// Assets/_Project/Scripts/Gameplay/PlayerTowerUpgrades.cs
using System.Collections.Generic;
using Unity.Netcode;
using UnityEngine;

namespace TD.Gameplay
{
    /// <summary>
    /// Per-player set of unlocked tower <b>upgrade nodes</b> — the tower types this player is
    /// allowed to convert an existing tower into. Lives on the Player prefab alongside
    /// <see cref="PlayerTowerDeck"/>.
    /// </summary>
    /// <remarks>
    /// <para><b>Distinct from the deck, deliberately.</b> <see cref="PlayerTowerDeck"/> is what you
    /// can <i>build from scratch</i>; this is what you can <i>upgrade into</i>. They have to be
    /// separate sets because the 2.0 model is two-step: a draft pick unlocks a node, and gold spent
    /// on an already-placed tower converts it. Unlocking an upgrade must not make it directly
    /// buildable, or the gold step — the entire cost of the upgrade — is bypassed.</para>
    ///
    /// <para><b>The tree lives in the data.</b> Edges are <c>TowerDefinition.UpgradePaths</c>; this
    /// component only records which nodes a player has earned the right to use. Whether a
    /// particular tower can take a particular upgrade is a question for the tree (is it a child of
    /// what's placed?) crossed with this set (has the player unlocked it?).</para>
    ///
    /// <para>Append-only within a match, mirroring the deck. Reset happens by re-initializing at
    /// match start, so Retry / return-to-lobby cycles start clean.</para>
    /// </remarks>
    public class PlayerTowerUpgrades : NetworkBehaviour
    {
        // ----- Static registry (mirrors PlayerTowerDeck / PlayerGoldManager) -----

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

        public static PlayerTowerUpgrades GetForClient(ulong clientId)
        {
            s_byClientId.TryGetValue(clientId, out var upgrades);
            return upgrades;
        }

        public static PlayerTowerUpgrades Local
        {
            get
            {
                var nm = NetworkManager.Singleton;
                if (nm == null || !nm.IsClient) return null;
                return GetForClient(nm.LocalClientId);
            }
        }

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

        // TowerTypeIds (catalog indices) this player may upgrade into.
        private NetworkList<int> unlockedNodes;

        /// <summary>Fired on every peer when the unlocked set changes. The HUD subscribes so a
        /// selected tower's upgrade buttons appear the moment a draft grants them.</summary>
        public event System.Action OnUpgradesChanged;

        private void Awake()
        {
            unlockedNodes = new NetworkList<int>();
        }

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

        public override void OnNetworkDespawn()
        {
            unlockedNodes.OnListChanged -= HandleListChanged;
            if (s_byClientId.TryGetValue(OwnerClientId, out var registered) && registered == this)
                s_byClientId.Remove(OwnerClientId);
        }

        private void HandleListChanged(NetworkListEvent<int> _) => OnUpgradesChanged?.Invoke();

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

        public int Count => unlockedNodes.Count;

        public int GetTypeIdAt(int index) => unlockedNodes[index];

        /// <summary>True if this player has unlocked the given upgrade node.</summary>
        public bool Contains(int towerTypeId)
        {
            for (int i = 0; i < unlockedNodes.Count; i++)
                if (unlockedNodes[i] == towerTypeId) return true;
            return false;
        }

        // ----- Server API -------------------------------------------------

        /// <summary>Server-only: clear the unlocked set. Called at match start.</summary>
        public void ServerInitialize()
        {
            if (!IsServer) return;
            unlockedNodes.Clear();
        }

        /// <summary>
        /// Server-only: unlock an upgrade node. Returns false if already unlocked (so a draft
        /// option can report a wasted pick rather than silently succeeding).
        /// </summary>
        public bool ServerUnlock(int towerTypeId)
        {
            if (!IsServer) return false;
            if (towerTypeId < 0 || Contains(towerTypeId)) return false;

            unlockedNodes.Add(towerTypeId);
            return true;
        }
    }
}