package code.ast;

/**
 * The Lexer class provides functionalities for parsing and iterating through
 * a source string of text character by character.
 *
 * @author s-yamagiwa;
 */
public class Lexer {
	private final String source;
	private int position;
	
	public Lexer(String source) {
		this.source = source;
		this.position = 0;
	}
	
	/**
	 * Retrieves the next character without advancing the position.
	 *
	 * @return The next character.
	 */
	public char peek() {
		if (position >= source.length()) {
			return '\0'; // End of line
		}
		
		return source.charAt(position);
	}
	
	/**
	 * Retrieves the next character after advancing the position.
	 *
	 * @return The next character.
	 */
	public char peekNext() {
		if (position + 1 >= source.length()) {
			return '\0'; // End of line
		}
		
		return source.charAt(position + 1);
	}
	
	/**
	 * Advances the position by one character.
	 *
	 * @return The character that was previously at the current position.
	 */
	public char advance() {
		char current = peek();
		position++;
		
		return current;
	}
}