using System;
using System.Collections.Generic;
using static PKHeX.Core.Legal;
using static PKHeX.Core.GameVersion;

namespace PKHeX.Core
{
    public static class MoveEgg
    {
        public static int[] GetEggMoves(PersonalInfo pi, int species, int form, GameVersion version, int generation)
        {
            if (species > GetMaxSpeciesOrigin(generation, version))
                return Array.Empty<int>();

            if (pi.Genderless && !FixedGenderFromBiGender.Contains(species))
                return Array.Empty<int>();

            if (!Breeding.CanGameGenerateEggs(version))
                return Array.Empty<int>();

            return GetEggMoves(generation, species, form, version);
        }

        public static int[] GetEggMoves(int generation, int species, int form, GameVersion version) => generation switch
        {
            1 or 2 => GetMovesSafe(version == C ? EggMovesC : EggMovesGS, species),
            3 => GetMovesSafe(EggMovesRS, species),
            4 when version is D or P or Pt => GetMovesSafe(EggMovesDPPt, species),
            4 when version is HG or SS => GetMovesSafe(EggMovesHGSS, species),
            5 => GetMovesSafe(EggMovesBW, species),

            6 when version is X or Y => GetMovesSafe(EggMovesXY, species),
            6 when version is OR or AS => GetMovesSafe(EggMovesAO, species),

            7 when version is SN or MN => GetFormEggMoves(species, form, EggMovesSM),
            7 when version is US or UM => GetFormEggMoves(species, form, EggMovesUSUM),
            8 when version is SW or SH => GetFormEggMoves(species, form, EggMovesSWSH),
            8 when version is BD or SP => GetMovesSafe(EggMovesBDSP, species),
            _ => Array.Empty<int>(),
        };

        private static int[] GetMovesSafe<T>(IReadOnlyList<T> moves, int species) where T : EggMoves
        {
            if ((uint)species >= moves.Count)
                return Array.Empty<int>();
            return moves[species].Moves;
        }

        private static int[] GetFormEggMoves(int species, int form, IReadOnlyList<EggMoves7> table)
        {
            if ((uint)species >= table.Count)
                return Array.Empty<int>();

            var entry = table[species];
            if (form <= 0 || entry.FormTableIndex <= species)
                return entry.Moves;

            // Sanity check form in the event it is out of range.
            var baseIndex = entry.FormTableIndex;
            var index = baseIndex + form - 1;
            if ((uint)index >= table.Count)
                return Array.Empty<int>();
            entry = table[index];
            if (entry.FormTableIndex != baseIndex)
                return Array.Empty<int>();

            return entry.Moves;
        }

        internal static int[] GetRelearnLVLMoves(PKM pkm, int species, int form, int lvl, GameVersion version = Any)
        {
            if (version == Any)
                version = (GameVersion)pkm.Version;
            // A pkm can only have levelup relearn moves from the game it originated on
            // eg Plusle/Minun have Charm/Fake Tears (respectively) only in OR/AS, not X/Y
            return version switch
            {
                X or Y => getMoves(LevelUpXY, PersonalTable.XY),
                OR or AS => getMoves(LevelUpAO, PersonalTable.AO),
                SN or MN when species <= MaxSpeciesID_7 => getMoves(LevelUpSM, PersonalTable.SM),
                US or UM => getMoves(LevelUpUSUM, PersonalTable.USUM),
                SW or SH => getMoves(LevelUpSWSH, PersonalTable.SWSH),
                BD or SP => getMoves(LevelUpBDSP, PersonalTable.BDSP),
                PLA => getMoves(LevelUpLA, PersonalTable.LA),
                _ => Array.Empty<int>(),
            };

            int[] getMoves(IReadOnlyList<Learnset> moves, PersonalTable table) => moves[table.GetFormIndex(species, form)].GetMoves(lvl);
        }

        public static bool GetIsSharedEggMove(PKM pkm, int gen, int move)
        {
            if (gen < 8 || pkm.IsEgg)
                return false;
            var egg = GetSharedEggMoves(pkm, gen);
            return Array.IndexOf(egg, move) >= 0;
        }

        public static int[] GetSharedEggMoves(PKM pkm, int gen)
        {
            if (gen < 8 || pkm.IsEgg)
                return Array.Empty<int>();

            if (pkm.LA)
                return Array.Empty<int>();

            if (pkm.BDSP)
            {
                var table = PersonalTable.BDSP;
                var entry = (PersonalInfoBDSP)table.GetFormEntry(pkm.Species, pkm.Form);
                var baseSpecies = entry.HatchSpecies;
                var baseForm = entry.HatchFormIndex;
                return GetEggMoves(8, baseSpecies, baseForm, BD);
            }
            else
            {
                var table = PersonalTable.SWSH;
                var entry = (PersonalInfoSWSH)table.GetFormEntry(pkm.Species, pkm.Form);
                var baseSpecies = entry.HatchSpecies;
                var baseForm = entry.HatchFormIndexEverstone;
                return GetEggMoves(8, baseSpecies, baseForm, SW);
            }
        }
    }
}