using ProjectM.Simulation;
using Unity.Burst;
using Unity.Collections;
using Unity.Entities;
using Unity.Mathematics;
using Unity.NetCode;
using Unity.Transforms;

namespace ProjectM.Server
{
    /// <summary>
    /// Server-only resource harvest + Blight-clutter clearing: sweeps each surviving projectile's this-tick travel
    /// segment against a UNIFIED target set of resource-node ghosts AND Blight-clutter ghosts, deposits the hit
    /// target's yield into the GLOBAL resource ledger (the CycleDirector's <see cref="StorageEntry"/> buffer,
    /// resolved via <see cref="ResourceLedger"/> — NEVER GetSingleton&lt;StorageEntry&gt;, which would collide with
    /// the base storage container) and decrements its Remaining; the target despawns at &lt;= 0. Nodes deposit
    /// <see cref="ResourceNode.ResourceId"/> @ HarvestPerHit; clutter deposits <see cref="BlightClutter.ScrapResourceId"/>
    /// @ ScrapPerHit (a small "minor scrap" trickle — carving through the frontier). UNIFYING the two into one sweep
    /// is a CORRECTNESS requirement: two separate sweeps would each DestroyEntity a projectile that overlaps a node
    /// AND a clutter piece — a double DestroyEntity throws at ECB playback. Runs in the plain server
    /// SimulationSystemGroup <c>[UpdateAfter(PredictedSimulationSystemGroup)]</c> — after ProjectileDamageSystem has
    /// consumed Health-target hits and range-expired projectiles, so this only sees true survivors. The swept
    /// segment is reconstructed from <see cref="Projectile.LastStep"/> (written by ProjectileMoveSystem in the
    /// fixed-step group), so it is tunnelling-safe WITHOUT depending on this plain group's variable-frame DeltaTime.
    /// A target hit by two projectiles in one tick deposits twice but is destroyed exactly once. Relies on the
    /// asserted ~1000-unit base/expedition coordinate gap so a base projectile can never reach an expedition target.
    /// </summary>
    [BurstCompile]
    [WorldSystemFilter(WorldSystemFilterFlags.ServerSimulation)]
    [UpdateInGroup(typeof(SimulationSystemGroup))]
    [UpdateAfter(typeof(PredictedSimulationSystemGroup))]
    public partial struct ResourceHarvestSystem : ISystem
    {
        const float k_ProjectileRadius = Tuning.HarvestProjectileRadius;

        ComponentLookup<GhostOwner> m_GhostOwnerLookup;
        BufferLookup<InventorySlot> m_InvLookup;

        [BurstCompile]
        public void OnCreate(ref SystemState state)
        {
            state.RequireForUpdate<Projectile>();
            state.RequireForUpdate<ResourceLedger>();
            m_GhostOwnerLookup = state.GetComponentLookup<GhostOwner>(true);
            m_InvLookup = state.GetBufferLookup<InventorySlot>(false);
        }

        [BurstCompile]
        public void OnUpdate(ref SystemState state)
        {
            var ledgerEntity = SystemAPI.GetSingletonEntity<ResourceLedger>();
            var ledger = SystemAPI.GetBuffer<StorageEntry>(ledgerEntity);

            // Resolve the harvesting player from the projectile's GhostOwner so yield lands in their PERSONAL
            // inventory. Owner read via a cached lookup (optional); the owner->player map + item catalog are
            // hoisted out of the per-hit sweep (invariant for the tick).
            m_GhostOwnerLookup.Update(ref state);
            m_InvLookup.Update(ref state);
            bool haveDb = SystemAPI.TryGetSingleton<ItemDatabase>(out var itemDb);

            var playerByConn = new NativeHashMap<int, Entity>(8, Allocator.Temp);
            foreach (var (owner, playerEntity) in
                     SystemAPI.Query<RefRO<GhostOwner>>().WithAll<PlayerTag, InventorySlot>().WithEntityAccess())
                playerByConn[owner.ValueRO.NetworkId] = playerEntity;

            // Snapshot all harvest/clear targets (nodes + clutter) once this tick into a UNIFIED set.
            var tgtEntity = new NativeList<Entity>(Allocator.Temp);
            var tgtPos = new NativeList<float2>(Allocator.Temp);
            var tgtRadius = new NativeList<float>(Allocator.Temp);
            var tgtRemaining = new NativeList<int>(Allocator.Temp);
            var tgtYieldId = new NativeList<byte>(Allocator.Temp);
            var tgtYieldPerHit = new NativeList<float>(Allocator.Temp);
            var tgtVariant = new NativeList<byte>(Allocator.Temp);
            var tgtIsClutter = new NativeList<bool>(Allocator.Temp);

            foreach (var (xform, hr, node, e) in
                     SystemAPI.Query<RefRO<LocalTransform>, RefRO<HitRadius>, RefRO<ResourceNode>>().WithEntityAccess())
            {
                tgtEntity.Add(e);
                tgtPos.Add(xform.ValueRO.Position.xz);
                tgtRadius.Add(hr.ValueRO.Value);
                tgtRemaining.Add(node.ValueRO.Remaining);
                tgtYieldId.Add(node.ValueRO.ResourceId);
                tgtYieldPerHit.Add(node.ValueRO.HarvestPerHit);
                tgtVariant.Add(0);
                tgtIsClutter.Add(false);
            }

            foreach (var (xform, hr, clutter, e) in
                     SystemAPI.Query<RefRO<LocalTransform>, RefRO<HitRadius>, RefRO<BlightClutter>>().WithEntityAccess())
            {
                tgtEntity.Add(e);
                tgtPos.Add(xform.ValueRO.Position.xz);
                tgtRadius.Add(hr.ValueRO.Value);
                tgtRemaining.Add(clutter.ValueRO.Remaining);
                tgtYieldId.Add(clutter.ValueRO.ScrapResourceId);
                tgtYieldPerHit.Add(clutter.ValueRO.ScrapPerHit);
                tgtVariant.Add(clutter.ValueRO.Variant);
                tgtIsClutter.Add(true);
            }

            var destroyed = new NativeArray<bool>(tgtEntity.Length, Allocator.Temp);
            var ecb = new EntityCommandBuffer(Allocator.Temp);

            foreach (var (xform, proj, projEntity) in
                     SystemAPI.Query<RefRO<LocalTransform>, RefRO<Projectile>>().WithEntityAccess())
            {
                float3 cur = xform.ValueRO.Position;
                float2 segEnd = cur.xz;
                float2 segStart = segEnd - proj.ValueRO.Direction * proj.ValueRO.LastStep;
                float2 seg = segEnd - segStart;
                float segLenSq = math.lengthsq(seg);

                int bestIdx = -1;
                float bestT = float.MaxValue;
                bool overlappedCleared = false; // struck a target a sibling projectile already cleared THIS tick
                for (int i = 0; i < tgtEntity.Length; i++)
                {
                    float2 tp = tgtPos[i];
                    float t = segLenSq > 1e-8f ? math.saturate(math.dot(tp - segStart, seg) / segLenSq) : 0f;
                    float2 closest = segStart + t * seg;
                    float hitDist = tgtRadius[i] + k_ProjectileRadius;
                    if (math.distancesq(tp, closest) > hitDist * hitDist)
                        continue;
                    if (destroyed[i]) { overlappedCleared = true; continue; }
                    if (t < bestT) { bestT = t; bestIdx = i; }
                }

                if (bestIdx < 0)
                {
                    // No LIVE target on the segment. If the shot still overlapped a target a sibling projectile
                    // cleared this same tick, consume it anyway (a hit always spends the shot); else it's a miss.
                    if (overlappedCleared)
                        ecb.DestroyEntity(projEntity);
                    continue;
                }

                // A positive baked yield must always make progress: a raw (int) truncation of a sub-1.0 per-hit
                // value would deposit 0 AND never decrement Remaining -> an immortal target that silently eats shots.
                int amount = math.max(1, (int)tgtYieldPerHit[bestIdx]);
                byte yieldId = tgtYieldId[bestIdx];

                // Route the yield into the HARVESTING player's PERSONAL inventory. The projectile carries the
                // firing player's GhostOwner (AbilityFireSystem); the owner is read OPTIONALLY (cached lookup) so
                // an un-owned projectile (or a test projectile with no GhostOwner) falls through to the ledger.
                int remainder = amount;
                if (m_GhostOwnerLookup.HasComponent(projEntity)
                    && playerByConn.TryGetValue(m_GhostOwnerLookup[projEntity].NetworkId, out var player)
                    && m_InvLookup.HasBuffer(player))
                {
                    int stackMax = Tuning.DefaultStackMax;
                    if (haveDb && itemDb.Value.IsCreated)
                    {
                        ref var itemBlob = ref itemDb.Value.Value;
                        if (itemBlob.TryGetItem(yieldId, out var def) && def.StackMax > 0)
                            stackMax = def.StackMax;
                    }
                    var inv = m_InvLookup[player];
                    remainder = InventoryMath.Deposit(inv, yieldId, amount, stackMax, Tuning.InventoryMaxSlots);
                }

                // Unresolvable owner or a full bag: the remainder credits the shared ledger (no-loss valve).
                if (remainder > 0)
                    StorageMath.Deposit(ledger, yieldId, remainder);
                int rem = tgtRemaining[bestIdx] - amount;
                tgtRemaining[bestIdx] = rem;
                ecb.DestroyEntity(projEntity);

                if (rem <= 0)
                {
                    if (!destroyed[bestIdx])
                    {
                        destroyed[bestIdx] = true;
                        ecb.DestroyEntity(tgtEntity[bestIdx]);
                    }
                }
                else if (tgtIsClutter[bestIdx])
                {
                    // Persist the decremented Remaining (replicated GhostField) so depletion carries across ticks.
                    SystemAPI.SetComponent(tgtEntity[bestIdx], new BlightClutter
                    {
                        Remaining = rem,
                        Variant = tgtVariant[bestIdx],
                        ScrapResourceId = tgtYieldId[bestIdx],
                        ScrapPerHit = tgtYieldPerHit[bestIdx],
                    });
                }
                else
                {
                    SystemAPI.SetComponent(tgtEntity[bestIdx], new ResourceNode
                    {
                        ResourceId = tgtYieldId[bestIdx],
                        Remaining = rem,
                        HarvestPerHit = tgtYieldPerHit[bestIdx],
                    });
                }
            }

            ecb.Playback(state.EntityManager);
            ecb.Dispose();
            playerByConn.Dispose();
            destroyed.Dispose();
            tgtEntity.Dispose();
            tgtPos.Dispose();
            tgtRadius.Dispose();
            tgtRemaining.Dispose();
            tgtYieldId.Dispose();
            tgtYieldPerHit.Dispose();
            tgtVariant.Dispose();
            tgtIsClutter.Dispose();
        }
    }
}