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>
    /// SOLE writer of the replicated run-lifecycle FSM (<see cref="RunInfo"/>) and its server-only working state
    /// (<see cref="RunRuntime"/>) — the expedition redesign's counterpart of CyclePhaseSystem's single-writer
    /// discipline (that system stays the sole writer of the BASE Calm↔Siege posture; the two FSMs are distinct).
    ///
    /// Step-7 = the REAL LINEAR traversal: Staging (ready-check) → Launching (3-2-1 telegraph, un-ready aborts) →
    /// InRoom (fight; the clear edge arrives as the replicated <see cref="ExpeditionObjective"/>.State == Cleared,
    /// consumed ONE-TICK-LATE by construction — RoomEnemyDirectorSystem writes it after this system each tick, so no
    /// system-ordering back-edge exists) → RoomReward (cleared room TORN DOWN at entry via <see cref="RoomTeardown"/>;
    /// boon picks gate the exit from Step 10, all-Pending==0 today) → advance (bump room/epoch, flip the ping-pong
    /// sub-slot, teleport — teardown-at-entry + spawn-on-advance guarantees ≥1 empty tick and exactly ONE room alive)
    /// → … → Boss clear → Returning (teleport home + the CLEAR-GATED terminal bank) → Staging. Branching route
    /// choice (RouteSelect) replaces the fixed col-0 advance at Step 8.
    ///
    /// The terminal bank (once per RunEpoch, equality-latched): ALWAYS records the honest depth
    /// (max(MaxDepthReached, RoomsClearedThisRun) — never the planned RoomCount) and re-stages; ONLY a genuine
    /// boss-clear terminal (<see cref="RunRuntime.LastTerminalCleared"/>) credits the win meter
    /// (<see cref="GoalProgress"/>.Charge, clamped), RunsCompleted, the retaliation inputs
    /// (<see cref="ThreatState"/>.PendingReturns/ExpeditionsCompleted — carried from the retired gate, C7) and
    /// requests a save. An abort/wipe banks NOTHING but the depth high-water (D-F3).
    ///
    /// Ordering: <c>[UpdateBefore(CyclePhaseSystem)]</c> ONLY (GoalReachedSystem is [UpdateAfter(CyclePhaseSystem)] —
    /// transitively after this system, so the Charge credit lands before it reads the edge). Per the hard rule,
    /// NOTHING in the room chain adds another CyclePhase edge (a sort cycle is invisible to EditMode and throws only
    /// at Play world creation).
    /// </summary>
    [BurstCompile]
    [WorldSystemFilter(WorldSystemFilterFlags.ServerSimulation)]
    [UpdateInGroup(typeof(SimulationSystemGroup))]
    [UpdateBefore(typeof(CyclePhaseSystem))]
    public partial struct RunDirectorSystem : ISystem
    {
        /// <summary>"All ready → 3-2-1 → go" telegraph (~3 s @ 60). An un-ready during the countdown aborts.</summary>
        const uint LaunchCountdownTicks = 180;

        /// <summary>Boon-pick grace (~30 s @ 60): RoomReward advances when every survivor picked OR this elapses
        /// (the AFK/disconnect backstop; the un-picked-offer policy lands with the boons at Step 10).</summary>
        const uint RewardGraceTicks = 1800;

        /// <summary>Route-choice grace (~30 s @ 60): the gate auto-picks the LOWEST-INDEX reachable option when it
        /// elapses (the AFK backstop; an accepted pick always beats a same-tick expiry — review F2).</summary>
        const uint RouteGraceTicks = 1800;

        EntityQuery m_RoomTagged;

        [BurstCompile]
        public void OnCreate(ref SystemState state)
        {
            state.RequireForUpdate<NetworkTime>();
            state.RequireForUpdate<RunInfo>();
            state.RequireForUpdate<RunRuntime>();
            m_RoomTagged = state.GetEntityQuery(ComponentType.ReadOnly<RoomTag>());
        }

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

            var dirEntity = SystemAPI.GetSingletonEntity<RunInfo>();
            var info = SystemAPI.GetComponent<RunInfo>(dirEntity);
            var run = SystemAPI.GetComponent<RunRuntime>(dirEntity);

            float3 baseCenter = new float3(0f, 1f, 0f);
            if (SystemAPI.TryGetSingleton<BaseAnchor>(out var anchor))
                baseCenter = BaseGridMath.PlotCenter(anchor);

            // Ready-check + party-presence derivation, shared across the states below. The party is co-located at
            // base while Staging (the N7 co-location invariant), so live PlayerTag ghosts ARE the roster; a
            // disconnect drops the counts (LinkedEntityGroup despawn) and the checks re-derive clean.
            int totalPlayers = 0, readyPlayers = 0, expeditionPlayers = 0;
            foreach (var (ready, region) in
                     SystemAPI.Query<RefRO<PlayerReady>, RefRO<RegionTag>>().WithAll<PlayerTag>())
            {
                totalPlayers++;
                if (ready.ValueRO.Value != 0) readyPlayers++;
                if (region.ValueRO.Region == RegionId.Expedition) expeditionPlayers++;
            }
            bool allReady = totalPlayers > 0 && readyPlayers == totalPlayers;

            switch (info.Lifecycle)
            {
                case RunLifecycle.Staging:
                {
                    // F2 cross-FSM launch guard: no new run while a final siege arms/runs or the outcome latched.
                    // Guards default OPEN when the server-only markers are absent (EditMode worlds).
                    bool launchAllowed =
                        (!SystemAPI.HasComponent<RunPhase>(dirEntity)
                         || SystemAPI.GetComponent<RunPhase>(dirEntity).Value == RunPhaseId.Normal)
                        && (!SystemAPI.HasComponent<RunOutcome>(dirEntity)
                            || SystemAPI.GetComponent<RunOutcome>(dirEntity).Value == RunOutcomeId.InProgress);

                    if (allReady && run.WasAllReady == 0 && launchAllowed)
                    {
                        // Rising edge → Launching. Seed the run: monotonic epoch + per-playthrough salt lineage,
                        // never a tick, never 0, equality-compared downstream.
                        run.RunEpoch += 1;
                        run.HostSalt = RunMapMath.Hash(run.HostSalt, (uint)run.RunEpoch);
                        run.RunSeed = math.max(1u, RunMapMath.Hash((uint)run.RunEpoch, run.HostSalt));
                        run.NodeBudgetRemaining = Tuning.ExpeditionNodeBudget;
                        run.RoomsClearedThisRun = 0;
                        run.BoonPickCounter = 0; // fresh boon-band provenance per run
                        run.LastTerminalCleared = 0;

                        var map = RunMapMath.Generate(run.RunSeed);
                        info.RunSeed = run.RunSeed;
                        info.RoomCount = map.LayerCount;
                        info.LaunchTick = TickUtil.NonZero(now + LaunchCountdownTicks);
                        info.Lifecycle = RunLifecycle.Launching;
                    }
                    run.WasAllReady = (byte)(allReady ? 1 : 0);
                    break;
                }

                case RunLifecycle.Launching:
                {
                    // Un-ready during the countdown aborts back to Staging (the telegraph's escape hatch).
                    if (!allReady)
                    {
                        info.LaunchTick = 0u;
                        info.Lifecycle = RunLifecycle.Staging;
                        run.WasAllReady = 0;
                        break;
                    }

                    bool due = info.LaunchTick == 0u || !new NetworkTick(info.LaunchTick).IsNewerThan(serverTick);
                    if (due)
                    {
                        // Conscript the party: the launch roster is EVERYONE connected (N7 co-location — all at
                        // base, all ready). Room advances teleport ONLY RunParticipants, so a mid-run late joiner
                        // is never yanked into the fight; the tag is released on the Returning edge.
                        var conscript = new EntityCommandBuffer(Allocator.Temp);
                        foreach (var (_, playerE) in
                                 SystemAPI.Query<RefRO<PlayerReady>>().WithAll<PlayerTag>().WithEntityAccess())
                            conscript.AddComponent<RunParticipant>(playerE);
                        conscript.Playback(state.EntityManager);
                        conscript.Dispose();

                        // Enter room 0 (the guaranteed Combat landing at column 0, sub-slot 0).
                        var map = RunMapMath.Generate(run.RunSeed);
                        EnterRoom(ref state, ref info, ref run, in map, layer: 0, col: 0, baseCenter, bumpEpoch: true);
                        info.LaunchTick = 0u;
                    }
                    break;
                }

                case RunLifecycle.InRoom:
                {
                    // All expedition players gone (disconnect/death-warp edge) → clean abort, no credit.
                    if (expeditionPlayers == 0)
                    {
                        run.LastTerminalCleared = 0;
                        info.Lifecycle = RunLifecycle.Returning;
                        break;
                    }

                    // The room clear edge — the replicated objective RoomEnemyDirectorSystem computed LAST tick
                    // (one-tick-late by construction; no ordering back-edge). Teardown happens AT THIS ENTRY, the
                    // next room spawns on the advance tick → ≥1 empty tick, exactly one room alive.
                    if (SystemAPI.HasComponent<ExpeditionObjective>(dirEntity)
                        && SystemAPI.GetComponent<ExpeditionObjective>(dirEntity).State == ExpeditionObjectiveState.Cleared)
                    {
                        // DR-046: teardown MOVED to the RoomExplore exit — the room + resource nodes persist through
                        // RoomReward + the loot window so the party can mine after clearing.

                        run.RoomsClearedThisRun += 1;
                        if (info.CurrentRoom >= info.RoomCount - 1)
                            run.LastTerminalCleared = 1; // the Boss fell — a genuine terminal clear
                        run.RewardGraceTick = TickUtil.NonZero(now + RewardGraceTicks);
                        info.Lifecycle = RunLifecycle.RoomReward;
                    }
                    break;
                }

                case RunLifecycle.RoomReward:
                {
                    if (expeditionPlayers == 0 && run.LastTerminalCleared == 0)
                    {
                        info.Lifecycle = RunLifecycle.Returning;
                        break;
                    }

                    // Exit gate: every SURVIVING player has picked (BoonOffer.Pending==0 — inert until Step 10)
                    // OR the grace elapsed (wrap-safe IsNewerThan, never raw uint — F4).
                    // Only EXPEDITION players hold the gate (BoonOfferSystem's documented contract): a player who
                    // died and respawned to base must not stall the party (post-impl review, confirmed major).
                    bool anyPending = false;
                    foreach (var (offer, pregion) in
                             SystemAPI.Query<RefRO<BoonOffer>, RefRO<RegionTag>>().WithAll<PlayerTag>())
                        if (pregion.ValueRO.Region == RegionId.Expedition && offer.ValueRO.Pending != 0)
                        { anyPending = true; break; }
                    bool graceElapsed = run.RewardGraceTick == 0u
                        || !new NetworkTick(run.RewardGraceTick).IsNewerThan(serverTick);
                    if (anyPending && !graceElapsed)
                        break;

                    run.RewardGraceTick = 0u;
                    // NO offer survives this gate: zero every straggler (a dead-respawned base player the
                    // auto-pick deliberately skips, a grace-expired AFK) so a stale Pending can never wedge the
                    // HUD modal open or stall a later reward gate (post-impl review, confirmed major).
                    foreach (var offer in SystemAPI.Query<RefRW<BoonOffer>>().WithAll<PlayerTag>())
                        offer.ValueRW = default;
                    // DR-046: don't advance yet — open the LOOT WINDOW. The cleared room + its resource nodes persist
                    // (teardown moved to the RoomExplore exit); a portal is up. Leave via the portal or a soft timeout.
                    run.ExploreGraceTick = TickUtil.NonZero(now + Tuning.ExploreGraceTicks);
                    if (SystemAPI.HasComponent<PortalCommand>(dirEntity))
                        SystemAPI.SetComponent(dirEntity, default(PortalCommand)); // fresh portal latch for this window
                    info.Lifecycle = RunLifecycle.RoomExplore;
                    break;
                }

                case RunLifecycle.RoomExplore:
                {
                    // DR-046 LOOT WINDOW: the cleared room + its resource nodes persist; a portal is up. Advance when a
                    // participant interacts the portal (PortalCommand, set by PortalInteractReceiveSystem) OR the soft
                    // timeout elapses (never a softlock). Abort if the expedition emptied (unless the boss already fell).
                    if (expeditionPlayers == 0) // DR-046 fix: an empty expedition advances NOW (boss -> Returning banks the win
                    {                              // immediately; non-boss -> abort no-credit) — no ~30s ExploreGrace dead-time on the win moment.
                        run.ExploreGraceTick = 0u;
                        info.Lifecycle = RunLifecycle.Returning;
                        break;
                    }
                    bool portalUsed = SystemAPI.HasComponent<PortalCommand>(dirEntity)
                        && SystemAPI.GetComponent<PortalCommand>(dirEntity).HasInteract != 0;
                    bool exploreTimedOut = run.ExploreGraceTick == 0u
                        || !new NetworkTick(run.ExploreGraceTick).IsNewerThan(serverTick);
                    if (!portalUsed && !exploreTimedOut)
                        break; // still looting

                    run.ExploreGraceTick = 0u;
                    if (SystemAPI.HasComponent<PortalCommand>(dirEntity))
                        SystemAPI.SetComponent(dirEntity, default(PortalCommand));

                    // The MOVED teardown: NOW destroy the cleared room (nodes + clutter), then advance.
                    var exploreEcb = new EntityCommandBuffer(Allocator.Temp);
                    RoomTeardown.DestroyRoom(m_RoomTagged, exploreEcb, (byte)(info.CurrentRoom & 0xFF));
                    exploreEcb.Playback(state.EntityManager);
                    exploreEcb.Dispose();

                    if (run.LastTerminalCleared != 0)
                    {
                        info.Lifecycle = RunLifecycle.Returning; // boss cleared — go home a winner
                    }
                    else
                    {
                        // Open the branching ROUTE GATE (relocated from RoomReward): publish authoritative reachable
                        // options; RouteSelect is the teardown gap (the room is gone now).
                        var map = RunMapMath.Generate(run.RunSeed);
                        int optionCount = RunMapMath.ReachableOptions(in map, info.CurrentRoom, info.CurrentCol, out var cols);
                        if (optionCount == 0)
                        {
                            info.RouteOptionCount = 0;
                            info.Lifecycle = RunLifecycle.Returning;
                        }
                        else
                        {
                            int nextLayer = info.CurrentRoom + 1;
                            info.RouteOptionCount = (byte)math.min(optionCount, 3);
                            info.RouteOpt0Col = cols.Length > 0 ? cols[0] : (byte)0;
                            info.RouteOpt1Col = cols.Length > 1 ? cols[1] : (byte)0;
                            info.RouteOpt2Col = cols.Length > 2 ? cols[2] : (byte)0;
                            info.RouteOpt0Type = cols.Length > 0 ? map.Node(nextLayer, cols[0]).RoomType : (byte)0;
                            info.RouteOpt1Type = cols.Length > 1 ? map.Node(nextLayer, cols[1]).RoomType : (byte)0;
                            info.RouteOpt2Type = cols.Length > 2 ? map.Node(nextLayer, cols[2]).RoomType : (byte)0;
                            run.RouteGraceTick = TickUtil.NonZero(now + RouteGraceTicks);
                            if (SystemAPI.HasComponent<RouteCommand>(dirEntity))
                                SystemAPI.SetComponent(dirEntity, default(RouteCommand));
                            info.Lifecycle = RunLifecycle.RouteSelect;
                        }
                    }
                    break;
                }

                
case RunLifecycle.RouteSelect:
                {
                    // Predicate order is LOAD-BEARING (review F2): abort → pick-consume → grace. A same-tick pick
                    // from a vanishing party must never resurrect the run (EnterRoom would conscript base players);
                    // an accepted pick must beat a same-tick grace expiry (the player was told "committed").
                    if (expeditionPlayers == 0)
                    {
                        info.RouteOptionCount = 0; // close the gate ON the abort edge itself (review F3)
                        run.LastTerminalCleared = 0;
                        info.Lifecycle = RunLifecycle.Returning;
                        break;
                    }

                    var cmd = SystemAPI.HasComponent<RouteCommand>(dirEntity)
                        ? SystemAPI.GetComponent<RouteCommand>(dirEntity)
                        : default;
                    bool routeGraceElapsed = run.RouteGraceTick == 0u
                        || !new NetworkTick(run.RouteGraceTick).IsNewerThan(serverTick);

                    if (cmd.HasPick != 0)
                    {
                        // The party's committed choice (first-accepted-wins latch; any-player-first-commits).
                        byte chosenCol = cmd.OptionIndex == 2 ? info.RouteOpt2Col
                            : cmd.OptionIndex == 1 ? info.RouteOpt1Col : info.RouteOpt0Col;
                        if (SystemAPI.HasComponent<RouteCommand>(dirEntity))
                            SystemAPI.SetComponent(dirEntity, default(RouteCommand));
                        run.RouteGraceTick = 0u;
                        var map = RunMapMath.Generate(run.RunSeed);
                        EnterRoom(ref state, ref info, ref run, in map, info.CurrentRoom + 1, chosenCol, baseCenter, bumpEpoch: true);
                    }
                    else if (routeGraceElapsed)
                    {
                        // AFK backstop: deterministic LOWEST-INDEX reachable option (RouteOpt0 is ascending-first).
                        run.RouteGraceTick = 0u;
                        var map = RunMapMath.Generate(run.RunSeed);
                        EnterRoom(ref state, ref info, ref run, in map, info.CurrentRoom + 1, info.RouteOpt0Col, baseCenter, bumpEpoch: true);
                    }
                    break;
                }

                case RunLifecycle.Returning:
                {
                    // PARTICIPANT teleport home + region flip + roster release. Only the launch roster comes
                    // home (a mid-run joiner already at base keeps its position); the tag removal re-opens the
                    // next run's conscription cleanly (post-impl review, confirmed medium).
                    int idx = 0;
                    var homebound = new EntityCommandBuffer(Allocator.Temp);
                    foreach (var (region, xform, playerE) in
                             SystemAPI.Query<RefRW<RegionTag>, RefRW<LocalTransform>>()
                                 .WithAll<PlayerTag, RunParticipant>().WithEntityAccess())
                    {
                        region.ValueRW.Region = RegionId.Base;
                        var p = baseCenter;
                        p.x += 1.5f * idx;
                        p.y = xform.ValueRO.Position.y;
                        xform.ValueRW.Position = p;
                        homebound.RemoveComponent<RunParticipant>(playerE);
                        idx++;
                    }
                    homebound.Playback(state.EntityManager);
                    homebound.Dispose();

                    // THE terminal bank — once per RunEpoch (equality latch, F7), CLEAR-GATED (D-F3).
                    if (run.LastBankedRunEpoch != run.RunEpoch)
                    {
                        run.LastBankedRunEpoch = run.RunEpoch;

                        // Always: the honest depth high-water (actual rooms cleared, never the planned count).
                        if (SystemAPI.HasComponent<MetaCounters>(dirEntity))
                        {
                            var meta = SystemAPI.GetComponent<MetaCounters>(dirEntity);
                            meta.MaxDepthReached = math.max(meta.MaxDepthReached, run.RoomsClearedThisRun);
                            if (run.LastTerminalCleared != 0)
                                meta.RunsCompleted += 1;
                            SystemAPI.SetComponent(dirEntity, meta);
                            info.RunsCompleted = meta.RunsCompleted;      // HUD mirror
                            info.MaxDepthReached = meta.MaxDepthReached;  // HUD mirror
                        }

                        // Boss-clear only: the win meter, the retaliation inputs (C7), and a save checkpoint.
                        if (run.LastTerminalCleared != 0)
                        {
                            if (SystemAPI.HasComponent<GoalProgress>(dirEntity))
                            {
                                var goal = SystemAPI.GetComponent<GoalProgress>(dirEntity);
                                goal.Charge = math.min(goal.Charge + 1, goal.Target);
                                SystemAPI.SetComponent(dirEntity, goal);
                            }
                            if (SystemAPI.HasComponent<ThreatState>(dirEntity))
                            {
                                var threat = SystemAPI.GetComponent<ThreatState>(dirEntity);
                                threat.PendingReturns += 1;
                                threat.ExpeditionsCompleted += 1;
                                SystemAPI.SetComponent(dirEntity, threat);
                            }
                            if (SystemAPI.HasComponent<SaveRequest>(dirEntity))
                                SystemAPI.SetComponent(dirEntity, new SaveRequest { Pending = 1 });
                        }
                    }

                    // TWO-CHANNEL strip (DR-037): run boons EXPIRE at home — one range-strip clears every
                    // boon-band StatModifier (replicates via the [GhostField] buffer; StatRecompute reverts the
                    // effective stats on both worlds) and zeroes any straggler offer. Class/meta/equip bands are
                    // disjoint and survive. Idempotent — safe on every Returning tick.
                    foreach (var (mods, offer) in
                             SystemAPI.Query<DynamicBuffer<StatModifier>, RefRW<BoonOffer>>().WithAll<PlayerTag>())
                    {
                        TimedModifierUtil.RemoveBySourceIdRange(mods, Tuning.BoonSourceIdBase,
                            Tuning.BoonSourceIdBase + Tuning.BoonSourceIdSpan);
                        TimedModifierUtil.RemoveBySourceIdRange(mods, Tuning.PrepSourceIdBase,
                            Tuning.PrepSourceIdBase + Tuning.PrepSourceIdSpan); // DR-046: strip the run-scoped prep loadout too

                        offer.ValueRW = default;
                    }

                    // Clear EVERY ready flag — the next run needs a fresh, deliberate ready-check from everyone.
                    foreach (var ready in SystemAPI.Query<RefRW<PlayerReady>>().WithAll<PlayerTag>())
                        ready.ValueRW.Value = 0;

                    run.RewardGraceTick = 0u;
                    run.RouteGraceTick = 0u; // gate hygiene (review F5): no stale grace into the next run
                    if (SystemAPI.HasComponent<RouteCommand>(dirEntity))
                        SystemAPI.SetComponent(dirEntity, default(RouteCommand)); // no leftover latch either
                    run.WasAllReady = 0;
                    run.LastTerminalCleared = 0;

                    info.CurrentRoom = 0;
                    info.RouteOptionCount = 0;
                    info.LaunchTick = 0u;
                    info.Lifecycle = RunLifecycle.Staging;
                    break;
                }
            }

            // Single write-back point — RunInfo/RunRuntime are ALWAYS published (F12: the HUD readout can never
            // freeze stale behind a branch's early-break).
            SystemAPI.SetComponent(dirEntity, info);
            SystemAPI.SetComponent(dirEntity, run);
        }

        /// <summary>
        /// Enter room (<paramref name="layer"/>, <paramref name="col"/>): publish the node as the single plan
        /// authority (<see cref="RunRuntime.CurrentNodeId"/>/<c>CurrentRoomType</c> — the field/enemy directors NEVER
        /// re-derive it), flip the ping-pong sub-slot, bump <see cref="RunRuntime.RoomEpoch"/> so the room systems
        /// reseed, and teleport the party onto the new origin (Position write in place — never FromPosition).
        /// </summary>
        void EnterRoom(ref SystemState state, ref RunInfo info, ref RunRuntime run, in RunMap map,
            int layer, int col, float3 baseCenter, bool bumpEpoch)
        {
            var node = map.Node(layer, col);
            run.ActiveSubSlot = (byte)(layer & 1);
            run.CurrentNodeId = RunMap.NodeId(layer, col);
            run.CurrentCol = (byte)col;
            run.CurrentRoomType = node.RoomType;
            if (bumpEpoch)
                run.RoomEpoch += 1;

            info.CurrentRoom = layer;
            info.CurrentCol = (byte)col;
            info.CurrentRoomType = node.RoomType;
            info.CurrentBiome = node.Biome;
            info.RouteOptionCount = 0;

            float3 roomOrigin = RegionMath.ExpeditionRoomOrigin(baseCenter, run.ActiveSubSlot);
            int idx = 0;
            foreach (var (region, xform) in
                     SystemAPI.Query<RefRW<RegionTag>, RefRW<LocalTransform>>().WithAll<PlayerTag, RunParticipant>())
            {
                region.ValueRW.Region = RegionId.Expedition;
                var p = roomOrigin;
                p.x += 1.5f * idx; // small spread so kinematic capsules don't stack
                p.y = xform.ValueRO.Position.y;
                xform.ValueRW.Position = p;
                idx++;
            }

            info.Lifecycle = RunLifecycle.InRoom;
        }
    }
}