import CoreGraphics
import Foundation
import Testing
@testable import Kanban

/// 04-interactions.md § Selection's pointer grammar and § The trash's extensions to it, branch by
/// branch — plus the anchor that makes ⇧-click mean anything, and the rubber band's arithmetic.
///
/// The grammar is written as a pure function precisely so it can be tested like one: a click, a
/// selection, an anchor and a snapshot in, a selection and an anchor out — no window, no gesture, no
/// modifier flags. The boards underneath are **real loads off real temp trees**, because every rule
/// here reads `isDeleted`, card ordering, or `TrashModel`'s sort, and a hand-built `BoardModel`
/// would let all three drift from what the loader actually produces.
///
/// `WriterFixture`, `Ident` and `Item` live in `WriterTestSupport.swift`.

// MARK: - Fixtures

/// More literal identities than `Ident` offers: a three-lane range needs five cards, and the trash's
/// interleaving needs entries whose folder names are distinguishable in the sort's tie-break.
private enum More {
    static let card5 = "aaaaaaaa-aaaa-4aaa-8aaa-aaaaaaaaaaaa"
    static let laneX = "bbbbbbbb-bbbb-4bbb-8bbb-bbbbbbbbbbbb"
    static let laneY = "cccccccc-cccc-4ccc-8ccc-cccccccccccc"
}

private func tombstoned(order: String, title: String, deleted: String = "2026-03-03T09:00:00Z") -> String {
    """
    ---
    schema: 1
    title: \(title)
    order: \(order)
    deleted: \(deleted)
    ---
    \(title) body.

    """
}

/// Three live lanes, five live cards and one tombstoned card — enough that a flatten-order range
/// crosses two lane boundaries and has something to *skip* on the way.
///
/// Flatten order of the live cards is `[card1, card2, card3, card5]`; `card4` carries its own
/// `deleted:` and is in none of it.
@MainActor
private func makeLiveBoard() 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: "Doing"))
    try fixture.item("\(Ident.lane2)/\(Ident.card3)", Item.rich(order: "1024", title: "Third"))
    try fixture.item("\(Ident.lane2)/\(Ident.card4)", tombstoned(order: "2048", title: "Fourth"))
    try fixture.item(Ident.lane3, Item.rich(order: "3072", title: "Done"))
    try fixture.item("\(Ident.lane3)/\(More.card5)", Item.rich(order: "1024", title: "Fifth"))
    return fixture
}

/// A trash whose two row kinds **interleave**, which is the only shape that can prove a range skips.
///
/// `TrashModel`'s sort is newest `deleted` first, so the entry order is
/// `[card1, laneX, card2, laneY, card3]` — a card range from `card1` to `card3` has two lane rows
/// sitting inside its span, and a lane range from `laneX` to `laneY` has a card row inside its own.
@MainActor
private func makeTrashBoard() 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)", tombstoned(order: "1024", title: "First", deleted: "2026-03-05T10:00:00Z"))
    try fixture.item("\(Ident.lane1)/\(Ident.card2)", tombstoned(order: "2048", title: "Second", deleted: "2026-03-05T08:00:00Z"))
    try fixture.item("\(Ident.lane1)/\(Ident.card3)", tombstoned(order: "3072", title: "Third", deleted: "2026-03-05T06:00:00Z"))
    try fixture.item(More.laneX, tombstoned(order: "2048", title: "Archive", deleted: "2026-03-05T09:00:00Z"))
    try fixture.item(More.laneY, tombstoned(order: "3072", title: "Old", deleted: "2026-03-05T07:00:00Z"))
    return fixture
}

private let lane1 = ItemID(rawValue: Ident.lane1)
private let lane2 = ItemID(rawValue: Ident.lane2)
private let lane3 = ItemID(rawValue: Ident.lane3)
private let card1 = ItemID(rawValue: Ident.card1)
private let card2 = ItemID(rawValue: Ident.card2)
private let card3 = ItemID(rawValue: Ident.card3)
private let card4 = ItemID(rawValue: Ident.card4)
private let card5 = ItemID(rawValue: More.card5)
private let laneX = ItemID(rawValue: More.laneX)
private let laneY = ItemID(rawValue: More.laneY)

private func load(_ fixture: WriterFixture) throws -> BoardModel {
    try BoardLoader.load(boardRoot: fixture.root).model
}

private func target(_ id: ItemID, _ kind: SelectionKind, _ side: Liveness = .live) -> SelectionTarget {
    SelectionTarget(id: id, kind: kind, side: side)
}

private func set(_ ids: Set<ItemID>, _ side: Liveness = .live) -> ItemReferenceSet {
    ItemReferenceSet(ids: ids, liveness: side)
}

/// One click, with the grammar's own defaults filled in.
private func click(
    _ target: SelectionTarget,
    _ modifier: ClickModifier,
    selection: ItemReferenceSet = .empty,
    anchor: ItemID? = nil,
    in snapshot: BoardModel,
    togglesOnRepeat: Bool = false
) -> SelectionGrammar.Outcome {
    SelectionGrammar.click(
        target,
        modifier: modifier,
        selection: selection,
        anchor: anchor,
        snapshot: snapshot,
        togglesOnRepeat: togglesOnRepeat
    )
}

// MARK: - The order lists

@MainActor
@Suite("SelectionGrammar ▸ order")
struct SelectionOrderTests {

    @Test("Live cards flatten lane order first, then card order — tombstones excluded")
    func flattenOrder() throws {
        let fixture = try makeLiveBoard()
        defer { fixture.tearDown() }
        let snapshot = try load(fixture)

        // "Lane `order` first, then card `order` (a cross-lane selection flattens left-to-right,
        // top-to-bottom)" — the multi-drag order (04-interactions.md ▸ Drag and drop).
        #expect(SelectionGrammar.liveCards(in: snapshot) == [card1, card2, card3, card5])
        #expect(SelectionGrammar.liveLanes(in: snapshot) == [lane1, lane2, lane3])
    }

    @Test("Trash order lists are one sort, filtered to one kind")
    func trashOrderPerKind() throws {
        let fixture = try makeTrashBoard()
        defer { fixture.tearDown() }
        let snapshot = try load(fixture)

        // The single ordering the quasi-lane shows, newest first.
        #expect(TrashModel.entries(of: snapshot).map(\.id) == [card1, laneX, card2, laneY, card3])
        // Each kind's list is that ordering with the other kind's rows dropped — which is exactly
        // what makes a ⇧-range step over them (04-interactions.md ▸ The trash).
        #expect(SelectionGrammar.trashEntries(of: .card, in: snapshot) == [card1, card2, card3])
        #expect(SelectionGrammar.trashEntries(of: .lane, in: snapshot) == [laneX, laneY])
    }

    @Test("A selection's kind is derived from the snapshot, and a ghost selection has none")
    func kindDerivation() throws {
        let fixture = try makeLiveBoard()
        defer { fixture.tearDown() }
        let snapshot = try load(fixture)

        #expect(SelectionGrammar.kind(of: set([card1, card3]), in: snapshot) == .card)
        #expect(SelectionGrammar.kind(of: set([lane2]), in: snapshot) == .lane)
        #expect(SelectionGrammar.kind(of: .empty, in: snapshot) == nil)
        // A tombstoned card is on neither side's live list, and the live side is what this set says.
        #expect(SelectionGrammar.kind(of: set([card4]), in: snapshot) == nil)
        // Members that name nothing are ignored; one that names something still answers.
        #expect(SelectionGrammar.kind(of: set([card4, card1]), in: snapshot) == .card)
    }
}

// MARK: - Plain

@MainActor
@Suite("SelectionGrammar ▸ plain click")
struct PlainClickTests {

    @Test("A plain click replaces the selection and becomes the anchor")
    func replacesAndAnchors() throws {
        let fixture = try makeLiveBoard()
        defer { fixture.tearDown() }
        let snapshot = try load(fixture)

        let outcome = click(target(card3, .card), .plain, selection: set([card1, card2]), anchor: card1, in: snapshot)
        #expect(outcome.selection == set([card3]))
        #expect(outcome.anchor == card3)
    }

    @Test("Click again unselects — but only where the design gives that behaviour, and only on a sole selection")
    func toggleOffIsSoleMembershipOnly() throws {
        let fixture = try makeLiveBoard()
        defer { fixture.tearDown() }
        let snapshot = try load(fixture)

        // "Single click selects the lane (click again to unselect)", and the header "toggles like
        // empty space (settled)".
        let off = click(target(lane1, .lane), .plain, selection: set([lane1]), anchor: lane1, in: snapshot, togglesOnRepeat: true)
        #expect(off.selection.isEmpty)
        #expect(off.anchor == nil)

        // A multi-lane selection containing this lane is *narrowed*, not wiped: the toggle is about
        // the lane the user already had alone, not about a set they built with ⌘.
        let narrowed = click(target(lane1, .lane), .plain, selection: set([lane1, lane2]), anchor: lane2, in: snapshot, togglesOnRepeat: true)
        #expect(narrowed.selection == set([lane1]))
        #expect(narrowed.anchor == lane1)

        // A card face never toggles off — Finder does not deselect a file by clicking it twice.
        let card = click(target(card1, .card), .plain, selection: set([card1]), anchor: card1, in: snapshot)
        #expect(card.selection == set([card1]))
        #expect(card.anchor == card1)

        // Nor does the toggle reach across the boundary: a live click on a trashed sole selection
        // of the same id is a replace.
        let crossed = click(target(lane1, .lane), .plain, selection: set([lane1], .trashed), anchor: lane1, in: snapshot, togglesOnRepeat: true)
        #expect(crossed.selection == set([lane1]))
    }
}

// MARK: - Command

@MainActor
@Suite("SelectionGrammar ▸ ⌘-click")
struct CommandClickTests {

    @Test("⌘-click toggles within one kind, and the click is the new anchor either way")
    func togglesWithinKind() throws {
        let fixture = try makeLiveBoard()
        defer { fixture.tearDown() }
        let snapshot = try load(fixture)

        let added = click(target(card3, .card), .command, selection: set([card1]), anchor: card1, in: snapshot)
        #expect(added.selection == set([card1, card3]))
        #expect(added.anchor == card3)

        let removed = click(target(card1, .card), .command, selection: set([card1, card3]), anchor: card3, in: snapshot)
        #expect(removed.selection == set([card3]))
        #expect(removed.anchor == card1)
    }

    @Test("Toggling the last member out leaves nothing selected and nothing to range from")
    func emptyingClearsTheAnchor() throws {
        let fixture = try makeLiveBoard()
        defer { fixture.tearDown() }
        let snapshot = try load(fixture)

        let outcome = click(target(card1, .card), .command, selection: set([card1]), anchor: card1, in: snapshot)
        #expect(outcome.selection.isEmpty)
        #expect(outcome.anchor == nil)
    }

    @Test("⌘-click across the kind boundary replaces — a selection is never mixed")
    func acrossKindReplaces() throws {
        let fixture = try makeLiveBoard()
        defer { fixture.tearDown() }
        let snapshot = try load(fixture)

        // "Selection is homogeneous: cards XOR lanes" (04-interactions.md § Selection).
        let ontoLane = click(target(lane2, .lane), .command, selection: set([card1, card2]), anchor: card2, in: snapshot)
        #expect(ontoLane.selection == set([lane2]))
        #expect(ontoLane.anchor == lane2)

        let ontoCard = click(target(card1, .card), .command, selection: set([lane1, lane2]), anchor: lane2, in: snapshot)
        #expect(ontoCard.selection == set([card1]))
        #expect(ontoCard.anchor == card1)
    }

    @Test("⌘-click across the liveness boundary replaces too")
    func acrossSideReplaces() throws {
        let fixture = try makeTrashBoard()
        defer { fixture.tearDown() }
        let snapshot = try load(fixture)

        // "Selection is homogeneous by liveness … a selection never mixes live and tombstoned"
        // (04 ▸ The trash). The live lane1 is the only live thing on this board.
        let intoTrash = click(target(card1, .card, .trashed), .command, selection: set([lane1]), anchor: lane1, in: snapshot)
        #expect(intoTrash.selection == set([card1], .trashed))

        let backOut = click(target(lane1, .lane), .command, selection: set([card1, card2], .trashed), anchor: card2, in: snapshot)
        #expect(backOut.selection == set([lane1]))

        // And within the trash, the second axis: card entries XOR lane entries.
        let ontoLaneEntry = click(target(laneX, .lane, .trashed), .command, selection: set([card1, card2], .trashed), anchor: card2, in: snapshot)
        #expect(ontoLaneEntry.selection == set([laneX], .trashed))
        #expect(ontoLaneEntry.anchor == laneX)
    }

    @Test("⌘-click with nothing — or nothing real — selected replaces")
    func emptyOrGhostSelectionReplaces() throws {
        let fixture = try makeLiveBoard()
        defer { fixture.tearDown() }
        let snapshot = try load(fixture)

        let fromEmpty = click(target(card1, .card), .command, in: snapshot)
        #expect(fromEmpty.selection == set([card1]))
        #expect(fromEmpty.anchor == card1)

        // A selection whose members all name nothing the board renders counts as empty: a ⌘-click
        // after a foreign delete starts a fresh set rather than extending a ghost.
        let fromGhost = click(target(card1, .card), .command, selection: set([card4]), anchor: card4, in: snapshot)
        #expect(fromGhost.selection == set([card1]))
    }
}

// MARK: - Shift

@MainActor
@Suite("SelectionGrammar ▸ ⇧-click")
struct ShiftClickTests {

    @Test("A ⇧-range spans the flatten order across lanes, skipping tombstones, and leaves the anchor put")
    func rangeAcrossLanes() throws {
        let fixture = try makeLiveBoard()
        defer { fixture.tearDown() }
        let snapshot = try load(fixture)

        let outcome = click(target(card5, .card), .shift, selection: set([card1]), anchor: card1, in: snapshot)
        #expect(outcome.selection == set([card1, card2, card3, card5]))
        // Finder-list style: the anchor is unchanged, so successive ⇧-clicks sweep from one origin.
        #expect(outcome.anchor == card1)
        // card4 is tombstoned and in no order list, so no range can pick it up.
        #expect(!outcome.selection.ids.contains(card4))
    }

    @Test("Direction does not matter — the range is the span between anchor and target")
    func rangeIsDirectionless() throws {
        let fixture = try makeLiveBoard()
        defer { fixture.tearDown() }
        let snapshot = try load(fixture)

        let backwards = click(target(card1, .card), .shift, selection: set([card5]), anchor: card5, in: snapshot)
        #expect(backwards.selection == set([card1, card2, card3, card5]))
        #expect(backwards.anchor == card5)
    }

    @Test("Lanes range in their own order list")
    func laneRange() throws {
        let fixture = try makeLiveBoard()
        defer { fixture.tearDown() }
        let snapshot = try load(fixture)

        let outcome = click(target(lane3, .lane), .shift, selection: set([lane1]), anchor: lane1, in: snapshot)
        #expect(outcome.selection == set([lane1, lane2, lane3]))
        #expect(outcome.anchor == lane1)
    }

    @Test("An invalid anchor makes ⇧ a plain click — nil, vanished, or across a boundary")
    func invalidAnchorActsPlain() throws {
        let fixture = try makeLiveBoard()
        defer { fixture.tearDown() }
        let snapshot = try load(fixture)

        // Nothing to range from.
        let noAnchor = click(target(card3, .card), .shift, selection: set([card1]), in: snapshot)
        #expect(noAnchor.selection == set([card3]))
        #expect(noAnchor.anchor == card3)

        // An anchor that names nothing the board renders (card4 is tombstoned).
        let vanished = click(target(card3, .card), .shift, selection: set([card1]), anchor: card4, in: snapshot)
        #expect(vanished.selection == set([card3]))
        #expect(vanished.anchor == card3)

        // An anchor in the *other* kind's list: the two lists are disjoint, so the anchor is not
        // findable and the click degrades — never a mixed range.
        let acrossKind = click(target(card3, .card), .shift, selection: set([lane1]), anchor: lane1, in: snapshot)
        #expect(acrossKind.selection == set([card3]))
        #expect(acrossKind.anchor == card3)

        // Same for a side crossing: the live card list holds no trash row.
        let acrossSide = click(target(card3, .card, .trashed), .shift, selection: set([card1]), anchor: card1, in: snapshot)
        #expect(acrossSide.selection == set([card3], .trashed))
    }

    @Test("A trash card range steps over the lane entries inside its span")
    func trashCardRangeSkipsLaneEntries() throws {
        let fixture = try makeTrashBoard()
        defer { fixture.tearDown() }
        let snapshot = try load(fixture)

        // Sorted order is [card1, laneX, card2, laneY, card3]; a card range collects card rows only.
        let outcome = click(target(card3, .card, .trashed), .shift, selection: set([card1], .trashed), anchor: card1, in: snapshot)
        #expect(outcome.selection == set([card1, card2, card3], .trashed))
        #expect(outcome.anchor == card1)
    }

    @Test("A trash lane range steps over the card entries inside its span")
    func trashLaneRangeSkipsCardEntries() throws {
        let fixture = try makeTrashBoard()
        defer { fixture.tearDown() }
        let snapshot = try load(fixture)

        let outcome = click(target(laneY, .lane, .trashed), .shift, selection: set([laneX], .trashed), anchor: laneX, in: snapshot)
        #expect(outcome.selection == set([laneX, laneY], .trashed))
        #expect(outcome.anchor == laneX)
    }
}

// MARK: - The rubber band

@Suite("MarqueeMath")
struct MarqueeMathTests {

    private static func card(_ id: ItemID, _ y: CGFloat, side: Liveness = .live) -> MarqueeTarget {
        MarqueeTarget(id: id, kind: .card, side: side, frame: CGRect(x: 0, y: y, width: 100, height: 40))
    }

    private static func laneEntry(_ id: ItemID, _ y: CGFloat) -> MarqueeTarget {
        MarqueeTarget(id: id, kind: .lane, side: .trashed, frame: CGRect(x: 0, y: y, width: 100, height: 40))
    }

    @Test("On the live side the band takes intersecting cards, and only cards")
    func liveSideTakesCards() {
        let targets = [
            Self.card(card1, 0),
            Self.card(card2, 100),
            // A lane registered by mistake is still never swept: "click-drag rubber-bands across
            // lanes" (04-interactions.md § Selection) — across, not over.
            MarqueeTarget(id: lane1, kind: .lane, side: .live, frame: CGRect(x: 0, y: 0, width: 200, height: 400)),
            // A trash row cannot be reached by a band that began on the board.
            Self.card(card3, 10, side: .trashed)
        ]
        let ids = MarqueeMath.selection(rect: CGRect(x: 0, y: 0, width: 50, height: 120), targets: targets, side: .live)
        #expect(ids == [card1, card2])
    }

    @Test("On the trash side the topmost intersecting row's kind wins")
    func trashSideIsHomogeneousByKind() {
        // Interleaved rows, the trash's own shape: card, lane, card.
        let targets = [
            Self.card(card1, 0, side: .trashed),
            Self.laneEntry(laneX, 50),
            Self.card(card2, 100, side: .trashed)
        ]
        let all = CGRect(x: 0, y: 0, width: 50, height: 200)

        // Begun on a card row: the lane row between the two cards is stepped over, exactly as a
        // ⇧-range does (04-interactions.md ▸ The trash).
        #expect(MarqueeMath.selection(rect: all, targets: targets, side: .trashed) == [card1, card2])

        // Begun below it, so the lane row is topmost: only lane entries come back.
        let lower = CGRect(x: 0, y: 60, width: 50, height: 200)
        #expect(MarqueeMath.selection(rect: lower, targets: targets, side: .trashed) == [laneX])
    }

    @Test("A band touching nothing selects nothing")
    func emptyBand() {
        let targets = [Self.card(card1, 0), Self.card(card2, 100)]
        #expect(MarqueeMath.selection(rect: CGRect(x: 500, y: 500, width: 10, height: 10), targets: targets, side: .live).isEmpty)
        #expect(MarqueeMath.selection(rect: .zero, targets: [], side: .trashed).isEmpty)
    }
}

// MARK: - The anchor's storage and its reload rule

/// One foreign reload, start to settled — `TransientBoardStateTests`' helper, borrowed for the one
/// piece of transient state this card adds.
@MainActor
private func reload(_ store: BoardStore) async {
    store.handleWatcherEvent(.treeChanged(.foreign))
    await store.awaitQuiescence()
}

@MainActor
@Suite("TransientBoardState ▸ the selection anchor")
struct SelectionAnchorTests {

    @Test("A sole selection anchors itself; a wholesale one does not; clearing drops it")
    func anchorDefaults() {
        let state = TransientBoardState()

        state.select([card1], liveness: .live)
        #expect(state.selectionAnchor == card1)

        // "A marquee and wholesale selections pass no anchor deliberately."
        state.select([card1, card2], liveness: .live)
        #expect(state.selectionAnchor == nil)

        // An explicit anchor wins over the default in both directions.
        state.select([card1, card2, card3], liveness: .live, anchor: card2)
        #expect(state.selectionAnchor == card2)

        state.clearSelection()
        #expect(state.selectionAnchor == nil)
    }

    @Test("A vanished anchor is dropped by the reload, and a surviving one is kept")
    func vanishedAnchorIsDropped() async throws {
        let fixture = try makeLiveBoard()
        defer { fixture.tearDown() }
        let store = try BoardStore(rootURL: fixture.root)

        store.select([card1, card2], liveness: .live, anchor: card1)
        // A survivor of the same reload proves the rule is about the anchor, not about reloading.
        try FileManager.default.removeItem(at: fixture.url("\(Ident.lane1)/\(Ident.card2)"))
        await reload(store)
        #expect(store.selection.ids == [card1])
        #expect(store.transient.selectionAnchor == card1)

        try FileManager.default.removeItem(at: fixture.url("\(Ident.lane1)/\(Ident.card1)"))
        await reload(store)
        #expect(store.selection.isEmpty)
        #expect(store.transient.selectionAnchor == nil)
    }

    @Test("A liveness flip is a vanish for the anchor too")
    func flippedAnchorIsDropped() async throws {
        let fixture = try makeLiveBoard()
        defer { fixture.tearDown() }
        let store = try BoardStore(rootURL: fixture.root)

        store.select([card1, card2], liveness: .live, anchor: card1)
        try fixture.item("\(Ident.lane1)/\(Ident.card1)", tombstoned(order: "1024", title: "First"))
        await reload(store)

        // "A flip is a vanish from its side of the boundary" (02-architecture.md's reload rule).
        #expect(store.selection.ids == [card2])
        #expect(store.transient.selectionAnchor == nil)
    }

    @Test("An anchor no longer in the selection still ranges — membership is not the rule")
    func anchorNeedNotBeSelected() throws {
        let fixture = try makeLiveBoard()
        defer { fixture.tearDown() }
        let snapshot = try load(fixture)
        let state = TransientBoardState()

        // A ⌘-click that toggled the anchor's own row out leaves the anchor standing.
        state.select([card2, card3], liveness: .live, anchor: card1)
        #expect(state.selectionAnchor == card1)
        let outcome = click(target(card3, .card), .shift, selection: state.selection, anchor: state.selectionAnchor, in: snapshot)
        #expect(outcome.selection == set([card1, card2, card3]))
    }
}

// MARK: - Select All

@MainActor
@Suite("BoardStore ▸ Select All")
struct SelectAllTests {

    @Test("Select All takes every rendered card — tombstones excluded, lanes never")
    func liveBranch() throws {
        let fixture = try makeLiveBoard()
        defer { fixture.tearDown() }
        let store = try BoardStore(rootURL: fixture.root)

        store.select([lane2], liveness: .live)
        store.selectAll()

        // "All visible cards on the board" (04-interactions.md ▸ The map).
        #expect(store.selection == set([card1, card2, card3, card5]))
        // The lane the anchor named is not in the new set, so the anchor goes with it.
        #expect(store.transient.selectionAnchor == nil)
    }

    @Test("An anchor inside the new set survives Select All")
    func anchorSurvivesWhenStillInside() throws {
        let fixture = try makeLiveBoard()
        defer { fixture.tearDown() }
        let store = try BoardStore(rootURL: fixture.root)

        store.select([card3], liveness: .live)
        store.selectAll()
        #expect(store.transient.selectionAnchor == card3)
    }

    @Test("On the trash side Select All stays within the selection's kind")
    func trashBranchIsHomogeneousByKind() throws {
        let fixture = try makeTrashBoard()
        defer { fixture.tearDown() }
        let store = try BoardStore(rootURL: fixture.root)
        store.transient.isTrashVisible = true

        store.select([card2], liveness: .trashed)
        store.selectAll()
        #expect(store.selection == set([card1, card2, card3], .trashed))

        store.select([laneX], liveness: .trashed)
        store.selectAll()
        #expect(store.selection == set([laneX, laneY], .trashed))
    }

    @Test("The trash branch is narrow: hidden, live, empty, or ghost selections take the board")
    func trashBranchFallsThrough() throws {
        let fixture = try makeTrashBoard()
        defer { fixture.tearDown() }
        let store = try BoardStore(rootURL: fixture.root)

        // Hidden — the column is invisible to every gesture (04 ▸ The trash).
        store.select([card1], liveness: .trashed)
        store.selectAll()
        #expect(store.selection.liveness == .live)

        // Shown, but nothing tombstoned is selected.
        store.transient.isTrashVisible = true
        store.clearSelection()
        store.selectAll()
        #expect(store.selection.liveness == .live)

        // Shown, trashed side, but the ids name no row: a guess would be worse than the board.
        store.select([card5], liveness: .trashed)
        store.selectAll()
        #expect(store.selection.liveness == .live)
    }

    @Test("Select All on a board with no rendered cards clears rather than selecting an empty set")
    func emptyBoardClears() throws {
        let fixture = try WriterFixture()
        defer { fixture.tearDown() }
        try fixture.item("", Item.board)
        try fixture.item(Ident.lane1, Item.rich(order: "1024", title: "Todo"))
        let store = try BoardStore(rootURL: fixture.root)

        store.select([lane1], liveness: .live)
        store.selectAll()
        #expect(store.selection.isEmpty)
        #expect(store.transient.selectionAnchor == nil)
    }
}