using System;
using System.Collections.Generic;
using UnityEngine;

namespace Game.Scripts.Runtime.Data
{
    [CreateAssetMenu(menuName = "Game/Spawning/Spawn Table", fileName = "SpawnTable")]
    public class SpawnTable : ScriptableObject
    {
        [Serializable]
        public class Entry
        {
            public EnemyDefinition Def;
            [Min(0)] public int Weight = 1;
            public int MinWave = 0;
            public int MaxWave = int.MaxValue;
            [Tooltip("Optional cap per wave. Values <= 0 mean unlimited.")]
            public int Cap = -1;

            public bool IsWaveValid(int wave) => wave >= MinWave && wave <= MaxWave;

            public bool IsUnderCap(int currentCount)
            {
                if (Cap <= 0)
                {
                    return true;
                }

                return currentCount < Cap;
            }
        }

        [SerializeField] private List<Entry> entries = new();

        private readonly List<Entry> _eligibleBuffer = new();

        public IReadOnlyList<Entry> Entries => entries;

        public EnemyDefinition Pick(int wave, System.Random rng)
        {
            if (entries == null || entries.Count == 0)
            {
                return null;
            }

            _eligibleBuffer.Clear();
            foreach (var entry in entries)
            {
                if (entry?.Def == null || entry.Weight <= 0)
                {
                    continue;
                }

                if (entry.IsWaveValid(wave))
                {
                    _eligibleBuffer.Add(entry);
                }
            }

            if (_eligibleBuffer.Count == 0)
            {
                return null;
            }

            var totalWeight = 0;
            foreach (var entry in _eligibleBuffer)
            {
                totalWeight += Mathf.Max(1, entry.Weight);
            }

            var roll = rng.Next(totalWeight);
            foreach (var entry in _eligibleBuffer)
            {
                var weight = Mathf.Max(1, entry.Weight);
                if (roll < weight)
                {
                    return entry.Def;
                }

                roll -= weight;
            }

            return _eligibleBuffer[^1].Def;
        }

        public IEnumerable<Entry> EnumerateEligibleEntries(int wave)
        {
            if (entries == null)
            {
                yield break;
            }

            foreach (var entry in entries)
            {
                if (entry?.Def == null || entry.Weight <= 0)
                {
                    continue;
                }

                if (entry.IsWaveValid(wave))
                {
                    yield return entry;
                }
            }
        }
    }
}