using System.Collections.Generic;
using UnityEngine;
using Ashwild.Inventory;

namespace Ashwild.Player
{
    /// <summary>
    /// Keeps a rig's Animator loaded with the clips of whatever item the player is holding. It owns
    /// exactly one concern — *which clips are in the controller right now* — while PlayerAnimatorDriver
    /// owns *which parameters are set*. Splitting them is what lets a new weapon ship without touching
    /// either: the driver keeps firing the same "Attack" trigger, the binder just points that slot at a
    /// different clip.
    ///
    /// It never assigns a fresh controller per item. Assigning runtimeAnimatorController rebinds the
    /// Animator, which resets the state machine to Entry and wipes the parameters — the player would
    /// visibly snap to idle every time he scrolled the hotbar. Instead one AnimatorOverrideController is
    /// built in Awake and only its overrides are mutated afterwards, which leaves the current state and
    /// all parameters untouched. That same property is what keeps FishNet's NetworkAnimator working on
    /// the third-person body: an override controller preserves the base controller's parameter list, so
    /// replication never sees the swap.
    /// </summary>
    [DisallowMultipleComponent]
    public class PlayerAnimationSetBinder : MonoBehaviour
    {
        #region Serialized Fields

        [Header("Target")]
        [SerializeField] private Animator animator;
        [Tooltip("Which rig this binder drives — it picks the matching set off the held ItemData.")]
        [SerializeField] private PlayerAnimationRig rig = PlayerAnimationRig.Arms;

        [Header("Sets")]
        [Tooltip("Set used with bare hands, and as the fallback for any slot the held item leaves empty.")]
        [SerializeField] private PlayerAnimationSet defaultSet;

        #endregion

        #region State

        private AnimatorOverrideController overrideController;
        private AnimationClip[] placeholders;
        private readonly List<KeyValuePair<AnimationClip, AnimationClip>> overrides = new List<KeyValuePair<AnimationClip, AnimationClip>>();
        private PlayerAnimationSet currentSet;
        private bool ready;

        #endregion

        #region Unity Lifecycle

        /// <summary>
        /// Wraps the authored controller in a single override controller and caches its placeholder
        /// clips, whose names are the slot keys every set is matched against. Done in Awake so the
        /// rebind happens once, before any driver seeds a parameter.
        /// </summary>
        private void Awake()
        {
            if (animator == null)
            {
                Debug.LogError($"[PlayerAnimationSetBinder] '{name}' has no Animator assigned — clips will never swap.", this);
                return;
            }

            RuntimeAnimatorController master = animator.runtimeAnimatorController;
            if (master == null)
            {
                Debug.LogError($"[PlayerAnimationSetBinder] '{name}' — the Animator has no controller assigned.", this);
                return;
            }

            overrideController = new AnimatorOverrideController(master) { name = $"{master.name} (Runtime)" };
            overrideController.GetOverrides(overrides);

            placeholders = new AnimationClip[overrides.Count];
            for (int i = 0; i < overrides.Count; i++)
                placeholders[i] = overrides[i].Key;

            animator.runtimeAnimatorController = overrideController;
            ready = true;

            ApplySet(defaultSet);
        }

        /// <summary>
        /// Subscribes to the held-item bus. HotbarController re-raises HeldItemChanged on its own first
        /// resolve, so a rig enabled after the player already drew an item still lands on the right set.
        /// </summary>
        private void OnEnable()
        {
            PlayerEvents.HeldItemChanged += HandleHeldItemChanged;
        }

        /// <summary>
        /// Unsubscribes — mirrors OnEnable exactly.
        /// </summary>
        private void OnDisable()
        {
            PlayerEvents.HeldItemChanged -= HandleHeldItemChanged;
        }

        #endregion

        #region Event Handlers

        /// <summary>
        /// Loads the set the newly drawn item authors for this rig (or the bare-hand set when the player
        /// empties his hands).
        /// </summary>
        private void HandleHeldItemChanged(ItemData item)
        {
            ApplySet(item != null ? item.GetAnimationSet(rig) : defaultSet);
        }

        #endregion

        #region Internal Helpers

        /// <summary>
        /// Rewrites every slot in one ApplyOverrides call rather than one indexer assignment per clip,
        /// because each individual assignment forces the controller to regenerate. Skips redundant work
        /// when the set has not actually changed — several items can legitimately share one set.
        /// </summary>
        private void ApplySet(PlayerAnimationSet set)
        {
            if (!ready) return;
            if (set == currentSet) return;

            currentSet = set;

            for (int i = 0; i < placeholders.Length; i++)
            {
                AnimationClip placeholder = placeholders[i];
                overrides[i] = new KeyValuePair<AnimationClip, AnimationClip>(placeholder, Resolve(placeholder.name, set));
            }

            overrideController.ApplyOverrides(overrides);
        }

        /// <summary>
        /// Picks the clip for a slot: the held item's set first, then the default set, then null — which
        /// means "no override" and leaves the master controller's own placeholder playing. That last
        /// step is the safety net: a slot nobody authored still animates instead of freezing the rig.
        /// </summary>
        private AnimationClip Resolve(string slotName, PlayerAnimationSet set)
        {
            AnimationClip clip = set != null ? set.GetClip(slotName) : null;
            if (clip == null && defaultSet != null) clip = defaultSet.GetClip(slotName);
            return clip;
        }

        #endregion
    }
}