using System;
using System.Collections.Generic;
using static System.Buffers.Binary.BinaryPrimitives;

namespace PKHeX.Core
{
    public static class PSS6
    {
        private const string Header = "PSS List";
        private static readonly string[] headers = { "PSS Data - Friends", "PSS Data - Acquaintances", "PSS Data - Passerby" };

        public static List<string> GetPSSParse(SAV6 SAV)
        {
            var result = new List<string> {Header};
            int offset = SAV.PSS;
            var data = SAV.Data;
            for (int g = 0; g < 3; g++)
            {
                result.Add("----");
                result.Add(headers[g]);
                result.Add("----");
                // uint count = ReadUInt32LittleEndian(data.AsSpan(offset + 0x4E20));
                ReadTrainers(result, data, offset, 100);
                offset += 0x5000; // Advance to next block
            }

            return result;
        }

        private static void ReadTrainers(ICollection<string> result, byte[] data, int offset, int count)
        {
            int r_offset = offset;
            const int size = 0xC8;
            for (int i = 0; i < count; i++)
            {
                if (!ReadTrainer(result, data.AsSpan(r_offset, size)))
                    break; // No data present here

                if (i > 0)
                    result.Add(string.Empty);

                r_offset += size; // Advance to next entry
            }
        }

        private static bool ReadTrainer(ICollection<string> result, ReadOnlySpan<byte> data)
        {
            ulong pssID = ReadUInt64LittleEndian(data);
            if (pssID == 0)
                return false; // no data

            string otname = StringConverter6.GetString(data.Slice(0x08, 0x1A));
            string message = StringConverter6.GetString(data.Slice(0x22, 0x22));

            // Trim terminated

            // uint unk1  = ReadUInt32LittleEndian(data[0x44..]);
            // ulong unk2 = ReadUInt64LittleEndian(data[0x48..]);
            // uint unk3  = ReadUInt32LittleEndian(data[0x50..]);
            // uint unk4  = ReadUInt16LittleEndian(data[0x54..]);
            byte regionID = data[0x56];
            byte countryID = data[0x57];
            byte game = data[0x5A];
            // ulong outfit = ReadUInt64LittleEndian(data.AsSpan(ofs + 0x5C));
            int favpkm = ReadUInt16LittleEndian(data[0x9C..]) & 0x7FF;

            string gamename = GetGameName(game);
            var (country, region) = GeoLocation.GetCountryRegionText(countryID, regionID, GameInfo.CurrentLanguage);
            result.Add($"OT: {otname}");
            result.Add($"Message: {message}");
            result.Add($"Game: {gamename}");
            result.Add($"Country: {country}");
            result.Add($"Region: {region}");
            result.Add($"Favorite: {GameInfo.Strings.specieslist[favpkm]}");
            return false;
        }

        private static string GetGameName(int game)
        {
            const string unk = "UNKNOWN GAME";
            if (game < 0)
                return unk;
            var list = GameInfo.Strings.gamelist;
            if (game >= list.Length)
                return unk;
            return list[game];
        }
    }
}