add-git answers at** (06 ▸ Interaction with external writers, ruled 2026-07-31 —
        // "Form-anchored operations answer at the form first"): inline while this sheet is up, the
        // banner once it is gone. Appearing claims the inline surface; disappearing gives it up,
        // which both dismisses the stale error and sends any answer still in flight to the banner
        // instead of to nobody.
        //
        // The section's visibility *is* the sheet's here, and stays so as pro-m2's sections arrive:
        // add-git exists only on mode `none`, and a successful one flips the mode — which is the one
        // disappearance that is not a dismissal, and it is the right one (the failure slot empties
        // because there is nothing left to fail).
        .onAppear { git.noteFormVisible(true) }
        .onDisappear { git.noteFormVisible(false) }
    }
}

// MARK: - Branch creation

/// **Branch creation** (06-history-undo.md ▸ Branch switching; 03-board-ui.md ▸ Board settings sheet:
/// "branch creation (switching stays in the popover; create-and-switch runs 06's identical settle
/// sequence from here)").
///
/// ### A standing field, not a reveal
///
/// In the popover this was a "New Branch…" entry inside the switch menu that revealed an inline field
/// — the right shape *there*, where the surface is a compact daily face and the field was a detour off
/// it. A form is a form: this sheet exists to hold setup controls standing, so the field stands, and
/// the reveal dance retires with the container that motivated it. The Create button validates on a
/// non-empty trimmed name, which is the only thing the dance was ever gating.
///
/// ### The sequence is not this view's
///
/// `GitBranchSwitcher.createAndSwitch(to:)` runs the identical settle → flush → stamp → switch
/// sequence the picker's switch does — "no at-HEAD fast path" (06, blessed 2026-07-31) — and this
/// view calls exactly that method. The save-or-discard step it may raise is an **alert over the
/// sheet**, which is one of the mechanical reasons the sheet exists at all: "confirmation alerts
/// present over the sheet without dismissing the flow that owns them" (03).
private struct BoardSettingsBranchSection: View {

    let git: HistoryStore
    let isEnabled: Bool

    @State private var draft = ""

    /// The same four facts the popover's branch line reads, so a paused repository, a read-only board
    /// and a switch in flight close this control exactly as they close that one — one rule, one
    /// derivation (`BoardGitBranchSurface`).
    private var surface: BoardGitBranchSurface {
        BoardGitBranchSurface.resolve(
            branch: git.branch,
            pause: git.committer?.pause,
            isSwitching: git.switcher?.isSwitching ?? false,
            isWritable: isEnabled
        )
    }

    var body: some View {
        VStack(alignment: .leading, spacing: 6) {
            HStack(spacing: 6) {
                TextField("New branch name", text: $draft)
                    .textFieldStyle(.roundedBorder)
                    .lineLimit(1)
                    .onSubmit { create() }
                    // **Escape steps outward one layer per press** (04-interactions.md ▸ Grammar),
                    // the rename field's rule: a dirty field abandons its draft and keeps the sheet
                    // up; an empty one lets the press through to the sheet's own dismissal.
                    .onKeyPress(.escape) {
                        guard !draft.isEmpty else { return .ignored }
                        draft = ""
                        return .handled
                    }
                    .accessibilityLabel("New branch name")

                Button("Create", action: create)
                    .disabled(trimmedDraft.isEmpty)

                if git.switcher?.isSwitching == true {
                    ProgressView()
                        .controlSize(.small)
                        .accessibilityLabel("Switching branches")
                }
            }
            .disabled(!surface.controlsEnabled)

            Text("Creates the branch from the current one and switches to it.")
                .font(.caption)
                .foregroundStyle(.secondary)
                .fixedSize(horizontal: false, vertical: true)

            // The switcher's last failure, said where it was asked for. The popover's own caption
            // stays (a switch asked *there* answers there); the two can never show at once, since
            // opening this sheet dismisses that popover.
            if let failure = git.switcher?.lastFailure {
                Text(failure.message)
                    .font(.caption)
                    .foregroundStyle(.red)
                    .fixedSize(horizontal: false, vertical: true)
            }
        }
        // The two reads `surface` needs that nothing else on this sheet takes — the branch name and
        // the pause — asked when the sheet appears, because neither is a fact the board's watcher
        // could deliver (`.git` is filtered out of the watch by design). The branch *list* is not
        // read here: this section creates, and only the popover's picker needs to know what exists.
        .task {
            await git.refreshBranch()
            await git.committer?.refreshPause()
        }
    }

    private var trimmedDraft: String {
        draft.trimmingCharacters(in: .whitespacesAndNewlines)
    }

    private func create() {
        let name = trimmedDraft
        guard !name.isEmpty, surface.controlsEnabled else { return }
        draft = ""
        Task { await git.switcher?.createAndSwitch(to: name) }
    }
}

// MARK: - Commit identity

/// **The name and email that repo-local `.git/config` carries** (06-history-undo.md ▸ Interaction
/// with external writers: "The board settings sheet's identity section … exposes name/email fields
/// that write that repo-local config — the setting *is* the file, portable to any git client,
/// per-board by nature").
///
/// It moved here whole from the popover with the 2026-07-31 split, poll included — 06 says the
/// visibility-scoped re-read "rides with the fields", so hosting the view here *is* the re-point:
/// the `.task` below now lives and dies with the sheet.
///
/// ### The placeholder is the whole of the identity rule made visible
///
/// An empty field shows the **derived default** — the macOS account's full name and
/// `shortname@hostname` — as a placeholder, never as a value. That is the difference between "this
/// repository says nothing, so the app signs commits with a sensible guess" and "this repository says
/// this", and the file is where the difference lives: 06 forbids the app writing its own derived
/// value into config, because it would then outrank the user's global `~/.gitconfig` for their own
/// terminal commits in that board. A field pre-filled with the derived value would write it on the
/// first focus loss.
///
/// ### The dirty-buffer courtesy, copied from `BoardRenameField`
///
/// A foreign config edit landing while the sheet is open updates an *unfocused* field and never a
/// focused one: "a focused field keeps the user's keystrokes" (03-board-ui.md ▸ Board popover). The
/// trigger is a poll rather than a reload, and that is honest rather than lazy: `FolderWatcher`
/// filters `.git` out of the watch by design, so no board event can ever carry a config change, and
/// the alternative to a small periodic read is a field that is stale for as long as the sheet stays
/// open.
private struct BoardGitIdentityFields: View {

    let git: HistoryStore
    let isEnabled: Bool

    @State private var name = ""
    @State private var email = ""
    @FocusState private var focused: Field?

    private enum Field: Hashable {
        case name
        case email
    }

    /// **The fields re-read the config at 2 s while the sheet is visible** (06 ▸ Interaction with
    /// external writers, blessed 2026-07-31): "the watcher never delivers `.git`, so no board event
    /// can carry a terminal-side config edit — the unfocused-resync courtesy needs its own signal, and
    /// a visibility-scoped poll is the 15 s paused-state re-read's shape at sheet cadence (a focused
    /// field keeps its keystrokes; dismissing the sheet stops the poll)."
    private static let pollInterval: Duration = .seconds(2)

    var body: some View {
        VStack(alignment: .leading, spacing: 6) {
            field("Name", text: $name, placeholder: git.derivedIdentity?.name ?? "", tag: .name)
            field("Email", text: $email, placeholder: git.derivedIdentity?.email ?? "", tag: .email)

            if let failure = git.identityFailure {
                Text(failure.message)
                    .font(.caption)
                    .foregroundStyle(.red)
                    .fixedSize(horizontal: false, vertical: true)
            }
        }
        .task {
            // The first read, then the courtesy poll. Cancellation is the view's disappearance, which
            // is the sheet closing.
            while !Task.isCancelled {
                await git.refreshIdentity()
                try? await Task.sleep(for: Self.pollInterval)
            }
        }
        .onAppear {
            name = git.identityName
            email = git.identityEmail
        }
        .onChange(of: git.identityName) { _, value in
            guard focused != .name else { return }
            name = value
        }
        .onChange(of: git.identityEmail) { _, value in
            guard focused != .email else { return }
            email = value
        }
        // A dismissal is a commit like any other click-away — `BoardRenameField`'s rule, and the same
        // idempotence makes the overlap harmless.
        .onDisappear { commit() }
    }

    private func field(
        _ label: String,
        text: Binding<String>,
        placeholder: String,
        tag: Field
    ) -> some View {
        HStack(spacing: 6) {
            Text(label)
                .font(.caption)
                .foregroundStyle(.secondary)
                .frame(
                    width: BoardSettingsSheetLayout.labelColumn(bodyPointSize: BoardMetrics.bodyPointSize),
                    alignment: .leading
                )
            TextField(placeholder, text: text)
                .textFieldStyle(.roundedBorder)
                .lineLimit(1)
                .focused($focused, equals: tag)
                .onSubmit { commit() }
                .disabled(!isEnabled)
                .accessibilityLabel("Commit \(label.lowercased())")
        }
        .onChange(of: focused) { previous, _ in
            // Focus leaving *this* field is this field's commit — the inline editors' exit, applied
            // to a form where Tab moves between two of them.
            guard previous == tag else { return }
            commit()
        }
    }

    /// Writes both fields, and only when one of them differs from what the file says — an unchanged
    /// value must not rewrite `.git/config` every time the sheet closes.
    private func commit() {
        guard isEnabled else { return }
        guard name != git.identityName || email != git.identityEmail else { return }
        Task { await git.writeIdentity(name: name, email: email) }
    }
}
