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

namespace Jovian.EncounterSystem {
    /// <summary>
    /// A ScriptableObject asset holding a named list of encounters. Encounters inside the list are
    /// authored via <c>[SerializeReference]</c> so different <see cref="IEncounter"/> implementations
    /// and <see cref="IEncounterKind"/> payloads can coexist.
    /// </summary>
    [CreateAssetMenu(fileName = "EncounterTable", menuName = "Jovian/Encounter System/Encounter Table", order = 1)]
    public class EncounterTable : ScriptableObject {
        /// <summary>Designer-facing table identifier (free-form).</summary>
        public string id;

        /// <summary>Ordered encounter list. Each element is a concrete <see cref="Encounter"/> whose
        /// type-specific payload is carried by its <see cref="IEncounterKind"/> (set in the inspector
        /// via the SubclassSelector dropdown on <see cref="Encounter.Kind"/>).</summary>
        public List<Encounter> encounters;

        /// <summary>Pick a uniformly random encounter, or <c>null</c> if the table is empty.</summary>
        public IEncounter GetRandomEncounter() {
            if(encounters == null || encounters.Count == 0) {
                return null;
            }

            return encounters[UnityEngine.Random.Range(0, encounters.Count)];
        }

        /// <summary>Pick a uniformly random encounter whose runtime type matches <paramref name="type"/>,
        /// or <c>null</c> if none match.</summary>
        /// <param name="type">The concrete <see cref="IEncounter"/> runtime type to filter on.</param>
        public IEncounter GetRandomEncounter(Type type) {
            if(encounters == null || encounters.Count == 0) {
                return null;
            }

            var encountersOfType = encounters.FindAll(encounter => encounter.GetType() == type);
            if(encountersOfType.Count > 0) {
                return encountersOfType[UnityEngine.Random.Range(0, encountersOfType.Count)];
            }

            return null;
        }

        /// <summary>Pick a uniformly random encounter matching <paramref name="filter"/>, or <c>null</c>
        /// if no element passes. Used by <see cref="QuestProgress.IsGated"/> integration to exclude
        /// gated quest encounters from rolls.</summary>
        /// <param name="filter">Predicate applied to each encounter before rolling.</param>
        public IEncounter GetRandomEncounter(Predicate<IEncounter> filter) {
            if(encounters == null || encounters.Count == 0 || filter == null) {
                return GetRandomEncounter();
            }

            var pool = encounters.FindAll(filter);
            if(pool.Count == 0) {
                return null;
            }

            return pool[UnityEngine.Random.Range(0, pool.Count)];
        }
    }
}