using System;
using System.Text;
using static PKHeX.Core.StringConverter7ZH;

namespace PKHeX.Core
{
    /// <summary>
    /// Logic for converting a <see cref="string"/> between the various generation specific encoding formats.
    /// </summary>
    public static class StringConverter
    {
        private const char TerminatorNull = (char)0;
        private const char TerminatorFFFF = (char)0xFFFF;

        /// <summary>
        /// Converts bytes to a string according to the input parameters.
        /// </summary>
        /// <param name="data">Encoded data</param>
        /// <param name="generation">Generation string format</param>
        /// <param name="jp">Encoding is Japanese</param>
        /// <param name="isBigEndian">Encoding is Big Endian</param>
        /// <param name="count">Length of data to read.</param>
        /// <param name="offset">Offset to read from</param>
        /// <returns>Decoded string.</returns>
        public static string GetString(byte[] data, int generation, bool jp, bool isBigEndian, int count, int offset = 0)
        {
            if (isBigEndian)
                return generation == 3 ? StringConverter3.GetBEString3(data, offset, count) : StringConverter4.GetBEString4(data, offset, count);

            return generation switch
            {
                1 or 2 => StringConverter12.GetString1(data, offset, count, jp),
                3 => StringConverter3.GetString3(data, offset, count, jp),
                4 => StringConverter4.GetString4(data, offset, count),
                5 => GetString5(data, offset, count),
                6 => GetString6(data, offset, count),
                7 => GetString7(data, offset, count),
                _ => GetString7b(data, offset, count),
            };
        }

        /// <summary>
        /// Gets the bytes for a Generation specific string according to the input parameters.
        /// </summary>
        /// <param name="value">Decoded string.</param>
        /// <param name="generation">Generation string format</param>
        /// <param name="jp">Encoding is Japanese</param>
        /// <param name="isBigEndian">Encoding is Big Endian</param>
        /// <param name="maxLength">Maximum length of the input <see cref="value"/></param>
        /// <param name="language">Language specific conversion (Chinese)</param>
        /// <param name="padTo">Pad the input <see cref="value"/> to given length</param>
        /// <param name="padWith">Pad the input <see cref="value"/> with this character value</param>
        /// <returns>Encoded data.</returns>
        public static byte[] SetString(string value, int generation, bool jp, bool isBigEndian, int maxLength, int language = 0, int padTo = 0, ushort padWith = 0)
        {
            if (isBigEndian)
                return generation == 3 ? StringConverter3.SetBEString3(value, maxLength, padTo, padWith) : StringConverter4.SetBEString4(value, maxLength, padTo, padWith);

            return generation switch
            {
                1 or 2 => StringConverter12.SetString1(value, maxLength, jp, padTo, (byte)padWith),
                3 => StringConverter3.SetString3(value, maxLength, jp, padTo, padWith),
                4 => StringConverter4.SetString4(value, maxLength, padTo, padWith),
                5 => SetString5(value, maxLength, padTo, padWith),
                6 => SetString6(value, maxLength, padTo, padWith),
                7 => SetString7(value, maxLength, language, padTo, padWith),
                _ => SetString7b(value, maxLength, padTo, padWith),
            };
        }

        /// <summary>Converts Generation 5 encoded data to decoded string.</summary>
        /// <param name="data">Encoded data</param>
        /// <param name="offset">Offset to read from</param>
        /// <param name="count">Length of data to read.</param>
        /// <returns>Decoded string.</returns>
        public static string GetString5(byte[] data, int offset, int count)
        {
            var raw = Encoding.Unicode.GetString(data, offset, count);
            var sb = new StringBuilder(raw);
            Util.TrimFromFirst(sb, TerminatorFFFF);
            SanitizeString(sb);
            return sb.ToString();
        }

        /// <summary>Gets the bytes for a Generation 5 string.</summary>
        /// <param name="value">Decoded string.</param>
        /// <param name="maxLength">Maximum length of the input <see cref="value"/></param>
        /// <param name="padTo">Pad the input <see cref="value"/> to given length</param>
        /// <param name="padWith">Pad the input <see cref="value"/> with this character value</param>
        /// <returns>Encoded data.</returns>
        public static byte[] SetString5(string value, int maxLength, int padTo = 0, ushort padWith = 0)
        {
            var sb = new StringBuilder(value, Math.Max(maxLength, padTo));
            var delta = sb.Length - maxLength;
            if (delta > 0)
                sb.Remove(maxLength, delta);

            // Replace Special Characters and add Terminator
            UnSanitizeString(sb, 5);
            sb.Append(TerminatorFFFF);
            var d2 = padTo - sb.Length;
            if (d2 > 0)
                sb.Append((char)padWith, d2);

            return Encoding.Unicode.GetBytes(sb.ToString());
        }

        /// <summary>Converts Generation 6 encoded data to decoded string.</summary>
        /// <param name="data">Encoded data</param>
        /// <param name="offset">Offset to read from</param>
        /// <param name="count">Length of data to read.</param>
        /// <returns>Decoded string.</returns>
        public static string GetString6(byte[] data, int offset, int count)
        {
            var raw = Encoding.Unicode.GetString(data, offset, count);
            var sb = new StringBuilder(raw);
            Util.TrimFromFirst(sb, TerminatorNull);
            SanitizeString(sb);
            return sb.ToString();
        }

        /// <summary>Gets the bytes for a Generation 6 string.</summary>
        /// <param name="value">Decoded string.</param>
        /// <param name="maxLength">Maximum length of the input <see cref="value"/></param>
        /// <param name="padTo">Pad the input <see cref="value"/> to given length</param>
        /// <param name="padWith">Pad the input <see cref="value"/> with this character value</param>
        /// <returns>Encoded data.</returns>
        public static byte[] SetString6(string value, int maxLength, int padTo = 0, ushort padWith = 0)
        {
            var sb = new StringBuilder(value);
            var delta = sb.Length - maxLength;
            if (delta > 0)
                sb.Remove(maxLength, delta);

            // Replace Special Characters and add Terminator
            UnSanitizeString(sb, 6);
            sb.Append(TerminatorNull);
            var d2 = padTo - sb.Length;
            if (d2 > 0)
                sb.Append((char)padWith, d2);

            return Encoding.Unicode.GetBytes(sb.ToString());
        }

        /// <summary>Converts Generation 7 encoded data to decoded string.</summary>
        /// <param name="data">Encoded data</param>
        /// <param name="offset">Offset to read from</param>
        /// <param name="count">Length of data to read.</param>
        /// <returns>Decoded string.</returns>
        public static string GetString7(byte[] data, int offset, int count)
        {
            var raw = Encoding.Unicode.GetString(data, offset, count);
            var sb = new StringBuilder(raw);
            Util.TrimFromFirst(sb, TerminatorNull);
            SanitizeString(sb);
            RemapChineseGlyphsBin2String(sb);
            return sb.ToString();
        }

        /// <summary>Converts Generation 7-Beluga encoded data to decoded string.</summary>
        /// <param name="data">Encoded data</param>
        /// <param name="offset">Offset to read from</param>
        /// <param name="count">Length of data to read.</param>
        /// <returns>Decoded string.</returns>
        public static string GetString7b(byte[] data, int offset, int count)
        {
            var raw = Encoding.Unicode.GetString(data, offset, count);
            var sb = new StringBuilder(raw);
            Util.TrimFromFirst(sb, TerminatorNull);
            SanitizeString(sb);
          //RemapChineseGlyphsBin2String(sb);
            return sb.ToString();
        }

        /// <summary>Gets the bytes for a Generation 7 string.</summary>
        /// <param name="value">Decoded string.</param>
        /// <param name="maxLength">Maximum length of the input <see cref="value"/></param>
        /// <param name="language">Language specific conversion (Chinese)</param>
        /// <param name="padTo">Pad the input <see cref="value"/> to given length</param>
        /// <param name="padWith">Pad the input <see cref="value"/> with this character value</param>
        /// <param name="chinese">Chinese string remapping should be attempted</param>
        /// <returns>Encoded data.</returns>
        public static byte[] SetString7(string value, int maxLength, int language, int padTo = 0, ushort padWith = 0, bool chinese = false)
        {
            var sb = new StringBuilder(value);
            var delta = sb.Length - maxLength;
            if (delta > 0)
                sb.Remove(maxLength, delta);
            if (chinese)
                ConvertString2BinG7_zh(sb, language);

            // Replace Special Characters and add Terminator
            UnSanitizeString(sb, 7);
            sb.Append(TerminatorNull);
            var d2 = padTo - sb.Length;
            if (d2 > 0)
                sb.Append((char)padWith, d2);

            return Encoding.Unicode.GetBytes(sb.ToString());
        }

        /// <summary>Gets the bytes for a Generation 7-Beluga string.</summary>
        /// <param name="value">Decoded string.</param>
        /// <param name="maxLength">Maximum length of the input <see cref="value"/></param>
        /// <param name="padTo">Pad the input <see cref="value"/> to given length</param>
        /// <param name="padWith">Pad the input <see cref="value"/> with this character value</param>
        /// <returns>Encoded data.</returns>
        public static byte[] SetString7b(string value, int maxLength, int padTo = 0, ushort padWith = 0)
        {
            var sb = new StringBuilder(value);
            var delta = sb.Length - maxLength;
            if (delta > 0)
                sb.Remove(maxLength, delta);

            // Replace Special Characters and add Terminator
            // No special characters!
            sb.Append(TerminatorNull);
            var d2 = padTo - sb.Length;
            if (d2 > 0)
                sb.Append((char)padWith, d2);

            return Encoding.Unicode.GetBytes(sb.ToString());
        }

        /// <summary>
        /// Converts full width to single width
        /// </summary>
        /// <param name="s">Input string to sanitize.</param>
        /// <returns></returns>
        internal static void SanitizeString(StringBuilder s)
        {
            if (s.Length == 0)
                return;

            // remap custom glyphs to unicode
            s.Replace('\uE08F', '♀'); // ♀ (gen6+)
            s.Replace('\uE08E', '♂'); // ♂ (gen6+)
            s.Replace('\u246E', '♀'); // ♀ (gen5)
            s.Replace('\u246D', '♂'); // ♂ (gen5)
        }

        /// <summary>
        /// Converts full width to half width when appropriate
        /// </summary>
        /// <param name="str">Input string to set.</param>
        /// <param name="generation">Generation specific context</param>
        /// <returns></returns>
        internal static void UnSanitizeString(StringBuilder str, int generation)
        {
            if (generation <= 5)
            {
                str.Replace('\u2640', '\u246E'); // ♀
                str.Replace('\u2642', '\u246D'); // ♂
                return;
            }

            bool fullwidth = GetIsFullWidthString(str);
            if (fullwidth) // jp/ko/zh strings
                return; // keep as full width

            // Convert back to half width glyphs
            str.Replace('\u2640', '\uE08F'); // ♀
            str.Replace('\u2642', '\uE08E'); // ♂
        }

        private static bool GetIsFullWidthString(StringBuilder str)
        {
            for (int i = 0; i < str.Length; i++)
            {
                var c = str[i];
                if (c >> 12 is (0 or 0xE))
                    continue;
                if (c is '\u2640' or '\u2642') // ♀♂
                    continue;
                return true;
            }
            return false;
        }

        public static bool HasEastAsianScriptCharacters(string str)
        {
            foreach (var c in str)
            {
                if (c is >= '\u4E00' and <= '\u9FFF')
                    return true;
            }
            return false;
        }
    }
}