using System.Collections.Generic;
using AcDream.App.Streaming;
using Xunit;

namespace AcDream.Core.Tests.Streaming;

/// <summary>
/// #138 — selection logic for re-hydrating server objects when a landblock
/// reloads after a dungeon collapse (or a Near→Far demote). See
/// <see cref="LandblockEntityRehydrator"/> for the retail/ACE rationale.
/// </summary>
public class LandblockEntityRehydratorTests
{
    private const uint PlayerGuid = 0x50000001u;
    // A door spawned in cell 0x00070123 of dungeon landblock 0x0007; its
    // cell-resolved spawn id must match the streamed canonical id 0x0007FFFF.
    private const uint DungeonLb = 0x0007FFFFu;
    private const uint DoorGuid = 0x7A9B4001u;
    private const uint DoorSpawnId = 0x00070123u;

    private static LandblockEntityRehydrator.RetainedSpawn Spawn(
        uint guid, uint spawnLbId, bool hasMesh = true)
        => new(guid, spawnLbId, hasMesh);

    [Fact]
    public void RetainedSpawnInLoadedLandblock_NotPresent_IsSelected()
    {
        var result = LandblockEntityRehydrator.SelectGuidsToRehydrate(
            DungeonLb,
            new[] { Spawn(DoorGuid, DoorSpawnId) },
            new HashSet<uint>(),
            PlayerGuid);

        Assert.Equal(new[] { DoorGuid }, result);
    }

    [Fact]
    public void CellResolvedSpawnId_MatchesCanonicalLoadedId()
    {
        // The streamed landblock id is canonical (0xAAAAFFFF); the spawn id is
        // cell-resolved (0xAAAA00CC). They name the same landblock, so the door
        // must be selected — the canonicalization is the load-bearing step.
        var result = LandblockEntityRehydrator.SelectGuidsToRehydrate(
            DungeonLb,                          // 0x0007FFFF
            new[] { Spawn(DoorGuid, 0x000701A9u) }, // a different cell, same landblock
            new HashSet<uint>(),
            PlayerGuid);

        Assert.Equal(new[] { DoorGuid }, result);
    }

    [Fact]
    public void SpawnInDifferentLandblock_IsNotSelected()
    {
        var result = LandblockEntityRehydrator.SelectGuidsToRehydrate(
            DungeonLb,
            new[] { Spawn(DoorGuid, 0xA9B30123u) }, // Holtburg, not the loaded dungeon
            new HashSet<uint>(),
            PlayerGuid);

        Assert.Empty(result);
    }

    [Fact]
    public void AlreadyPresentGuid_IsNotSelected()
    {
        // Already rendered (server re-sent it, or it was never dropped) — a
        // re-hydrate would be a redundant mesh rebuild.
        var result = LandblockEntityRehydrator.SelectGuidsToRehydrate(
            DungeonLb,
            new[] { Spawn(DoorGuid, DoorSpawnId) },
            new HashSet<uint> { DoorGuid },
            PlayerGuid);

        Assert.Empty(result);
    }

    [Fact]
    public void PlayerGuid_IsNeverSelected()
    {
        // The player has a retained spawn too, but the persistent-rescue path
        // owns it (preserves its live pose). Re-hydrating would reset it.
        var result = LandblockEntityRehydrator.SelectGuidsToRehydrate(
            DungeonLb,
            new[] { Spawn(PlayerGuid, DoorSpawnId) },
            new HashSet<uint>(),
            PlayerGuid);

        Assert.Empty(result);
    }

    [Fact]
    public void SpawnWithoutWorldMesh_IsNotSelected()
    {
        // Inventory items / setup-less spawns build no visible entity.
        var result = LandblockEntityRehydrator.SelectGuidsToRehydrate(
            DungeonLb,
            new[] { Spawn(DoorGuid, DoorSpawnId, hasMesh: false) },
            new HashSet<uint>(),
            PlayerGuid);

        Assert.Empty(result);
    }

    [Fact]
    public void MixedSet_SelectsOnlyAbsentWorldObjectsInLoadedLandblock()
    {
        uint npcGuid = 0x7A9B4002u;       // same dungeon landblock, absent → select
        uint chestGuid = 0x7A9B4003u;     // same landblock but already present → skip
        uint holtburgGuid = 0x7A9B4004u;  // different landblock → skip
        uint heldItemGuid = 0x7A9B4005u;  // no world mesh → skip

        var spawns = new[]
        {
            Spawn(DoorGuid, DoorSpawnId),                 // select
            Spawn(npcGuid, 0x00070177u),                  // select (same lb, different cell)
            Spawn(chestGuid, 0x00070123u),                // skip (present)
            Spawn(holtburgGuid, 0xA9B30100u),             // skip (other lb)
            Spawn(heldItemGuid, 0x00070123u, hasMesh: false), // skip (no mesh)
            Spawn(PlayerGuid, 0x00070100u),               // skip (player)
        };

        var result = LandblockEntityRehydrator.SelectGuidsToRehydrate(
            DungeonLb, spawns, new HashSet<uint> { chestGuid }, PlayerGuid);

        Assert.Equal(new HashSet<uint> { DoorGuid, npcGuid }, new HashSet<uint>(result));
    }
}