// Assets/_Project/Scripts/Gameplay/PlayerSpellLoadout.cs
using System.Collections;
using System.Collections.Generic;
using Unity.Netcode;
using UnityEngine;
using TD.Core;
using TD.Gameplay.BuilderSpells;

namespace TD.Gameplay
{
    /// <summary>
    /// Per-player set of granted builder spells and their cooldowns. Lives on the Player
    /// prefab alongside <see cref="BuilderUpgradeManager"/> and <see cref="PlayerDraft"/>.
    /// </summary>
    /// <remarks>
    /// <para><b>Slot == grant order == hotkey.</b> <see cref="spells"/> is append-only; a
    /// slot's index in the list is both its identity and the index into
    /// <see cref="SpellHotkeys.Layout"/>. There is no player-configurable rebinding.</para>
    ///
    /// <para><b>Cast flow.</b> The owning client calls <see cref="RequestCastSpellRpc"/> with a
    /// slot index and an aimed world point. The server re-validates everything (slot exists,
    /// off cooldown, <see cref="MatchPhase.Playing"/>) since client-side checks in
    /// <see cref="BuilderSpellCastController"/> are UX-only, resolves the
    /// <see cref="BuilderSpellDefinition"/> via <see cref="BuilderSpellPool"/>. An <b>instant</b>
    /// spell (<see cref="BuilderSpellDefinition.ImpactDelay"/> == 0) resolves on cast: a hit starts
    /// the cooldown and fires <see cref="PlayVfxClientRpc"/>; a miss is a no-op. A <b>delayed</b>
    /// spell (a projectile, e.g. the Fireball meteor) commits on the throw — cooldown + the falling
    /// visual fire immediately — while its damage and impact sound are held until the projectile
    /// lands <see cref="BuilderSpellDefinition.ImpactDelay"/> seconds later.</para>
    /// </remarks>
    public class PlayerSpellLoadout : NetworkBehaviour
    {
        /// <summary>Hard cap on granted spells, matching the number of hotkey slots available.</summary>
        public const int MaxSpellSlots = 4;

        // ----- Static registry (mirrors BuilderUpgradeManager) -----

        private static readonly Dictionary<ulong, PlayerSpellLoadout> s_byClientId
            = new Dictionary<ulong, PlayerSpellLoadout>();

        /// <summary>Returns the loadout owned by the given client, or null.</summary>
        public static PlayerSpellLoadout GetForClient(ulong clientId)
        {
            s_byClientId.TryGetValue(clientId, out var loadout);
            return loadout;
        }

        /// <summary>Convenience: the local client's own loadout.</summary>
        public static PlayerSpellLoadout Local
        {
            get
            {
                var nm = NetworkManager.Singleton;
                if (nm == null || !nm.IsClient) return null;
                return GetForClient(nm.LocalClientId);
            }
        }

        // ----- Networked state --------------------------------------------

        private readonly NetworkList<SpellSlot> spells = new NetworkList<SpellSlot>();

        /// <summary>Fired on every peer when a spell is granted or a cooldown changes.</summary>
        public event System.Action OnLoadoutChanged;

        // ----- NGO lifecycle ------------------------------------------------

        public override void OnNetworkSpawn()
        {
            s_byClientId[OwnerClientId] = this;
            spells.OnListChanged += HandleSpellsChanged;
        }

        public override void OnNetworkDespawn()
        {
            spells.OnListChanged -= HandleSpellsChanged;

            if (s_byClientId.TryGetValue(OwnerClientId, out var registered) && registered == this)
                s_byClientId.Remove(OwnerClientId);
        }

        private void HandleSpellsChanged(NetworkListEvent<SpellSlot> change) => OnLoadoutChanged?.Invoke();

        // ----- Read API -----------------------------------------------------

        /// <summary>Number of spells currently granted.</summary>
        public int SlotCount => spells.Count;

        /// <summary>True if this player has already been granted the given spell.</summary>
        public bool PlayerHasSpell(BuilderSpellKind kind)
        {
            for (int i = 0; i < spells.Count; i++)
            {
                if (spells[i].Kind == kind) return true;
            }
            return false;
        }

        /// <summary>The spell kind occupying <paramref name="slot"/>, or null if out of range.</summary>
        public BuilderSpellKind? GetKind(int slot)
            => (slot >= 0 && slot < spells.Count) ? spells[slot].Kind : (BuilderSpellKind?)null;

        /// <summary>True if <paramref name="slot"/> is out of range, empty, or still cooling down.</summary>
        public bool IsSlotOnCooldown(int slot)
        {
            if (slot < 0 || slot >= spells.Count) return true;

            var nm = NetworkManager.Singleton;
            if (nm == null) return false;

            return spells[slot].CooldownEndServerTime > nm.ServerTime.Time;
        }

        /// <summary>Seconds remaining on <paramref name="slot"/>'s cooldown, or 0 if ready/invalid.</summary>
        public float GetCooldownRemaining(int slot)
        {
            if (slot < 0 || slot >= spells.Count) return 0f;

            var nm = NetworkManager.Singleton;
            if (nm == null) return 0f;

            double remaining = spells[slot].CooldownEndServerTime - nm.ServerTime.Time;
            return remaining > 0d ? (float)remaining : 0f;
        }

        // ----- Server mutation -----------------------------------------------

        /// <summary>
        /// Server-only: grants the given spell (a draft pick) into the next free slot.
        /// No-op if already granted or slots are full. Returns true if actually granted.
        /// </summary>
        public bool ServerGrantSpell(BuilderSpellKind kind)
        {
            if (!IsServer) return false;
            if (spells.Count >= MaxSpellSlots) return false;
            if (PlayerHasSpell(kind)) return false;

            spells.Add(SpellSlot.CreateReady(kind));
            return true;
        }

        /// <summary>
        /// Server-only: replaces a previously granted spell with a different one (an upgrade
        /// pick), in place — the upgraded spell keeps the base spell's hotkey slot and starts
        /// off cooldown. No-op if the old spell isn't currently granted or the new one already
        /// is. Returns true if the swap happened.
        /// </summary>
        public bool ServerUpgradeSpell(BuilderSpellKind oldKind, BuilderSpellKind newKind)
        {
            if (!IsServer) return false;
            if (PlayerHasSpell(newKind)) return false;

            for (int i = 0; i < spells.Count; i++)
            {
                if (spells[i].Kind == oldKind)
                {
                    spells[i] = SpellSlot.CreateReady(newKind);
                    return true;
                }
            }
            return false;
        }

        // ----- Cast RPC -----------------------------------------------------

        /// <summary>
        /// Owning-client entry point. Requests the server resolve a cast of the spell in
        /// <paramref name="slot"/> at <paramref name="targetPoint"/>. All validation happens
        /// here on the server; the client only uses this to trigger an attempt.
        /// </summary>
        [Rpc(SendTo.Server, InvokePermission = RpcInvokePermission.Owner)]
        public void RequestCastSpellRpc(int slot, Vector3 targetPoint)
        {
            if (MatchState.Instance == null || MatchState.Instance.Phase != MatchPhase.Playing)
                return;

            if (slot < 0 || slot >= spells.Count) return;

            var slotValue = spells[slot];
            if (slotValue.CooldownEndServerTime > NetworkManager.ServerTime.Time) return;

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

            if (definition.ImpactDelay <= 0f)
            {
                // Instant spell (e.g. Slow Area): resolve on cast. A miss (hit nothing) is a no-op
                // and does NOT start the cooldown — unchanged behavior.
                if (!definition.ServerCast(OwnerClientId, targetPoint)) return;

                StartCooldown(slot, definition);
                PlayVfxClientRpc(slotValue.Kind, targetPoint);
            }
            else
            {
                // Delayed spell (e.g. the Fireball meteor): the projectile has to fall before it
                // lands, so the cast is COMMITTED on the throw — cooldown starts and the falling
                // visual spawns now — while damage and the impact sound wait until it hits the
                // ground (ImpactDelay later). Enemies are re-scanned at impact, so movement during
                // the fall resolves correctly.
                StartCooldown(slot, definition);
                PlayVfxClientRpc(slotValue.Kind, targetPoint);
                StartCoroutine(ServerResolveImpactAfterDelay(
                    slotValue.Kind, OwnerClientId, targetPoint, definition.ImpactDelay));
            }
        }

        // Server-only: stamp the slot's cooldown from the definition and replicate it.
        private void StartCooldown(int slot, BuilderSpellDefinition definition)
        {
            var slotValue = spells[slot];
            slotValue.CooldownEndServerTime = NetworkManager.ServerTime.Time + definition.Cooldown;
            spells[slot] = slotValue;
        }

        // Server-only: apply a delayed spell's effect once its projectile has landed. Re-resolves
        // targets at impact — the enemy set may have shifted during the fall.
        private IEnumerator ServerResolveImpactAfterDelay(
            BuilderSpellKind kind, ulong clientId, Vector3 targetPoint, float delay)
        {
            yield return new WaitForSeconds(delay);
            if (!IsServer) yield break;
            BuilderSpellPool.Instance?.Get(kind)?.ServerCast(clientId, targetPoint);
        }

        [ClientRpc]
        private void PlayVfxClientRpc(BuilderSpellKind kind, Vector3 targetPoint)
        {
            var def = BuilderSpellPool.Instance?.Get(kind);
            if (def == null) return;

            def.ClientSpawnVfx(targetPoint); // spawn the (possibly falling) visual now

            if (def.ImpactDelay <= 0f)
                def.ClientPlayImpact(targetPoint);
            else
                StartCoroutine(ClientPlayImpactAfterDelay(kind, targetPoint, def.ImpactDelay));
        }

        // Client-side: play the impact (sound + any contact visual) when the projectile lands.
        // Timed locally off the same ImpactDelay so it stays in lockstep with this peer's own
        // falling visual — no second RPC, no double latency.
        private IEnumerator ClientPlayImpactAfterDelay(
            BuilderSpellKind kind, Vector3 targetPoint, float delay)
        {
            yield return new WaitForSeconds(delay);
            BuilderSpellPool.Instance?.Get(kind)?.ClientPlayImpact(targetPoint);
        }
    }
}