using System;
using static PKHeX.Core.Region3DSFlags;

namespace PKHeX.Core;

/// <summary>
/// Provides information for Vivillon origins with respect to the 3DS game data.
/// </summary>
public static class Vivillon3DS
{
    public const byte MaxWildFormID = 17; // 0-17 valid form indexes
    public const byte FancyFormID = 18;

    /// <summary>
    /// List of valid regions as bitflags indexed by Vivillon form.
    /// </summary>
    private static ReadOnlySpan<Region3DSFlags> VivillonRegionTable => new[]
    {
        /* 0 Icy Snow    */          Americas | Europe,
        /* 1 Polar       */          Americas | Europe | China,
        /* 2 Tundra      */ Japan  |            Europe,
        /* 3 Continental */ Japan  | Americas | Europe | China | Korea | Taiwan,
        /* 4 Garden      */                     Europe,
        /* 5 Elegant     */ Japan,
        /* 6 Meadow      */                     Europe,
        /* 7 Modern      */          Americas,
        /* 8 Marine      */          Americas | Europe,
        /* 9 Archipelago */          Americas | Europe,
        /*10 High Plains */          Americas | Europe | China,
        /*11 Sandstorm   */          Americas | Europe,
        /*12 River       */                     Europe,
        /*13 Monsoon     */ Japan  |            Europe | China |        Taiwan,
        /*14 Savanna     */          Americas,
        /*15 Sun         */          Americas | Europe,
        /*16 Ocean       */          Americas | Europe,
        /*17 Jungle      */          Americas | Europe,
    };

    private static Region3DSFlags GetConsoleRegionFlag(in byte consoleRegion) => (Region3DSFlags)(1 << consoleRegion);

    /// <summary>
    /// Compares the Vivillon pattern against its console region to determine if the pattern is legal.
    /// </summary>
    public static bool IsPatternValid(in byte form, in byte consoleRegion)
    {
        if (form >= VivillonRegionTable.Length)
            return false;
        var permit = GetConsoleRegionFlag(consoleRegion);
        return VivillonRegionTable[form].HasFlag(permit);
    }

    /// <summary>
    /// Compares the Vivillon pattern against its country and subregion to determine if the pattern could have been natively obtained.
    /// </summary>
    /// <param name="form">Alternate Form Pattern</param>
    /// <param name="country">Country ID</param>
    /// <param name="region">Subregion ID</param>
    /// <returns>True if valid</returns>
    public static bool IsPatternNative(in byte form, in byte country, in byte region)
    {
        if (form > MaxWildFormID)
            return false;

        if (country >= SameCountry.Length)
            return false;
        var same = SameCountry[country];
        if (same is not XX)
            return form == same;

        var tuple = (ushort)(country << 8 | region);
        var index = DiffCountryRegion.BinarySearch(tuple);
        if (index >= 0)
            return form == DiffForm[index];

        return false;
    }

    /// <summary>
    /// Gets a compatible Vivillon pattern based on its country and subregion.
    /// </summary>
    /// <param name="country">Country ID</param>
    /// <param name="region">Subregion ID</param>
    public static byte GetPattern(in byte country, in byte region)
    {
        if (country >= SameCountry.Length)
            return 0;
        var same = SameCountry[country];
        if (same is not XX)
            return same;

        var tuple = (ushort)(country << 8 | region);
        var index = DiffCountryRegion.BinarySearch(tuple);
        if (index >= 0)
            return DiffForm[index];

        return 0;
    }

    // The game stores an equirectangular projection byte map of forms, laid out over a map of Earth.
    // The game then determines form based on the player's selected Country and Region via its latitude and longitude stored in the 3DS' system files.
    // Since we have dumped these country,region->latitude,longitude mappings, we can determine the form that would be obtained in-game.
    // Using the data from @abcboy101 located here: https://github.com/abcboy101/vivillon/blob/main/data_points.json
    // Provide efficient and quick lookups for checking if a form can originate from a given country/region.
    // Reminder: Vivillon form is set when you start the Save File. Changing Country/Region after will update Country/Region for OT, not the form available.

    // 93 countries have the same form. This is about half the total amount of countries [0,186].
    // Instead of doing a index = lookup(country) -> form[index], can do array[country] with a sentinel to indicate the country is different by region.
    // This results in O(1) performance, better than O(log(n)) for the binary search approach.
    // None of the these countries with same form have form 0, so we can use that as a sentinel value.
    private const byte XX = 0;

    private static ReadOnlySpan<byte> SameCountry => new byte[]
    {
        XX, XX, XX, XX, XX, XX, XX, XX, 09, 09, XX, 09, 09, 09, 15, 14,
        XX, 09, XX, 15, XX, XX, XX, 09, 09, 17, 15, 17, 09, 09, 15, 17,
        09, 15, 09, 09, XX, 09, 09, 15, 17, 14, XX, 09, 09, 09, 17, 09,
        09, XX, 14, 09, XX, XX, XX, XX, XX, XX, XX, XX, XX, XX, XX, XX,
        08, XX, XX, 03, 08, 12, 08, 08, 11, XX, XX, 03, XX, XX, XX, 08,
        08, 02, 04, XX, 03, XX, 06, 03, 06, 08, 08, 08, 15, 12, 03, 04,
        XX, 03, 08, 08, XX, 08, 08, 08, XX, XX, 15, XX, 06, XX, 04, 15,
        15, 10, 12, 12, 12, 12, 11, 11, 11, 11, 06, 08, 08, 04, 08, 06,
        XX, XX, XX, XX, XX, XX, XX, XX, 03, XX, XX, XX, XX, XX, XX, XX,
        03, XX, XX, XX, XX, XX, XX, XX, XX, 17, XX, XX, 17, XX, XX, XX,
        XX, XX, XX, XX, XX, XX, XX, XX, 11, XX, XX, XX, XX, XX, 11, XX,
        XX, XX, XX, XX, XX, XX, XX, XX, 08, 08, 07,
    };

    // (country:X2_region:X2)
    // do it this way instead of region_country so that the byte[] form is better ordered for better file compression :)
    // 777 entries, so we can use a binary search to find the form. Worst case is log2(777) = 10 comparisons.
    private static ReadOnlySpan<ushort> DiffCountryRegion => new ushort[]
    {
        0x0100, 0x0102, 0x0103, 0x0104, 0x0105, 0x0106, 0x0107, 0x0108, 0x0109, 0x010A, 0x010B, 0x010C, 0x010D, 0x010E, 0x010F, 0x0110,
        0x0111, 0x0112, 0x0113, 0x0114, 0x0115, 0x0116, 0x0117, 0x0118, 0x0119, 0x011A, 0x011B, 0x011C, 0x011D, 0x011E, 0x011F, 0x0120,
        0x0121, 0x0122, 0x0123, 0x0124, 0x0125, 0x0126, 0x0127, 0x0128, 0x0129, 0x012A, 0x012B, 0x012C, 0x012D, 0x012E, 0x012F, 0x0130,
        0x0A00, 0x0A02, 0x0A03, 0x0A04, 0x0A05, 0x0A06, 0x0A07, 0x0A08, 0x0A09, 0x0A0A, 0x0A0B, 0x0A0C, 0x0A0D, 0x0A0E, 0x0A0F, 0x0A10,
        0x0A11, 0x0A12, 0x0A13, 0x0A14, 0x0A15, 0x0A16, 0x0A17, 0x0A18, 0x0A19, 0x1000, 0x1002, 0x1003, 0x1004, 0x1005, 0x1006, 0x1007,
        0x1008, 0x1009, 0x100A, 0x100B, 0x100C, 0x100D, 0x100E, 0x100F, 0x1010, 0x1011, 0x1012, 0x1013, 0x1014, 0x1015, 0x1016, 0x1017,
        0x1018, 0x1019, 0x101A, 0x101B, 0x101C, 0x1200, 0x1202, 0x1203, 0x1204, 0x1205, 0x1206, 0x1207, 0x1208, 0x1209, 0x120A, 0x120B,
        0x120C, 0x120D, 0x120E, 0x1400, 0x1402, 0x1403, 0x1404, 0x1405, 0x1406, 0x1407, 0x1408, 0x1409, 0x140A, 0x140B, 0x140C, 0x140D,
        0x140E, 0x1500, 0x1502, 0x1503, 0x1504, 0x1505, 0x1506, 0x1507, 0x1508, 0x1509, 0x150A, 0x150B, 0x150C, 0x150D, 0x150E, 0x150F,
        0x1510, 0x1511, 0x1512, 0x1513, 0x1514, 0x1515, 0x1516, 0x1517, 0x1518, 0x1519, 0x151A, 0x151B, 0x151C, 0x151D, 0x151E, 0x151F,
        0x1520, 0x1521, 0x1522, 0x1600, 0x1602, 0x1603, 0x1604, 0x1605, 0x1606, 0x1607, 0x1608, 0x2400, 0x2402, 0x2403, 0x2404, 0x2405,
        0x2406, 0x2407, 0x2408, 0x2409, 0x240A, 0x240B, 0x240C, 0x240D, 0x240E, 0x240F, 0x2410, 0x2411, 0x2412, 0x2413, 0x2414, 0x2415,
        0x2416, 0x2417, 0x2418, 0x2419, 0x241A, 0x241B, 0x241C, 0x241D, 0x241E, 0x241F, 0x2420, 0x2421, 0x2A00, 0x2A02, 0x2A03, 0x2A04,
        0x2A05, 0x2A06, 0x2A07, 0x2A08, 0x2A09, 0x2A0A, 0x2A0B, 0x2A0C, 0x2A0D, 0x2A0E, 0x2A0F, 0x2A10, 0x2A11, 0x2A12, 0x2A13, 0x2A14,
        0x2A15, 0x2A16, 0x2A17, 0x2A18, 0x2A19, 0x2A1A, 0x3100, 0x3102, 0x3103, 0x3104, 0x3105, 0x3106, 0x3107, 0x3108, 0x3109, 0x310A,
        0x310B, 0x310C, 0x310D, 0x310E, 0x310F, 0x3110, 0x3111, 0x3112, 0x3113, 0x3114, 0x3115, 0x3116, 0x3117, 0x3118, 0x3119, 0x311A,
        0x311B, 0x311C, 0x311D, 0x311E, 0x311F, 0x3120, 0x3121, 0x3122, 0x3123, 0x3124, 0x3125, 0x3126, 0x3127, 0x3128, 0x3129, 0x312A,
        0x312B, 0x312C, 0x312D, 0x312E, 0x312F, 0x3130, 0x3131, 0x3132, 0x3133, 0x3134, 0x3135, 0x3400, 0x3402, 0x3403, 0x3404, 0x3405,
        0x3406, 0x3407, 0x3408, 0x3409, 0x340A, 0x340B, 0x340C, 0x340D, 0x340E, 0x340F, 0x3410, 0x3411, 0x3412, 0x3413, 0x3414, 0x3415,
        0x3416, 0x3417, 0x3418, 0x3419, 0x341A, 0x4100, 0x4102, 0x4103, 0x4104, 0x4105, 0x4106, 0x4107, 0x4108, 0x4109, 0x4200, 0x4202,
        0x4203, 0x4204, 0x4205, 0x4206, 0x4207, 0x4208, 0x4209, 0x420A, 0x4900, 0x4902, 0x4903, 0x4904, 0x4905, 0x4906, 0x4907, 0x4908,
        0x4909, 0x490A, 0x490B, 0x490C, 0x490D, 0x490E, 0x490F, 0x4A00, 0x4A12, 0x4A13, 0x4A14, 0x4A15, 0x4A16, 0x4A17, 0x4A18, 0x4C00,
        0x4C08, 0x4C09, 0x4C0A, 0x4C0B, 0x4C0C, 0x4C0D, 0x4C0E, 0x4C0F, 0x4C10, 0x4C11, 0x4C12, 0x4C13, 0x4C14, 0x4C15, 0x4C16, 0x4C17,
        0x4C18, 0x4C19, 0x4C1A, 0x4C1B, 0x4D00, 0x4D02, 0x4D03, 0x4D04, 0x4D05, 0x4D06, 0x4D07, 0x4D08, 0x4D09, 0x4D0A, 0x4D0B, 0x4D0C,
        0x4D0D, 0x4D0E, 0x4D0F, 0x4D10, 0x4D11, 0x4D12, 0x4D13, 0x4D14, 0x4D15, 0x4D16, 0x4D17, 0x4D18, 0x4D19, 0x4D1A, 0x4D1B, 0x4E00,
        0x4E02, 0x4E03, 0x4E04, 0x4E05, 0x4E06, 0x4E07, 0x4E08, 0x4E09, 0x4E0A, 0x4E0B, 0x4E0C, 0x4E0D, 0x4E0E, 0x4E0F, 0x4E10, 0x4E11,
        0x5300, 0x5302, 0x5303, 0x5304, 0x5305, 0x5306, 0x5307, 0x5308, 0x5309, 0x530A, 0x530B, 0x530C, 0x530D, 0x530E, 0x530F, 0x5310,
        0x5311, 0x5312, 0x5313, 0x5314, 0x5315, 0x5500, 0x5502, 0x5503, 0x5504, 0x5505, 0x5506, 0x5507, 0x5508, 0x5509, 0x550A, 0x550B,
        0x6000, 0x6007, 0x6008, 0x6009, 0x600A, 0x600B, 0x600C, 0x600D, 0x600E, 0x600F, 0x6010, 0x6011, 0x6012, 0x6013, 0x6014, 0x6015,
        0x6016, 0x6017, 0x6018, 0x6019, 0x601A, 0x6400, 0x6409, 0x640A, 0x640B, 0x640C, 0x640D, 0x640E, 0x640F, 0x6410, 0x6411, 0x6412,
        0x6413, 0x6414, 0x6415, 0x6416, 0x6417, 0x6418, 0x6419, 0x641A, 0x641B, 0x641C, 0x641D, 0x641E, 0x641F, 0x6420, 0x6421, 0x6422,
        0x6423, 0x6424, 0x6425, 0x6426, 0x6427, 0x6428, 0x6429, 0x642A, 0x642B, 0x642C, 0x642D, 0x642E, 0x642F, 0x6430, 0x6431, 0x6432,
        0x6433, 0x6434, 0x6435, 0x6436, 0x6437, 0x6438, 0x6439, 0x643A, 0x643B, 0x643C, 0x643D, 0x643E, 0x643F, 0x6440, 0x6441, 0x6442,
        0x6443, 0x6444, 0x6445, 0x6446, 0x6447, 0x6448, 0x6449, 0x644A, 0x644B, 0x644C, 0x644D, 0x644E, 0x644F, 0x6450, 0x6451, 0x6452,
        0x6453, 0x6454, 0x6455, 0x6456, 0x6457, 0x6458, 0x6459, 0x645A, 0x645B, 0x6800, 0x6802, 0x6803, 0x6804, 0x6805, 0x6806, 0x6807,
        0x6808, 0x6809, 0x680A, 0x6900, 0x6902, 0x6903, 0x6904, 0x6905, 0x6906, 0x6907, 0x6908, 0x6909, 0x690A, 0x690B, 0x690C, 0x690D,
        0x690E, 0x690F, 0x6910, 0x6911, 0x6912, 0x6913, 0x6914, 0x6B00, 0x6B02, 0x6B03, 0x6B04, 0x6B05, 0x6B06, 0x6B07, 0x6B08, 0x6B09,
        0x6B0A, 0x6B0B, 0x6B0C, 0x6B0D, 0x6B0E, 0x6B0F, 0x6B10, 0x6B11, 0x6B12, 0x6B13, 0x6B14, 0x6B15, 0x6B16, 0x6D00, 0x6D02, 0x6D03,
        0x6D04, 0x6D05, 0x6D06, 0x6D07, 0x6D08, 0x6D09, 0x6D0A, 0x6D0B, 0x6D0C, 0x6D0E, 0x6D0F, 0x6D10, 0x6D11, 0x6D12, 0x6D13, 0x6D14,
        0x6D15, 0x6D16, 0x6D17, 0x6D18, 0x6D19, 0x6D1A, 0x6D1B, 0x6D1C, 0x6D1D, 0x6D1E, 0x6D1F, 0x6D20, 0x6D21, 0x6D22, 0x6D23, 0x6D24,
        0x6D25, 0x6D26, 0x6D27, 0x6D28, 0x6D29, 0x6D2A, 0x6D2B, 0x6D2C, 0x6D2D, 0x6D2E, 0x6D2F, 0x6D30, 0x6D31, 0x6D32, 0x6D33, 0x6D34,
        0x6D35, 0x6D36, 0x6D37, 0x6D38, 0x6D39, 0x6D3A, 0x6D3B, 0x6D3C, 0x6D3D, 0x6D3E, 0x6D3F, 0x6D40, 0x6D41, 0x6D42, 0x6D43, 0x6D44,
        0x6D45, 0x6D46, 0x6D47, 0x6D48, 0x6D49, 0x6D4A, 0x6D4B, 0x6D4C, 0x6D4D, 0x6D4E, 0x6D4F, 0x6D50, 0x6D51, 0x6D52, 0x6D53, 0x8000,
        0x8002, 0x8003, 0x8004, 0x8005, 0x8006, 0x8007, 0x8008, 0x8009, 0x800A, 0x800B, 0x800C, 0x800E, 0x800F, 0x8010, 0x8011, 0x8014,
        0x8015, 0x8016, 0x8017, 0x8018, 0x8019, 0x801A, 0xA000, 0xA002, 0xA003, 0xA004, 0xA005, 0xA006, 0xA007, 0xA008, 0xA009, 0xA00A,
        0xA00B, 0xA00C, 0xA00D, 0xA00E, 0xA00F, 0xA010, 0xA011, 0xA012, 0xA013, 0xA014, 0xA015, 0xA016, 0xA017, 0xA018, 0xA019, 0xA01A,
        0xA01B, 0xA01D, 0xA01E, 0xA01F, 0xA020, 0xA021, 0xA900, 0xA902, 0xA903, 0xA904, 0xA905, 0xA906, 0xA907, 0xA908, 0xA909, 0xA90A,
        0xA90C, 0xA90D, 0xA90E, 0xA90F, 0xA910, 0xA911, 0xA912, 0xA913, 0xA914, 0xA915, 0xA916, 0xA917, 0xA918, 0xA919, 0xA91A, 0xA91C,
        0xA91D, 0xA91E, 0xA91F, 0xA920, 0xA921, 0xA922, 0xA923, 0xA924, 0xA925,
    };

    private static ReadOnlySpan<byte> DiffForm => new byte[]
    {
        05, 05, 02, 02, 05, 05, 05, 05, 05, 05, 05, 05, 05, 05, 05, 05,
        05, 05, 05, 05, 05, 05, 05, 05, 05, 05, 05, 05, 05, 05, 05, 05,
        05, 05, 05, 05, 05, 05, 05, 05, 05, 05, 03, 05, 05, 05, 05, 13,
        14, 14, 14, 14, 14, 03, 03, 14, 03, 14, 14, 03, 14, 03, 14, 03,
        03, 14, 03, 03, 01, 03, 14, 01, 14, 14, 14, 17, 14, 17, 17, 14,
        14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 17, 17, 14,
        14, 14, 14, 14, 14, 01, 01, 01, 10, 07, 01, 01, 01, 01, 01, 01,
        00, 00, 00, 08, 08, 08, 08, 08, 08, 08, 08, 08, 08, 08, 01, 08,
        08, 17, 17, 17, 17, 17, 17, 09, 09, 17, 17, 17, 17, 09, 17, 17,
        17, 17, 17, 09, 09, 17, 17, 17, 17, 17, 17, 15, 17, 17, 17, 17,
        17, 17, 17, 17, 17, 15, 17, 15, 17, 17, 17, 15, 15, 10, 10, 10,
        15, 15, 10, 10, 15, 10, 10, 15, 10, 10, 15, 15, 15, 10, 10, 15,
        15, 10, 15, 10, 10, 10, 15, 10, 15, 15, 09, 10, 14, 14, 17, 17,
        14, 14, 14, 17, 14, 14, 14, 17, 14, 14, 17, 17, 17, 14, 14, 14,
        17, 14, 17, 14, 17, 17, 07, 07, 01, 07, 07, 10, 10, 10, 01, 07,
        07, 07, 16, 07, 10, 07, 07, 07, 07, 07, 01, 07, 01, 01, 07, 07,
        07, 10, 07, 07, 07, 01, 01, 10, 10, 01, 07, 07, 10, 01, 01, 07,
        07, 07, 07, 10, 07, 01, 10, 01, 07, 07, 09, 09, 09, 17, 09, 17,
        09, 17, 17, 09, 17, 17, 09, 17, 09, 17, 09, 17, 09, 17, 09, 17,
        17, 09, 09, 09, 09, 12, 12, 12, 15, 12, 12, 04, 12, 12, 08, 08,
        08, 08, 08, 08, 08, 08, 08, 06, 03, 03, 03, 08, 08, 03, 03, 03,
        03, 03, 08, 08, 08, 08, 08, 03, 00, 03, 03, 03, 03, 03, 02, 00,
        00, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00,
        00, 00, 00, 01, 06, 06, 06, 08, 06, 08, 06, 08, 06, 06, 06, 06,
        06, 06, 06, 06, 06, 03, 08, 06, 06, 06, 06, 09, 09, 17, 16, 03,
        03, 03, 06, 08, 03, 03, 03, 03, 03, 03, 06, 06, 03, 03, 03, 03,
        08, 08, 06, 06, 06, 06, 08, 08, 08, 08, 08, 08, 08, 08, 08, 08,
        08, 08, 08, 08, 08, 12, 12, 12, 12, 12, 12, 09, 12, 09, 09, 12,
        03, 03, 03, 03, 03, 00, 01, 02, 02, 01, 01, 01, 03, 02, 01, 03,
        01, 03, 03, 03, 00, 03, 03, 10, 01, 01, 01, 00, 10, 01, 03, 03,
        01, 10, 01, 00, 01, 10, 10, 01, 01, 10, 03, 10, 03, 01, 10, 00,
        01, 01, 01, 00, 01, 00, 01, 08, 01, 01, 03, 03, 03, 01, 01, 01,
        03, 00, 00, 01, 03, 01, 01, 01, 03, 01, 01, 01, 03, 08, 03, 00,
        01, 01, 03, 01, 10, 03, 10, 01, 01, 01, 01, 03, 03, 01, 01, 01,
        01, 01, 10, 03, 03, 00, 03, 01, 01, 12, 12, 09, 12, 09, 15, 12,
        12, 15, 12, 08, 08, 08, 08, 08, 08, 12, 08, 08, 08, 06, 08, 08,
        08, 08, 08, 08, 08, 08, 08, 03, 03, 03, 03, 03, 03, 03, 03, 01,
        00, 00, 03, 01, 01, 03, 03, 01, 03, 03, 03, 03, 03, 11, 11, 08,
        08, 08, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 08, 11, 11, 08,
        11, 11, 08, 08, 11, 08, 08, 08, 11, 08, 11, 11, 08, 08, 11, 08,
        11, 11, 11, 11, 08, 08, 11, 08, 11, 11, 08, 08, 11, 08, 11, 08,
        10, 10, 08, 10, 08, 11, 11, 08, 11, 08, 08, 11, 08, 08, 11, 11,
        08, 10, 08, 11, 08, 11, 08, 11, 11, 11, 10, 08, 11, 11, 08, 13,
        13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13,
        13, 13, 13, 03, 03, 03, 03, 03, 13, 03, 03, 03, 03, 03, 03, 13,
        03, 03, 01, 03, 03, 03, 03, 03, 01, 01, 03, 03, 03, 03, 03, 13,
        03, 13, 10, 03, 10, 13, 13, 13, 13, 13, 13, 03, 13, 13, 03, 03,
        17, 13, 13, 13, 13, 13, 13, 13, 13, 03, 13, 13, 13, 13, 13, 13,
        13, 13, 13, 13, 13, 13, 13, 03, 13,
    };
}

/// <summary>
/// Console Region Flags for the 3DS.
/// </summary>
/// <remarks>Not to be confused with <see cref="Region3DSIndex"/>.</remarks>
[Flags]
public enum Region3DSFlags : byte
{
    None = 0,
    Japan = 1 << 0,
    Americas = 1 << 1,
    Europe = 1 << 2,
    China = 1 << 4,
    Korea = 1 << 5,
    Taiwan = 1 << 6,
}