import Foundation

/// 用于修复 HEIC 文件中的 Apple MakerNotes，添加 LivePhotoVideoIndex 字段
/// CGImageDestination 无法正确写入 Int64 类型的 MakerNotes 字段，
/// 所以我们使用预制的模板并在运行时替换关键字段
public struct MakerNotesPatcher {

    // MARK: - 模板中的偏移量（基于原生 iPhone 照片的 MakerNotes 分析）

    /// ContentIdentifier 在 MakerNotes 模板中的偏移（36 字节 ASCII UUID + null）
    private static let contentIdentifierOffset = 0x580  // 1408
    private static let contentIdentifierLength = 36

    /// LivePhotoVideoIndex 在 MakerNotes 模板中的偏移（8 字节 Big-Endian Int64）
    private static let livePhotoVideoIndexOffset = 0x5a6  // 1446
    private static let livePhotoVideoIndexLength = 8

    /// 原生 iPhone MakerNotes 模板（从 iPhone 13 Pro Max 拍摄的 Live Photo 提取）
    /// 包含完整的 Apple MakerNotes 结构，需要替换 ContentIdentifier 和 LivePhotoVideoIndex
    private static let makerNotesTemplate: Data = {
        // Base64 编码的 MakerNotes 模板
        let base64 = """
        QXBwbGUgaU9TAAABTU0APQABAAkAAAABAAAAEAACAAcAAAIAAAAC8AADAAcAAABoAAAE8AAEAAkA\
        AAABAAAAAQAFAAkAAAABAAAAqQAGAAkAAAABAAAApQAHAAkAAAABAAAAAQAIAAoAAAADAAAFWAAM\
        AAoAAAACAAAFcAANAAkAAAABAAAAFwAOAAkAAAABAAAABAAQAAkAAAABAAAAAQARAAIAAAAlAAAF\
        gAAUAAkAAAABAAAACgAXABAAAAABAAAFpgAZAAkAAAABAAAAAgAaAAIAAAAGAAAFrgAfAAkAAAAB\
        AAAAAAAgAAIAAAAlAAAFtAAhAAoAAAABAAAF2gAjAAkAAAACAAAF4gAlABAAAAABAAAF6gAmAAkA\
        AAABAAAAAwAnAAoAAAABAAAF8gAoAAkAAAABAAAAAQArAAIAAAAlAAAF+gAtAAkAAAABAAATXAAu\
        AAkAAAABAAAAAQAvAAkAAAABAAAAMAAwAAoAAAABAAAGIAAzAAkAAAABAAAQAAA0AAkAAAABAAAA\
        BAA1AAkAAAABAAAAAwA2AAkAAAABAADnJAA3AAkAAAABAAAABAA4AAkAAAABAAACPgA5AAkAAAAB\
        AAAAAAA6AAkAAAABAAAAAAA7AAkAAAABAAAAAAA8AAkAAAABAAAABAA9AAkAAAABAAAAAAA/AAkA\
        AAABAAAAOwBAAAcAAABQAAAGKABBAAkAAAABAAAAAABCAAkAAAABAAAAAABDAAkAAAABAAAAAABE\
        AAkAAAABAAAAAABFAAkAAAABAAAAAABGAAkAAAABAAAAAABIAAkAAAABAAACPgBJAAkAAAABAAAA\
        AABKAAkAAAABAAAAAgBNAAoAAAABAAAGeABOAAcAAAB5AAAGgABPAAcAAAArAAAG+gBSAAkAAAAB\
        AAAAAQBTAAkAAAABAAAAAQBVAAkAAAABAAAAAQBYAAkAAAABAAAHAwBgAAkAAAABAAASAABhAAkA\
        AAABAAAAGgAAAAC9AtMCxAKWAlsCIALqAbwBkgFrAUYBJQEIAfEA3QDMAAMDMwNAA/QCmQJWAg0C\
        1QGoAX4BUwEtAQ8B9QDhAM0ALANqA2oDTAPrAnUCKALpAb4BhgFWATABEAH0AN4AyQA9A7oDwgNP\
        A7gCXAIYAugBqwF2AUwBJgEGAeoA0gC+ANECrwPSAxIDZAIVAt4BqwF8AVABKQEHAekA0AC6AKgA\
        zwFCAnYCBAK/AZYBcwFQAS8BDQHvANQAvQCpAJgAigDUAP8AGgEVARoB5QC6AMUAsACsAJkAggBy\
        AGQAXABTAGAAaABqAGYAXABMAEcARwBCAEEAPgAvACQAJAAlACoARgBIAEcARAA/ADcAMwAvACoA\
        KAAnACEAHQAfAB8AIAAxADIAMQAwAC4AKwAnACcAJQAfABwAGgAXABkAEwAUACkAKgAmACQAIgAg\
        ACEAIgAgAB4AHAAZABgAFAAXABUAIgAcABoAGwAaABcAHAAdABkAGAAYABgAFwAaABgAGAAaABsA\
        GgAYABUAEwAWABcAEwAWABcAFQAVABYAEwAUABoAFwAWABMAEgATABAADwATABMAEgANAA8ADwAP\
        AAwAEwAVABIAEwANABUAEwATABIADAAPAAsAEAASAA8ADgARABEADwAMAAwADwAWABMAEgASABQA\
        DQAPAAoADAAOAGJwbGlzdDAw1AECAwQFBgcIVWZsYWdzVXZhbHVlWXRpbWVzY2FsZVVlcG9jaBAB\
        EwABVEUBR7fxEjuaygAQAAgRFx0nLS84PQAAAAAAAAEBAAAAAAAAAAkAAAAAAAAAAAAAAAAAAAA/\
        ///J3gAANk3//8R4AAe+////5bUAAVy+AAAAOwAAAQAAAAAnAAABAAAAAAAAAAAAAAAAAAAAALtA\
        AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAABI\
        RUlDAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA\
        AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA\
        AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAbwBwAGwAaQBzAHQAMAAwANQBAgMEBQYHCFEzUTFR\
        MlEwEAQiAAAAACQ/AAAAEAEIERMVFxkbICUAAAAAAAABAQAAAAAAAAAJAAAAAAAAAAAAAAAAAAAA\
        JwAC8/UAABV+YnBsaXN0MDDSAQIDSFExUTIQA6IFCtIGBwgJUzIuMVMyLjIjQEsf2IAAAACJQAAA\
        AAAAAADSBgcLDCM/4hqAAAAAAKNAVMAAAAAAAAgNDxETFhsfIywlOkMAAAAAAAABAQAAAAAAAAAL\
        AAAAAAAAAAAAAAAAAAAAQQAAAAA=
        """
        return Data(base64Encoded: base64.replacingOccurrences(of: "\\\n", with: "").replacingOccurrences(of: "\n", with: ""))!
    }()

    /// 创建自定义的 MakerNotes 数据
    /// - Parameters:
    ///   - contentIdentifier: Live Photo 的 Content Identifier (UUID 字符串格式)
    ///   - livePhotoVideoIndex: Live Photo Video Index (通常是帧索引的 Float32 bitPattern)
    /// - Returns: 修改后的 MakerNotes 数据
    public static func createMakerNotes(
        contentIdentifier: String,
        livePhotoVideoIndex: Int64
    ) -> Data {
        var data = makerNotesTemplate

        // 替换 ContentIdentifier
        let uuidData = contentIdentifier.data(using: .ascii)!
        let paddedUUID = uuidData + Data(repeating: 0, count: max(0, contentIdentifierLength - uuidData.count))
        data.replaceSubrange(contentIdentifierOffset..<(contentIdentifierOffset + contentIdentifierLength), with: paddedUUID.prefix(contentIdentifierLength))

        // 替换 LivePhotoVideoIndex (Big-Endian)
        var bigEndianValue = UInt64(bitPattern: livePhotoVideoIndex).bigEndian
        let indexData = Data(bytes: &bigEndianValue, count: livePhotoVideoIndexLength)
        data.replaceSubrange(livePhotoVideoIndexOffset..<(livePhotoVideoIndexOffset + livePhotoVideoIndexLength), with: indexData)

        return data
    }
}