using System.Collections.Generic;
using System.Text;
using ivf_tl_Operate.Debug;
using Xunit;

namespace IvfTl.ControlHost.Tests
{
    public class MjpegFrameParserTests
    {
        // 造一个 multipart 帧字节(与 control MjpegStreamWriter.FrameBytes 同格式)。
        private static byte[] MakeFrame(byte[] jpeg)
        {
            string head = $"--frame\r\nContent-Type: image/jpeg\r\nContent-Length: {jpeg.Length}\r\n\r\n";
            var ms = new List<byte>();
            ms.AddRange(Encoding.ASCII.GetBytes(head));
            ms.AddRange(jpeg);
            ms.AddRange(Encoding.ASCII.GetBytes("\r\n"));
            return ms.ToArray();
        }

        private static List<byte[]> FeedAll(MjpegFrameParser p, byte[] data)
        {
            var all = new List<byte[]>();
            all.AddRange(p.Feed(data, data.Length));
            return all;
        }

        [Fact]
        public void SingleWholeFrame_YieldsOneJpeg()
        {
            var jpeg = new byte[] { 0xFF, 0xD8, 1, 2, 3, 0xFF, 0xD9 };
            var p = new MjpegFrameParser();
            var frames = FeedAll(p, MakeFrame(jpeg));
            Assert.Single(frames);
            Assert.Equal(jpeg, frames[0]);
        }

        [Fact]
        public void TwoFramesInOneChunk_YieldsTwo()
        {
            var j1 = new byte[] { 0xFF, 0xD8, 1, 0xFF, 0xD9 };
            var j2 = new byte[] { 0xFF, 0xD8, 9, 8, 0xFF, 0xD9 };
            var combined = new List<byte>();
            combined.AddRange(MakeFrame(j1));
            combined.AddRange(MakeFrame(j2));
            var p = new MjpegFrameParser();
            var frames = FeedAll(p, combined.ToArray());
            Assert.Equal(2, frames.Count);
            Assert.Equal(j1, frames[0]);
            Assert.Equal(j2, frames[1]);
        }

        [Fact]
        public void FrameSplitAcrossChunks_Reassembles()
        {
            var jpeg = new byte[] { 0xFF, 0xD8, 5, 6, 7, 8, 0xFF, 0xD9 };
            byte[] full = MakeFrame(jpeg);
            var p = new MjpegFrameParser();
            // 在帧中间切两半喂
            int mid = full.Length / 2;
            var first = new byte[mid];
            var second = new byte[full.Length - mid];
            System.Array.Copy(full, 0, first, 0, mid);
            System.Array.Copy(full, mid, second, 0, second.Length);

            var frames = new List<byte[]>();
            frames.AddRange(p.Feed(first, first.Length));
            Assert.Empty(frames);  // 半帧,还吐不出
            frames.AddRange(p.Feed(second, second.Length));
            Assert.Single(frames);
            Assert.Equal(jpeg, frames[0]);
        }

        [Fact]
        public void BadHeaderWithoutContentLength_SkippedThenRecovers()
        {
            var jpeg = new byte[] { 0xFF, 0xD8, 7, 0xFF, 0xD9 };
            var bad = Encoding.ASCII.GetBytes("--frame\r\nContent-Type: image/jpeg\r\n\r\n"); // 无 Content-Length
            var data = new List<byte>();
            data.AddRange(bad);
            data.AddRange(MakeFrame(jpeg));
            var p = new MjpegFrameParser();
            var frames = new List<byte[]>(p.Feed(data.ToArray(), data.Count));
            Assert.Single(frames);
            Assert.Equal(jpeg, frames[0]);
        }

        [Fact]
        public void EmptyInput_ReturnsEmpty_NoThrow()
        {
            var p = new MjpegFrameParser();
            var frames = new List<byte[]>(p.Feed(new byte[0], 0));
            Assert.Empty(frames);
        }
    }
}