using System;
using System.Collections.Generic;
using System.Linq;
using static PKHeX.Core.LegalityCheckStrings;

namespace PKHeX.Core
{
    /// <summary>
    /// Verifies the <see cref="PKM"/> Ribbon values.
    /// </summary>
    public sealed class RibbonVerifier : Verifier
    {
        protected override CheckIdentifier Identifier => CheckIdentifier.Ribbon;

        public override void Verify(LegalityAnalysis data)
        {
            var enc = data.EncounterMatch;
            var pkm = data.pkm;

            // Check Unobtainable Ribbons
            if (pkm.IsEgg)
            {
                if (GetIncorrectRibbonsEgg(pkm, enc))
                    data.AddLine(GetInvalid(LRibbonEgg));
                return;
            }

            int gen = enc.Generation; // Flag VC (Gen1/2) ribbons using Gen7 origin rules.
            var result = GetIncorrectRibbons(pkm, enc, gen);
            if (result.Count != 0)
            {
                var msg = string.Join(Environment.NewLine, result);
                data.AddLine(GetInvalid(msg));
            }
            else
            {
                data.AddLine(GetValid(LRibbonAllValid));
            }
        }

        private static List<string> GetIncorrectRibbons(PKM pkm, IEncounterable enc, int gen)
        {
            List<string> missingRibbons = new();
            List<string> invalidRibbons = new();
            var ribs = GetRibbonResults(pkm, enc, gen);
            foreach (var bad in ribs)
                (bad.Invalid ? invalidRibbons : missingRibbons).Add(bad.Name);

            var result = new List<string>();
            if (missingRibbons.Count > 0)
                result.Add(string.Format(LRibbonFMissing_0, string.Join(", ", missingRibbons).Replace(RibbonInfo.PropertyPrefix, string.Empty)));
            if (invalidRibbons.Count > 0)
                result.Add(string.Format(LRibbonFInvalid_0, string.Join(", ", invalidRibbons).Replace(RibbonInfo.PropertyPrefix, string.Empty)));
            return result;
        }

        private static bool GetIncorrectRibbonsEgg(PKM pkm, IEncounterable enc)
        {
            var names = ReflectUtil.GetPropertiesStartWithPrefix(pkm.GetType(), RibbonInfo.PropertyPrefix);
            if (enc is IRibbonSetEvent3 event3)
                names = names.Except(event3.RibbonNames());
            if (enc is IRibbonSetEvent4 event4)
                names = names.Except(event4.RibbonNames());

            foreach (var value in names.Select(name => ReflectUtil.GetValue(pkm, name)))
            {
                if (value is null)
                    continue;
                if (HasFlag(value) || HasCount(value))
                    return true;

                static bool HasFlag(object o) => o is bool z && z;
                static bool HasCount(object o) => o is int z && z > 0;
            }
            return false;
        }

        private static IEnumerable<RibbonResult> GetRibbonResults(PKM pkm, IEncounterable enc, int gen)
        {
            return GetInvalidRibbons(pkm, enc, gen)
                .Concat(GetInvalidRibbonsEvent1(pkm, enc))
                .Concat(GetInvalidRibbonsEvent2(pkm, enc));
        }

        private static IEnumerable<RibbonResult> GetInvalidRibbons(PKM pkm, IEncounterable enc, int gen)
        {
            if (pkm is IRibbonSetOnly3 o3)
            {
                if (o3.RibbonWorld) // is a part of Event4, but O3 doesn't have the others
                    yield return new RibbonResult(nameof(o3.RibbonWorld));
            }
            if (pkm is IRibbonSetUnique3 u3)
            {
                if (gen != 3)
                {
                    if (u3.RibbonWinning)
                        yield return new RibbonResult(nameof(u3.RibbonWinning));
                    if (u3.RibbonVictory)
                        yield return new RibbonResult(nameof(u3.RibbonVictory));
                }
                else
                {
                    if (u3.RibbonWinning && !CanHaveRibbonWinning(pkm, enc, 3))
                        yield return new RibbonResult(nameof(u3.RibbonWinning));
                    if (u3.RibbonVictory && !CanHaveRibbonVictory(pkm, 3))
                        yield return new RibbonResult(nameof(u3.RibbonVictory));
                }
            }

            if (pkm is IRibbonSetUnique4 u4)
            {
                if (!IsAllowedBattleFrontier(pkm.Species, pkm.Form, 4) || gen > 4)
                {
                    foreach (var z in GetInvalidRibbonsNone(u4.RibbonBitsAbility(), u4.RibbonNamesAbility()))
                        yield return z;
                }

                var c3 = u4.RibbonBitsContest3();
                var c3n = u4.RibbonNamesContest3();
                var iter3 = gen == 3 ? GetMissingContestRibbons(c3, c3n) : GetInvalidRibbonsNone(c3, c3n);
                foreach (var z in iter3)
                    yield return z;

                var c4 = u4.RibbonBitsContest4();
                var c4n = u4.RibbonNamesContest4();
                var iter4 = (gen is 3 or 4) && IsAllowedInContest4(pkm.Species) ? GetMissingContestRibbons(c4, c4n) : GetInvalidRibbonsNone(c4, c4n);
                foreach (var z in iter4)
                    yield return z;
            }
            if (pkm is IRibbonSetCommon4 s4)
            {
                bool inhabited4 = gen is 3 or 4;
                var iterate = GetInvalidRibbons4Any(pkm, s4, gen);
                if (!inhabited4)
                    iterate = iterate.Concat(GetInvalidRibbonsNone(s4.RibbonBitsOnly(), s4.RibbonNamesOnly()));
                foreach (var z in iterate)
                    yield return z;
            }
            if (pkm is IRibbonSetCommon6 s6)
            {
                bool inhabited6 = gen is >= 3 and <= 6;

                var iterate = inhabited6
                    ? GetInvalidRibbons6Any(pkm, s6, gen, enc)
                    : GetInvalidRibbonsNone(s6.RibbonBits(), s6.RibbonNamesBool());
                foreach (var z in iterate)
                    yield return z;

                if (!inhabited6)
                {
                    if (s6.RibbonCountMemoryContest > 0)
                        yield return new RibbonResult(nameof(s6.RibbonCountMemoryContest));
                    if (s6.RibbonCountMemoryBattle > 0)
                        yield return new RibbonResult(nameof(s6.RibbonCountMemoryBattle));
                }

                // Gen8+ replaced with Max Friendship. Gen6/7 uses affection.
                if (pkm is IAffection a && s6.RibbonBestFriends) // can't lower affection
                {
                    if (a.OT_Affection < 255 && pkm.IsUntraded)
                        yield return new RibbonResult(nameof(s6.RibbonBestFriends));
                }
            }
            if (pkm is IRibbonSetCommon7 s7)
            {
                bool inhabited7 = gen <= 7 && !pkm.GG;
                var iterate = inhabited7 ? GetInvalidRibbons7Any(pkm, s7) : GetInvalidRibbonsNone(s7.RibbonBits(), s7.RibbonNames());
                foreach (var z in iterate)
                    yield return z;
            }
            if (pkm is IRibbonSetCommon3 s3)
            {
                if (s3.RibbonChampionG3Hoenn && gen != 3)
                    yield return new RibbonResult(nameof(s3.RibbonChampionG3Hoenn)); // RSE HoF
                if (s3.RibbonArtist && gen != 3)
                    yield return new RibbonResult(nameof(s3.RibbonArtist)); // RSE Master Rank Portrait
                if (s3.RibbonEffort && gen == 5 && pkm.Format == 5) // unobtainable in Gen 5
                    yield return new RibbonResult(nameof(s3.RibbonEffort));
            }
            if (pkm is IRibbonSetCommon8 s8)
            {
                bool inhabited8 = gen <= 8;
                var iterate = inhabited8 ? GetInvalidRibbons8Any(pkm, s8) : GetInvalidRibbonsNone(s8.RibbonBits(), s8.RibbonNames());
                foreach (var z in iterate)
                    yield return z;
            }
        }

        private static IEnumerable<RibbonResult> GetMissingContestRibbons(IReadOnlyList<bool> bits, IReadOnlyList<string> names)
        {
            for (int i = 0; i < bits.Count; i += 4)
            {
                bool required = false;
                for (int j = i + 3; j >= i; j--)
                {
                    if (bits[j])
                        required = true;
                    else if (required) yield return new RibbonResult(names[j], false);
                }
            }
        }

        private static IEnumerable<RibbonResult> GetInvalidRibbons4Any(PKM pkm, IRibbonSetCommon4 s4, int gen)
        {
            if (s4.RibbonRecord)
                yield return new RibbonResult(nameof(s4.RibbonRecord)); // Unobtainable
            if (s4.RibbonFootprint && !CanHaveFootprintRibbon(pkm, gen))
                yield return new RibbonResult(nameof(s4.RibbonFootprint));

            bool gen34 = gen is 3 or 4;
            bool not6 = pkm.Format < 6 || gen is > 6 or < 3;
            bool noDaily = !gen34 && not6;
            bool noCosmetic = !gen34 && (not6 || (pkm.XY && pkm.IsUntraded));

            if (noDaily)
            {
                foreach (var z in GetInvalidRibbonsNone(s4.RibbonBitsDaily(), s4.RibbonNamesDaily()))
                    yield return z;
            }

            if (noCosmetic)
            {
                foreach (var z in GetInvalidRibbonsNone(s4.RibbonBitsCosmetic(), s4.RibbonNamesCosmetic()))
                    yield return z;
            }
        }

        private static IEnumerable<RibbonResult> GetInvalidRibbons6Any(PKM pkm, IRibbonSetCommon6 s6, int gen, IEncounterable enc)
        {
            foreach (var p in GetInvalidRibbons6Memory(pkm, s6, gen, enc))
                yield return p;

            bool untraded = pkm.IsUntraded;
            var iter = untraded ? GetInvalidRibbons6Untraded(pkm, s6) : GetInvalidRibbons6Traded(pkm, s6);
            foreach (var p in iter)
                yield return p;

            var contest = s6.RibbonBitsContest();
            bool allContest = contest.All(z => z);
            if ((allContest ^ s6.RibbonContestStar) && !(untraded && pkm.XY)) // if not already checked
                yield return new RibbonResult(nameof(s6.RibbonContestStar), s6.RibbonContestStar);

            // Each contest victory requires a contest participation; each participation gives 20 OT affection (not current trainer).
            // Affection is discarded on PK7->PK8 in favor of friendship, which can be lowered.
            if (pkm is IAffection a)
            {
                var affect = a.OT_Affection;
                var contMemory = s6.RibbonNamesContest();
                int contCount = 0;
                var present = contMemory.Where((_, i) => contest[i] && affect < 20 * ++contCount);
                foreach (var rib in present)
                    yield return new RibbonResult(rib);
            }

            const int memChatelaine = 30;
            bool hasChampMemory = pkm.Format <= 7 && pkm is ITrainerMemories m && (m.HT_Memory == memChatelaine || m.OT_Memory == memChatelaine);
            if (!IsAllowedBattleFrontier(pkm.Species))
            {
                if (hasChampMemory || s6.RibbonBattlerSkillful) // having memory and not ribbon is too rare, just flag here.
                    yield return new RibbonResult(nameof(s6.RibbonBattlerSkillful));
                if (s6.RibbonBattlerExpert)
                    yield return new RibbonResult(nameof(s6.RibbonBattlerExpert));
                yield break;
            }
            if (!hasChampMemory || s6.RibbonBattlerSkillful || s6.RibbonBattlerExpert)
                yield break;

            var result = new RibbonResult(nameof(s6.RibbonBattlerSkillful), false);
            result.Combine(new RibbonResult(nameof(s6.RibbonBattlerExpert)));
            yield return result;
        }

        private static IEnumerable<RibbonResult> GetInvalidRibbons6Memory(PKM pkm, IRibbonSetCommon6 s6, int gen, IEncounterable enc)
        {
            int contest = 0;
            int battle = 0;
            switch (gen)
            {
                case 3:
                    contest = IsAllowedInContest4(pkm.Species) ? 40 : 20;
                    battle = IsAllowedBattleFrontier(pkm.Species) ? CanHaveRibbonWinning(pkm, enc, 3) ? 8 : 7 : 0;
                    break;
                case 4:
                    contest = IsAllowedInContest4(pkm.Species) ? 20 : 0;
                    battle = IsAllowedBattleFrontier(pkm.Species) ? 6 : 0;
                    break;
            }
            if (s6.RibbonCountMemoryContest > contest)
                yield return new RibbonResult(nameof(s6.RibbonCountMemoryContest));
            if (s6.RibbonCountMemoryBattle > battle)
                yield return new RibbonResult(nameof(s6.RibbonCountMemoryBattle));
        }

        private static IEnumerable<RibbonResult> GetInvalidRibbons6Untraded(PKM pkm, IRibbonSetCommon6 s6)
        {
            if (pkm.XY)
            {
                if (s6.RibbonChampionG6Hoenn)
                    yield return new RibbonResult(nameof(s6.RibbonChampionG6Hoenn));

                if (s6.RibbonContestStar)
                    yield return new RibbonResult(nameof(s6.RibbonContestStar));
                if (s6.RibbonMasterCoolness)
                    yield return new RibbonResult(nameof(s6.RibbonMasterCoolness));
                if (s6.RibbonMasterBeauty)
                    yield return new RibbonResult(nameof(s6.RibbonMasterBeauty));
                if (s6.RibbonMasterCuteness)
                    yield return new RibbonResult(nameof(s6.RibbonMasterCuteness));
                if (s6.RibbonMasterCleverness)
                    yield return new RibbonResult(nameof(s6.RibbonMasterCleverness));
                if (s6.RibbonMasterToughness)
                    yield return new RibbonResult(nameof(s6.RibbonMasterToughness));
            }
            else if (pkm.AO)
            {
                if (s6.RibbonChampionKalos)
                    yield return new RibbonResult(nameof(s6.RibbonChampionKalos));
            }
        }

        private static IEnumerable<RibbonResult> GetInvalidRibbons6Traded(PKM pkm, IRibbonSetCommon6 s6)
        {
            // Medal count is wiped on transfer to pk8
            if (s6.RibbonTraining && pkm.Format <= 7)
            {
                const int req = 12; // only first 12
                int count = ((ISuperTrain)pkm).SuperTrainingMedalCount(req);
                if (count < req)
                    yield return new RibbonResult(nameof(s6.RibbonTraining));
            }

            const int memChampion = 27;
            bool hasChampMemory = pkm is ITrainerMemories m && ((pkm.Format < 8 && m.HT_Memory == memChampion) || (pkm.Gen6 && m.OT_Memory == memChampion));
            if (!hasChampMemory || s6.RibbonChampionKalos || s6.RibbonChampionG6Hoenn)
                yield break;

            var result = new RibbonResult(nameof(s6.RibbonChampionKalos), false);
            result.Combine(new RibbonResult(nameof(s6.RibbonChampionG6Hoenn)));
            yield return result;
        }

        private static IEnumerable<RibbonResult> GetInvalidRibbons7Any(PKM pkm, IRibbonSetCommon7 s7)
        {
            if (!IsAllowedBattleFrontier(pkm.Species))
            {
                if (s7.RibbonBattleRoyale)
                    yield return new RibbonResult(nameof(s7.RibbonBattleRoyale));
                if (s7.RibbonBattleTreeGreat && !pkm.USUM && pkm.IsUntraded)
                    yield return new RibbonResult(nameof(s7.RibbonBattleTreeGreat));
                if (s7.RibbonBattleTreeMaster)
                    yield return new RibbonResult(nameof(s7.RibbonBattleTreeMaster));
            }
        }

        private static IEnumerable<RibbonResult> GetInvalidRibbons8Any(PKM pkm, IRibbonSetCommon8 s8)
        {
            if (!pkm.InhabitedGeneration(8) || !((PersonalInfoSWSH)PersonalTable.SWSH[pkm.Species]).IsPresentInGame)
            {
                if (s8.RibbonChampionGalar)
                    yield return new RibbonResult(nameof(s8.RibbonChampionGalar));
                if (s8.RibbonTowerMaster && !pkm.SWSH && pkm.IsUntraded)
                    yield return new RibbonResult(nameof(s8.RibbonTowerMaster));
                if (s8.RibbonMasterRank)
                    yield return new RibbonResult(nameof(s8.RibbonMasterRank));
            }
            else
            {
                const int memChampion = 27;
                {
                    bool hasChampMemory = (pkm.Format == 8 && pkm is IMemoryHT {HT_Memory: memChampion}) ||
                                          (pkm.Gen8 && pkm is IMemoryOT {OT_Memory: memChampion});
                    if (hasChampMemory && !s8.RibbonChampionGalar)
                        yield return new RibbonResult(nameof(s8.RibbonChampionGalar));
                }

                // Legends cannot compete in Ranked, thus cannot reach Master Rank and obtain the ribbon.
                // Past gen Pokemon can get the ribbon only if they've been reset.
                if (s8.RibbonMasterRank && !CanParticipateInRankedSWSH(pkm))
                    yield return new RibbonResult(nameof(s8.RibbonMasterRank));

                if (s8.RibbonTowerMaster)
                {
                    if (!pkm.SWSH && pkm.IsUntraded)
                        yield return new RibbonResult(nameof(s8.RibbonTowerMaster));
                }
                else
                {
                    // If the Tower Master ribbon is not present but a memory hint implies it should...
                    // This memory can also be applied in Gen6/7 via defeating the Chatelaines, where legends are disallowed.
                    const int strongest = 30;
                    if (pkm is IMemoryOT {OT_Memory: strongest} || pkm is IMemoryHT {HT_Memory: strongest})
                    {
                        if (pkm.Gen8 || !IsAllowedBattleFrontier(pkm.Species) || pkm is IRibbonSetCommon6 {RibbonBattlerSkillful: false})
                            yield return new RibbonResult(nameof(s8.RibbonTowerMaster));
                    }
                }
            }
        }

        private static bool CanParticipateInRankedSWSH(PKM pkm)
        {
            if (!pkm.SWSH && pkm is IBattleVersion {BattleVersion: 0})
                return false;

            // Clamp to permitted species
            var species = pkm.Species;
            if (species > Legal.MaxSpeciesID_8_R2)
                return false;
            if (Legal.Legends.Contains(species))
                return false;
            var pi = (PersonalInfoSWSH)PersonalTable.SWSH[species];
            return pi.IsPresentInGame;
        }

        private static IEnumerable<RibbonResult> GetInvalidRibbonsEvent1(PKM pkm, IEncounterable enc)
        {
            if (pkm is not IRibbonSetEvent3 set1)
                yield break;
            var names = set1.RibbonNames();
            var sb = set1.RibbonBits();
            var eb = enc is IRibbonSetEvent3 e3 ? e3.RibbonBits() : new bool[sb.Length];

            if (enc.Generation == 3)
            {
                eb[0] = sb[0]; // permit Earth Ribbon
                if (pkm.Version == 15 && enc is EncounterStaticShadow s)
                {
                    // only require national ribbon if no longer on origin game
                    eb[1] = s.Version == GameVersion.XD
                        ? pkm is not XK3 x || x.RibbonNational
                        : pkm is not CK3 c || c.RibbonNational;
                }
            }

            for (int i = 0; i < sb.Length; i++)
            {
                if (sb[i] != eb[i])
                    yield return new RibbonResult(names[i], !eb[i]); // only flag if invalid
            }
        }

        private static IEnumerable<RibbonResult> GetInvalidRibbonsEvent2(PKM pkm, IEncounterable enc)
        {
            if (pkm is not IRibbonSetEvent4 set2)
                yield break;
            var names = set2.RibbonNames();
            var sb = set2.RibbonBits();
            var eb = enc is IRibbonSetEvent4 e4 ? e4.RibbonBits() : new bool[sb.Length];

            if (enc is EncounterStatic7 {Species: (int)Species.Magearna})
                eb[1] = true; // require Wishing Ribbon

            for (int i = 0; i < sb.Length; i++)
            {
                if (sb[i] != eb[i])
                    yield return new RibbonResult(names[i], !eb[i]); // only flag if invalid
            }
        }

        private static IEnumerable<RibbonResult> GetInvalidRibbonsNone(IReadOnlyList<bool> bits, IReadOnlyList<string> names)
        {
            for (int i = 0; i < bits.Count; i++)
            {
                if (bits[i])
                    yield return new RibbonResult(names[i]);
            }
        }

        private static bool IsAllowedInContest4(int species) => species != 201 && species != 132; // Disallow Unown and Ditto

        private static bool IsAllowedBattleFrontier(int species) => !Legal.BattleFrontierBanlist.Contains(species);

        private static bool IsAllowedBattleFrontier(int species, int form, int gen)
        {
            if (gen == 4 && species == (int)Species.Pichu && form == 1) // spiky
                return false;
            return IsAllowedBattleFrontier(species);
        }

        private static bool CanHaveFootprintRibbon(PKM pkm, int gen)
        {
            if (gen <= 4) // Friendship Check unnecessary - can decrease after obtaining ribbon.
                return true;
            // Gen5: Can't obtain
            // Gen6/7: Increase level by 30 from original level
            if (pkm.Format >= 6 && (gen != 8 && !pkm.GG) && (pkm.CurrentLevel - pkm.Met_Level >= 30))
                return true;

            // Gen8: Can't obtain
            return false;
        }

        private static bool CanHaveRibbonWinning(PKM pkm, IEncounterable enc, int gen)
        {
            if (gen != 3)
                return false;
            if (!IsAllowedBattleFrontier(pkm.Species))
                return false;
            if (pkm.Format == 3)
                return pkm.Met_Level <= 50;

            // Most encounter types can be below level 50; only Shadow Dragonite & Tyranitar, and select Gen3 Event Gifts.
            // These edge cases can't be obtained below level 50, unlike some wild Pokémon which can be encountered at different locations for lower levels.
            if (enc.LevelMin <= 50)
                return true;

            return enc is not EncounterStaticShadow or WC3;
        }

        private static bool CanHaveRibbonVictory(PKM pkm, int gen)
        {
            return gen == 3 && IsAllowedBattleFrontier(pkm.Species);
        }
    }
}