using System.Buffers.Binary;
using System.Text;
using AcDream.Core.Items;
using AcDream.Core.Net.Messages;

namespace AcDream.Core.Net.Tests.Messages;

public sealed class CreateObjectTests
{
    [Fact]
    public void TryParse_WeenieHeaderPrefix_ReturnsNameAndItemType()
    {
        byte[] body = BuildMinimalCreateObjectWithWeenieHeader(
            guid: 0x50000002u,
            name: "Drudge",
            itemType: (uint)ItemType.Creature);

        var parsed = CreateObject.TryParse(body);

        Assert.NotNull(parsed);
        Assert.Equal(0x50000002u, parsed.Value.Guid);
        Assert.Equal("Drudge", parsed.Value.Name);
        Assert.Equal((uint)ItemType.Creature, parsed.Value.ItemType);
    }

    // -----------------------------------------------------------------------
    // Commit A of 2026-04-29 live-entity collision port:
    // PhysicsState (post-flags u32) + ObjectDescriptionFlags (PWD bitfield)
    // must be surfaced for downstream collision registration.
    // -----------------------------------------------------------------------

    [Fact]
    public void TryParse_PhysicsState_Parsed()
    {
        // ETHEREAL_PS = 0x4 + IGNORE_COLLISIONS_PS = 0x10 → 0x14
        byte[] body = BuildMinimalCreateObjectWithWeenieHeader(
            guid: 0x50000003u, name: "GhostNpc",
            itemType: (uint)ItemType.Creature,
            physicsState: 0x14u);

        var parsed = CreateObject.TryParse(body);

        Assert.NotNull(parsed);
        Assert.Equal(0x14u, parsed!.Value.PhysicsState);
    }

    [Fact]
    public void TryParse_ObjectDescriptionFlags_PlayerKillerBitsSurface()
    {
        // BF_PLAYER (0x8) | BF_PLAYER_KILLER (0x20) → a PK player.
        byte[] body = BuildMinimalCreateObjectWithWeenieHeader(
            guid: 0x50000004u, name: "+PkPlayer",
            itemType: (uint)ItemType.Creature,
            objectDescriptionFlags: 0x8u | 0x20u);

        var parsed = CreateObject.TryParse(body);

        Assert.NotNull(parsed);
        Assert.Equal(0x28u, parsed!.Value.ObjectDescriptionFlags);
    }

    [Fact]
    public void TryParse_ObjectDescriptionFlags_PkLiteBit()
    {
        // BF_PLAYER (0x8) | BF_PKLITE_PKSTATUS (0x2000000) → a PK-lite player.
        byte[] body = BuildMinimalCreateObjectWithWeenieHeader(
            guid: 0x50000005u, name: "+PklPlayer",
            itemType: (uint)ItemType.Creature,
            objectDescriptionFlags: 0x8u | 0x2000000u);

        var parsed = CreateObject.TryParse(body);

        Assert.NotNull(parsed);
        Assert.Equal(0x2000008u, parsed!.Value.ObjectDescriptionFlags);
    }

    // -----------------------------------------------------------------------
    // 2026-05-15: WeenieHeader optional-tail walker landed for Useability +
    // UseRadius (acclient.h ITEM_USEABLE enum at line 6478). The R-key Use
    // gate consumes Useability; signs without USEABLE_REMOTE (0x20) silently
    // ignore Use.
    // -----------------------------------------------------------------------

    [Fact]
    public void TryParse_NoWeenieFlags_LeavesUseabilityNull()
    {
        // Sign-like entity: weenieFlags=0 (no optional fields).
        // Useability stays null (parser walked past nothing).
        byte[] body = BuildMinimalCreateObjectWithWeenieHeader(
            guid: 0x50000006u, name: "Holtburg Sign",
            itemType: 0x8000u);

        var parsed = CreateObject.TryParse(body);

        Assert.NotNull(parsed);
        Assert.Null(parsed!.Value.Useability);
        Assert.Null(parsed.Value.UseRadius);
    }

    [Fact]
    public void TryParse_WeenieFlagsUsable_ReadsUseability()
    {
        // Useable NPC: weenieFlags has bit 0x10 set, body carries
        // ITEM_USEABLE = USEABLE_REMOTE (0x20).
        byte[] body = BuildMinimalCreateObjectWithWeenieHeader(
            guid: 0x50000007u, name: "Tirenia",
            itemType: (uint)ItemType.Creature,
            weenieFlags: 0x10u,
            useability: 0x20u);

        var parsed = CreateObject.TryParse(body);

        Assert.NotNull(parsed);
        Assert.Equal(0x20u, parsed!.Value.Useability);
    }

    [Fact]
    public void TryParse_WeenieFlagsUsable_ReadsUseableNoValue()
    {
        // Holtburg sign case (observed 2026-05-16): ACE sends
        // weenieFlags=0x10 + Useability=USEABLE_NO (0x01) for signs.
        // The parser must read this verbatim — downstream code
        // distinguishes USEABLE_NO from USEABLE_REMOTE for the
        // pickup vs use gate.
        byte[] body = BuildMinimalCreateObjectWithWeenieHeader(
            guid: 0x7A9B3001u, name: "Holtburg",
            itemType: 0x80u,           // Misc
            weenieFlags: 0x10u,
            useability: 0x01u);        // USEABLE_NO

        var parsed = CreateObject.TryParse(body);

        Assert.NotNull(parsed);
        Assert.Equal(0x01u, parsed!.Value.Useability);
    }

    [Fact]
    public void TryParse_WeenieFlagsValueAndUsableAndUseRadius_AllReadInOrder()
    {
        // Verify the walker skips Value (bit 0x8, 4 bytes) BEFORE reading
        // Useability (bit 0x10) and UseRadius (bit 0x20). Wire order in
        // ACE WorldObject_Networking.cs:99-106 is Value, Useable, UseRadius.
        byte[] body = BuildMinimalCreateObjectWithWeenieHeader(
            guid: 0x50000008u, name: "PriceyDoor",
            itemType: (uint)ItemType.Misc,
            weenieFlags: 0x8u | 0x10u | 0x20u,
            value: 0x12345678u,
            useability: 0x20u,
            useRadius: 2.5f);

        var parsed = CreateObject.TryParse(body);

        Assert.NotNull(parsed);
        Assert.Equal(0x20u, parsed!.Value.Useability);
        Assert.NotNull(parsed.Value.UseRadius);
        Assert.Equal(2.5f, parsed.Value.UseRadius!.Value, precision: 3);
    }

    private static byte[] BuildMinimalCreateObjectWithWeenieHeader(
        uint guid,
        string name,
        uint itemType,
        uint physicsState = 0,
        uint objectDescriptionFlags = 0,
        uint weenieFlags = 0,
        uint? value = null,
        uint? useability = null,
        float? useRadius = null)
    {
        var bytes = new List<byte>();
        WriteU32(bytes, CreateObject.Opcode);
        WriteU32(bytes, guid);

        // ModelData header: marker, subpalette count, texture count, animpart count.
        bytes.Add(0x11);
        bytes.Add(0);
        bytes.Add(0);
        bytes.Add(0);

        // PhysicsData: physics flags = 0, then PhysicsState u32, then 9 seq stamps.
        WriteU32(bytes, 0);
        WriteU32(bytes, physicsState);
        for (int i = 0; i < 9; i++)
            WriteU16(bytes, 0);
        Align4(bytes);

        // Fixed WeenieHeader prefix per ACE SerializeCreateObject.
        WriteU32(bytes, weenieFlags);    // weenieFlags
        WriteString16L(bytes, name);
        WritePackedDword(bytes, 0x1234); // WeenieClassId
        WritePackedDword(bytes, 0);      // IconId via known-type writer
        WriteU32(bytes, itemType);
        WriteU32(bytes, objectDescriptionFlags);
        Align4(bytes);

        // Optional WeenieHeader tail (2026-05-15) — same order as ACE
        // WorldObject_Networking.cs:87-114. Each field is written only when
        // its weenieFlags bit is set, matching the parser's walker exactly.
        if ((weenieFlags & 0x00000008u) != 0)         // Value u32
            WriteU32(bytes, value ?? 0u);
        if ((weenieFlags & 0x00000010u) != 0)         // Useability u32
            WriteU32(bytes, useability ?? 0u);
        if ((weenieFlags & 0x00000020u) != 0)         // UseRadius f32
        {
            Span<byte> tmp = stackalloc byte[4];
            BinaryPrimitives.WriteSingleLittleEndian(tmp, useRadius ?? 0f);
            bytes.AddRange(tmp.ToArray());
        }

        return bytes.ToArray();
    }

    private static void WriteU32(List<byte> bytes, uint value)
    {
        Span<byte> tmp = stackalloc byte[4];
        BinaryPrimitives.WriteUInt32LittleEndian(tmp, value);
        bytes.AddRange(tmp.ToArray());
    }

    private static void WriteU16(List<byte> bytes, ushort value)
    {
        Span<byte> tmp = stackalloc byte[2];
        BinaryPrimitives.WriteUInt16LittleEndian(tmp, value);
        bytes.AddRange(tmp.ToArray());
    }

    private static void WritePackedDword(List<byte> bytes, uint value)
    {
        if (value <= 0x7FFF)
        {
            WriteU16(bytes, (ushort)value);
            return;
        }

        WriteU16(bytes, (ushort)(((value >> 16) & 0x7FFF) | 0x8000));
        WriteU16(bytes, (ushort)(value & 0xFFFF));
    }

    private static void WriteString16L(List<byte> bytes, string value)
    {
        byte[] encoded = Encoding.GetEncoding(1252).GetBytes(value);
        WriteU16(bytes, checked((ushort)encoded.Length));
        bytes.AddRange(encoded);
        Align4(bytes);
    }

    private static void Align4(List<byte> bytes)
    {
        while ((bytes.Count & 3) != 0)
            bytes.Add(0);
    }
}