// Assets/_Project/Scripts/Gameplay/EnemyUpgrades/EnemyUpgradePool.cs
using System.Collections.Generic;
using UnityEngine;

namespace TD.Gameplay.EnemyUpgrades
{
    /// <summary>
    /// Scene singleton holding every <see cref="EnemyUpgradeOption"/> that can appear anywhere in
    /// this match. The array index is the option's <c>EnemyUpgradeOptionId</c> — the stable
    /// identifier used to replicate vote offers, ballots, and the upgrades recorded on wave slots.
    /// </summary>
    /// <remarks>
    /// <b>Why a flat pool <i>and</i> per-phase groups.</b> The pool supplies network identity: one
    /// array, one index per card, identical on every peer. <c>PhaseDefinition.EnemyUpgradeGroups</c>
    /// supplies gating: which of those cards a given phase may offer. Folding gating into the pool
    /// would make ids phase-relative and therefore unstable across a phase change, which is
    /// exactly when replicated slot upgrades are being cleared and rewritten.
    ///
    /// <para>Plain MonoBehaviour — identical assets on every peer, so there is nothing to sync.
    /// The server reads it to generate and resolve votes; clients read it to render vote cards
    /// from replicated ids.</para>
    /// </remarks>
    public class EnemyUpgradePool : MonoBehaviour
    {
        public static EnemyUpgradePool Instance { get; private set; }

        [Tooltip("Every EnemyUpgradeOption asset that can appear this match. Array index is the " +
                 "id used over the network — reordering mid-development is fine, but not between " +
                 "a host and its clients.")]
        [SerializeField] private EnemyUpgradeOption[] options;

        private void Awake()
        {
            if (Instance != null && Instance != this)
            {
                Debug.LogError("[EnemyUpgradePool] Multiple instances detected. Only one per scene.");
                return;
            }
            Instance = this;
        }

        private void OnDestroy()
        {
            if (Instance == this) Instance = null;
        }

        /// <summary>Number of options in the pool.</summary>
        public int Count => options?.Length ?? 0;

        /// <summary>Returns the option at <paramref name="id"/>, or null if out of range.</summary>
        public EnemyUpgradeOption Get(int id)
            => (options != null && id >= 0 && id < options.Length) ? options[id] : null;

        /// <summary>Resolves an option asset back to its pool id, or -1 if it isn't in the pool.</summary>
        public int GetId(EnemyUpgradeOption option)
        {
            if (options == null || option == null) return -1;
            for (int i = 0; i < options.Length; i++)
                if (options[i] == option) return i;
            return -1;
        }

        /// <summary>
        /// Collects the pool ids of every card the given phase groups allow. Cards missing from
        /// the pool are reported once and skipped — an authored group referencing an unpooled
        /// card is a wiring mistake that would otherwise silently shrink the vote.
        /// </summary>
        public void CollectAllowedIds(EnemyUpgradeGroup[] phaseGroups,
                                      List<EnemyUpgradePoolEntry> entryScratch,
                                      List<int> intoIds,
                                      List<float> intoWeights)
        {
            intoIds.Clear();
            intoWeights.Clear();

            EnemyUpgradeGroup.CollectCandidates(phaseGroups, entryScratch);

            foreach (var entry in entryScratch)
            {
                int id = GetId(entry.Option);
                if (id < 0)
                {
                    Debug.LogWarning($"[EnemyUpgradePool] '{entry.Option.name}' is referenced by a " +
                                     $"phase's upgrade groups but is not in the pool — it can " +
                                     $"never be offered. Add it to the pool's options array.");
                    continue;
                }

                intoIds.Add(id);
                intoWeights.Add(entry.Weight);
            }
        }
    }
}