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

namespace ProjectM.Client
{
    /// <summary>
    /// Client-only twin-stick input gather. Samples the new Input System action map (the generated
    /// <c>ProjectMInput</c> wrapper over <c>Assets/Settings/Project M Input.inputactions</c>) once per
    /// frame and writes <see cref="PlayerInput"/> on the locally-owned player ghost (filtered to
    /// <see cref="GhostOwnerIsLocal"/>). Runs in <see cref="GhostInputSystemGroup"/> — NOT the
    /// prediction loop — so devices are read once per frame, never re-read during rollback.
    /// <para>
    /// Implemented as a managed <see cref="SystemBase"/> (not a Burst <c>ISystem</c>) because it holds
    /// and reads the managed Input System wrapper. Fire is an <see cref="InputEvent"/>: the event field
    /// is reset each frame and raised via <c>Set()</c> on the press edge, so a single click fires
    /// exactly once; netcode accumulates the absolute <c>Count</c> into the command buffer across the
    /// frame→tick boundary (read back in <c>AbilityFireSystem</c> as the predicted-spawn key).
    /// </para>
    /// <para>
    /// NOTE: Input System types are fully qualified (e.g. <c>UnityEngine.Vector2</c>) and
    /// <c>using UnityEngine.InputSystem;</c> is intentionally omitted — that namespace defines a
    /// <c>PlayerInput</c> type that collides with <see cref="ProjectM.Simulation.PlayerInput"/> and
    /// makes the Entities generator bind <c>RefRW&lt;PlayerInput&gt;</c> to the managed class (a
    /// spurious CS8377). The generated <c>ProjectMInput</c> wrapper lives in this assembly.
    /// </para>
    /// </summary>
    [UpdateInGroup(typeof(GhostInputSystemGroup))]
    [WorldSystemFilter(WorldSystemFilterFlags.ClientSimulation)]
    public partial class PlayerInputGatherSystem : SystemBase
    {
        private ProjectMInput _controls;

        // Active input scheme (last meaningful actuation wins). Selects KBM-cursor vs gamepad-stick aim and
        // is published to AimPresentation for the on-screen cursor / world reticle. Starts on mouse+keyboard.
        private byte _scheme = InputSchemeId.KeyboardMouse;

        // Last valid KBM cursor aim, held when the projection is degenerate (cursor over the player / above the
        // horizon) so facing never snaps to zero while the mouse is the active device.
        private float2 _lastKbmAim = new float2(0f, 1f);

        // Main camera for cursor -> ground projection; re-resolved when null (e.g. after a domain reload).
        private UnityEngine.Camera _camera;

        // World radius around the player inside which mouse facing is HELD (no spin when the cursor passes
        // over/near the character). Passed to AimMath.PlanarAimFromRay's deadZoneRadius.
        private const float KbmAimDeadZone = 0.6f;

        protected override void OnCreate()
        {
            RequireForUpdate<PlayerInput>();
            _controls = new ProjectMInput();
            _controls.Gameplay.Enable();
        }

        protected override void OnDestroy()
        {
            if (_controls != null)
            {
                _controls.Gameplay.Disable();
                _controls.Dispose();
                _controls = null;
            }
        }

        protected override void OnUpdate()
        {
            var gameplay = _controls.Gameplay;

            // Movement is source-agnostic (WASD or left stick) — read from the merged action.
            float2 move = (float2)gameplay.Move.ReadValue<UnityEngine.Vector2>();
            bool firePressed = gameplay.Fire.WasPressedThisFrame() && !BuildPaletteState.Active; // no fire while placing a build

            // --- Active-device detection: last meaningful actuation wins; hold last when idle ---
            var gamepad = UnityEngine.InputSystem.Gamepad.current;
            var mouse = UnityEngine.InputSystem.Mouse.current;
            var keyboard = UnityEngine.InputSystem.Keyboard.current;
            bool dashPressed = ((keyboard != null && keyboard.leftShiftKey.wasPressedThisFrame) || (gamepad != null && gamepad.buttonEast.wasPressedThisFrame)) && !BuildPaletteState.Active;

            float2 rightStick = float2.zero;
            bool gamepadActive = false;
            if (gamepad != null)
            {
                rightStick = (float2)gamepad.rightStick.ReadValue();
                float2 leftStick = (float2)gamepad.leftStick.ReadValue();
                gamepadActive =
                    math.lengthsq(rightStick) > 0.04f || math.lengthsq(leftStick) > 0.04f ||
                    gamepad.rightTrigger.isPressed || gamepad.leftTrigger.isPressed ||
                    gamepad.buttonSouth.isPressed || gamepad.buttonEast.isPressed ||
                    gamepad.buttonWest.isPressed || gamepad.buttonNorth.isPressed;
            }

            bool kbmActive = false;
            if (mouse != null)
            {
                float2 delta = (float2)mouse.delta.ReadValue();
                kbmActive = math.lengthsq(delta) > 0.5f || mouse.leftButton.isPressed || mouse.rightButton.isPressed;
            }
            if (!kbmActive && keyboard != null)
            {
                kbmActive =
                    keyboard.wKey.isPressed || keyboard.aKey.isPressed || keyboard.sKey.isPressed || keyboard.dKey.isPressed ||
                    keyboard.upArrowKey.isPressed || keyboard.downArrowKey.isPressed ||
                    keyboard.leftArrowKey.isPressed || keyboard.rightArrowKey.isPressed || keyboard.spaceKey.isPressed || keyboard.leftShiftKey.isPressed;
            }

            if (gamepadActive && kbmActive)
            {
                // Both actuated this frame: break the tie by whichever device updated most recently.
                double gpT = gamepad != null ? gamepad.lastUpdateTime : double.MinValue;
                double kbmT = math.max(
                    mouse != null ? mouse.lastUpdateTime : double.MinValue,
                    keyboard != null ? keyboard.lastUpdateTime : double.MinValue);
                _scheme = gpT > kbmT ? InputSchemeId.Gamepad : InputSchemeId.KeyboardMouse;
            }
            else if (gamepadActive) _scheme = InputSchemeId.Gamepad;
            else if (kbmActive) _scheme = InputSchemeId.KeyboardMouse;
            // else: neither actuated — keep the previous scheme.

            // Publish for the presentation layer (cursor visibility / world reticle).
            AimPresentation.Scheme = _scheme;

            // Mouse cursor projection needs the camera; resolve/cache it (Camera.main or the rig's camera).
            if (_camera == null) _camera = ResolveCamera();
            UnityEngine.Vector2 cursorScreen = mouse != null ? mouse.position.ReadValue() : default;

            foreach (var (input, xform) in
                     SystemAPI.Query<RefRW<PlayerInput>, RefRO<LocalTransform>>().WithAll<GhostOwnerIsLocal>())
            {
                float2 aim;
                if (_scheme == InputSchemeId.Gamepad)
                {
                    // Right-stick directional aim. A resting stick yields zero so PlayerAimSystem falls back to
                    // the movement heading (existing controller-first behaviour).
                    aim = rightStick;
                    if (math.lengthsq(aim) < 0.04f) aim = float2.zero;
                }
                else
                {
                    // Mouse: face the cursor. Project the cursor ray onto the player's movement plane and aim
                    // from the player toward that point. Held to the last valid aim when degenerate, so the
                    // character keeps facing the cursor even while standing still (the core jank fix).
                    float3 playerPos = xform.ValueRO.Position;
                    if (_camera != null && mouse != null)
                    {
                        UnityEngine.Ray ray = _camera.ScreenPointToRay(new UnityEngine.Vector3(cursorScreen.x, cursorScreen.y, 0f));
                        _lastKbmAim = AimMath.PlanarAimFromRay(
                            (float3)ray.origin, (float3)ray.direction, playerPos, playerPos.y, _lastKbmAim, KbmAimDeadZone);
                    }
                    aim = _lastKbmAim;
                }

                input.ValueRW.Move = move;
                input.ValueRW.Aim = aim;
                input.ValueRW.Scheme = _scheme;

                // Reset the per-frame event, then raise it on the press edge. Netcode latches the absolute
                // Count into the command buffer; AbilityFireSystem reads it as the SpawnId key.
                input.ValueRW.Fire = default;
                if (firePressed)
                    input.ValueRW.Fire.Set();
                input.ValueRW.Dash = default;
                if (dashPressed)
                    input.ValueRW.Dash.Set();
            }
        }

        private UnityEngine.Camera ResolveCamera()
        {
            var cam = UnityEngine.Camera.main;
            if (cam == null)
            {
                var rig = UnityEngine.Object.FindAnyObjectByType<PrototypeCameraRig>();
                if (rig != null) cam = rig.GetComponent<UnityEngine.Camera>();
            }
            return cam;
        }
    }
}