import CryptoKit
import Foundation
import XCTest
@testable import VelodyPersistence

final class MP3EmbeddedArtworkExtractorTests: XCTestCase {
    func testExtractorReadsEmbeddedPNGArtworkFromID3APICFrame() throws {
        let fileManager = FileManager.default
        let tempDirectory = fileManager.temporaryDirectory.appendingPathComponent(
            UUID().uuidString,
            isDirectory: true
        )
        let fileURL = tempDirectory.appendingPathComponent("artwork-test.mp3")
        let extractor = MP3EmbeddedArtworkExtractor()
        let artworkData = sampleArtworkData()

        defer {
            try? fileManager.removeItem(at: tempDirectory)
        }

        try fileManager.createDirectory(at: tempDirectory, withIntermediateDirectories: true)
        try makeMP3FileWithEmbeddedArtwork(
            artworkData: artworkData,
            mimeType: "image/png",
            at: fileURL
        )

        let extractedArtwork = try XCTUnwrap(
            extractor.extractArtwork(from: fileURL)
        )

        XCTAssertEqual(extractedArtwork.data, artworkData)
        XCTAssertEqual(extractedArtwork.mimeType, "image/png")
        XCTAssertEqual(extractedArtwork.width, 1)
        XCTAssertEqual(extractedArtwork.height, 1)
        XCTAssertEqual(extractedArtwork.sha256, sha256Hex(artworkData))
    }

    func testExtractorReturnsNilWhenMP3HasNoEmbeddedArtwork() throws {
        let fileManager = FileManager.default
        let tempDirectory = fileManager.temporaryDirectory.appendingPathComponent(
            UUID().uuidString,
            isDirectory: true
        )
        let fileURL = tempDirectory.appendingPathComponent("no-artwork.mp3")
        let extractor = MP3EmbeddedArtworkExtractor()

        defer {
            try? fileManager.removeItem(at: tempDirectory)
        }

        try fileManager.createDirectory(at: tempDirectory, withIntermediateDirectories: true)
        try Data([
            0x49, 0x44, 0x33, 0x03, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
        ]).write(to: fileURL)

        XCTAssertNil(try extractor.extractArtwork(from: fileURL))
    }
}

private func makeMP3FileWithEmbeddedArtwork(
    artworkData: Data,
    mimeType: String,
    at fileURL: URL
) throws {
    let mimeTypeData = Data(mimeType.utf8) + Data([0x00])
    let frameBody = Data([0x00]) // ISO-8859-1 encoding
        + mimeTypeData
        + Data([0x03]) // front cover
        + Data([0x00]) // empty description
        + artworkData

    let frameSize = UInt32(frameBody.count)
    let frameHeader = Data("APIC".utf8)
        + Data([
            UInt8((frameSize >> 24) & 0xff),
            UInt8((frameSize >> 16) & 0xff),
            UInt8((frameSize >> 8) & 0xff),
            UInt8(frameSize & 0xff),
            0x00,
            0x00,
        ])
    let tagBody = frameHeader + frameBody
    let tagSize = synchsafeBytes(for: tagBody.count)
    let id3Header = Data([0x49, 0x44, 0x33, 0x03, 0x00, 0x00]) + tagSize
    let mp3Bytes = id3Header + tagBody + Data([
        0xff, 0xfb, 0x90, 0x64, 0x00, 0x00, 0x00, 0x00,
    ])

    try mp3Bytes.write(to: fileURL)
}

private func synchsafeBytes(for value: Int) -> Data {
    Data([
        UInt8((value >> 21) & 0x7f),
        UInt8((value >> 14) & 0x7f),
        UInt8((value >> 7) & 0x7f),
        UInt8(value & 0x7f),
    ])
}

private func sampleArtworkData() -> Data {
    Data(
        base64Encoded:
            "iVBORw0KGgoAAAANSUhEUgAAAAEAAAABCAYAAAAfFcSJAAAADUlEQVQIW2P8z8DwHwAFgwJ/lBi4NwAAAABJRU5ErkJggg=="
    )!
}

private func sha256Hex(_ data: Data) -> String {
    SHA256.hash(data: data)
        .map { String(format: "%02x", $0) }
        .joined()
}