using System.Collections;
using System.Text;
using Nbt.Type;

namespace Nbt;

internal static class NbtUtils
{
    public const char ESCAPE_CHAR = '\\';
    public const char SINGLE_QUOTE_CHAR = '\'';
    public const char DOUBLE_QUOTE_CHAR = '"';

    public static readonly INbtRegistry Registry = new NbtRegistry();

    static NbtUtils()
    {
        Registry.AddAll(NbtByteType.Value, NbtShortType.Value, NbtIntType.Value, NbtLongType.Value, NbtFloatType.Value, NbtDoubleType.Value, NbtStringType.Value, NbtListType.Value, NbtCompoundType.Value, NbtEndType.Value, NbtByteArrayType.Value, NbtIntArrayType.Value, NbtLongArrayType.Value);
    }

    public static INbtType GetTagType(NbtTagType tagType) => Registry.TryGet(tagType, out var value) ? value : throw new UnknownTagTypeException(tagType, $"Unknown tag type: {tagType}");

    public static NbtTagType GetValueTagType<T>() => GetValueTagType(typeof(T));

    public static NbtTagType GetValueTagType(System.Type type) =>
        type == typeof(sbyte) ? NbtTagType.Byte :
        type == typeof(short) ? NbtTagType.Short :
        type == typeof(int) ? NbtTagType.Int :
        type == typeof(long) ? NbtTagType.Long :
        type == typeof(float) ? NbtTagType.Float :
        type == typeof(double) ? NbtTagType.Double :
        type == typeof(string) ? NbtTagType.String :
        NbtTagType.Unknown;

    public static NbtTagType GetArrayTagType<T>() => GetArrayTagType(typeof(T));

    public static NbtTagType GetArrayTagType(System.Type type) =>
        type == typeof(sbyte) ? NbtTagType.ByteArray :
        type == typeof(int) ? NbtTagType.IntArray :
        type == typeof(long) ? NbtTagType.LongArray :
        NbtTagType.Unknown;

    public static NbtTagType EnsureValueType<T>()
    {
        var type = typeof(T);
        var tagType = GetValueTagType(type);
        return tagType is NbtTagType.Unknown ? throw new UnknownTagTypeException(tagType, $"Unknown value type: {type.Name}") : tagType;
    }

    public static NbtTagType EnsureArrayType<T>()
    {
        var type = typeof(T);
        var tagType = GetArrayTagType(type);
        return tagType is NbtTagType.Unknown ? throw new UnknownTagTypeException(tagType, $"Unknown array type: {type.Name}") : tagType;
    }

    public static NbtTagType ToArrayType(this NbtTagType tagType) => tagType switch
    {
        NbtTagType.Byte => NbtTagType.ByteArray,
        NbtTagType.Int => NbtTagType.IntArray,
        NbtTagType.Long => NbtTagType.LongArray,
        _ => NbtTagType.Unknown
    };

    public static NbtTagType ToValueType(this NbtTagType tagType) => tagType switch
    {
        NbtTagType.ByteArray => NbtTagType.Byte,
        NbtTagType.IntArray => NbtTagType.Int,
        NbtTagType.LongArray => NbtTagType.Long,
        _ => NbtTagType.Unknown
    };

    public static string QuoteString(string s, bool onlyIfNeeded = false)
    {
        if (s.Length == 0)
        {
            return $"{DOUBLE_QUOTE_CHAR}{DOUBLE_QUOTE_CHAR}";
        }

        var sb = new StringBuilder();
        var needQuotes = false;
        var quoteChar = '\0';

        foreach (var c in s)
        {
            needQuotes |= QuoteString(sb, c, ref quoteChar);
        }

        if (!onlyIfNeeded || needQuotes)
        {
            quoteChar = quoteChar == DOUBLE_QUOTE_CHAR ? SINGLE_QUOTE_CHAR : DOUBLE_QUOTE_CHAR;

            sb.Insert(0, quoteChar);
            sb.Append(quoteChar);
        }

        return sb.ToString();
    }

    private static bool QuoteString(StringBuilder sb, char c, ref char quoteChar)
    {
        var needQuotes = false;
        var escape = false;

        switch (c)
        {
            case '\t':
                escape = true;
                c = 't';
                break;

            case '\r':
                escape = true;
                c = 'r';
                break;

            case '\n':
                escape = true;
                c = 'n';
                break;

            case ESCAPE_CHAR:
                escape = true;
                break;

            case SINGLE_QUOTE_CHAR:
            case DOUBLE_QUOTE_CHAR:
                if (quoteChar == '\0')
                {
                    quoteChar = c;
                }
                else if (c != quoteChar)
                {
                    escape = true;
                }

                needQuotes = true;
                break;

            case '.':
            case '_':
            case '-':
            case '+':
            case >= 'a' and <= 'z' or >= 'A' and <= 'Z' or >= '0' and <= '9':
                break;

            default:
                needQuotes = true;
                break;
        }

        if (escape)
        {
            sb.Append(ESCAPE_CHAR);
        }

        sb.Append(c);

        return needQuotes || escape;
    }
}