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

namespace ProjectM.Simulation
{
    /// <summary>
    /// MC-1 — the predicted dodge dash. On a fresh <see cref="PlayerInput.Dash"/> press (cooldown ready and not
    /// already mid-dash) it captures the dash heading from <see cref="PlayerFacing"/> and opens a HALF-OPEN i-frame
    /// window [StartTick, IFrameUntilTick) plus a recovery tail. While the i-frame window is active it OVERRIDES
    /// <see cref="CharacterControl.MoveVelocity"/> with the dash velocity and raises
    /// <see cref="CharacterComponent.GroundedMovementSharpness"/> to ~200 so the move reads as a BLINK (the CC
    /// processor lerps RelativeVelocity toward MoveVelocity at that sharpness — no CharacterProcessor edit needed).
    /// During the recovery tail movement is locked to zero (no i-frames) so a panic-dash is punishable.
    /// <see cref="ProjectM.Server"/>'s HealthApplyDamageSystem reads the window to negate hits authored inside it.
    /// <para>
    /// Runs in <see cref="PredictedSimulationSystemGroup"/> AFTER <see cref="PlayerControlSystem"/> (it overrides
    /// the input-derived MoveVelocity that system wrote this tick) and is gated
    /// <c>.WithAll&lt;Simulate&gt;().WithDisabled&lt;Dead&gt;()</c>. The START is an idempotent pure function of
    /// replicated input + tick (no IsFirstTimeFullyPredictingTick guard); the OVERRIDE re-applies on EVERY predicted
    /// pass so rollback re-simulation converges. All ticks routed through <c>TickUtil.NonZero</c>; compared via
    /// <see cref="NetworkTick"/> only. DashSystem owns GroundedMovementSharpness on the player (base = the CC default
    /// 15); PlayerDeathStateSystem restores it + clears the window on death.
    /// </para>
    /// </summary>
    [UpdateInGroup(typeof(PredictedSimulationSystemGroup))]
    [UpdateAfter(typeof(PlayerControlSystem))]
    [BurstCompile]
    public partial struct DashSystem : ISystem
    {
        // Baked-first feel knobs (MC-1; promote to a live TuningConfig later). Sim runs at 60 ticks/sec.
        const float DashDistance = 4.0f;     // world units covered during the i-frame window
        const uint  IFrameWindowTicks = 12;  // ~0.20 s of i-frames
        const uint  RecoverTailTicks = 9;    // ~0.15 s movement-locked tail (punishes spam)
        const uint  DashCooldownTicks = 45;  // ~0.75 s
        const float DashSharpness = 200f;    // GroundedMovementSharpness during the dash -> blink
        const float DefaultSharpness = 15f;  // CharacterComponent.GetDefault() base
        const float SimTickRate = 60f;

        [BurstCompile]
        public void OnUpdate(ref SystemState state)
        {
            if (!SystemAPI.TryGetSingleton<NetworkTime>(out var netTime) || !netTime.ServerTick.IsValid)
                return;
            var serverTick = netTime.ServerTick;
            uint now = serverTick.TickIndexForValidTick;
            float dashSpeed = DashDistance / (IFrameWindowTicks / SimTickRate);

            foreach (var (ds, cd, control, character, input, facing) in
                     SystemAPI.Query<RefRW<DashState>, RefRW<DashCooldown>, RefRW<CharacterControl>,
                                     RefRW<CharacterComponent>, RefRO<PlayerInput>, RefRO<PlayerFacing>>()
                         .WithAll<Simulate>().WithDisabled<Dead>())
            {
                // --- START (idempotent: fresh press + cooldown ready + not already mid-dash) ---
                bool ready = cd.ValueRO.NextTick == 0u
                             || !new NetworkTick(cd.ValueRO.NextTick).IsNewerThan(serverTick);
                bool inWindow = ds.ValueRO.RecoverUntilTick != 0u
                                && new NetworkTick(ds.ValueRO.RecoverUntilTick).IsNewerThan(serverTick);
                if (input.ValueRO.Dash.IsSet && ready && !inWindow)
                {
                    float2 dir = facing.ValueRO.Direction;
                    if (math.lengthsq(dir) < 1e-6f) dir = new float2(0f, 1f);
                    dir = math.normalize(dir);
                    ds.ValueRW.Dir = dir;
                    ds.ValueRW.StartTick = TickUtil.NonZero(now);
                    ds.ValueRW.IFrameUntilTick = TickUtil.NonZero(now + IFrameWindowTicks);
                    ds.ValueRW.RecoverUntilTick = TickUtil.NonZero(now + IFrameWindowTicks + RecoverTailTicks);
                    cd.ValueRW.NextTick = TickUtil.NonZero(now + DashCooldownTicks);
                }

                // --- OVERRIDE (runs every predicted pass so rollback re-simulation re-applies it) ---
                // The lower bound matters: DashState is non-replicated, so prediction rollback does NOT restore
                // it — a re-simulated PRE-dash tick (serverTick < StartTick) still sees the post-press window and,
                // gated on the upper bound alone, would stomp dash velocity onto ticks that never had it
                // (dash-start overshoot under real latency). Membership = the half-open [StartTick, …) test.
                bool inDashWindow = ds.ValueRO.StartTick != 0u
                                    && !new NetworkTick(ds.ValueRO.StartTick).IsNewerThan(serverTick);
                bool iFrameActive = inDashWindow && ds.ValueRO.IFrameUntilTick != 0u
                                    && new NetworkTick(ds.ValueRO.IFrameUntilTick).IsNewerThan(serverTick);
                bool recoverActive = inDashWindow && ds.ValueRO.RecoverUntilTick != 0u
                                     && new NetworkTick(ds.ValueRO.RecoverUntilTick).IsNewerThan(serverTick);
                if (iFrameActive)
                {
                    float2 d = ds.ValueRO.Dir;
                    control.ValueRW.MoveVelocity = new float3(d.x, 0f, d.y) * dashSpeed;
                    character.ValueRW.GroundedMovementSharpness = DashSharpness;
                }
                else if (recoverActive)
                {
                    control.ValueRW.MoveVelocity = float3.zero; // movement locked during the punishable tail
                    character.ValueRW.GroundedMovementSharpness = DefaultSharpness;
                }
                else
                {
                    if (character.ValueRO.GroundedMovementSharpness != DefaultSharpness)
                        character.ValueRW.GroundedMovementSharpness = DefaultSharpness; // restore after the dash

                    // Window-close edge: score a wasted dash (negated nothing) ONCE, then clear the window.
                    // SERVER-only — the DevTelemetry singleton exists only in the (editor) server world; the
                    // client keeps its copy un-zeroed so rollback re-simulation of the tail stays intact. All
                    // in-window strikes drain >= 9 ticks before this edge, so clearing can't eat a negation.
                    if (ds.ValueRO.RecoverUntilTick != 0u && SystemAPI.TryGetSingletonRW<DevTelemetry>(out var telem))
                    {
                        if (ds.ValueRO.NegatedCount == 0u)
                            telem.ValueRW.DashesWasted++;
                        ds.ValueRW = default;
                    }
                }
            }
        }
    }
}