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

namespace EdiApiGateway.Services;

/// <summary>
/// ACMSCTL1.DLL P/Invokeラッパー（クライアントモード）
/// </summary>
/// <remarks>
/// ACMS DLLからのメッセージはShift-JISエンコーディングで返されるため、
/// byte配列で受け取り、呼び出し側で明示的にShift-JIS → UTF-8変換を行う必要があります。
/// </remarks>
public static class AcmsApiWrapper
{
    private const int MSG_BUFFER_SIZE = 256;

    [DllImport("ACMSCTL1.DLL", CharSet = CharSet.Ansi)]
    public static extern int ACMSCallSend(
        [MarshalAs(UnmanagedType.LPStr)] string uid,
        [MarshalAs(UnmanagedType.LPStr)] string fid,
        [MarshalAs(UnmanagedType.LPStr)] string fname,
        int cycle,
        [MarshalAs(UnmanagedType.LPArray, SizeConst = MSG_BUFFER_SIZE)] byte[] msg);

    [DllImport("ACMSCTL1.DLL", CharSet = CharSet.Ansi)]
    public static extern int ACMSCallRecv(
        [MarshalAs(UnmanagedType.LPStr)] string uid,
        [MarshalAs(UnmanagedType.LPStr)] string fid,
        [MarshalAs(UnmanagedType.LPStr)] string fname,
        int cycle,
        int denbun,
        [MarshalAs(UnmanagedType.LPArray, SizeConst = MSG_BUFFER_SIZE)] byte[] msg);

    [DllImport("ACMSCTL1.DLL", CharSet = CharSet.Ansi)]
    public static extern int ACMSCallSendNoDisc(
        [MarshalAs(UnmanagedType.LPStr)] string uid,
        [MarshalAs(UnmanagedType.LPStr)] string fid,
        [MarshalAs(UnmanagedType.LPStr)] string fname,
        int cycle,
        [MarshalAs(UnmanagedType.LPArray, SizeConst = MSG_BUFFER_SIZE)] byte[] msg);

    [DllImport("ACMSCTL1.DLL", CharSet = CharSet.Ansi)]
    public static extern int ACMSCallRecvNoDisc(
        [MarshalAs(UnmanagedType.LPStr)] string uid,
        [MarshalAs(UnmanagedType.LPStr)] string fid,
        [MarshalAs(UnmanagedType.LPStr)] string fname,
        int cycle,
        int denbun,
        [MarshalAs(UnmanagedType.LPArray, SizeConst = MSG_BUFFER_SIZE)] byte[] msg);

    [DllImport("ACMSCTL1.DLL", CharSet = CharSet.Ansi)]
    public static extern int ACMSCallStartup(
        [MarshalAs(UnmanagedType.LPStr)] string uid,
        [MarshalAs(UnmanagedType.LPArray, SizeConst = MSG_BUFFER_SIZE)] byte[] msg);

    [DllImport("ACMSCTL1.DLL", CharSet = CharSet.Ansi)]
    public static extern bool ACMSCallAdd(
        [MarshalAs(UnmanagedType.LPStr)] string uid,
        [MarshalAs(UnmanagedType.LPStr)] string fid,
        [MarshalAs(UnmanagedType.LPStr)] string fname,
        int sndrcv,
        int cycle,
        int denbun,
        [MarshalAs(UnmanagedType.LPArray, SizeConst = MSG_BUFFER_SIZE)] byte[] msg);

    [DllImport("ACMSCTL1.DLL", CharSet = CharSet.Ansi)]
    public static extern int ACMSCallExecute(
        int handle,
        int reserved,
        ref int fnum,
        [MarshalAs(UnmanagedType.LPArray, SizeConst = MSG_BUFFER_SIZE)] byte[] msg);

    [DllImport("ACMSCTL1.DLL", CharSet = CharSet.Ansi)]
    public static extern bool ACMSInitCallInfo(
        [MarshalAs(UnmanagedType.LPArray, SizeConst = MSG_BUFFER_SIZE)] byte[] msg,
        int handle);

    /// <summary>
    /// ACMS API用のメッセージバッファを作成
    /// </summary>
    /// <returns>256バイトのbyte配列</returns>
    public static byte[] CreateMessageBuffer() => new byte[MSG_BUFFER_SIZE];

    /// <summary>
    /// ACMS APIから返されたメッセージバッファをShift-JISからUTF-8文字列に変換
    /// </summary>
    /// <param name="msgBuffer">ACMS APIから返されたバッファ</param>
    /// <returns>UTF-8文字列</returns>
    public static string DecodeMessage(byte[] msgBuffer)
    {
        // Shift-JISエンコーディング取得
        var shiftJis = Encoding.GetEncoding("Shift_JIS");

        // null終端文字を探す
        int length = Array.IndexOf(msgBuffer, (byte)0);
        if (length < 0) length = msgBuffer.Length;

        // Shift-JIS → UTF-8変換
        return shiftJis.GetString(msgBuffer, 0, length);
    }
}