import Foundation
import Testing
@testable import Kanban

/// **Nearest-`.git`-wins, freshly at every open** (06-history-undo.md ▸ Rules ▸ Detection) — the one
/// question every git surface starts from, pinned against real directories rather than against a
/// mocked filesystem, because what it is *about* is what is on disk.
///
/// The rule has four claims and this file is one test per claim: root wins, an ancestor is nested,
/// neither is `none`, and the answer is re-derived rather than remembered — "a board can therefore
/// change mode between opens (e.g. the user ran `git init` in a terminal) — the app just reflects
/// what it finds."

// MARK: - Fixtures

/// A `.git` **directory** with a plausible ref inside — what `git init` leaves.
private func makeGitDirectory(at parent: URL) throws {
    let gitDirectory = parent.appendingPathComponent(".git", isDirectory: true)
    try FileManager.default.createDirectory(at: gitDirectory, withIntermediateDirectories: true)
    try Data("ref: refs/heads/main\n".utf8).write(to: gitDirectory.appendingPathComponent("HEAD"))
}

/// A `.git` **file** — what a linked worktree or a submodule leaves. Still a repository, and the
/// reason detection asks `fileExists` rather than `isDirectory`.
private func makeGitPointerFile(at parent: URL, to target: String) throws {
    try Data("gitdir: \(target)\n".utf8).write(to: parent.appendingPathComponent(".git"))
}

/// A board folder inside the fixture, so an *ancestor* can carry the repository.
private func makeSubfolder(_ fixture: WriterFixture, named name: String) throws -> URL {
    let url = fixture.root.appendingPathComponent(name, isDirectory: true)
    try FileManager.default.createDirectory(at: url, withIntermediateDirectories: true)
    return url
}

// MARK: - Detection

@Suite("Board git mode ▸ detection")
struct BoardGitModeTests {

    @Test("A `.git` at the board root is git mode")
    func rootRepositoryIsGitMode() throws {
        let fixture = try WriterFixture()
        defer { fixture.tearDown() }
        try fixture.item("", Item.board)
        try makeGitDirectory(at: fixture.root)

        #expect(BoardGitMode.detect(boardRoot: fixture.root) == .git)
    }

    @Test("A `.git` *file* is a repository too — a worktree is not mode none")
    func aWorktreePointerIsGitMode() throws {
        let fixture = try WriterFixture()
        defer { fixture.tearDown() }
        try fixture.item("", Item.board)
        try makeGitPointerFile(at: fixture.root, to: "/somewhere/else/.git/worktrees/board")

        #expect(BoardGitMode.detect(boardRoot: fixture.root) == .git)
    }

    @Test("No `.git` at the root and none above it is mode none")
    func aPlainFolderIsModeNone() throws {
        let fixture = try WriterFixture()
        defer { fixture.tearDown() }
        try fixture.item("", Item.board)

        #expect(BoardGitMode.detect(boardRoot: fixture.root) == .none)
    }

    @Test("A `.git` at an ancestor and none at the root is repo-nested")
    func anEnclosingRepositoryIsRepoNested() throws {
        let fixture = try WriterFixture()
        defer { fixture.tearDown() }
        try makeGitDirectory(at: fixture.root)
        let board = try makeSubfolder(fixture, named: "project/docs/board")

        #expect(BoardGitMode.detect(boardRoot: board) == .repoNested)
        #expect(BoardGitMode.enclosingRepositoryRoot(above: board)?.standardizedFileURL
            == fixture.root.standardizedFileURL)
    }

    @Test("Nearest wins: a board with its own `.git` inside a repository is git mode, not nested")
    func theNearestRepositoryWins() throws {
        let fixture = try WriterFixture()
        defer { fixture.tearDown() }
        try makeGitDirectory(at: fixture.root)
        let board = try makeSubfolder(fixture, named: "board")
        try makeGitDirectory(at: board)

        #expect(BoardGitMode.detect(boardRoot: board) == .git)
    }

    @Test("The walk terminates above a board at the filesystem root, finding nothing")
    func theAncestorWalkTerminates() {
        // The one hazard this walk has ever had: NSURL-bridged URLs whose
        // `deletingLastPathComponent` grows "/.." forever instead of settling at "/". The temp
        // directory has no repository above it, so the honest answer is `nil` — reached, not hung.
        #expect(BoardGitMode.enclosingRepositoryRoot(above: URL(fileURLWithPath: "/")) == nil)
    }

    // MARK: Freshness

    @Test("Detection is re-derived at every open: a board that gains a `.git` opens in git mode next time")
    func modeChangesBetweenOpens() throws {
        let fixture = try WriterFixture()
        defer { fixture.tearDown() }
        try fixture.item("", Item.board)

        #expect(BoardGitMode.detect(boardRoot: fixture.root) == .none, "the first open")

        // What a user does in a terminal under a closed board.
        try makeGitDirectory(at: fixture.root)

        #expect(BoardGitMode.detect(boardRoot: fixture.root) == .git, "the next open reflects what it finds")
    }

    @Test("And a board that loses its `.git` opens back in mode none")
    func modeChangesBackBetweenOpens() throws {
        let fixture = try WriterFixture()
        defer { fixture.tearDown() }
        try fixture.item("", Item.board)
        try makeGitDirectory(at: fixture.root)
        #expect(BoardGitMode.detect(boardRoot: fixture.root) == .git)

        try FileManager.default.removeItem(at: fixture.root.appendingPathComponent(".git"))

        #expect(BoardGitMode.detect(boardRoot: fixture.root) == .none)
    }
}