// Assets/_Project/Scripts/Gameplay/BuilderSpellCastController.cs
using UnityEngine;
using UnityEngine.InputSystem;
using UnityEngine.Rendering.Universal;
using TD.Core;
using TD.UI;
using TD.Gameplay.BuilderSpells;

namespace TD.Gameplay
{
    /// <summary>
    /// Per-client controller for the builder-spell casting UX. Watches
    /// <see cref="SpellHotkeys"/> to enter aim mode, raycasts against a broad ground layer
    /// (must cover the enemy path, not just buildable tiles), previews the aim point, and
    /// dispatches the cast to <see cref="PlayerSpellLoadout"/> via RPC on confirm.
    /// </summary>
    /// <remarks>
    /// <para><b>Plain MonoBehaviour.</b> Aiming visuals are purely cosmetic and local, same
    /// rationale as <see cref="TowerPlacementController"/>. All server-authoritative
    /// resolution lives in <see cref="PlayerSpellLoadout.RequestCastSpellRpc"/>.</para>
    ///
    /// <para><b>Point vs. area preview.</b> <see cref="SpellTargetType.PointTarget"/> shows a
    /// small fixed-size reticle, even if the spell has an internal splash radius.
    /// <see cref="SpellTargetType.AreaOfEffect"/> scales the same decal to the spell's
    /// <see cref="BuilderSpellDefinition.Radius"/>, mirroring <see cref="BuildRangeIndicator"/>'s
    /// diameter-sizing idiom.</para>
    ///
    /// <para><b>Single-shot only.</b> Unlike tower placement, there is no chained/shift-held
    /// casting — one keypress aims one cast.</para>
    /// </remarks>
    public class BuilderSpellCastController : MonoBehaviour
    {
        // ----- Inspector --------------------------------------------------

        [Tooltip("Physics layer(s) the aim raycast hits. Must cover the whole level's ground " +
                 "(including over the enemy path), not just buildable tiles — set this to " +
                 "'TerrainGeometry', not 'BuildablePlane'.")]
        [SerializeField] private LayerMask groundLayerMask;

        [Tooltip("Maximum raycast distance from the camera to the ground.")]
        [SerializeField] private float raycastMaxDistance = 500f;

        [Tooltip("Ground decal used for both the point reticle and the area-of-effect " +
                 "radius preview. Auto-found in children if empty.")]
        [SerializeField] private DecalProjector aimDecal;

        [Tooltip("Fixed diameter of the reticle shown for PointTarget spells, regardless of " +
                 "any internal splash radius the spell may use server-side.")]
        [SerializeField] private float pointReticleDiameter = 1.5f;

        [Tooltip("Vertical thickness of the decal projector's projection volume. Should " +
                 "exceed the map's vertical range so it projects onto terrain at any height.")]
        [SerializeField] private float projectionDepth = 50f;

        // ----- Active-aim state ---------------------------------------------

        // -1 when not aiming.
        private int activeSlot = -1;

        // Frame on which the confirming cast click was consumed. Lets the selection controller
        // ignore that click order-independently — see ConsumedCastClickThisFrame.
        private int lastCastClickFrame = -1;

        /// <summary>True while a spell is being aimed (awaiting the confirming click). The
        /// selection input controller treats this as a modal state, so the click that confirms
        /// the cast doesn't also fall through to selection and deselect the builder.</summary>
        public bool IsAiming => activeSlot >= 0;

        /// <summary>True during the frame the confirming cast click was consumed. Aim mode exits
        /// the same frame the cast is submitted, flipping <see cref="IsAiming"/> false; this stays
        /// true for the rest of that frame so the selection controller ignores the click no matter
        /// which controller's Update ran first.</summary>
        public bool ConsumedCastClickThisFrame => lastCastClickFrame == Time.frameCount;
        private BuilderSpellDefinition activeDefinition;

        private bool lastHitValid;
        private Vector3 lastHitPoint;

        // ----- Lifecycle ----------------------------------------------------

        private void Awake()
        {
            if (aimDecal == null) aimDecal = GetComponentInChildren<DecalProjector>();
            if (aimDecal != null)
            {
                aimDecal.transform.localRotation = Quaternion.Euler(90f, 0f, 0f);
                aimDecal.enabled = false;
            }
        }

        private void OnDisable()
        {
            ExitAimMode();
        }

        private void Update()
        {
            if (!HUDController.IsTextInputActive)
                ScanHotkeys();

            if (activeSlot < 0) return; // idle — nothing to aim

            // Deselecting the builder mid-aim cancels the cast, so you can't start aiming while
            // selected and then deselect to sneak a cast past the gate above.
            if (!LocalBuilderSelected())
            {
                ExitAimMode();
                return;
            }

            var keyboard = Keyboard.current;
            if (keyboard != null && keyboard.escapeKey.wasPressedThisFrame)
            {
                ExitAimMode();
                return;
            }

            var mouse = Mouse.current;
            if (mouse == null) return;

            if (mouse.rightButton.wasPressedThisFrame)
            {
                ExitAimMode();
                return;
            }

            if (TryGetGroundHit(mouse.position.ReadValue(), out Vector3 hitPoint))
            {
                lastHitValid = true;
                lastHitPoint = hitPoint;
                ShowAimDecal(hitPoint);
            }
            else
            {
                lastHitValid = false;
                HideAimDecal();
            }

            if (mouse.leftButton.wasPressedThisFrame && lastHitValid)
            {
                // Record the frame so the selection controller ignores this click even though
                // TrySubmitCast exits aim mode this same frame (IsAiming flips false). Without
                // this, whether the click also deselected the builder depended on Update order.
                lastCastClickFrame = Time.frameCount;
                TrySubmitCast();
            }
        }

        // ----- Hotkey scan --------------------------------------------------

        // True when the local player's own builder is the current selection. Casting is gated
        // on this so it matches the spell HUD (shown only for the selected builder).
        private static bool LocalBuilderSelected()
        {
            var selected = SelectionState.Instance?.SelectedObject;
            return selected is Builder builder && builder.IsOwner;
        }

        private void ScanHotkeys()
        {
            if (activeSlot >= 0) return; // already aiming — hotkeys re-scanned only when idle

            // Spells cast only while the local player's OWN builder is selected — keeps casting
            // in sync with the spell HUD, which is shown only for the selected builder.
            if (!LocalBuilderSelected()) return;

            var loadout = PlayerSpellLoadout.Local;
            if (loadout == null) return;

            var keyboard = Keyboard.current;
            if (keyboard == null) return;

            var layout = SpellHotkeys.Layout;
            int slotCount = Mathf.Min(loadout.SlotCount, layout.Length);

            for (int i = 0; i < slotCount; i++)
            {
                if (!keyboard[layout[i]].wasPressedThisFrame) continue;
                if (loadout.IsSlotOnCooldown(i)) continue;

                BeginAiming(i, loadout);
                break;
            }
        }

        private void BeginAiming(int slot, PlayerSpellLoadout loadout)
        {
            var kind = loadout.GetKind(slot);
            if (kind == null) return;

            var definition = BuilderSpellPool.Instance?.Get(kind.Value);
            if (definition == null)
            {
                Debug.LogWarning($"[BuilderSpellCastController] No BuilderSpellDefinition for {kind.Value}.");
                return;
            }

            activeSlot = slot;
            activeDefinition = definition;
            lastHitValid = false;
        }

        private void ExitAimMode()
        {
            activeSlot = -1;
            activeDefinition = null;
            lastHitValid = false;
            HideAimDecal();
        }

        // ----- Raycasting ---------------------------------------------------

        private bool TryGetGroundHit(Vector2 screenPos, out Vector3 hitPoint)
        {
            hitPoint = Vector3.zero;

            var cam = Camera.main;
            if (cam == null) return false;

            Ray ray = cam.ScreenPointToRay(new Vector3(screenPos.x, screenPos.y, 0f));
            if (Physics.Raycast(ray, out RaycastHit hit, raycastMaxDistance, groundLayerMask))
            {
                hitPoint = hit.point;
                return true;
            }
            return false;
        }

        // ----- Aim decal -----------------------------------------------------

        private void ShowAimDecal(Vector3 point)
        {
            if (aimDecal == null) return;

            float diameter = activeDefinition.TargetType == SpellTargetType.AreaOfEffect
                ? activeDefinition.Radius * 2f
                : pointReticleDiameter;

            aimDecal.size = new Vector3(diameter, diameter, projectionDepth);
            aimDecal.pivot = Vector3.zero;
            aimDecal.transform.position = point;
            aimDecal.enabled = true;
        }

        private void HideAimDecal()
        {
            if (aimDecal != null) aimDecal.enabled = false;
        }

        // ----- Cast submission ------------------------------------------------

        private void TrySubmitCast()
        {
            var loadout = PlayerSpellLoadout.Local;
            if (loadout == null)
            {
                ExitAimMode();
                return;
            }

            loadout.RequestCastSpellRpc(activeSlot, lastHitPoint);
            ExitAimMode();
        }
    }
}