using System;
using System.Collections.Generic;
using System.Linq;

namespace pkNX.Structures;

public static partial class PawnUtil
{
    // FireFly's (github.com/FireyFly) concise decompression (ported c->c#):
    // https://github.com/FireyFly/poketools/blob/e74538a5b5e5dab1e78c1cd313c55d158f37534d/src/formats/script.c#L61
    public static uint[] QuickDecompress(byte[] data, int count)
    {
        uint[] code = new uint[count];
        uint i = 0, j = 0, x = 0, f = 0;
        while (i < code.Length)
        {
            int b = data[f++],
                v = b & 0x7F,
                c = b & 0x80;
            if (++j == 1)                                                  // sign extension possible
                x = (uint)((((v >> 6 == 0 ? 1 : 0) - 1) << 6) | v); // only for bit6 being set
            else
                x = (x << 7) | (byte)v; // shift data into place

            if (c > 0)
                continue; // more data to read

            code[i++] = x;
            j = 0; // write finalized instruction
        }

        return code;
    }

    // https://github.com/gameswop/mtasa-resources/blob/d557a72fefef57ac34780a76edf16383d3dff0e8/%5Bgamemodes%5D/%5Bamx%5D/amx-deps/src/amx/amx.c#L1119
    // Slightly more readable, but potentially slower
    public static uint[] QuickDecompress2(byte[] data, int count)
    {
        var memsize = count * sizeof(uint);
        var instructions = new uint[count];
        int i = data.Length;

        while (i > 0)
        {
            uint cell = 0;
            var shift = 0;

            do
            {
                i--;
                cell |= (uint)(data[i] & 0x7f) << shift;
                shift += 7;
            }
            while (i > 0 && (data[i - 1] & 0x80) != 0);

            if ((data[i] & 0x40) != 0)
            {
                while (shift < 8 * sizeof(uint))
                {
                    cell |= (uint)0xff << shift;
                    shift += 8;
                }
            }

            memsize -= sizeof(uint);
            instructions[memsize / sizeof(uint)] = cell;
        }

        return instructions;
    }

    // Compression
    /*public static byte[] CompressScript(byte[] data)
    {
        if (data == null || data.Length % 4 != 0) // Bad Input
            return null;
        using (MemoryStream mn = new MemoryStream())
        using (BinaryWriter bw = new BinaryWriter(mn))
        {
            for ( var pos = 0; pos < data.Length; pos += 4 )
            {
                byte[] db = data.Skip(pos).Take(4).ToArray();
                byte[] cb = CompressBytes(db);
                bw.Write(cb);
            }
            return mn.ToArray();
        }
    }*/

    public static byte[] CompressScript(uint[] instructions)
        => instructions.SelectMany(CompressInstruction).ToArray();

    private static byte[] CompressInstruction(uint instruction)
    {
        var bytes = new List<byte>();
        var sign = (instruction & 0x80000000) > 0;

        // Signed (negative) values are handled opposite of unsigned (positive) values.
        // Positive values are "done" when we've shifted the value down to zero, but
        // we don't need to store the highest 1s in a signed value. We handle this by
        // tracking the loop via a NOTed shadow copy of the instruction if it's signed.
        var shadow = sign ? ~instruction : instruction;

        do
        {
            var least7 = instruction & 0b01111111;
            var byteVal = (byte)least7;

            if (bytes.Count > 0)
            {
                // Continuation bit on all but the lowest byte
                byteVal |= 0x80;
            }

            bytes.Add(byteVal);

            instruction >>= 7;
            shadow >>= 7;
        }
        while (shadow != 0);

        if (bytes.Count < 5)
        {
            // Ensure "sign bit" (bit just to the right of highest continuation bit) is
            // correct. Add an extra empty continuation byte if we need to. Values can't
            // be longer than 5 bytes, though.

            var signBit = sign ? 0x40 : 0x00;

            if ((bytes.Last() & 0x40) != signBit)
                bytes.Add(sign ? (byte)0xFF : (byte)0x80);
        }

        // Little endian to big endian
        bytes.Reverse();

        return bytes.ToArray();
    }

    // Interpreting
    public static string[] ParseScript(uint[] cmd, int sanity = -1)
    {
        // sub_148CBC Moon v1.0
        List<string> parse = new();
        const int sanityMode = 0; // todo

        string ErrorNear(int line, string error)
        {
            var start = Math.Max(line - 6, 0);
            var end = Math.Min(line + 6, cmd.Length - 1);
            var toPrint = cmd.Skip(start).Take(end - start);
            var message = $"Error at line {line}:" + Environment.NewLine;

            message += string.Join(" ", toPrint.Select(b => $"{b:X2}")) + Environment.NewLine;

            for (var x = 0; x < line - start; x++)
                message += "   ";

            message += "^^" + Environment.NewLine;
            message += error;

            return message;
        }

        int i = 0;               // Current Offset of decompressed instructions
        while (i < cmd.Length) // read away
        {
            // Read a Command

            string instrLine;
            var line = i;
            var opcodeval = cmd[i++];
            var opcodesafe = opcodeval & 0xFFFF;

            if (!Enum.IsDefined(typeof(AmxOpCode), opcodesafe))
                throw new ArgumentException(ErrorNear(line, $"Invalid command ID: {opcodesafe:X4} ({opcodesafe})"));

            var opcode = (AmxOpCode)opcodesafe;

            if (!OpCodeTypes.TryGetValue(opcode, out var optype))
                throw new ArgumentException(ErrorNear(line, $"Unknown OpCode: {opcodesafe:X4} ({opcodesafe})"));

            switch (optype)
            {
                default:
                    throw new ArgumentException("Invalid Command Type");

                case AmxOpCodeType.NoParams:
                {
                    instrLine = EchoIntCommand(opcode);
                    break;
                }

                case AmxOpCodeType.OneParam:
                {
                    var param = (int)cmd[i++];

                    instrLine = EchoIntCommand(opcode, param);
                    break;
                }

                case AmxOpCodeType.TwoParams:
                {
                    var param1 = (int)cmd[i++];
                    var param2 = (int)cmd[i++];

                    instrLine = EchoIntCommand(opcode, param1, param2);
                    break;
                }

                case AmxOpCodeType.ThreeParams:
                {
                    var param1 = (int)cmd[i++];
                    var param2 = (int)cmd[i++];
                    var param3 = (int)cmd[i++];

                    instrLine = EchoIntCommand(opcode, param1, param2, param3);
                    break;
                }

                case AmxOpCodeType.FourParams:
                {
                    var param1 = (int)cmd[i++];
                    var param2 = (int)cmd[i++];
                    var param3 = (int)cmd[i++];
                    var param4 = (int)cmd[i++];

                    instrLine = EchoIntCommand(opcode, param1, param2, param3, param4);
                    break;
                }

                case AmxOpCodeType.FiveParams:
                {
                    var param1 = (int)cmd[i++];
                    var param2 = (int)cmd[i++];
                    var param3 = (int)cmd[i++];
                    var param4 = (int)cmd[i++];
                    var param5 = (int)cmd[i++];

                    instrLine = EchoIntCommand(opcode, param1, param2, param3, param4, param5);
                    break;
                }

                case AmxOpCodeType.Jump:
                {
                    var jumpOffset = (int)cmd[i++];
                    var jumpDest = (line * 4) + jumpOffset;

                    instrLine = $"{Commands[opcode].PadRight(MaxCommandLength, ' ')} => 0x{jumpDest:X4} ({jumpOffset})";
                    break;
                }

                case AmxOpCodeType.Packed:
                {
                    var param = (short)(opcodeval >> 16);

                    instrLine = EchoIntCommand(opcode, param);
                    break;
                }

                case AmxOpCodeType.CaseTable:
                {
                    //var jOffset = (i * 4) - 4; // this may be the correct jump start point...
                    var count = cmd[i++]; // switch case table
                    // sanity check

                    // Populate Switch-Case Tree
                    var tree = new List<string>();

                    // Cases
                    for (int j = 0; j < count; j++)
                    {
                        var jmp = (int)cmd[i++];
                        var toOffset = ((i - 2) * 4) + jmp;
                        var ifValue = (int)cmd[i++];
                        tree.Add($"\t{ifValue} => 0x{toOffset:X4} ({jmp})");
                    }

                    // Default
                    {
                        int jmp = (int)cmd[i++];
                        var toOffset = ((i - 2) * 4) + jmp;
                        tree.Add($"\t* => 0x{toOffset:X4} ({jmp})");
                    }

                    instrLine = Commands[opcode] + Environment.NewLine + string.Join(Environment.NewLine, tree);
                    break;
                }
            }

            if (opcode is AmxOpCode.RET or AmxOpCode.RETN or AmxOpCode.IRETN)
            {
                // Newline after return
                instrLine += Environment.NewLine;
            }

            if (parse.Count == 0 && opcode == AmxOpCode.HALT_P)
            {
                // Newline after 0x0000 HALT.P
                instrLine += Environment.NewLine;
            }

            parse.Add($"0x{line * 4:X4}: [{opcodeval & 0x7FF:X2}] {instrLine}");
        }

        if (sanity >= 0 && sanity != sanityMode)
            throw new ArgumentException();

        return parse.ToArray();
    }

    internal static string[] ParseMovement(uint[] cmd) => Util.GetHexLines(cmd);

    internal static string EchoIntCommand(AmxOpCode c, params int[] arr)
    {
        static string FormatParameter(int param)
        {
            if (param is < -100 or > 100)
                return $"0x{param:X4}";
            return param.ToString();
        }

        string commandLeft = Commands[c].PadRight(MaxCommandLength, ' ');
        string parameters = arr.Length == 0 ? "" : string.Join(", ", arr.Select(FormatParameter));
        return $"{commandLeft} {parameters}";
    }

    private static readonly Func<uint, float> getFloat = val => BitConverter.ToSingle(BitConverter.GetBytes(val), 0);

    internal static string EchoFloatCommand(AmxOpCode c, params uint[] arr)
    {
        string commandLeft = Commands[c].PadRight(MaxCommandLength, ' ');
        string parameters = arr.Length == 1 ? "" : string.Join(", ", arr.Select(getFloat));
        return $"{commandLeft} {parameters}";
    }

    private static readonly Dictionary<AmxOpCode, string> Commands = Enum.GetValues(typeof(AmxOpCode))
        .Cast<AmxOpCode>()
        .ToDictionary(v => v, v => v.ToString().Replace('_', '.'));

    private static readonly int MaxCommandLength = Commands.Values.Max(cmd => cmd.Length);
}