using System;
using static PKHeX.Core.LegalityCheckStrings;

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

        public override void Verify(LegalityAnalysis data)
        {
            switch (data.EncounterMatch)
            {
                case EncounterStatic s:
                    VerifyIVsStatic(data, s);
                    break;
                case EncounterSlot w:
                    VerifyIVsSlot(data, w);
                    break;
                case MysteryGift g:
                    VerifyIVsMystery(data, g);
                    break;
            }

            var pkm = data.pkm;
            {
                var hpiv = pkm.IV_HP;
                if (hpiv < 30 && AllIVsEqual(pkm, hpiv))
                    data.AddLine(Get(string.Format(LIVAllEqual_0, hpiv), Severity.Fishy));
            }
        }

        public static bool AllIVsEqual(PKM pkm) => AllIVsEqual(pkm, pkm.IV_HP);

        private static bool AllIVsEqual(PKM pkm, int hpiv)
        {
            return (pkm.IV_ATK == hpiv) && (pkm.IV_DEF == hpiv) && (pkm.IV_SPA == hpiv) && (pkm.IV_SPD == hpiv) && (pkm.IV_SPE == hpiv);
        }

        private void VerifyIVsMystery(LegalityAnalysis data, MysteryGift g)
        {
            if (!g.HasFixedIVs)
                return; // PID/IV style instead of fixed IVs.

            Span<int> IVs = stackalloc int[6];
            g.GetIVs(IVs);
            var ivflag = IVs.Find(iv => (byte)(iv - 0xFC) < 3);
            if (ivflag == 0) // Random IVs
            {
                bool valid = Legal.GetIsFixedIVSequenceValidSkipRand(IVs, data.pkm);
                if (!valid)
                    data.AddLine(GetInvalid(LEncGiftIVMismatch));
            }
            else
            {
                int IVCount = ivflag - 0xFB;  // IV2/IV3
                VerifyIVsFlawless(data, IVCount);
            }
        }

        private void VerifyIVsSlot(LegalityAnalysis data, EncounterSlot w)
        {
            switch (w.Generation)
            {
                case 6: VerifyIVsGen6(data, w); break;
                case 7: VerifyIVsGen7(data); break;
                case 8: VerifyIVsGen8(data); break;
            }
        }

        private void VerifyIVsGen7(LegalityAnalysis data)
        {
            var pkm = data.pkm;
            if (pkm.GO)
                VerifyIVsGoTransfer(data);
            else if (pkm.AbilityNumber == 4 && !AbilityVerifier.CanAbilityPatch(pkm.Format, pkm.PersonalInfo.Abilities, pkm.Species))
                VerifyIVsFlawless(data, 2); // Chain of 10 yields 5% HA and 2 flawless IVs
        }

        private void VerifyIVsGen8(LegalityAnalysis data)
        {
            var pkm = data.pkm;
            if (pkm.GO)
                VerifyIVsGoTransfer(data);

            if (data.EncounterMatch is EncounterSlot8a s)
                VerifyIVsFlawless(data, s.FlawlessIVCount);
        }

        private void VerifyIVsGen6(LegalityAnalysis data, EncounterSlot w)
        {
            if (w is EncounterSlot6XY xy)
            {
                if (PersonalTable.XY[data.EncounterMatch.Species].IsEggGroup(15)) // Undiscovered
                    VerifyIVsFlawless(data, 3);
                if (xy.IsFriendSafari)
                    VerifyIVsFlawless(data, 2);
            }
        }

        private void VerifyIVsFlawless(LegalityAnalysis data, int count)
        {
            if (data.pkm.FlawlessIVCount < count)
                data.AddLine(GetInvalid(string.Format(LIVF_COUNT0_31, count)));
        }

        private void VerifyIVsStatic(LegalityAnalysis data, EncounterStatic s)
        {
            if (s.FlawlessIVCount != 0)
                VerifyIVsFlawless(data, s.FlawlessIVCount);
        }

        private void VerifyIVsGoTransfer(LegalityAnalysis data)
        {
            if (data.EncounterMatch is EncounterSlotGO g && !g.GetIVsValid(data.pkm))
                data.AddLine(GetInvalid(LIVNotCorrect));
        }
    }
}