import Foundation
import Testing
@testable import Kanban

/// The snapshot summarizer — 10-accessibility.md ▸ Live board announcements' "one polite digest per
/// reload debounce", and (later) pro-m1's commit-message engine, whose counting rules these are too.
///
/// Every case here is **two real loads of a real board**, written and mutated on disk the way an
/// outside writer mutates one: `BoardDiff` compares what a reload compares, and a suite that
/// hand-built its `BoardModel` values could pass while disagreeing with the loader about what a
/// board even is.

// MARK: - Fixture

private let lane1 = Ident.lane1
private let lane2 = Ident.lane2
private let lane3 = Ident.lane3
private let card1 = Ident.card1
private let card2 = Ident.card2
private let card3 = Ident.card3
private let card4 = Ident.card4

/// Three lanes; two cards in the first, one in the second, none in the third.
private func makeBoard() throws -> WriterFixture {
    let fixture = try WriterFixture()
    try fixture.board()
    try fixture.lane(lane1, order: "1024", title: "Todo")
    try fixture.lane(lane2, order: "2048", title: "Doing")
    try fixture.lane(lane3, order: "3072", title: "Done")
    try fixture.card(card1, in: lane1, order: "1024", title: "First", body: "one")
    try fixture.card(card2, in: lane1, order: "2048", title: "Second", body: "two")
    try fixture.card(card3, in: lane2, order: "1024", title: "Third", body: "three")
    return fixture
}

@Suite("BoardDiff")
struct BoardDiffTests {

    // MARK: - Nothing happened

    @Test("Two reads of an untouched board are silent")
    func unchangedBoardIsSilent() throws {
        let fixture = try makeBoard()
        defer { fixture.tearDown() }

        let diff = BoardDiff.between(try fixture.snapshot(), try fixture.snapshot())

        #expect(diff.isSilent)
        #expect(!diff.boardChanged)
    }

    // MARK: - Cards

    @Test("A retitled card is one edit")
    func retitledCard() throws {
        let fixture = try makeBoard()
        defer { fixture.tearDown() }
        let before = try fixture.snapshot()

        try fixture.card(card1, in: lane1, order: "1024", title: "Renamed", body: "one")
        let diff = BoardDiff.between(before, try fixture.snapshot())

        #expect(diff.cards.edited == [ItemID(rawValue: card1)])
        #expect(diff.cards.added.isEmpty && diff.cards.moved.isEmpty && diff.cards.deleted.isEmpty)
        #expect(diff.lanes.isEmpty)
    }

    @Test("An edited body is an edit — the card's content is the whole point of one")
    func editedBody() throws {
        let fixture = try makeBoard()
        defer { fixture.tearDown() }
        let before = try fixture.snapshot()

        try fixture.card(card1, in: lane1, order: "1024", title: "First", body: "rewritten by an agent")
        let diff = BoardDiff.between(before, try fixture.snapshot())

        #expect(diff.cards.edited == [ItemID(rawValue: card1)])
    }

    /// The `modified` stamp is not on the board, so bumping it is not a change the board can show.
    /// It still trips `boardChanged`, which is the backstop's job — see `bareBoardChange`.
    @Test("A bumped timestamp is not an edit")
    func touchedTimestampIsNotAnEdit() throws {
        let fixture = try makeBoard()
        defer { fixture.tearDown() }
        let before = try fixture.snapshot()

        try fixture.card(card1, in: lane1, order: "1024", title: "First", body: "one", modified: "2026-07-29T09:00:00Z")
        let diff = BoardDiff.between(before, try fixture.snapshot())

        #expect(diff.cards.isEmpty)
        #expect(diff.boardChanged, "the snapshot did differ — the backstop still fires")
    }

    @Test("A new card in an existing lane is one addition")
    func addedCard() throws {
        let fixture = try makeBoard()
        defer { fixture.tearDown() }
        let before = try fixture.snapshot()

        try fixture.card(card4, in: lane2, order: "2048", title: "Fourth")
        let diff = BoardDiff.between(before, try fixture.snapshot())

        #expect(diff.cards.added == [ItemID(rawValue: card4)])
        #expect(diff.cards.edited.isEmpty && diff.cards.moved.isEmpty)
    }

    /// Deletion is a move into `.trash/` (01-storage-format.md § Deletion): the card leaves the
    /// board's universe, which is the only thing the digest describes.
    @Test("A card moved into the trash reads as deleted from the board")
    func deletedCard() throws {
        let fixture = try makeBoard()
        defer { fixture.tearDown() }
        let before = try fixture.snapshot()

        try fixture.move("\(lane1)/\(card1)", toTrash: card1)
        let diff = BoardDiff.between(before, try fixture.snapshot())

        #expect(diff.cards.deleted == [ItemID(rawValue: card1)])
        #expect(diff.cards.added.isEmpty, "it did not also arrive somewhere")
    }

    @Test("A card moved between lanes is one move, not an addition plus a deletion")
    func movedCard() throws {
        let fixture = try makeBoard()
        defer { fixture.tearDown() }
        let before = try fixture.snapshot()

        try fixture.moveFolder("\(lane1)/\(card1)", to: "\(lane2)/\(card1)")
        let diff = BoardDiff.between(before, try fixture.snapshot())

        #expect(diff.cards.moved == [ItemID(rawValue: card1)])
        #expect(diff.cards.added.isEmpty && diff.cards.deleted.isEmpty)
    }

    @Test("A reordered card is moved, not edited — `order` is the position axis")
    func reorderedCard() throws {
        let fixture = try makeBoard()
        defer { fixture.tearDown() }
        let before = try fixture.snapshot()

        try fixture.card(card1, in: lane1, order: "4096", title: "First", body: "one")
        let diff = BoardDiff.between(before, try fixture.snapshot())

        #expect(diff.cards.moved == [ItemID(rawValue: card1)])
        #expect(diff.cards.edited.isEmpty)
    }

    /// One card, one change to the board — two fragments counting it would read as two cards.
    @Test("A card that both moved and was retitled counts once, as moved")
    func movedAndEditedCountsOnce() throws {
        let fixture = try makeBoard()
        defer { fixture.tearDown() }
        let before = try fixture.snapshot()

        try fixture.moveFolder("\(lane1)/\(card1)", to: "\(lane2)/\(card1)")
        try fixture.card(card1, in: lane2, order: "1024", title: "Renamed", body: "one")
        let diff = BoardDiff.between(before, try fixture.snapshot())

        #expect(diff.cards.moved == [ItemID(rawValue: card1)])
        #expect(diff.cards.edited.isEmpty)
    }

    // MARK: - Lanes

    @Test("A retitled lane is one lane edit and touches no card")
    func retitledLane() throws {
        let fixture = try makeBoard()
        defer { fixture.tearDown() }
        let before = try fixture.snapshot()

        try fixture.lane(lane1, order: "1024", title: "Backlog")
        let diff = BoardDiff.between(before, try fixture.snapshot())

        #expect(diff.lanes.edited == [ItemID(rawValue: lane1)])
        #expect(diff.cards.isEmpty, "a lane's cards are diffed as cards, never folded into its own change")
    }

    @Test("A resized lane is an edit — width is a lane's own visible property")
    func resizedLane() throws {
        let fixture = try makeBoard()
        defer { fixture.tearDown() }
        let before = try fixture.snapshot()

        try fixture.lane(lane1, order: "1024", title: "Todo", width: 2)
        let diff = BoardDiff.between(before, try fixture.snapshot())

        #expect(diff.lanes.edited == [ItemID(rawValue: lane1)])
    }

    @Test("A reordered lane is moved, not edited")
    func reorderedLane() throws {
        let fixture = try makeBoard()
        defer { fixture.tearDown() }
        let before = try fixture.snapshot()

        try fixture.lane(lane1, order: "5120", title: "Todo")
        let diff = BoardDiff.between(before, try fixture.snapshot())

        #expect(diff.lanes.moved == [ItemID(rawValue: lane1)])
        #expect(diff.lanes.edited.isEmpty)
    }

    // MARK: - Implied events don't steal the subject

    /// 06-history-undo.md's composer discipline, which 10-accessibility.md applies to speech: a
    /// board that says "1 lane deleted, 2 cards deleted" has reported one event twice.
    @Test("A deleted lane does not also count the cards that went with it")
    func deletedLaneSwallowsItsCards() throws {
        let fixture = try makeBoard()
        defer { fixture.tearDown() }
        let before = try fixture.snapshot()

        try FileManager.default.removeItem(at: fixture.url(lane1))
        let diff = BoardDiff.between(before, try fixture.snapshot())

        #expect(diff.lanes.deleted == [ItemID(rawValue: lane1)])
        #expect(diff.cards.deleted.isEmpty, "the two cards left with their lane — that is the lane's event")
    }

    @Test("A new lane does not also count the cards that arrived in it")
    func addedLaneSwallowsItsCards() throws {
        let fixture = try makeBoard()
        defer { fixture.tearDown() }
        let before = try fixture.snapshot()

        try fixture.lane(Ident.lane4, order: "4096", title: "Blocked")
        try fixture.card(card4, in: Ident.lane4, order: "1024", title: "Fourth")
        let diff = BoardDiff.between(before, try fixture.snapshot())

        #expect(diff.lanes.added == [ItemID(rawValue: Ident.lane4)])
        #expect(diff.cards.added.isEmpty)
    }

    /// The complement, and the reason the rule is stated on the *lane's* membership rather than on
    /// the card's presence: a card that survived by moving into the new lane is its own event.
    @Test("A card that moved into a new lane is still a move of its own")
    func cardMovedIntoANewLane() throws {
        let fixture = try makeBoard()
        defer { fixture.tearDown() }
        let before = try fixture.snapshot()

        try fixture.lane(Ident.lane4, order: "4096", title: "Blocked")
        try fixture.moveFolder("\(lane1)/\(card1)", to: "\(Ident.lane4)/\(card1)")
        let diff = BoardDiff.between(before, try fixture.snapshot())

        #expect(diff.lanes.added == [ItemID(rawValue: Ident.lane4)])
        #expect(diff.cards.moved == [ItemID(rawValue: card1)])
    }

    // MARK: - The trash and the backstop

    /// A purge moves nothing on the board, and the trash column is hidden by default — not worth
    /// interrupting a VoiceOver user for.
    @Test("Churn inside the trash is not a change to the board")
    func trashChurnIsSilent() throws {
        let fixture = try makeBoard()
        defer { fixture.tearDown() }
        try fixture.trashCard(card4, order: "1024", title: "Old")
        let before = try fixture.snapshot()

        try FileManager.default.removeItem(at: fixture.url(".trash/\(card4)"))
        let diff = BoardDiff.between(before, try fixture.snapshot())

        #expect(diff.isSilent)
    }

    /// "Silence about a mutating board is a lie" — so a change no bucket counts still reports
    /// *something*, which `AccessibilityPhrases.boardChanged(_:)` speaks as the bare sentence.
    @Test("A renamed board is a bare board change with no buckets")
    func bareBoardChange() throws {
        let fixture = try makeBoard()
        defer { fixture.tearDown() }
        let before = try fixture.snapshot()

        try fixture.board(title: "Renamed")
        let diff = BoardDiff.between(before, try fixture.snapshot())

        #expect(diff.boardChanged)
        #expect(diff.cards.isEmpty && diff.lanes.isEmpty)
        #expect(!diff.isSilent)
    }
}