using System;

namespace Unity.Collections
{
    [GenerateTestsForBurstCompatibility]
    public unsafe static partial class FixedStringMethods
    {
        /// <summary>
        /// Append two characters to this IUTF8Bytes.  This is used as a helper for internal formatting.
        /// </summary>
        [GenerateTestsForBurstCompatibility(GenericTypeArguments = new[] { typeof(FixedString128Bytes) })]
        internal static FormatError Append<T>(ref this T fs, char a, char b)
            where T : unmanaged, INativeList<byte>, IUTF8Bytes
        {
            FormatError err = FormatError.None;
            err |= fs.Append((Unicode.Rune) a);
            err |= fs.Append((Unicode.Rune) b);
            if (err != FormatError.None)
                return FormatError.Overflow;
            return FormatError.None;
        }

        /// <summary>
        /// Append three characters to this IUTF8Bytes.  This is used as a helper for internal formatting.
        /// </summary>
        [GenerateTestsForBurstCompatibility(GenericTypeArguments = new[] { typeof(FixedString128Bytes) })]
        internal static FormatError Append<T>(ref this T fs, char a, char b, char c)
            where T : unmanaged, INativeList<byte>, IUTF8Bytes
        {
            FormatError err = FormatError.None;
            err |= fs.Append((Unicode.Rune) a);
            err |= fs.Append((Unicode.Rune) b);
            err |= fs.Append((Unicode.Rune) c);
            if (err != FormatError.None)
                return FormatError.Overflow;
            return FormatError.None;
        }

        /// <summary>
        /// Append 'I' 'n' 'f' 'i' 'n' 'i' 't' 'y' characters to this IUTF8Bytes.  This is used as a helper for internal formatting.
        /// </summary>
        [GenerateTestsForBurstCompatibility(GenericTypeArguments = new[] { typeof(FixedString128Bytes) })]
        internal static FormatError Append<T>(ref this T fs, char a, char b, char c, char d, char e, char f, char g, char h)
            where T : unmanaged, INativeList<byte>, IUTF8Bytes
        {
            FormatError err = FormatError.None;
            err |= fs.Append((Unicode.Rune) a);
            err |= fs.Append((Unicode.Rune) b);
            err |= fs.Append((Unicode.Rune) c);
            err |= fs.Append((Unicode.Rune) d);
            err |= fs.Append((Unicode.Rune) e);
            err |= fs.Append((Unicode.Rune) f);
            err |= fs.Append((Unicode.Rune) g);
            err |= fs.Append((Unicode.Rune) h);
            if (err != FormatError.None)
                return FormatError.Overflow;
            return FormatError.None;
        }

        [GenerateTestsForBurstCompatibility(GenericTypeArguments = new[] { typeof(FixedString128Bytes) })]
        internal static FormatError AppendScientific<T>(ref this T fs, char *source, int sourceLength, int decimalExponent, char decimalSeparator = '.')
            where T : unmanaged, INativeList<byte>, IUTF8Bytes
        {
            FormatError error;
            if ((error = fs.Append(source[0])) != FormatError.None)
                return error;
            if (sourceLength > 1)
            {
                if ((error = fs.Append(decimalSeparator)) != FormatError.None)
                    return error;
                for (var i = 1; i < sourceLength; ++i)
                {
                    if ((error = fs.Append(source[i])) != FormatError.None)
                        return error;
                }
            }
            if ((error = fs.Append('E')) != FormatError.None)
                return error;
            if (decimalExponent < 0)
            {
                if ((error = fs.Append('-')) != FormatError.None)
                    return error;
                decimalExponent *= -1;
                decimalExponent -= sourceLength - 1;
            }
            else
            {
                if ((error = fs.Append('+')) != FormatError.None)
                    return error;
                decimalExponent += sourceLength - 1;
            }
            var ascii = stackalloc char[2];
            const int decimalDigits = 2;
            for (var i = 0; i < decimalDigits; ++i)
            {
                var decimalDigit = decimalExponent % 10;
                ascii[1 - i] = (char)('0' + decimalDigit);
                decimalExponent /= 10;
            }
            for (var i = 0; i < decimalDigits; ++i)
                if ((error = fs.Append(ascii[i])) != FormatError.None)
                    return error;
            return FormatError.None;
        }

        /// <summary>
        /// Check if runes a, b, c are found at offset offset
        /// </summary>
        /// <param name="offset">The target offset</param>
        /// <param name="a">rune a</param>
        /// <param name="b">rune b</param>
        /// <param name="c">rune c</param>
        /// <returns></returns>
        [GenerateTestsForBurstCompatibility(GenericTypeArguments = new[] { typeof(FixedString128Bytes) })]
        internal static bool Found<T>(ref this T fs, ref int offset, char a, char b, char c)
            where T : unmanaged, INativeList<byte>, IUTF8Bytes
        {
            int old = offset;
            if ((fs.Read(ref offset).value | 32) == a
                && (fs.Read(ref offset).value | 32) == b
                && (fs.Read(ref offset).value | 32) == c)
                return true;
            offset = old;
            return false;
        }

        /// <summary>
        ///
        /// </summary>
        /// <param name="offset"></param>
        /// <param name="a"></param>
        /// <param name="b"></param>
        /// <param name="c"></param>
        /// <param name="d"></param>
        /// <param name="e"></param>
        /// <param name="f"></param>
        /// <param name="g"></param>
        /// <param name="h"></param>
        /// <returns></returns>
        [GenerateTestsForBurstCompatibility(GenericTypeArguments = new[] { typeof(FixedString128Bytes) })]
        internal static bool Found<T>(ref this T fs, ref int offset, char a, char b, char c, char d, char e, char f, char g, char h)
            where T : unmanaged, INativeList<byte>, IUTF8Bytes
        {
            int old = offset;
            if ((fs.Read(ref offset).value | 32) == a
                && (fs.Read(ref offset).value | 32) == b
                && (fs.Read(ref offset).value | 32) == c
                && (fs.Read(ref offset).value | 32) == d
                && (fs.Read(ref offset).value | 32) == e
                && (fs.Read(ref offset).value | 32) == f
                && (fs.Read(ref offset).value | 32) == g
                && (fs.Read(ref offset).value | 32) == h)
                return true;
            offset = old;
            return false;
        }
    }
}