namespace PKHeX.Core
{
    /// <summary>
    /// Calculations for <see cref="PKM.EXP"/> and <see cref="PKM.CurrentLevel"/>.
    /// </summary>
    public static class Experience
    {
        /// <summary>
        /// Gets the current level of a species.
        /// </summary>
        /// <param name="exp">Experience points</param>
        /// <param name="species">National Dex number of the Pokémon.</param>
        /// <param name="forme">AltForm ID (starters in Let's Go)</param>
        /// <returns>Current level of the species.</returns>
        public static int GetLevel(uint exp, int species, int forme = 0)
        {
            int growth = PKX.Personal.GetFormeEntry(species, forme).EXPGrowth;
            if (exp >= ExpTable[99, growth])
                return 100;
            int tl = 1; // Initial Level. Iterate upwards to find the level
            while (exp >= ExpTable[tl, growth])
                ++tl;
            return tl;
        }

        /// <summary>
        /// Gets the minimum Experience points for the specified level.
        /// </summary>
        /// <param name="level">Current level</param>
        /// <param name="species">National Dex number of the Pokémon.</param>
        /// <param name="forme">AltForm ID (starters in Let's Go)</param>
        /// <returns>Experience points needed to have specified level.</returns>
        public static uint GetEXP(int level, int species, int forme = 0)
        {
            if (level <= 1)
                return 0;
            if (level > 100)
                level = 100;
            return ExpTable[level - 1, PKX.Personal.GetFormeEntry(species, forme).EXPGrowth];
        }

        /// <summary>
        /// Gets the <see cref="PKM.Nature"/> value for <see cref="PK1"/> / <see cref="PK2"/> entries based on the <see cref="PKM.EXP"/>
        /// </summary>
        /// <param name="experience">Current Experience</param>
        /// <returns>Nature ID (<see cref="Nature"/>)</returns>
        public static int GetNatureVC(uint experience) => (int)(experience % 25);

        /// <summary>
        /// Gets the amount of EXP to be earned until the next level-up occurs.
        /// </summary>
        /// <param name="level">Current Level</param>
        /// <param name="species"><see cref="PKM.Species"/></param>
        /// <param name="forme">AltForm ID (starters in Let's Go)</param>
        /// <returns>Percentage [0,1.00)</returns>
        public static uint GetEXPToLevelUp(int level, int species, int forme = 0)
        {
            if (level >= 100)
                return 0;
            var growth = PKX.Personal.GetFormeEntry(species, forme).EXPGrowth;
            var current = ExpTable[level - 1, growth];
            var next = ExpTable[level, growth];
            return next - current;
        }

        /// <summary>
        /// Gets a percentage for Experience Bar progress indication.
        /// </summary>
        /// <param name="level">Current Level</param>
        /// <param name="exp">Current Experience</param>
        /// <param name="species"><see cref="PKM.Species"/></param>
        /// <param name="forme">AltForm ID (starters in Let's Go)</param>
        /// <returns>Percentage [0,1.00)</returns>
        public static double GetEXPToLevelUpPercentage(int level, uint exp, int species, int forme = 0)
        {
            if (level >= 100)
                return 0;
            var growth = PKX.Personal.GetFormeEntry(species, forme).EXPGrowth;
            var current = ExpTable[level - 1, growth];
            var next = ExpTable[level, growth];
            var amount = next - current;
            double progress = exp - current;
            return progress / amount;
        }

        #region ExpTable

        /// <summary>
        /// Experience required for next level [0,99]
        /// </summary>
        private static readonly uint[,] ExpTable =
        {
            {0000000, 0000000, 0000000, 0000000, 0000000, 0000000},
            {0000008, 0000015, 0000004, 0000009, 0000006, 0000010},
            {0000027, 0000052, 0000013, 0000057, 0000021, 0000033},
            {0000064, 0000122, 0000032, 0000096, 0000051, 0000080},
            {0000125, 0000237, 0000065, 0000135, 0000100, 0000156},
            {0000216, 0000406, 0000112, 0000179, 0000172, 0000270},
            {0000343, 0000637, 0000178, 0000236, 0000274, 0000428},
            {0000512, 0000942, 0000276, 0000314, 0000409, 0000640},
            {0000729, 0001326, 0000393, 0000419, 0000583, 0000911},
            {0001000, 0001800, 0000540, 0000560, 0000800, 0001250},
            {0001331, 0002369, 0000745, 0000742, 0001064, 0001663},
            {0001728, 0003041, 0000967, 0000973, 0001382, 0002160},
            {0002197, 0003822, 0001230, 0001261, 0001757, 0002746},
            {0002744, 0004719, 0001591, 0001612, 0002195, 0003430},
            {0003375, 0005737, 0001957, 0002035, 0002700, 0004218},
            {0004096, 0006881, 0002457, 0002535, 0003276, 0005120},
            {0004913, 0008155, 0003046, 0003120, 0003930, 0006141},
            {0005832, 0009564, 0003732, 0003798, 0004665, 0007290},
            {0006859, 0011111, 0004526, 0004575, 0005487, 0008573},
            {0008000, 0012800, 0005440, 0005460, 0006400, 0010000},
            {0009261, 0014632, 0006482, 0006458, 0007408, 0011576},
            {0010648, 0016610, 0007666, 0007577, 0008518, 0013310},
            {0012167, 0018737, 0009003, 0008825, 0009733, 0015208},
            {0013824, 0021012, 0010506, 0010208, 0011059, 0017280},
            {0015625, 0023437, 0012187, 0011735, 0012500, 0019531},
            {0017576, 0026012, 0014060, 0013411, 0014060, 0021970},
            {0019683, 0028737, 0016140, 0015244, 0015746, 0024603},
            {0021952, 0031610, 0018439, 0017242, 0017561, 0027440},
            {0024389, 0034632, 0020974, 0019411, 0019511, 0030486},
            {0027000, 0037800, 0023760, 0021760, 0021600, 0033750},
            {0029791, 0041111, 0026811, 0024294, 0023832, 0037238},
            {0032768, 0044564, 0030146, 0027021, 0026214, 0040960},
            {0035937, 0048155, 0033780, 0029949, 0028749, 0044921},
            {0039304, 0051881, 0037731, 0033084, 0031443, 0049130},
            {0042875, 0055737, 0042017, 0036435, 0034300, 0053593},
            {0046656, 0059719, 0046656, 0040007, 0037324, 0058320},
            {0050653, 0063822, 0050653, 0043808, 0040522, 0063316},
            {0054872, 0068041, 0055969, 0047846, 0043897, 0068590},
            {0059319, 0072369, 0060505, 0052127, 0047455, 0074148},
            {0064000, 0076800, 0066560, 0056660, 0051200, 0080000},
            {0068921, 0081326, 0071677, 0061450, 0055136, 0086151},
            {0074088, 0085942, 0078533, 0066505, 0059270, 0092610},
            {0079507, 0090637, 0084277, 0071833, 0063605, 0099383},
            {0085184, 0095406, 0091998, 0077440, 0068147, 0106480},
            {0091125, 0100237, 0098415, 0083335, 0072900, 0113906},
            {0097336, 0105122, 0107069, 0089523, 0077868, 0121670},
            {0103823, 0110052, 0114205, 0096012, 0083058, 0129778},
            {0110592, 0115015, 0123863, 0102810, 0088473, 0138240},
            {0117649, 0120001, 0131766, 0109923, 0094119, 0147061},
            {0125000, 0125000, 0142500, 0117360, 0100000, 0156250},
            {0132651, 0131324, 0151222, 0125126, 0106120, 0165813},
            {0140608, 0137795, 0163105, 0133229, 0112486, 0175760},
            {0148877, 0144410, 0172697, 0141677, 0119101, 0186096},
            {0157464, 0151165, 0185807, 0150476, 0125971, 0196830},
            {0166375, 0158056, 0196322, 0159635, 0133100, 0207968},
            {0175616, 0165079, 0210739, 0169159, 0140492, 0219520},
            {0185193, 0172229, 0222231, 0179056, 0148154, 0231491},
            {0195112, 0179503, 0238036, 0189334, 0156089, 0243890},
            {0205379, 0186894, 0250562, 0199999, 0164303, 0256723},
            {0216000, 0194400, 0267840, 0211060, 0172800, 0270000},
            {0226981, 0202013, 0281456, 0222522, 0181584, 0283726},
            {0238328, 0209728, 0300293, 0234393, 0190662, 0297910},
            {0250047, 0217540, 0315059, 0246681, 0200037, 0312558},
            {0262144, 0225443, 0335544, 0259392, 0209715, 0327680},
            {0274625, 0233431, 0351520, 0272535, 0219700, 0343281},
            {0287496, 0241496, 0373744, 0286115, 0229996, 0359370},
            {0300763, 0249633, 0390991, 0300140, 0240610, 0375953},
            {0314432, 0257834, 0415050, 0314618, 0251545, 0393040},
            {0328509, 0267406, 0433631, 0329555, 0262807, 0410636},
            {0343000, 0276458, 0459620, 0344960, 0274400, 0428750},
            {0357911, 0286328, 0479600, 0360838, 0286328, 0447388},
            {0373248, 0296358, 0507617, 0377197, 0298598, 0466560},
            {0389017, 0305767, 0529063, 0394045, 0311213, 0486271},
            {0405224, 0316074, 0559209, 0411388, 0324179, 0506530},
            {0421875, 0326531, 0582187, 0429235, 0337500, 0527343},
            {0438976, 0336255, 0614566, 0447591, 0351180, 0548720},
            {0456533, 0346965, 0639146, 0466464, 0365226, 0570666},
            {0474552, 0357812, 0673863, 0485862, 0379641, 0593190},
            {0493039, 0367807, 0700115, 0505791, 0394431, 0616298},
            {0512000, 0378880, 0737280, 0526260, 0409600, 0640000},
            {0531441, 0390077, 0765275, 0547274, 0425152, 0664301},
            {0551368, 0400293, 0804997, 0568841, 0441094, 0689210},
            {0571787, 0411686, 0834809, 0590969, 0457429, 0714733},
            {0592704, 0423190, 0877201, 0613664, 0474163, 0740880},
            {0614125, 0433572, 0908905, 0636935, 0491300, 0767656},
            {0636056, 0445239, 0954084, 0660787, 0508844, 0795070},
            {0658503, 0457001, 0987754, 0685228, 0526802, 0823128},
            {0681472, 0467489, 1035837, 0710266, 0545177, 0851840},
            {0704969, 0479378, 1071552, 0735907, 0563975, 0881211},
            {0729000, 0491346, 1122660, 0762160, 0583200, 0911250},
            {0753571, 0501878, 1160499, 0789030, 0602856, 0941963},
            {0778688, 0513934, 1214753, 0816525, 0622950, 0973360},
            {0804357, 0526049, 1254796, 0844653, 0643485, 1005446},
            {0830584, 0536557, 1312322, 0873420, 0664467, 1038230},
            {0857375, 0548720, 1354652, 0902835, 0685900, 1071718},
            {0884736, 0560922, 1415577, 0932903, 0707788, 1105920},
            {0912673, 0571333, 1460276, 0963632, 0730138, 1140841},
            {0941192, 0583539, 1524731, 0995030, 0752953, 1176490},
            {0970299, 0591882, 1571884, 1027103, 0776239, 1212873},
            {1000000, 0600000, 1640000, 1059860, 0800000, 1250000},
        };

        #endregion
    }
}