using System;
using System.Collections.Generic;
using AcDream.App.Streaming;
using AcDream.Core.Terrain;
using AcDream.Core.World;
using DatReaderWriter.DBObjs;
using Xunit;

namespace AcDream.Core.Tests.Streaming;

public class StreamingControllerPriorityApplyTests
{
    private static LandblockStreamResult.Loaded LoadedOf(uint canonicalId)
        => new(canonicalId, LandblockStreamTier.Near,
               new LoadedLandblock(canonicalId, new LandBlock(), Array.Empty<WorldEntity>()),
               new LandblockMeshData(Array.Empty<TerrainVertex>(), Array.Empty<uint>()));

    [Fact]
    public void PriorityLandblock_isApplied_evenWhenBeyondPerFrameCap()
    {
        uint priority = StreamingRegion.EncodeLandblockIdForTest(169, 180);
        var outbox = new Queue<LandblockStreamResult>(new LandblockStreamResult[]
        {
            LoadedOf(StreamingRegion.EncodeLandblockIdForTest(0, 0)),
            LoadedOf(StreamingRegion.EncodeLandblockIdForTest(0, 1)),
            LoadedOf(StreamingRegion.EncodeLandblockIdForTest(0, 2)),
            LoadedOf(StreamingRegion.EncodeLandblockIdForTest(0, 3)),
            LoadedOf(priority),
        });

        var applied = new List<uint>();
        var state = new GpuWorldState();
        var ctrl = new StreamingController(
            enqueueLoad: (_, _) => { },
            enqueueUnload: _ => { },
            drainCompletions: max =>
            {
                var batch = new List<LandblockStreamResult>();
                while (batch.Count < max && outbox.Count > 0) batch.Add(outbox.Dequeue());
                return batch;
            },
            applyTerrain: (lb, _) => applied.Add(lb.LandblockId),
            state: state, nearRadius: 4, farRadius: 12)
        { MaxCompletionsPerFrame = 4 };

        ctrl.PriorityLandblockId = priority;
        ctrl.Tick(169, 180);

        Assert.Contains(priority, applied);   // priority applied THIS tick
        Assert.True(applied.Count <= 5);       // did not blindly flush the whole outbox
    }

    [Fact]
    public void Deferred_nonPriority_completions_applyOnLaterFrames_withoutLoss()
    {
        // After the priority is found, the non-priority items drained past it must
        // still be applied (over subsequent ticks), never dropped.
        uint priority = StreamingRegion.EncodeLandblockIdForTest(169, 180);
        var outbox = new Queue<LandblockStreamResult>(new LandblockStreamResult[]
        {
            LoadedOf(StreamingRegion.EncodeLandblockIdForTest(0, 0)),
            LoadedOf(StreamingRegion.EncodeLandblockIdForTest(0, 1)),
            LoadedOf(StreamingRegion.EncodeLandblockIdForTest(0, 2)),
            LoadedOf(StreamingRegion.EncodeLandblockIdForTest(0, 3)),
            LoadedOf(StreamingRegion.EncodeLandblockIdForTest(0, 4)),
            LoadedOf(priority),
        });
        var applied = new List<uint>();
        var state = new GpuWorldState();
        var ctrl = new StreamingController(
            (_, _) => { }, _ => { },
            max => { var b = new List<LandblockStreamResult>(); while (b.Count < max && outbox.Count > 0) b.Add(outbox.Dequeue()); return b; },
            (lb, _) => applied.Add(lb.LandblockId),
            state, 4, 12) { MaxCompletionsPerFrame = 4 };
        ctrl.PriorityLandblockId = priority;

        ctrl.Tick(169, 180);  // priority + some others
        ctrl.PriorityLandblockId = 0u;
        ctrl.Tick(169, 180);  // drains the deferred remainder
        ctrl.Tick(169, 180);

        Assert.Contains(priority, applied);
        Assert.Equal(6, applied.Count);  // all six applied, none lost
    }
}