import SwiftUI

/// **The Git tab's two setup controls** — add-git and the commit-identity fields (03-board-ui.md ▸
/// Board popover ▸ Git tab; 06-history-undo.md ▸ Rules ▸ Opt-in init and ▸ Interaction with external
/// writers).
///
/// ### One configuration home again (ruled 2026-08-07)
///
/// These two lived in the popover, moved to the board settings sheet with the **2026-07-31
/// popover/sheet split**, and came back with the **2026-08-07 reversal** that retired that sheet: the
/// popover is the board's one configuration surface, and its Git tab is where a board's repository is
/// both operated and set up. Nothing about either control's *substance* moved in either direction —
/// what moved is the container, and every rule stated below is the same rule the sheet carried,
/// re-pointed at the tab.
///
/// The one thing the reversal does change is what "the form is visible" means: it is the **popover's**
/// visibility now, and a popover is transient where a sheet was not. That is fine for both rules that
/// depend on it — add-git's inline-answer window and the identity fields' poll are both scoped to "the
/// surface the user asked from is still under their eye", and a popover dismissed by a stray click
/// ends that window exactly as Done ended the sheet's (06 ▸ Rules: "inline while the asking surface is
/// up, banner once it is gone").
///
/// They live in their own file rather than in `BoardGitTabView.swift` because they are the *setup*
/// half — the tab's postures and its daily branch face are that file's and `BoardGitControls.swift`'s
/// — and because a pro-m2 card adding the remote and credential surfaces adds them beside these,
/// under the same rules, rather than into the posture switch.

// MARK: - Geometry

/// The setup form's one figure, **derived from the body font** like every other surface's
/// (10-accessibility.md ▸ Text scaling: "relative text styles everywhere, no fixed point sizes").
///
/// It is what survives `BoardSettingsSheetLayout`, which retired with the sheet 2026-08-07: the
/// sheet's width and section inset were a *window's* geometry and the popover supplies both itself
/// (`BoardInfoView`), but the identity form's label column is the form's own and travelled with it.
enum BoardGitSetupLayout {

    /// 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 renders inline in the Git tab's no-repository posture** since the 2026-08-07 reversal — under
/// the note that states the fact, where the Board Settings… door stood between 2026-07-31 and that
/// day. The posture is unchanged in every other respect: the fact, then the offer.
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 popover **stays open** under the lock and disables in place, which is the style popover's
    /// settled precedent (03 ▸ Board popover).
    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 control is on
        // screen, 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 control's visibility *is* the Git tab's, and the tab's is the popover's — a narrower
        // window than the sheet's was until 2026-08-07, and the right one: a popover dismissed by a
        // click outside is precisely the user leaving the form. Two other disappearances are not
        // dismissals and both are correct: switching to Info or Theme, which puts the question away
        // as surely as closing the popover, and a *successful* add-git flipping the mode out from
        // under this posture — the failure slot empties because there is nothing left to fail.
        .onAppear { git.noteFormVisible(true) }
        .onDisappear { git.noteFormVisible(false) }
    }
}

// MARK: - Commit identity

/// **The name and email that repo-local `.git/config` carries** (06-history-undo.md ▸ Interaction
/// with external writers: "the 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").
///
/// The fields moved to the sheet with the 2026-07-31 split and back to the popover's Git tab with the
/// 2026-08-07 reversal, 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 tab.
///
/// ### 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 tab 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 surface stays
/// open.
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 they are 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 form cadence (a focused
    /// field keeps its keystrokes; dismissing the surface stops the poll)." The surface the ruling
    /// named was the sheet; since 2026-08-07 it is the popover's Git tab, which is a *shorter* life
    /// than the sheet's and therefore a strictly smaller 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 popover closing or the tab strip moving off Git.
            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: BoardGitSetupLayout.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 popover 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) }
    }
}