import Foundation
import Testing
@testable import Kanban

/// `AppModel` is mostly window bookkeeping that only means anything with a window on screen, but two
/// of its members are pure facts about a snapshot and both are load-bearing: the counts a welcome row
/// advertises, and the name a window title shows. Neither is observable from a unit test any other
/// way once it is wrong — a stale count looks like staleness, which the design accepts, and a wrong
/// count looks exactly the same.

// MARK: - Fixtures

/// Live and tombstoned at both levels, plus the case the ancestor walk exists for: live cards
/// underneath a tombstoned lane.
///
/// - lane 1 (live): two live cards, one tombstoned card
/// - lane 2 (**tombstoned**): two live cards, which render nowhere and must not count
/// - lane 3 (live): empty
@MainActor
private func makeMixedBoard() throws -> WriterFixture {
    let fixture = try WriterFixture()
    try fixture.item("", Item.board)

    try fixture.item(Ident.lane1, Item.rich(order: "1024", title: "Todo"))
    try fixture.item("\(Ident.lane1)/\(Ident.card1)", Item.rich(order: "1024", title: "First"))
    try fixture.item("\(Ident.lane1)/\(Ident.card2)", Item.rich(order: "2048", title: "Second"))

    try fixture.item(Ident.lane2, Item.rich(order: "2048", title: "Archive"))

    // The trash: cards in a sibling container, never lanes (03-board-ui.md § Trash).
    try fixture.item(".trash/\(Ident.card3)", Item.rich(order: "1024", title: "Gone"))
    try fixture.item(".trash/\(Ident.card4)", Item.rich(order: "2048", title: "Also gone"))
    return fixture
}

/// An `AppModel` whose app-side state lives in temp rather than in the app's real Application
/// Support home — both halves of it: the registry file, and the clipboard's staging store, whose
/// launch sweep would otherwise collect the developer's own staged copy.
@MainActor
private func makeModel() throws -> (model: AppModel, tearDown: () -> Void) {
    let folder = FileManager.default.temporaryDirectory
        .appendingPathComponent("AppModelTests-\(UUID().uuidString)", isDirectory: true)
    try FileManager.default.createDirectory(at: folder, withIntermediateDirectories: true)
    let model = AppModel(
        registryStorageURL: folder.appendingPathComponent("board-registry.json"),
        clipboardStagingRoot: folder.appendingPathComponent("Clipboard", isDirectory: true)
    )
    return (model, { try? FileManager.default.removeItem(at: folder) })
}

/// Opens a board the way `BoardWindowHost` does — record, acquire, name it for real, flag, begin —
/// so the close tests are closing something the app would recognise.
@MainActor
@discardableResult
private func openBoard(_ model: AppModel, at url: URL) throws -> BoardWindowRef {
    let ref = BoardWindowRef(url: url)
    let recordID = model.boardRegistry.recordOpen(of: url)
    let store = try model.storeRegistry.acquire(url)
    model.boardRegistry.syncDisplayState(id: recordID, title: AppModel.displayName(of: store), icon: nil, iconColor: nil)
    model.boardRegistry.setOpenNow(id: recordID)
    model.beginSession(ref: ref, store: store, recordID: recordID, access: nil)
    return ref
}

/// The same board with a **real repository** at its root, root commit and all — what a Pro session
/// detects as mode `git`, and therefore the only shape that composes a branch switcher to test the
/// settle step's seams through.
@MainActor
private func makeProGitBoard() throws -> WriterFixture {
    let fixture = try makeMixedBoard()
    guard case .success = GitRepository.create(at: fixture.root) else {
        fixture.tearDown()
        Issue.record("could not initialize a repository for the fixture board")
        throw CocoaError(.fileWriteUnknown)
    }
    return fixture
}

/// Opens a card window the way its host does — registered with the board's session — and leaves it
/// holding one fine step and an open Edit session, so it both *has* a stack to lose and answers the
/// save-or-discard step's `needsSettling` with `true`.
///
/// The step is registered through `BoardStore.registerStep` rather than pushed onto the provider, so
/// it is routed by the same line production routes a card-window gesture with (`on:` → the window's
/// stack) and carries the raw write the close fold would look for.
@MainActor
@discardableResult
private func openCardWindow(
    _ model: AppModel,
    board: BoardWindowRef,
    card id: String,
    store: BoardStore
) -> CardWindowSession {
    let window = CardWindowSession()
    model.registerCardWindow(CardWindowRef(board: board, cardID: ItemID(rawValue: id)), session: window)
    window.body.beginEditSession()
    store.registerStep(
        "Edit Card",
        on: window.undo,
        undoExpects: [.present(.card(ItemID(rawValue: id)), .body("after\n"))],
        redoExpects: [.present(.card(ItemID(rawValue: id)), .body("before\n"))],
        undo: { _ in },
        redo: { _ in }
    )
    return window
}

// MARK: - Tests

@MainActor
@Suite("AppModel")
struct AppModelTests {

    // MARK: Live-only counts

    @Test("The recents counts are working items only — the trash is an errand, not inventory")
    func liveCountsExcludeTheTrash() throws {
        let fixture = try makeMixedBoard()
        defer { fixture.tearDown() }
        let snapshot = try BoardLoader.load(boardRoot: fixture.root).model

        // The snapshot itself keeps everything — the trash is a sibling container — so this is a
        // genuine exclusion, not a property of the load.
        #expect(snapshot.lanes.count == 2)
        #expect(snapshot.trash.count == 2)

        let counts = AppModel.liveCounts(of: snapshot)
        #expect(counts.lanes == 2)
        // 02 § Per-board app state, re-grounded 2026-07-28: "cards in `.trash/` don't count; the row
        // advertises the board's working size". The walk reads `snapshot.lanes` and the trash is
        // `snapshot.trash`, so the exclusion is by construction and none could be forgotten.
        #expect(counts.cards == 2)
    }

    @Test("A board with nothing on it counts zero rather than declining to answer")
    func liveCountsOfAnEmptyBoard() throws {
        let fixture = try WriterFixture()
        defer { fixture.tearDown() }
        try fixture.item("", Item.board)
        try fixture.item(".trash/\(Ident.card1)", Item.rich(order: "1024", title: "Gone"))

        let counts = AppModel.liveCounts(of: try BoardLoader.load(boardRoot: fixture.root).model)
        #expect(counts.lanes == 0)
        #expect(counts.cards == 0, "a board whose only content is trash advertises no working size")
    }

    // MARK: Display name

    @Test("A board's display name is its title, falling back to the folder name sans extension")
    func displayNameFallsBackToTheFolderName() throws {
        let fixture = try WriterFixture()
        defer { fixture.tearDown() }

        try fixture.item("Weekly.kanban", "---\nschema: 1\ntitle: Weekly Review\n---\nbody\n")
        let titled = try BoardStore(rootURL: fixture.url("Weekly.kanban"))
        #expect(AppModel.displayName(of: titled) == "Weekly Review")

        try fixture.item("Untitled Board.kanban", "---\nschema: 1\n---\nbody\n")
        let untitled = try BoardStore(rootURL: fixture.url("Untitled Board.kanban"))
        #expect(AppModel.displayName(of: untitled) == "Untitled Board", "sans extension, per 01 § Board naming")
    }

    // MARK: Record before load

    /// `BoardWindowHost.start()`'s own sequence for a board whose load fails fail-fast: record
    /// first, then attempt the load, then (on failure) file the launch failure and refresh the
    /// cached recents this test reads back through `WelcomeRow.derive`, exactly as welcome would.
    @Test("A first open that fails fail-fast still records — a folder-name row carrying the failure")
    func failFastOpenStillRecordsAndSurfacesRowLevel() async throws {
        let fixture = try WriterFixture()
        defer { fixture.tearDown() }
        // The board root's own `index.md` fails to parse — fail-fast's own case, thrown the moment
        // `BoardStore.init` (behind `storeRegistry.acquire`) walks it.
        try fixture.item("", "---\nschema: 1\nlabels: [a, b\n---\nbody\n")
        let (model, tearDown) = try makeModel()
        defer { tearDown() }

        let ref = BoardWindowRef(url: fixture.root)
        let recordID = model.boardRegistry.recordOpen(of: fixture.root)

        var failureMessage: String?
        do throws(BoardLoadFailure) {
            _ = try model.storeRegistry.acquire(fixture.root)
            Issue.record("expected the load to fail fail-fast")
        } catch {
            failureMessage = error.description
            model.recordLaunchFailure(path: ref.path, message: error.description)
        }
        model.refreshRecents()

        // The record exists, provisionally named after the folder — nothing loaded, so nothing else
        // was there to trust (02 § Per-board app state).
        let record = try #require(model.boardRegistry.record(id: recordID))
        #expect(record.displayName == fixture.root.deletingPathExtension().lastPathComponent)
        #expect(record.laneCount == nil, "never opened successfully, so nothing was ever counted")

        // And the failure lands on that very row — uniform with a failed restoration's row, never
        // the separate list of failures naming no record.
        let derived = WelcomeRow.derive(recents: model.recents, failures: model.launchFailures)
        let row = try #require(derived.rows.first { $0.id == recordID })
        guard case let .failed(message) = row.caption else {
            Issue.record("expected the row to carry the failure, got \(row.caption)")
            return
        }
        #expect(message == failureMessage)
        #expect(derived.unmatched.isEmpty, "the failure landed on a row it already had, not the fallback list")
    }

    @Test("Retrying a fail-fast open reuses the same record, and a later success replaces its name")
    func retryingAFailFastOpenReusesTheRecord() async throws {
        let fixture = try WriterFixture()
        defer { fixture.tearDown() }
        let brokenIndex = "---\nschema: 1\nlabels: [a, b\n---\nbody\n"
        try fixture.item("", brokenIndex)
        let (model, tearDown) = try makeModel()
        defer { tearDown() }

        let ref = BoardWindowRef(url: fixture.root)
        let firstAttempt = model.boardRegistry.recordOpen(of: fixture.root)
        do throws(BoardLoadFailure) {
            _ = try model.storeRegistry.acquire(fixture.root)
            Issue.record("expected the load to fail fail-fast")
        } catch {
            model.recordLaunchFailure(path: ref.path, message: error.description)
        }
        model.refreshRecents()
        #expect(model.boardRegistry.recents().count == 1, "a retry updates the one record, it does not add one")

        // The user fixes the file and retries — `BoardWindowHost.start()`'s exact sequence again.
        try fixture.item("", "---\nschema: 1\ntitle: Fixed Board\n---\nbody\n")
        let secondAttempt = model.boardRegistry.recordOpen(of: fixture.root)
        #expect(secondAttempt == firstAttempt, "the same folder is the same board, failed or not")

        let store = try model.storeRegistry.acquire(fixture.root)
        model.boardRegistry.syncDisplayState(id: secondAttempt, title: AppModel.displayName(of: store), icon: nil, iconColor: nil)

        let record = try #require(model.boardRegistry.record(id: secondAttempt))
        #expect(record.displayName == "Fixed Board", "the first success replaces the provisional folder name")
    }

    // MARK: Sessions

    @Test("A user close stamps live counts, unflags the board, and lets the store go")
    func closingABoardRunsTheRealFlush() async throws {
        let fixture = try makeMixedBoard()
        defer { fixture.tearDown() }
        let (model, tearDown) = try makeModel()
        defer { tearDown() }

        let ref = try openBoard(model, at: fixture.root)
        let recordID = try #require(model.session(for: ref)?.recordID)
        #expect(model.hasOpenBoards)
        #expect(model.storeRegistry.liveStore(for: fixture.root) != nil)

        await model.closeBoard(ref: ref, cause: .userClose)

        #expect(model.session(for: ref) == nil)
        #expect(!model.hasOpenBoards)
        #expect(model.storeRegistry.liveStore(for: fixture.root) == nil, "the last reference went with the session")

        let record = try #require(model.boardRegistry.record(id: recordID))
        #expect(record.laneCount == 2, "the counts the welcome row will show are the working ones")
        #expect(record.cardCount == 2)
        #expect(!record.isOpenNow)
        #expect(model.boardRegistry.restorables().isEmpty)

        // Twice is a no-op, which is what lets the window's close interception and its disappear both
        // call this without the sequence running twice.
        await model.closeBoard(ref: ref, cause: .userClose)
        #expect(model.boardRegistry.record(id: recordID)?.isOpenNow == false)
    }

    @Test("Quit closes every board and leaves them all flagged for the next launch")
    func quitFlushesEveryBoardAndPreservesTheRestorationSet() async throws {
        let first = try makeMixedBoard()
        defer { first.tearDown() }
        let second = try makeMixedBoard()
        defer { second.tearDown() }
        let (model, tearDown) = try makeModel()
        defer { tearDown() }

        try openBoard(model, at: first.root)
        try openBoard(model, at: second.root)
        #expect(model.storeRegistry.openBoardCount == 2)

        await model.flushAllBoardsForQuit()

        #expect(!model.hasOpenBoards)
        #expect(model.storeRegistry.openBoardCount == 0, "every board's store was released, not just the first")
        #expect(model.boardRegistry.restorables().count == 2, "the flags describe what was open at quit")
        for row in model.boardRegistry.restorables() {
            #expect(row.record.laneCount == 2, "and every board was stamped on the way out")
        }
    }

    @Test("Card windows join and leave their board's session")
    func cardWindowMembershipIsTracked() throws {
        let fixture = try makeMixedBoard()
        defer { fixture.tearDown() }
        let (model, tearDown) = try makeModel()
        defer { tearDown() }

        let ref = try openBoard(model, at: fixture.root)
        let card = CardWindowRef(board: ref, cardID: ItemID(rawValue: Ident.card1))
        let session = CardWindowSession()

        model.registerCardWindow(card, session: session)
        #expect(model.session(for: ref)?.cardRefs == [card])

        // A card window against a board with no session is the one thing the ownership rule forbids;
        // registering it would leave an entry the close flush never drains.
        let orphan = CardWindowRef(boardPath: "/nowhere", cardID: Ident.card2)
        model.registerCardWindow(orphan, session: CardWindowSession())
        #expect(model.session(for: orphan.board) == nil)

        model.unregisterCardWindow(card)
        #expect(model.session(for: ref)?.cardRefs.isEmpty == true)

        model.storeRegistry.release(try #require(model.session(for: ref)?.store))
    }

    // MARK: The branch switch's settle

    /// **"The settle also clears each open card window's fine undo stack"** (06-history-undo.md
    /// ▸ Branch switching, ruled 2026-07-31): "pre-switch steps describe the branch being left — Save
    /// All and Discard alike end with every window's stack empty … the windows stay open, following
    /// their cards onto the new branch with fresh stacks."
    ///
    /// This is an `AppModel` test rather than a `GitBranchSwitcher` one because the clear is a fact
    /// about the **composition**: the switcher's settle seam, the card-window registry and the stacks
    /// themselves only meet in `wireBranchSwitching`, and a switcher wired by hand would be a test
    /// asserting its own wiring (the `a381fac` lesson, applied one card later).
    @Test(
        "The branch switch's settle empties every open card window's fine stack",
        arguments: [SessionSettleChoice.saveAll, .discard]
    )
    func theSettleClearsEveryFineStack(answering choice: SessionSettleChoice) async throws {
        let board = try makeProGitBoard()
        defer { board.tearDown() }
        let (model, tearDown) = try makeModel()
        defer { tearDown() }
        model.currentTier = { .pro }

        let ref = try openBoard(model, at: board.root)
        let session = try #require(model.session(for: ref))
        let switcher = try #require(session.git?.switcher)

        let windows = [Ident.card1, Ident.card2].map { id in
            openCardWindow(model, board: ref, card: id, store: session.store)
        }
        #expect(windows.allSatisfy { $0.undo.stack.canUndo })
        #expect(windows.allSatisfy { $0.undo.netEffect() != nil }, "a session with a net effect to fold")

        model.settleAsk = { _ in choice }
        #expect(await switcher.settleSessions?() == .proceed)

        for window in windows {
            #expect(!window.undo.stack.canUndo, "the stack describes the branch being left")
            #expect(!window.undo.manager.canUndo, "and ⌘Z in that window answers with it")
        }
        // "The windows stay open, following their cards onto the new branch with fresh stacks."
        #expect(model.session(for: ref)?.cardRefs.count == 2)
    }

    /// **Closing the stack is not closing the window.** The coarse step a card window owes its board is
    /// registered at *close*, folded from this stack (13-native-undo.md ▸ Rules ▸ "Window close
    /// coarsens"); a settle clear registers nothing at all, which is exactly what
    /// `registerCardSession` answering `false` — and the deferred purge staying the caller's — says.
    @Test("A settle clear registers no coarse step — the fold that would have run finds nothing")
    func theClearRegistersNoCoarseStep() async throws {
        let board = try makeProGitBoard()
        defer { board.tearDown() }
        let (model, tearDown) = try makeModel()
        defer { tearDown() }
        model.currentTier = { .pro }

        let ref = try openBoard(model, at: board.root)
        let session = try #require(model.session(for: ref))
        let switcher = try #require(session.git?.switcher)
        let window = openCardWindow(model, board: ref, card: Ident.card1, store: session.store)

        model.settleAsk = { _ in .saveAll }
        #expect(await switcher.settleSessions?() == .proceed)

        #expect(window.undo.netEffect() == nil, "nothing left to fold")
        var purged = false
        let registered = session.store.registerCardSession(
            window.undo,
            inCard: ItemID(rawValue: Ident.card1),
            retiring: { purged = true }
        )
        #expect(!registered, "a close arriving right after the switch registers nothing")
        #expect(!purged, "and the deferred purge is still the caller's, not a step's")
    }

    /// "**Cancel** keeps the current branch and the sessions" — and now their stacks with them. The
    /// same `if` that withholds the staging release withholds this.
    @Test("Cancel clears nothing")
    func cancelKeepsTheFineStacks() async throws {
        let board = try makeProGitBoard()
        defer { board.tearDown() }
        let (model, tearDown) = try makeModel()
        defer { tearDown() }
        model.currentTier = { .pro }

        let ref = try openBoard(model, at: board.root)
        let session = try #require(model.session(for: ref))
        let switcher = try #require(session.git?.switcher)
        let window = openCardWindow(model, board: ref, card: Ident.card1, store: session.store)

        model.settleAsk = { _ in .cancel }
        #expect(await switcher.settleSessions?() == .cancelled)
        #expect(window.undo.stack.canUndo)
        #expect(window.undo.netEffect() != nil)
    }

    // MARK: Launch restoration

    /// App ▸ Settings…'s "Restore open boards at launch" (11-command-nexus.md) gates the flagged set
    /// by AND, not by either half alone: the preference off never restores even with boards flagged
    /// (a user who turned it off gets welcome, full stop), and the preference on restores nothing when
    /// there is nothing flagged (an ordinary first launch, which shows welcome exactly as it always
    /// has, not an empty restoration pass).
    @Test(
        "The launch-restoration gate is the preference AND something to restore",
        arguments: [
            (preference: true, hasRestorables: true, expected: true),
            (preference: true, hasRestorables: false, expected: false),
            (preference: false, hasRestorables: true, expected: false),
            (preference: false, hasRestorables: false, expected: false),
        ]
    )
    func launchRestorationGate(preference: Bool, hasRestorables: Bool, expected: Bool) {
        #expect(AppModel.shouldRestoreAtLaunch(preference: preference, hasRestorables: hasRestorables) == expected)
    }
}