using System;
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using System.IO;
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using System.Text;
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using System.Threading;
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using System.Threading.Tasks;
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using CanSimulator;
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using Xunit;
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namespace Aging.MvpTests
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{
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/// <summary>
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/// CAN 模拟器 TCP 线协议分帧编解码器测试。
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/// 线格式：4 字节大端长度前缀 + UTF8 文本（与 BrokerIpc 同惯用法）。
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/// </summary>
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public class SimulatorFramingTests
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{
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[Fact]
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public void Encode_RoundTrip_DecodesOriginalText()
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{
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string msg = "HELLO:CAN_BUS_1:0:HOST/PID";
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byte[] frame = SimulatorFraming.Encode(msg);
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Assert.Equal(4 + Encoding.UTF8.GetByteCount(msg), frame.Length);
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var ms = new MemoryStream(frame);
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byte[] all = ms.ToArray();
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var got = SimulatorFraming.Decode(all, SimulatorFraming.HeaderSize, all.Length - SimulatorFraming.HeaderSize);
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Assert.Equal(msg, got);
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}
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[Fact]
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public void ReadFrameAsync_TwoFramesInOneBuffer_DecodesBothInOrder()
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{
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// 粘包：两个完整帧连续写入同一流
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var ms = new MemoryStream();
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byte[] f1 = SimulatorFraming.Encode("OK:TX:0x100:8");
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ms.Write(f1, 0, f1.Length);
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byte[] f2 = SimulatorFraming.Encode("EV:RECV:0x123:AA BB:12:00:00.111:2");
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ms.Write(f2, 0, f2.Length);
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ms.Position = 0;
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string? r1 = SimulatorFraming.ReadFrameAsync(ms, CancellationToken.None).GetAwaiter().GetResult();
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string? r2 = SimulatorFraming.ReadFrameAsync(ms, CancellationToken.None).GetAwaiter().GetResult();
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Assert.Equal("OK:TX:0x100:8", r1);
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Assert.Equal("EV:RECV:0x123:AA BB:12:00:00.111:2", r2);
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}
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[Fact]
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public void ReadFrameAsync_FrameSplitAcrossTwoReads_ReassemblesFullFrame()
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{
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// 半包：帧体被拆成两次到达（用分段流模拟）
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byte[] frame = SimulatorFraming.Encode("SEND:0x777:DE AD BE EF");
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var chunked = new ChunkedStream(frame, chunk: 6); // 头部 6 字节后切断
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string? got = SimulatorFraming.ReadFrameAsync(chunked, CancellationToken.None).GetAwaiter().GetResult();
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Assert.Equal("SEND:0x777:DE AD BE EF", got);
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}
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[Fact]
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public void ReadFrameAsync_LengthExceedsMax_Throws()
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{
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// 非法长度前缀：超过 MaxFrameBytes
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byte[] bad = new byte[4];
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bad[0] = 0x7F; bad[1] = 0xFF; bad[2] = 0xFF; bad[3] = 0xFF; // ~2GB
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var ms = new MemoryStream(bad);
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Assert.Throws<InvalidDataException>(() =>
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SimulatorFraming.ReadFrameAsync(ms, CancellationToken.None).GetAwaiter().GetResult());
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}
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[Fact]
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public void ReadFrameAsync_ZeroLengthPrefix_Throws()
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{
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byte[] bad = new byte[4]; // 长度 0
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var ms = new MemoryStream(bad);
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Assert.Throws<InvalidDataException>(() =>
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SimulatorFraming.ReadFrameAsync(ms, CancellationToken.None).GetAwaiter().GetResult());
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}
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[Fact]
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public void ReadFrameAsync_EmptyStream_ReturnsNull()
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{
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// 对端正常关闭：读不到任何字节时返回 null（断线感知契约）
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var ms = new MemoryStream(new byte[0]);
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string? got = SimulatorFraming.ReadFrameAsync(ms, CancellationToken.None).GetAwaiter().GetResult();
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Assert.Null(got);
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}
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[Fact]
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public void ReadFrameAsync_TruncatedBody_ReturnsNull()
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{
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// 头完整但体中途 EOF：返回 null 触发重连
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byte[] frame = SimulatorFraming.Encode("QUERY:RECV_ALL");
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var truncated = new byte[frame.Length - 3];
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Array.Copy(frame, truncated, truncated.Length);
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var ms = new MemoryStream(truncated);
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string? got = SimulatorFraming.ReadFrameAsync(ms, CancellationToken.None).GetAwaiter().GetResult();
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Assert.Null(got);
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}
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/// <summary>每次 Read 只从内部缓冲区取固定片段，模拟网络分片到达</summary>
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private sealed class ChunkedStream : Stream
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{
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private readonly byte[] _data;
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private readonly int _chunk;
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private int _pos;
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public ChunkedStream(byte[] data, int chunk) { _data = data; _chunk = chunk; }
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public override bool CanRead => true;
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public override bool CanSeek => false;
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public override bool CanWrite => false;
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public override long Length => _data.Length;
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public override long Position { get => _pos; set => throw new NotSupportedException(); }
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public override void Flush() { }
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public override int Read(byte[] buffer, int offset, int count)
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{
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if (_pos >= _data.Length) return 0;
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int n = Math.Min(Math.Min(count, _chunk), _data.Length - _pos);
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Array.Copy(_data, _pos, buffer, offset, n);
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_pos += n;
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return n;
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}
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public override long Seek(long o, SeekOrigin s) => throw new NotSupportedException();
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public override void SetLength(long v) => throw new NotSupportedException();
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public override void Write(byte[] b, int o, int c) => throw new NotSupportedException();
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}
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}
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}
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