using System.Text;
using WxAgent.Core;
using Xunit;
using ZstdSharp;

namespace WxAgent.Core.Tests;

public sealed class WechatDbMessageTests
{
    [Fact]
    public void TableNameForMatchesMd5HexOfChatId()
    {
        Assert.Equal("Msg_" + Md5Hex("wxid_test"), WechatDbMessage.TableNameFor("wxid_test"));
        Assert.Equal("Msg_" + Md5Hex("测试群组"), WechatDbMessage.TableNameFor("测试群组"));
    }

    [Fact]
    public void DecodeContentHandlesPlainHexUtf8()
    {
        Assert.Equal("hello", WechatDbMessage.DecodeContent(Convert.ToHexString(Encoding.UTF8.GetBytes("hello")), compressed: false));
        Assert.Empty(WechatDbMessage.DecodeContent("", compressed: false));
        Assert.Empty(WechatDbMessage.DecodeContent("not-hex!", compressed: false));
    }

    [Fact]
    public void DecodeContentDecompressesZstdPayloads()
    {
        var payload = Encoding.UTF8.GetBytes("wx-agent-zstd-roundtrip-消息测试");
        using var compressor = new CompressionStream(new MemoryStream());
        // ZstdSharp.CompressionStream writes on dispose; wrap in a memory stream instead.
        var compressed = Compress(payload);
        var hex = Convert.ToHexString(compressed);
        var decoded = WechatDbMessage.DecodeContent(hex, compressed: true);
        Assert.Equal("wx-agent-zstd-roundtrip-消息测试", decoded);
    }

    [Fact]
    public void DecodeContentTreatsCompressedFlagWithoutMagicAsUndecodable()
    {
        var hex = Convert.ToHexString(Encoding.UTF8.GetBytes("plain"));
        Assert.Empty(WechatDbMessage.DecodeContent(hex, compressed: true));
    }

    [Fact]
    public void IsSelfUsesWxIdPrefixOfAccountDirectory()
    {
        Assert.True(WechatDbMessage.IsSelf("wxid_abc123", "wxid_abc123_def456"));
        Assert.False(WechatDbMessage.IsSelf("wxid_other", "wxid_abc123_def456"));
        Assert.Null(WechatDbMessage.IsSelf(null, "wxid_abc123_def456"));
        Assert.Null(WechatDbMessage.IsSelf("wxid_abc123", null));
    }

    private static string Md5Hex(string value) =>
        Convert.ToHexString(System.Security.Cryptography.MD5.HashData(Encoding.UTF8.GetBytes(value))).ToLowerInvariant();

    private static byte[] Compress(byte[] payload)
    {
        using var output = new MemoryStream();
        using (var compressor = new CompressionStream(output))
        {
            compressor.Write(payload);
        }

        return output.ToArray();
    }
}