using System.Collections.Generic;
using System.Text;
using UnityEngine;

namespace UnityExplorer.CSConsole.Lexers
{
    public class KeywordLexer : Lexer
    {
        // system blue
        protected override Color HighlightColor => new(0.33f, 0.61f, 0.83f, 1.0f);

        public static readonly HashSet<string> keywords = new()
        {
// reserved keywords
"abstract", "as", "base", "bool", "break", "byte", "case", "catch", "char", "checked", "class", "const", "continue",
"decimal", "default", "delegate", "do", "double", "else", "enum", "event", "explicit", "extern", "false", "finally",
"fixed", "float", "for", "foreach", "goto", "if", "implicit", "in", "int", "interface", "internal", "is", "lock",
"long", "namespace", "new", "null", "object", "operator", "out", "override", "params", "private", "protected", "public",
"readonly", "ref", "return", "sbyte", "sealed", "short", "sizeof", "stackalloc", "static", "string", "struct", "switch",
"this", "throw", "true", "try", "typeof", "uint", "ulong", "unchecked", "unsafe", "ushort", "using", "virtual", "void",
"volatile", "while",
// contextual keywords
"add", "and", "alias", "ascending", "async", "await", "by", "descending", "dynamic", "equals", "from", "get",
"global", "group", "init", "into", "join", "let", "managed", "nameof",  "not", "notnull", "on",
"or", "orderby", "partial", "record", "remove", "select", "set", "unmanaged", "value", "var", "when", "where",
"where", "with", "yield", "nint", "nuint"
        };

        public override bool TryMatchCurrent(LexerBuilder lexer)
        {
            char prev = lexer.Previous;
            char first = lexer.Current;

            // check for keywords
            if (lexer.IsDelimiter(prev, true) && char.IsLetter(first))
            {
                // can be a keyword...

                StringBuilder sb = new();
                sb.Append(lexer.Current);
                while (!lexer.EndOfInput && char.IsLetter(lexer.PeekNext()))
                    sb.Append(lexer.Current);

                // next must be whitespace or delimiter
                if (!lexer.EndOfInput && !(char.IsWhiteSpace(lexer.Current) || lexer.IsDelimiter(lexer.Current)))
                    return false;

                if (keywords.Contains(sb.ToString()))
                {
                    if (!lexer.EndOfInput)
                        lexer.RollbackBy(1);
                    lexer.Commit();
                    return true;
                }

                return false;

            }
            else
                return false;
        }
    }
}