using System;
using Xunit;
using XWorld.Framework.Protocol;

namespace XWorld.Framework.Tests
{
    public class PacketCodecTests
    {
        [Theory]
        [InlineData(0u)]
        [InlineData(1u)]
        [InlineData(127u)]
        [InlineData(128u)]
        [InlineData(16384u)]
        [InlineData(uint.MaxValue)]
        public void VarUInt_RoundTrips(uint value)
        {
            var w = new PacketWriter();
            w.WriteVarUInt(value);
            var r = new PacketReader(w.ToArray());
            Assert.Equal(value, r.ReadVarUInt());
            Assert.False(r.HasMore);
        }

        [Theory]
        [InlineData(0)]
        [InlineData(1)]
        [InlineData(-1)]
        [InlineData(int.MaxValue)]
        [InlineData(int.MinValue)]
        public void VarInt_RoundTrips(int value)
        {
            var w = new PacketWriter();
            w.WriteVarInt(value);
            var r = new PacketReader(w.ToArray());
            Assert.Equal(value, r.ReadVarInt());
        }

        [Theory]
        [InlineData(0L)]
        [InlineData(-1234567890123L)]
        [InlineData(long.MaxValue)]
        [InlineData(long.MinValue)]
        public void VarLong_RoundTrips(long value)
        {
            var w = new PacketWriter();
            w.WriteVarLong(value);
            var r = new PacketReader(w.ToArray());
            Assert.Equal(value, r.ReadVarLong());
        }

        [Fact]
        public void MixedSequence_RoundTrips_InOrder()
        {
            var w = new PacketWriter();
            w.WriteBool(true);
            w.WriteByte(200);
            w.WriteUInt16(50000);
            w.WriteVarInt(-42);
            w.WriteSingle(3.14159f);
            w.WriteString("héllo 世界");
            w.WriteBytes(new byte[] { 1, 2, 3, 0, 255 });

            var r = new PacketReader(w.ToArray());
            Assert.True(r.ReadBool());
            Assert.Equal((byte)200, r.ReadByte());
            Assert.Equal((ushort)50000, r.ReadUInt16());
            Assert.Equal(-42, r.ReadVarInt());
            Assert.Equal(3.14159f, r.ReadSingle(), 5);
            Assert.Equal("héllo 世界", r.ReadString());
            Assert.Equal(new byte[] { 1, 2, 3, 0, 255 }, r.ReadBytes());
            Assert.False(r.HasMore);
        }

        [Fact]
        public void EmptyAndNull_String_Bytes_RoundTripAsEmpty()
        {
            var w = new PacketWriter();
            w.WriteString(null);
            w.WriteString("");
            w.WriteBytes(null);
            w.WriteBytes(Array.Empty<byte>());

            var r = new PacketReader(w.ToArray());
            Assert.Equal("", r.ReadString());
            Assert.Equal("", r.ReadString());
            Assert.Empty(r.ReadBytes());
            Assert.Empty(r.ReadBytes());
        }

        [Fact]
        public void ReadPastEnd_Throws()
        {
            var r = new PacketReader(Array.Empty<byte>());
            Assert.Throws<FormatException>(() => r.ReadByte());
        }

        [Fact]
        public void ReadBytes_WithBogusLength_Throws()
        {
            // 长度前缀声称 10 字节，实际无数据
            var w = new PacketWriter();
            w.WriteVarUInt(10);
            var r = new PacketReader(w.ToArray());
            Assert.Throws<FormatException>(() => r.ReadBytes());
        }

        [Fact]
        public void ReadVarUInt_SixthByte_Throws()
        {
            // 5 个延续字节后还有第 6 字节 → 过长，必须抛异常而非静默损坏
            var r = new PacketReader(new byte[] { 0xFF, 0xFF, 0xFF, 0xFF, 0x8F, 0x00 });
            Assert.Throws<FormatException>(() => r.ReadVarUInt());
        }

        [Fact]
        public void ReadVarUInt_LastByteOverflow_Throws()
        {
            // 第 5 字节 0x10 表示值超过 uint.MaxValue
            var r = new PacketReader(new byte[] { 0xFF, 0xFF, 0xFF, 0xFF, 0x10 });
            Assert.Throws<FormatException>(() => r.ReadVarUInt());
        }

        [Fact]
        public void ReadVarLong_EleventhByte_Throws()
        {
            var r = new PacketReader(new byte[] { 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0x81, 0x00 });
            Assert.Throws<FormatException>(() => r.ReadVarLong());
        }

        [Fact]
        public void ReadVarLong_LastByteOverflow_Throws()
        {
            // 第 10 字节 0x02 表示值超过 ulong 的 64 位
            var r = new PacketReader(new byte[] { 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0x02 });
            Assert.Throws<FormatException>(() => r.ReadVarLong());
        }
    }
}