package com.zavada.core;

import java.util.ArrayList;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

import com.zavada.symbol.Token;

public class Lexer {

	private static String[] regex = {
			":(.+?):",					//VARIABLE
			"(\\d+)?(\\.?\\d+)",		//DIGIT LITERAL
			"\".*\"",					//STRING LITERAL
			"[%*+-\\/]",				//OPERATOR
			"=",						//ASSIGNMENT
			"P",						//PRINT
	};

	public static ArrayList<Token> lex(String in){

		ArrayList<Token> tokens = new ArrayList<Token>();

		while(in.trim().length() > 0) {

			int index = in.length();
			String foundRegex = null;
			for(String a : regex) {

				int testIndex = indexOf(Pattern.compile(a),in);

				if( testIndex < index && testIndex > -1) {
					index = testIndex;
					foundRegex = a;
				}

			}
			System.out.println(in);
			Pattern pattern = Pattern.compile(foundRegex);
			Matcher matcher = pattern.matcher(in);

			if(matcher.find()) {
				tokens.add(new Token(foundRegex, matcher.group(0)));
			}

			in = in.replaceFirst(foundRegex, "");

		}

		return tokens;
	}

    /** @return index of pattern in s or -1, if not found */
	public static int indexOf(Pattern pattern, String s) {

		Matcher matcher = pattern.matcher(s);
		return matcher.find() ? matcher.start() : -1;

	}

}