using System;
using System.Runtime.InteropServices;
using System.Text;

// 導(dǎo)入kernel32.dll中的核心文件API
[DllImport("kernel32.dll", CharSet = CharSet.Auto, SetLastError = true)]
public static extern IntPtr CreateFile(
    string lpFileName,               // 文件路徑
    uint dwDesiredAccess,            // 訪(fǎng)問(wèn)模式（讀/寫(xiě)/執(zhí)行）
    uint dwShareMode,                // 共享模式
    IntPtr lpSecurityAttributes,     // 安全屬性（通常為IntPtr.Zero）
    uint dwCreationDisposition,      // 創(chuàng)建/打開(kāi)方式
    uint dwFlagsAndAttributes,       // 文件屬性（如FILE_ATTRIBUTE_NORMAL）
    IntPtr hTemplateFile             // 模板文件句柄（通常為IntPtr.Zero）
);

[DllImport("kernel32.dll", SetLastError = true)]
public static extern bool ReadFile(
    IntPtr hFile,                    // 文件句柄
    byte[] lpBuffer,                 // 讀取緩沖區(qū)
    uint nNumberOfBytesToRead,       // 要讀取的字節(jié)數(shù)
    out uint lpNumberOfBytesRead,    // 實(shí)際讀取的字節(jié)數(shù)
    IntPtr lpOverlapped              // 異步操作參數(shù)（同步操作設(shè)為IntPtr.Zero）
);

[DllImport("kernel32.dll", SetLastError = true)]
public static extern bool WriteFile(
    IntPtr hFile,                    // 文件句柄
    byte[] lpBuffer,                 // 寫(xiě)入緩沖區(qū)
    uint nNumberOfBytesToWrite,      // 要寫(xiě)入的字節(jié)數(shù)
    out uint lpNumberOfBytesWritten, // 實(shí)際寫(xiě)入的字節(jié)數(shù)
    IntPtr lpOverlapped              // 異步操作參數(shù)（同步操作設(shè)為IntPtr.Zero）
);

[DllImport("kernel32.dll", SetLastError = true)]
public static extern bool CloseHandle(IntPtr hObject); // 關(guān)閉句柄

[DllImport("kernel32.dll", SetLastError = true)]
public static extern uint SetFilePointer(
    IntPtr hFile,                    // 文件句柄
    int lDistanceToMove,             // 移動(dòng)偏移量（正負(fù)均可）
    IntPtr lpDistanceToMoveHigh,     // 高32位偏移量（通常為IntPtr.Zero）
    uint dwMoveMethod                // 移動(dòng)方式（如FILE_BEGIN）
);

// 文件訪(fǎng)問(wèn)模式
public const uint GENERIC_READ = 0x80000000;
public const uint GENERIC_WRITE = 0x40000000;

// 文件共享模式
public const uint FILE_SHARE_READ = 0x00000001;
public const uint FILE_SHARE_WRITE = 0x00000002;

// 文件創(chuàng)建方式
public const uint CREATE_NEW = 1;           // 創(chuàng)建新文件（失敗條件：文件已存在）
public const uint CREATE_ALWAYS = 2;        // 總是創(chuàng)建（覆蓋已有文件）
public const uint OPEN_EXISTING = 3;        // 打開(kāi)已有文件（失敗條件：文件不存在）

// 文件移動(dòng)方式
public const uint FILE_BEGIN = 0;           // 從文件開(kāi)頭移動(dòng)
public const uint FILE_CURRENT = 1;         // 從當(dāng)前位置移動(dòng)
public const uint FILE_END = 2;             // 從文件末尾移動(dòng)

// 文件屬性
public const uint FILE_ATTRIBUTE_NORMAL = 0x80; // 普通文件

public static IntPtr CreateFileExample(string filePath) {
    // 打開(kāi)或創(chuàng)建文件（覆蓋模式）
    IntPtr hFile = CreateFile(
        filePath,
        GENERIC_WRITE,                  // 寫(xiě)入權(quán)限
        0,                              // 不共享
        IntPtr.Zero,
        CREATE_ALWAYS,                  // 總是創(chuàng)建新文件
        FILE_ATTRIBUTE_NORMAL,
        IntPtr.Zero
    );

    if (hFile == IntPtr.Zero || hFile == new IntPtr(-1)) {
        throw new Win32Exception(Marshal.GetLastWin32Error(), "創(chuàng)建文件失敗");
    }

    return hFile;
}

public static void WriteFileExample(IntPtr hFile, string data) {
    byte[] buffer = Encoding.UTF8.GetBytes(data); // 將字符串轉(zhuǎn)為字節(jié)數(shù)組
    uint bytesWritten;

    bool success = WriteFile(
        hFile,
        buffer,
        (uint)buffer.Length,
        out bytesWritten,
        IntPtr.Zero
    );

    if (!success) {
        throw new Win32Exception(Marshal.GetLastWin32Error(), "寫(xiě)入文件失敗");
    }

    Console.WriteLine($"成功寫(xiě)入 {bytesWritten} 字節(jié)");
}

public static string ReadFileExample(IntPtr hFile, int bufferSize = 1024) {
    byte[] buffer = new byte[bufferSize];
    uint bytesRead;

    bool success = ReadFile(
        hFile,
        buffer,
        (uint)bufferSize,
        out bytesRead,
        IntPtr.Zero
    );

    if (!success) {
        throw new Win32Exception(Marshal.GetLastWin32Error(), "讀取文件失敗");
    }

    return Encoding.UTF8.GetString(buffer, 0, (int)bytesRead);
}

public static void CloseFileExample(IntPtr hFile) {
    if (!CloseHandle(hFile)) {
        throw new Win32Exception(Marshal.GetLastWin32Error(), "關(guān)閉文件失敗");
    }
}

public static void CopyFileUsingAPI(string sourcePath, string destPath) {
    IntPtr hSource = CreateFile(
        sourcePath,
        GENERIC_READ,
        FILE_SHARE_READ,
        IntPtr.Zero,
        OPEN_EXISTING,
        FILE_ATTRIBUTE_NORMAL,
        IntPtr.Zero
    );

    if (hSource == IntPtr.Zero || hSource == new IntPtr(-1)) {
        throw new Win32Exception(Marshal.GetLastWin32Error(), "打開(kāi)源文件失敗");
    }

    IntPtr hDest = CreateFileExample(destPath);

    try {
        byte[] buffer = new byte[4096]; // 4KB緩沖區(qū)
        uint bytesRead;

        do {
            // 讀取源文件
            if (!ReadFile(hSource, buffer, (uint)buffer.Length, out bytesRead, IntPtr.Zero)) {
                throw new Win32Exception(Marshal.GetLastWin32Error(), "讀取源文件失敗");
            }

            if (bytesRead > 0) {
                // 寫(xiě)入目標(biāo)文件
                uint bytesWritten;
                if (!WriteFile(hDest, buffer, bytesRead, out bytesWritten, IntPtr.Zero)) {
                    throw new Win32Exception(Marshal.GetLastWin32Error(), "寫(xiě)入目標(biāo)文件失敗");
                }
            }
        } while (bytesRead > 0); // 循環(huán)直到讀取完成
    } finally {
        CloseHandle(hSource);
        CloseHandle(hDest);
    }
}

public static void MoveFilePointerExample(IntPtr hFile, int offset, uint moveMethod) {
    uint newPointer = SetFilePointer(
        hFile,
        offset,
        IntPtr.Zero,
        moveMethod
    );

    if (newPointer == 0xFFFFFFFF) {
        throw new Win32Exception(Marshal.GetLastWin32Error(), "移動(dòng)文件指針失敗");
    }

    Console.WriteLine($"文件指針新位置: {newPointer} 字節(jié)");
}

public static void RandomAccessExample(string filePath) {
    IntPtr hFile = CreateFile(
        filePath,
        GENERIC_READ | GENERIC_WRITE,
        0,
        IntPtr.Zero,
        OPEN_EXISTING,
        FILE_ATTRIBUTE_NORMAL,
        IntPtr.Zero
    );

    if (hFile == IntPtr.Zero || hFile == new IntPtr(-1)) {
        throw new Win32Exception(Marshal.GetLastWin32Error(), "打開(kāi)文件失敗");
    }

    try {
        // 移動(dòng)指針到文件開(kāi)頭
        MoveFilePointerExample(hFile, 0, FILE_BEGIN);

        // 讀取前10字節(jié)
        byte[] buffer = new byte[10];
        uint bytesRead;
        ReadFile(hFile, buffer, 10, out bytesRead, IntPtr.Zero);
        Console.WriteLine($"前10字節(jié)內(nèi)容: {Encoding.UTF8.GetString(buffer, 0, (int)bytesRead)}");

        // 移動(dòng)指針到文件末尾
        MoveFilePointerExample(hFile, 0, FILE_END);

        // 寫(xiě)入新內(nèi)容到末尾
        string newData = " - 附加內(nèi)容";
        byte[] newBuffer = Encoding.UTF8.GetBytes(newData);
        uint bytesWritten;
        WriteFile(hFile, newBuffer, (uint)newBuffer.Length, out bytesWritten, IntPtr.Zero);
        Console.WriteLine($"成功追加 {bytesWritten} 字節(jié)");
    } finally {
        CloseHandle(hFile);
    }
}

public static void BackupFile(string source, string backup) {
    try {
        // 創(chuàng)建備份文件
        IntPtr hBackup = CreateFileExample(backup);

        // 打開(kāi)源文件
        IntPtr hSource = CreateFile(
            source,
            GENERIC_READ,
            FILE_SHARE_READ,
            IntPtr.Zero,
            OPEN_EXISTING,
            FILE_ATTRIBUTE_NORMAL,
            IntPtr.Zero
        );

        if (hSource == IntPtr.Zero || hSource == new IntPtr(-1)) {
            throw new Win32Exception(Marshal.GetLastWin32Error(), "打開(kāi)源文件失敗");
        }

        try {
            byte[] buffer = new byte[8192]; // 8KB緩沖區(qū)
            uint bytesRead;

            do {
                // 讀取源文件
                if (!ReadFile(hSource, buffer, (uint)buffer.Length, out bytesRead, IntPtr.Zero)) {
                    throw new Win32Exception(Marshal.GetLastWin32Error(), "讀取源文件失敗");
                }

                if (bytesRead > 0) {
                    // 寫(xiě)入備份文件
                    uint bytesWritten;
                    if (!WriteFile(hBackup, buffer, bytesRead, out bytesWritten, IntPtr.Zero)) {
                        throw new Win32Exception(Marshal.GetLastWin32Error(), "寫(xiě)入備份文件失敗");
                    }
                }
            } while (bytesRead > 0);

            Console.WriteLine("文件備份完成！");
        } finally {
            CloseHandle(hSource);
            CloseHandle(hBackup);
        }
    } catch (Exception ex) {
        Console.WriteLine($"備份失敗: {ex.Message}");
    }
}