import Foundation
import SwiftUI

/// **The board popover's Git tab** (03-board-ui.md § Board popover ▸ Git tab, settled 2026-08-07) —
/// the pre-tab closing git section rehomed *whole*, and nothing more: **the daily face, and only
/// that** (the 2026-07-31 popover/sheet split stands, unchanged by the move). A repository-facts
/// dossier in the Info tab's register — commit counts, last-commit dates — was considered in the Git
/// session and declined: the popover's git surface is for *operating*, and per-item history is the
/// card window's History section (05-card-window.md).
///
/// ### No "Git" header anywhere in this tab
///
/// The tab's own label does the naming work the section's header used to (the design's phrasing), so
/// every posture below renders its content bare where the pre-tab section stacked it under a
/// `sectionHeader("Git")` and a `Divider()`. The tabs already sit under the popover header's own
/// divider; a second rule and a second "Git" would be the surface naming itself twice.
///
/// ### Membership is the posture, so this view never renders an empty state
///
/// `BoardInfoTab.available(tier:mode:hasGitDirectory:)` drops the Git tab from the strip exactly when
/// `BoardGitSection` resolves to `.absent`, so this view is never built for the free tier's ordinary
/// board. That is 12-editions.md's "absent, no placeholder" rule carried up to the tab strip — a
/// standing Git tab on every free board would be the standing ad for Pro that 12 forbids.

// MARK: - The posture

/// **What the Git tab shows, for one board** (03-board-ui.md ▸ Board popover ▸ Git tab;
/// 06-history-undo.md ▸ Rules; 12-editions.md ▸ The free tier and `.git`) — a pure function of two
/// facts, so the posture matrix is provable without a popover on screen.
///
/// The free tier's two cases are settled 2026-07-27: absent on an ordinary board, a one-line Pro
/// pointer on a board carrying an inert `.git`. The Pro cases are the mode, one to one — and the
/// mode-`none` and repo-nested pair is where the design is most insistent: a repo-nested board gets
/// **prose, not a disabled button**. "The option is absent because it *can't* apply, and the UI
/// should teach that rather than look broken" (06 ▸ Rules). `unverifiable` (the git-detection axis)
/// joins as a fourth Pro case, structurally identical to `repoNested` but worded as its own honest
/// prose — a denial is not a nesting.
///
/// **The 2026-07-31 popover/sheet split thinned two of these cases without removing either.** Setup
/// left the popover for the board settings sheet, so mode `none` no longer renders an action here at
/// all (the case was called `.addGit` when it did — a name that would now be describing a control
/// that lives in another file, so it is `.noRepository`), and the git-mode case lost branch creation
/// and the identity fields. What each case still *is* is a posture, which is why the matrix and its
/// test survived the move unchanged.
///
/// **The 2026-08-07 tab restructure rehomed the surface, not the matrix** — the same six cases, now
/// rendered as one tab each by `BoardGitTabView` rather than as a closing section of the popover's
/// single pane. `.absent` grew one further job in the move: it is what `BoardInfoTab.available` reads
/// to decide whether the Git tab is in the strip at all, which is why membership can never disagree
/// with what the tab would have rendered.
enum BoardGitSection: Equatable, CaseIterable {

    /// Nothing at all — the free tier's ordinary board, where "the popover is rename + style,
    /// complete in itself". Since the restructure this is a **missing tab**, not an empty one
    /// (`BoardInfoTab.available`).
    case absent

    /// The free tier's one-line explanation of an inert `.git`, and the app's one in-context pointer
    /// to Pro (12 ▸ Tier naming).
    case proPointer

    /// Pro, mode `none`: a board that could have a history and has none. There is no daily surface
    /// for that — the tab is one caption stating the fact above the Board Settings… door, where
    /// add-git now lives (03 ▸ Board settings sheet). The header-plus-door posture blessed
    /// 2026-08-06, restated for a surface whose header is now the tab label.
    case noRepository

    /// Pro, repo-nested: the honest explanation, no action — and no Board Settings… row either,
    /// since nothing setup-shaped can apply (`BoardSettingsAvailability`).
    case repoNested

    /// Pro, unverifiable: **not** `.repoNested` — a denied ancestor check, not a found repository
    /// (06 ▸ Rules ▸ Detection, "Denial is not absence"). Structurally identical to `.repoNested`
    /// (no action, no Board Settings… row, `BoardSettingsAvailability` false), but its own case so
    /// the view renders its own honest prose rather than the nested sentence — "unverifiable" is not
    /// "nested".
    case unverifiable

    /// Pro, git mode: the branch/source line with the **switch** picker, the abnormal-state
    /// explanation when the surface is held, and the Board Settings… row. The remote half —
    /// tracking, Pull/Push, the status badges — is 07-sync-collab.md's own card and joins this same
    /// posture.
    case branch

    static func resolve(tier: Tier, mode: BoardGitMode, hasGitDirectory: Bool) -> BoardGitSection {
        switch tier {
        case .free:
            // Detection never runs under the free tier, so the mode is not consulted here — the one
            // question asked is whether the folder carries a `.git`, which is what the pointer is
            // about (12: "any `.git` is inert … a stray like any other, preserved verbatim").
            return hasGitDirectory ? .proPointer : .absent
        case .pro:
            switch mode {
            case .none: return .noRepository
            case .git: return .branch
            case .repoNested: return .repoNested
            case .unverifiable: return .unverifiable
            }
        }
    }
}

// MARK: - The notes

/// **The no-repository caption** (03-board-ui.md ▸ Board popover ▸ Git tab) — the fact, stated, above
/// the Board Settings… door.
///
/// One sentence in its siblings' register, and deliberately not a header: the tab label already says
/// "Git", so what is left to say is what this board's git story currently *is*. "Yet" is the whole
/// posture in a word — the door directly below it is where a user says otherwise.
private struct BoardGitNoRepositoryNote: View {

    var body: some View {
        Text("This board has no git history yet.")
            .font(.caption)
            .foregroundStyle(.secondary)
            .fixedSize(horizontal: false, vertical: true)
    }
}

/// **The repo-nested explanation** (06-history-undo.md ▸ Rules), worded as the design words it:
/// short prose in place of an action, never a hidden or greyed-out add-git.
private struct BoardGitNestedNote: View {

    var body: some View {
        Text("This board lives inside a repository; Lanework leaves it to that repository.")
            .font(.caption)
            .foregroundStyle(.secondary)
            .fixedSize(horizontal: false, vertical: true)
    }
}

/// **The unverifiable explanation** (06-history-undo.md ▸ Rules ▸ Detection, "Denial is not
/// absence", ruled 2026-07-31), worded as its own honest sentence rather than borrowing
/// `BoardGitNestedNote`'s — a denied ancestor check is not a found repository, and telling a user
/// their board is nested when the truth is "couldn't check" would be a lie dressed as caution.
private struct BoardGitUnverifiableNote: View {

    var body: some View {
        Text("Lanework couldn't verify whether this board sits inside a repository, so it isn't offering to add one here.")
            .font(.caption)
            .foregroundStyle(.secondary)
            .fixedSize(horizontal: false, vertical: true)
    }
}

/// The contextual git note — **a quiet signpost, not a feature** (12-editions.md ▸ The free tier and
/// `.git`, settled 2026-07-27, carried through the one-app collapse). The free tier has no git
/// integration (that is the Pro subscription's), so this is not a grow-in-place slot the way the old
/// `BoardGitSlot` placeholder was: there is nothing here to grow. The free tier's whole git story is
/// one line, shown only when it is true — and it is **the one in-context pointer to Pro**, the second
/// of the three places the app names it (12 ▸ Tier naming; the other two are `AboutBox` and the
/// Settings Pro section).
///
/// On an ordinary board nothing instantiates this type at all — the board has no Git tab to put it in
/// (`BoardInfoTab.available`), matching the card window's absent History section (12: "absent, no
/// placeholder"). Only a board that carries an inert `.git` (12 ▸ the inert posture: "any `.git` is
/// inert" — the free tier never reads or writes it, whether the board's own or one a lapsed
/// subscription left behind) earns this note, worded exactly as 12 rules: an honest explanation of
/// what the folder is, named exactly where the question arises, never a standing ad for Pro.
///
/// Not `private`: `hasGitDirectory(at:)` is the pure seam `BoardInfoPopoverTests.swift` pins directly
/// (a fixture board with `.git` → true, without → false), and `BoardInfoView.init` is its one caller
/// in the app — the popover asks the question once at open and hands the answer down, both to this
/// tab and to `BoardInfoTab.available`.
struct BoardGitNote: View {

    var body: some View {
        Text("This board has a git history. Lanework Pro works with it.")
            .font(.caption)
            .foregroundStyle(.secondary)
            .fixedSize(horizontal: false, vertical: true)
    }

    /// Whether `boardRoot` carries a `.git` entry — the free tier's entire detection story, and a deliberately
    /// small one: nothing in `BoardStore`, `BoardModel`, or `BoardLoader` tracks this as a live fact
    /// today, because nothing needs it to be live. `FolderWatcher` filters `.git` out of the folder
    /// watch by design (§ .git filtering — it exists to ignore git churn), so there is no reload
    /// event this could hang off even if it wanted to; a plain, read-only `FileManager` check taken
    /// once, at the moment the popover is built, is the honest amount of machinery for a single quiet
    /// line. A `.git` added or removed while the popover happens to be open is stale until the next
    /// open — a gap this note's own posture makes harmless, since it is a signpost, not a control.
    static func hasGitDirectory(at boardRoot: URL) -> Bool {
        FileManager.default.fileExists(atPath: boardRoot.appendingPathComponent(".git").path)
    }
}

// MARK: - The tab

/// The Git tab's surface: whichever of the six postures this board is in, and the Board Settings…
/// door where it applies.
struct BoardGitTabView: View {

    let store: BoardStore

    /// The tier and the git state this board's **session** composed with, handed down from
    /// `BoardInfoView` rather than re-derived — 12-editions.md ▸ The entitlement ("a lapse never
    /// interrupts an open session"). `git` is `@Observable`, so a branch switch or a pause landing
    /// while the tab is open repaints it.
    let tier: Tier
    let git: HistoryStore?

    /// The window's settings sheet, so this tab can carry the **Board Settings…** row that opens it.
    /// `nil` where there is no window to present a sheet on, which reads as a tab with no door.
    let settings: BoardSettingsPresentation?

    /// The free tier's one question about the board's folder, asked once in `BoardInfoView.init` and
    /// passed down — the same answer the tab strip's membership was computed from, so the tab and its
    /// content can never disagree about which posture this board is in.
    let hasGitDirectory: Bool

    /// The popover's own padding figure (`BoardInfoView.inset`), matching `BoardInfoTabView`'s and
    /// `BoardThemeTabView`'s own parameter — the tab pads by this amount instead of restating the
    /// derivation.
    let inset: CGFloat

    /// **The popover's own dismissal**, used by exactly one control: the Board Settings… row, whose
    /// job is to close this surface and open the sheet. The popover is presented by `isPresented`, so
    /// the environment action drives the same flag the widget's button does — nothing here has to be
    /// handed the widget's binding to put it down.
    @Environment(\.dismiss) private var dismiss

    var body: some View {
        posture
            .padding(inset)
            .frame(maxWidth: .infinity, alignment: .leading)
    }

    /// The tab's content, posture by posture — see `BoardGitSection`. No section header and no
    /// dividers: the tab label names this surface, and the tabs already sit under the popover
    /// header's rule.
    @ViewBuilder
    private var posture: some View {
        switch BoardGitSection.resolve(tier: tier, mode: git?.mode ?? .none, hasGitDirectory: hasGitDirectory) {
        case .absent:
            // Unreachable, and kept honest rather than fatal: `BoardInfoTab.available` drops the Git
            // tab from the strip on exactly this posture, so nothing ever selects a tab that would
            // land here. Written as `EmptyView` because that is what the case *means* — if the
            // membership rule ever loosened, the free tier's ordinary board would render nothing,
            // which is still the design's answer for it (12: "absent, no placeholder").
            EmptyView()

        case .proPointer:
            BoardGitNote()

        case .noRepository:
            // Nothing daily to show on a board with no repository — so the tab is the fact and the
            // door. Add-git itself moved to the sheet with the 2026-07-31 split; what stays here is
            // the honest signpost that this board *could* have a history and where to say so.
            VStack(alignment: .leading, spacing: 6) {
                BoardGitNoRepositoryNote()
                boardSettingsRow
            }

        case .repoNested:
            BoardGitNestedNote()

        case .unverifiable:
            BoardGitUnverifiableNote()

        case .branch:
            VStack(alignment: .leading, spacing: 6) {
                if let git {
                    BoardGitControls(git: git, isEnabled: store.acceptsBoardMutations)
                }
                boardSettingsRow
            }
        }
    }

    /// **The popover's one setup affordance** (03-board-ui.md ▸ Board popover) — the sheet's first
    /// door, the menu row being the second (11-command-nexus.md).
    ///
    /// **Shown only where the sheet is reachable** (`BoardSettingsAvailability`): this tab describes
    /// *this board*, so a row pointing at a surface this board cannot have would be the disabled
    /// button 06 rules out one level up. The menu row is the opposite case and stays visible — a menu
    /// is an inventory of the app.
    ///
    /// **Dismiss first, then present.** The popover is transient and the sheet is not; leaving a
    /// transient surface hanging over a modal one would read as two surfaces arguing about which the
    /// user is in.
    ///
    /// Not disabled by the read-only lock: opening a configuration surface is not a mutation, and the
    /// controls inside it disable themselves (the Board Info ⌘I rule).
    @ViewBuilder
    private var boardSettingsRow: some View {
        if let settings, BoardSettingsAvailability.resolve(
            tier: tier,
            mode: git?.mode ?? .none,
            isRepositoryUnreadable: git?.isRepositoryUnreadable ?? false
        ) {
            Button("Board Settings…") {
                dismiss()
                settings.present()
            }
            .accessibilityHint("Opens the board settings sheet")
        }
    }
}