shotdeck/Tests/ShotdeckCoreTests/AtomicFileTests.swift

import Foundation
import Testing
import ShotdeckCore

@Test
func atomicWriteProducesByteIdenticalFileAndLeavesNoTmp() throws {
    let directory = try makeTemporaryDirectory(prefix: "shotdeck-atomic-write")
    defer { try? FileManager.default.removeItem(at: directory) }

    let url = directory.appendingPathComponent("payload.bin")
    let data = Data("shotdeck-durable-bytes".utf8)

    try AtomicFile.write(data, to: url)

    let onDisk = try Data(contentsOf: url)
    #expect(onDisk == data)
    #expect(!FileManager.default.fileExists(atPath: url.path + ".tmp"))
}

@Test
func atomicWriteToTheSameURLTwiceKeepsTheSecondPayload() throws {
    let directory = try makeTemporaryDirectory(prefix: "shotdeck-atomic-rewrite")
    defer { try? FileManager.default.removeItem(at: directory) }

    let url = directory.appendingPathComponent("payload.bin")
    let first = Data("first-pass".utf8)
    let second = Data("second-pass-wins".utf8)

    try AtomicFile.write(first, to: url)
    try AtomicFile.write(second, to: url)

    let onDisk = try Data(contentsOf: url)
    #expect(onDisk == second)
    #expect(!FileManager.default.fileExists(atPath: url.path + ".tmp"))
}

@Test
func atomicWriteThrowsWhenParentDirectoryDoesNotExist() throws {
    let missingParent = FileManager.default.temporaryDirectory
        .appendingPathComponent("shotdeck-atomic-missing-\(UUID().uuidString)", isDirectory: true)
    let url = missingParent.appendingPathComponent("payload.bin")
    let data = Data("never-written".utf8)

    let error = try #require(throws: ShotdeckError.self) {
        try AtomicFile.write(data, to: url)
    }
    guard case .spoolWriteFailed(let path, _) = error else {
        Issue.record("expected spoolWriteFailed, got \(error)")
        return
    }
    #expect(path == url.path)
    #expect(!FileManager.default.fileExists(atPath: url.path))
}

@Test
func atomicWriteClearsAStaleTmpAndWritesTheNewPayload() throws {
    let directory = try makeTemporaryDirectory(prefix: "shotdeck-atomic-stale-tmp")
    defer { try? FileManager.default.removeItem(at: directory) }

    let url = directory.appendingPathComponent("payload.bin")
    let tmpURL = directory.appendingPathComponent(url.lastPathComponent + ".tmp")
    let garbage = Data("stale-crash-garbage".utf8)
    let newData = Data("recovered-payload".utf8)

    try garbage.write(to: tmpURL)
    #expect(FileManager.default.fileExists(atPath: tmpURL.path))

    try AtomicFile.write(newData, to: url)

    let onDisk = try Data(contentsOf: url)
    #expect(onDisk == newData)
    #expect(!FileManager.default.fileExists(atPath: tmpURL.path))
}

@Test
func writeJSONSortsKeysPrettyPrintsAndEncodesDatesAsISO8601() throws {
    let directory = try makeTemporaryDirectory(prefix: "shotdeck-atomic-json-format")
    defer { try? FileManager.default.removeItem(at: directory) }

    let url = directory.appendingPathComponent("session.json")
    let date = try iso8601Date(year: 2026, month: 8, day: 30, hour: 9, minute: 42, second: 5)
    let value = JSONProbe(zebra: "last", apple: 7, capturedAt: date)

    try AtomicFile.writeJSON(value, to: url)

    let raw = try Data(contentsOf: url)
    let text = try #require(String(data: raw, encoding: .utf8))

    let apple = try #require(text.range(of: "\"apple\""))
    let capturedAt = try #require(text.range(of: "\"capturedAt\""))
    let zebra = try #require(text.range(of: "\"zebra\""))
    #expect(apple.lowerBound < capturedAt.lowerBound)
    #expect(capturedAt.lowerBound < zebra.lowerBound)
    #expect(text.contains("\n"))
    #expect(text.contains("  \"apple\""))
    #expect(text.contains("2026-08-30T09:42:05Z"))
    #expect(!text.contains("\(date.timeIntervalSinceReferenceDate)"))
    #expect(!FileManager.default.fileExists(atPath: url.path + ".tmp"))
}

@Test
func writeJSONRoundTripsThroughISO8601Decoder() throws {
    let directory = try makeTemporaryDirectory(prefix: "shotdeck-atomic-json-roundtrip")
    defer { try? FileManager.default.removeItem(at: directory) }

    let url = directory.appendingPathComponent("session.json")
    let date = try iso8601Date(year: 2026, month: 8, day: 31, hour: 13, minute: 5, second: 9)
    let original = JSONProbe(zebra: "keep", apple: 42, capturedAt: date)

    try AtomicFile.writeJSON(original, to: url)

    let decoder = JSONDecoder()
    decoder.dateDecodingStrategy = .iso8601
    let decoded = try decoder.decode(JSONProbe.self, from: Data(contentsOf: url))
    #expect(decoded == original)
}

@Test
func fsyncDirectorySucceedsOnADirectoryAndThrowsOnMissingOrFilePaths() throws {
    let directory = try makeTemporaryDirectory(prefix: "shotdeck-atomic-fsync-dir")
    defer { try? FileManager.default.removeItem(at: directory) }

    try AtomicFile.fsyncDirectory(at: directory)

    let missing = directory.appendingPathComponent("does-not-exist", isDirectory: true)
    let missingError = try #require(throws: ShotdeckError.self) {
        try AtomicFile.fsyncDirectory(at: missing)
    }
    guard case .spoolWriteFailed = missingError else {
        Issue.record("expected spoolWriteFailed for a missing path, got \(missingError)")
        return
    }

    let fileURL = directory.appendingPathComponent("not-a-directory.bin")
    try AtomicFile.write(Data("file".utf8), to: fileURL)
    let fileError = try #require(throws: ShotdeckError.self) {
        try AtomicFile.fsyncDirectory(at: fileURL)
    }
    guard case .spoolWriteFailed = fileError else {
        Issue.record("expected spoolWriteFailed for a file path, got \(fileError)")
        return
    }
}

private struct JSONProbe: Codable, Equatable {
    var zebra: String
    var apple: Int
    var capturedAt: Date
}

private func makeTemporaryDirectory(prefix: String) throws -> URL {
    let url = FileManager.default.temporaryDirectory
        .appendingPathComponent("\(prefix)-\(UUID().uuidString)", isDirectory: true)
    try FileManager.default.createDirectory(at: url, withIntermediateDirectories: true)
    return url
}

private func iso8601Date(
    year: Int,
    month: Int,
    day: Int,
    hour: Int,
    minute: Int,
    second: Int
) throws -> Date {
    var calendar = Calendar(identifier: .gregorian)
    calendar.timeZone = try #require(TimeZone(secondsFromGMT: 0))
    return try #require(
        calendar.date(from: DateComponents(
            year: year,
            month: month,
            day: day,
            hour: hour,
            minute: minute,
            second: second
        ))
    )
}