import Foundation
import Testing
@testable import Kanban

/// File ▸ Duplicate's copy (03-board-ui.md § Welcome screen & templates).
///
/// Three promises, and all three are about what the copy *doesn't* do:
///
/// - it doesn't remint — "The copy keeps every GUID", 01-storage-format.md's whole-board carve-out,
///   and the thing that keeps a copied `.git` history naming paths that still exist;
/// - it doesn't drop the trash — "Tombstoned items are carried too (settled) ... the duplicate is
///   born exactly matching its history";
/// - it doesn't overwrite — the Finder-style `copy` ladder renames instead.
///
/// Tested against real folders, because every one of those is a claim about bytes on disk. The
/// window flow around the copy (the flush, the banner row, the open that follows) is the command's,
/// not this type's.

// MARK: - Fixtures

/// A board with a live lane, a tombstoned lane, a live card, a tombstoned card, and a stray file —
/// everything a literal copy has to carry through untouched.
@MainActor
private func makeBoard(named name: String) throws -> (fixture: WriterFixture, root: URL) {
    let fixture = try WriterFixture()
    let root = fixture.url(name)
    try FileManager.default.createDirectory(at: root, withIntermediateDirectories: true)

    try fixture.item(name, Item.board)
    try fixture.item("\(name)/\(Ident.lane1)", Item.rich(order: "1024", title: "Todo"))
    try fixture.item("\(name)/\(Ident.lane1)/\(Ident.card1)", Item.rich(order: "1024", title: "First"))
    try fixture.item(
        "\(name)/\(Ident.lane1)/\(Ident.card2)",
        "---\nschema: 1\norder: 2048\ntitle: Gone\ndeleted: 2026-01-01T00:00:00Z\n---\nbody\n"
    )
    try fixture.item(
        "\(name)/\(Ident.lane2)",
        "---\nschema: 1\norder: 2048\ntitle: Archive\ndeleted: 2026-01-01T00:00:00Z\n---\nbody\n"
    )
    try fixture.item("\(name)/\(Ident.lane2)/\(Ident.card3)", Item.rich(order: "1024", title: "Buried"))
    try fixture.file("\(name)/CLAUDE.user.md", Data("board instructions\n".utf8))

    return (fixture, root)
}

/// Every path under `root`, board-root-relative, hidden entries included — what "a literal copy"
/// means as an assertion.
private func tree(of root: URL) throws -> Set<String> {
    var paths: Set<String> = []
    let walker = FileManager.default.enumerator(at: root, includingPropertiesForKeys: nil, options: [])
    while let url = walker?.nextObject() as? URL {
        paths.insert(url.path.replacingOccurrences(of: root.path + "/", with: ""))
    }
    return paths
}

// MARK: - Tests

@MainActor
@Suite("BoardDuplicator")
struct BoardDuplicatorTests {

    // MARK: The name ladder

    @Test("The first duplicate is a 'copy' sibling, extension carried")
    func firstCopyIsNamedFinderStyle() throws {
        let board = try makeBoard(named: "Roadmap.kanban")
        defer { board.fixture.tearDown() }

        let destination = BoardDuplicator.copyDestination(for: board.root)

        #expect(destination.lastPathComponent == "Roadmap copy.kanban")
        #expect(destination.deletingLastPathComponent().path == board.root.deletingLastPathComponent().path,
                "a sibling — where the user is already looking")
    }

    @Test("An extension-less board has none to carry")
    func extensionlessBoardCopiesWithoutOne() throws {
        let board = try makeBoard(named: "Plain")
        defer { board.fixture.tearDown() }

        #expect(BoardDuplicator.copyDestination(for: board.root).lastPathComponent == "Plain copy")
    }

    @Test("The collision ladder counts up from 2, one collision at a time")
    func collisionLadderCountsUp() throws {
        let board = try makeBoard(named: "Roadmap.kanban")
        defer { board.fixture.tearDown() }

        let first = try BoardDuplicator.duplicate(boardAt: board.root, titled: "Roadmap")
        #expect(first.lastPathComponent == "Roadmap copy.kanban")

        let second = try BoardDuplicator.duplicate(boardAt: board.root, titled: "Roadmap")
        #expect(second.lastPathComponent == "Roadmap copy 2.kanban")

        let third = try BoardDuplicator.duplicate(boardAt: board.root, titled: "Roadmap")
        #expect(third.lastPathComponent == "Roadmap copy 3.kanban")

        // And duplicating a duplicate ladders off *its* name, exactly as Finder does.
        let ofACopy = try BoardDuplicator.duplicate(boardAt: first, titled: "Roadmap copy")
        #expect(ofACopy.lastPathComponent == "Roadmap copy copy.kanban")
    }

    @Test("Anything already wearing the name blocks it, folder or file alike")
    func anyExistingEntryBlocksTheName() throws {
        let board = try makeBoard(named: "Roadmap.kanban")
        defer { board.fixture.tearDown() }
        // Not a board — just a file in the way. A duplicate must rename around it, never through it.
        try board.fixture.file("Roadmap copy.kanban", Data("in the way".utf8))

        #expect(BoardDuplicator.copyDestination(for: board.root).lastPathComponent == "Roadmap copy 2.kanban")
    }

    // MARK: What lands in the copy

    @Test("Every GUID is kept — the whole-board carve-out from the remint rule")
    func guidsArePreserved() throws {
        let board = try makeBoard(named: "Roadmap.kanban")
        defer { board.fixture.tearDown() }

        let copy = try BoardDuplicator.duplicate(boardAt: board.root, titled: "Roadmap")

        #expect(try tree(of: copy) == tree(of: board.root),
                "same identities, same nesting — a copied history keeps naming paths that exist")
        #expect(FileManager.default.fileExists(atPath: copy.appendingPathComponent(Ident.lane1).path))
        #expect(FileManager.default.fileExists(
            atPath: copy.appendingPathComponent("\(Ident.lane1)/\(Ident.card1)").path
        ))
    }

    @Test("Tombstoned lanes and cards are carried, trash included")
    func tombstonesAreCarried() throws {
        let board = try makeBoard(named: "Roadmap.kanban")
        defer { board.fixture.tearDown() }

        let copy = try BoardDuplicator.duplicate(boardAt: board.root, titled: "Roadmap")
        let loaded = try BoardLoader.load(boardRoot: copy).model

        let archive = try #require(loaded.lanes.first { $0.id.rawValue == Ident.lane2 })
        #expect(archive.isDeleted, "the tombstoned lane came along — Duplicate is a full fork")
        #expect(archive.cards.contains { $0.id.rawValue == Ident.card3 }, "and everything beneath it")

        let todo = try #require(loaded.lanes.first { $0.id.rawValue == Ident.lane1 })
        #expect(todo.cards.contains { $0.id.rawValue == Ident.card2 && $0.isDeleted })
    }

    @Test("The copy is byte-for-byte, strays and stale attribution included")
    func contentIsCopiedVerbatim() throws {
        let board = try makeBoard(named: "Roadmap.kanban")
        defer { board.fixture.tearDown() }

        let copy = try BoardDuplicator.duplicate(boardAt: board.root, titled: "Roadmap")

        func bytes(_ root: URL, _ relative: String) throws -> Data {
            try Data(contentsOf: root.appendingPathComponent(relative))
        }
        #expect(try bytes(copy, "index.md") == bytes(board.root, "index.md"))
        #expect(try bytes(copy, "\(Ident.lane1)/\(Ident.card1)/index.md")
                    == bytes(board.root, "\(Ident.lane1)/\(Ident.card1)/index.md"),
                "created, unknown keys and modified-by all survive — nothing here reads a board file")
        #expect(try bytes(copy, "CLAUDE.user.md") == bytes(board.root, "CLAUDE.user.md"))
    }

    @Test("The original is untouched by its own duplication")
    func originalSurvivesUnchanged() throws {
        let board = try makeBoard(named: "Roadmap.kanban")
        defer { board.fixture.tearDown() }
        let before = try tree(of: board.root)

        _ = try BoardDuplicator.duplicate(boardAt: board.root, titled: "Roadmap")

        #expect(try tree(of: board.root) == before)
    }

    // MARK: Failure

    @Test("A source that isn't there fails as a duplicate, naming the board")
    func missingSourceFailsInTheDuplicateVocabulary() throws {
        let board = try makeBoard(named: "Roadmap.kanban")
        defer { board.fixture.tearDown() }
        let missing = board.fixture.url("Never.kanban")

        let error = writeFailure { _ = try BoardDuplicator.duplicate(boardAt: missing, titled: "Never") }

        #expect(error?.operation == .duplicateBoard(title: "Never"),
                "the user pressed Duplicate; the banner must say so")
        #expect(BannerCenter.headline(for: try #require(error)).hasPrefix("Couldn't duplicate 'Never'"))
    }
}