using ProjectM.Simulation;
using Unity.Burst;using Unity.Collections;

using Unity.Entities;
using Unity.Mathematics;
using Unity.NetCode;

namespace ProjectM.Server
{
    /// <summary>
    /// Server-authoritative macro-loop director for the PLAYER-DRIVEN loop. The base sits in <c>Calm</c>
    /// (persistent, unhurried — build/prep at your pace, no countdown) until the <see cref="ThreatState"/> arms a
    /// siege, then flips to <c>Siege</c> (the base-defense wave) and back to <c>Calm</c> when the wave is cleared.
    /// There is no global "Expedition" phase — being out on an expedition is per-player presence (server-only
    /// <see cref="RegionTag"/>), read client-side by the HUD, so one global byte never has to represent
    /// "player A out / player B home." Maintains the replicated <see cref="CycleState"/> singleton and gates
    /// <see cref="WaveSystem"/> (waves spawn only during Siege). Runs in the plain server SimulationSystemGroup
    /// before WaveSystem. All timing is wrap-safe NetworkTick math (<see cref="ProjectM.Simulation.TickUtil.NonZero"/>
    /// + <see cref="Unity.NetCode.NetworkTick.IsNewerThan"/>), never raw uint compares. Lives on the
    /// runtime-spawned CycleDirector ghost. Supersedes the forced timed Expedition→Defend→Build cycle.
    /// </summary>
    [BurstCompile]
    [WorldSystemFilter(WorldSystemFilterFlags.ServerSimulation)]
    [UpdateInGroup(typeof(SimulationSystemGroup))]
    [UpdateBefore(typeof(WaveSystem))]
    public partial struct CyclePhaseSystem : ISystem
    {
        [BurstCompile]
        public void OnCreate(ref SystemState state)
        {
            state.RequireForUpdate<NetworkTime>();
            state.RequireForUpdate<CycleState>();
        }

        [BurstCompile]
        public void OnUpdate(ref SystemState state)
        {
            var serverTick = SystemAPI.GetSingleton<NetworkTime>().ServerTick;
            if (!serverTick.IsValid)
                return;
            uint now = serverTick.TickIndexForValidTick;

            var cycleEntity = SystemAPI.GetSingletonEntity<CycleState>();
            var cycle = SystemAPI.GetComponent<CycleState>(cycleEntity);
            var runtime = SystemAPI.GetComponent<CycleRuntime>(cycleEntity);

            if (cycle.Phase == CyclePhase.Calm)
            {
                // Default calm: no pending siege => no countdown.
                cycle.PhaseEndTick = 0;

                if (SystemAPI.HasComponent<ThreatState>(cycleEntity))
                {
                    var threat = SystemAPI.GetComponent<ThreatState>(cycleEntity);
                    if (threat.PendingSiegeSize > 0)
                    {
                        // Telegraph: mirror the arm tick into the replicated PhaseEndTick so the HUD can show an
                        // "incursion in Ns" countdown (reuses the existing HUD countdown path) while it arms.
                        cycle.PhaseEndTick = threat.ArmTick;

                        bool armed = threat.ArmTick == 0
                                     || !new NetworkTick(threat.ArmTick).IsNewerThan(serverTick);

                        if (armed && SystemAPI.TryGetSingletonEntity<WaveState>(out var waveEntity))
                        {
                            // ---- Calm -> Siege: seed WaveSystem's own Spawning entry atomically. Writing
                            // Phase=Spawning bypasses its Lull escalation recompute (WaveSystem only recomputes
                            // RemainingToSpawn while Phase==Lull), so the siege spawns EXACTLY the director-chosen
                            // size and WaveSystem stays the sole WaveState writer thereafter. ----
                            var w = SystemAPI.GetComponent<WaveState>(waveEntity);
                            runtime.DefendStartWave = w.WaveNumber;     // capture BEFORE the bump (DefendCleared tests > this)
                            w.WaveNumber += 1;
                            w.Phase = WavePhase.Spawning;
                            w.RemainingToSpawn = math.max(1, threat.PendingSiegeSize);
                            w.NextActionTick = TickUtil.NonZero(now);   // spawn the first Husk this tick
                            SystemAPI.SetComponent(waveEntity, w);

                            cycle.Phase = CyclePhase.Siege;
                            cycle.PhaseEndTick = 0;                      // Siege is wave-driven, not timed.

                            threat.PendingSiegeSize = 0;                 // consume once
                            threat.ArmTick = 0;
                            SystemAPI.SetComponent(cycleEntity, threat);
                        }
                    }
                }
            }
            else if (cycle.Phase == CyclePhase.Siege)
            {
                // END-2: is this the FINAL siege (the goal cap armed it)? Server-only RunPhase marker; HasComponent-
                // guarded so EditMode worlds without RunPhase keep the pre-END-2 (normal) soft-loss + survival paths.
                bool isFinal = SystemAPI.HasComponent<RunPhase>(cycleEntity)
                               && SystemAPI.GetComponent<RunPhase>(cycleEntity).Value == RunPhaseId.FinalDefense;

                // The Engine Core breached to 0 during the siege (checked BEFORE survival). CyclePhaseSystem stays the
                // sole Phase/WaveState writer; it is ALSO the sole RunOutcome writer (END-2 single-writer).
                bool overrun = SystemAPI.HasComponent<CoreIntegrity>(cycleEntity)
                               && SystemAPI.GetComponent<CoreIntegrity>(cycleEntity).Current <= 0;
                if (overrun)
                {
                    cycle.Phase = CyclePhase.Calm;
                    cycle.PhaseEndTick = 0;

                    // The siege ends: despawn the base siege Husks (the locked despawn-on-breach fork) + reset the
                    // wave so the NEXT armed siege starts clean (WaveSystem idles in Calm anyway). Shared by both paths.
                    var ecb = new EntityCommandBuffer(Allocator.Temp);
                    // Slice 3: cull the BASE wave only — an Expedition wave runs in its own region and must
                    // survive a base Core breach. A region-blind EnemyTag wipe would also spuriously trip the
                    // zone director's aliveZone==0 clear/reward edge. Mirrors ThreatDirectorSystem + DefendCleared.
                    foreach (var (hr, he) in SystemAPI.Query<RefRO<RegionTag>>().WithAll<EnemyTag>().WithEntityAccess())
                        if (hr.ValueRO.Region == RegionId.Base)
                            ecb.DestroyEntity(he);
                    ecb.Playback(state.EntityManager);
                    ecb.Dispose();
                    if (SystemAPI.TryGetSingletonEntity<WaveState>(out var waveLost))
                    {
                        var wl = SystemAPI.GetComponent<WaveState>(waveLost);
                        wl.RemainingToSpawn = 0;
                        wl.Phase = WavePhase.Lull;
                        wl.NextActionTick = 0;
                        SystemAPI.SetComponent(waveLost, wl);
                    }

                    if (isFinal)
                    {
                        // END-2 TERMINAL LOSS: the final stand fell. Latch Loss + halt (the director stops arming). NO
                        // ledger drain and NO OverrunTick stamp -> the client shows the dedicated terminal Loss banner
                        // (from the replicated RunOutcome), not the soft "the Core will recover" flash.
                        SystemAPI.SetComponent(cycleEntity, new RunOutcome { Value = RunOutcomeId.Loss });
                    }
                    else
                    {
                        // END-1 SOFT LOSS (unchanged): drain a fraction of the shared ledger + stamp the transient
                        // overrun pulse; the base persists wounded and the Core regenerates in Calm (the DR-029 fork).
                        var tuneL = SystemAPI.TryGetSingleton<TuningConfig>(out var tcfgL) ? tcfgL : TuningConfig.Defaults();
                        if (SystemAPI.HasBuffer<StorageEntry>(cycleEntity))
                        {
                            var ledger = SystemAPI.GetBuffer<StorageEntry>(cycleEntity);
                            StorageMath.DrainFraction(ledger, tuneL.CoreOverrunDrainPct);
                        }
                        var coreL = SystemAPI.GetComponent<CoreIntegrity>(cycleEntity);
                        coreL.OverrunTick = TickUtil.NonZero(now);
                        SystemAPI.SetComponent(cycleEntity, coreL);
                    }

                    // Autosave the checkpoint (a breach / final loss is a meaningful save point).
                    if (SystemAPI.HasComponent<SaveRequest>(cycleEntity))
                        SystemAPI.SetComponent(cycleEntity, new SaveRequest { Pending = 1 });
                }
                else if (DefendCleared(ref state, runtime.DefendStartWave))
                {
                    cycle.Phase = CyclePhase.Calm;
                    cycle.PhaseEndTick = 0;
                    if (isFinal)
                    {
                        // END-2 TERMINAL WIN: the final siege was survived -> the Engine holds. Latch Victory + halt;
                        // do NOT increment the (already-capped) goal.
                        SystemAPI.SetComponent(cycleEntity, new RunOutcome { Value = RunOutcomeId.Victory });
                        if (SystemAPI.HasComponent<SaveRequest>(cycleEntity))
                            SystemAPI.SetComponent(cycleEntity, new SaveRequest { Pending = 1 });
                    }
                    // DR-042: a SURVIVED base siege no longer advances the win meter — that was the AFK/passive win
                    // path (scheduled sieges auto-armed + auto-collapsed on timeout, so standing still won). The win-
                    // driver moved to EXPEDITION CLEARS: GoalProgress.Charge is now credited per cleared expedition by
                    // ExpeditionGateSystem on the player's RETURN. Surviving a normal siege is still its own reward
                    // (resources kept, Core intact) but is not progress toward Victory. The final-siege Victory latch
                    // above is unchanged — GoalReachedSystem still arms the climactic final siege once Charge hits Target.
                }
            }

            // Surface the live wave number on the replicated CycleState for the HUD (single writer).
            if (SystemAPI.TryGetSingleton<WaveState>(out var waveSync))
                cycle.WaveNumber = waveSync.WaveNumber;

            SystemAPI.SetComponent(cycleEntity, cycle);
            SystemAPI.SetComponent(cycleEntity, runtime);
        }

        // The Siege wave has run for this phase (WaveNumber advanced past the captured start), is fully spawned,
        // and no Husks remain alive.
        bool DefendCleared(ref SystemState state, int defendStartWave)
        {
            if (!SystemAPI.TryGetSingleton<WaveState>(out var wave))
                return false;
            // Cleared only when no BASE husk remains: expedition zone enemies (EnemyTag + RegionTag{Expedition})
            // must not hold the base siege open (DR-040 BLOCKER 3 — same global-count soft-lock as WaveSystem).
            int baseHusks = 0;
            foreach (var hr in SystemAPI.Query<RefRO<RegionTag>>().WithAll<EnemyTag>())
                if (hr.ValueRO.Region == RegionId.Base) baseHusks++;
            return wave.WaveNumber > defendStartWave
                   && wave.RemainingToSpawn == 0
                   && baseHusks == 0;
        }
    }
}