import java.util.ArrayList;

public class Lexer {
    public String code;
    public int cursorPosition;

    public Lexer(String code) {
        this.code = code;
    }

    public ArrayList<Token> lex() {
        ArrayList<Token> tokens = new ArrayList<Token>();

        cursorPosition = -1;

        try {
            while (true) {
                char currentChar;

                try {
                    currentChar = getNext();
                } catch (Exception e) {
                    break;
                }

                // Espaces, sauts de lignes, ...
                if (isWhitespace(currentChar)) {
                    // Ne rien faire
                // +, =, (, ), [, ]
                } else if (isSymbol(currentChar)) {
                    TokenType type = TokenType.getFromChar(currentChar);
                    Token token = new Token(type, currentChar);
                    tokens.add(token);
                // a..z | A..Z | _
                } else if (isAlpha(currentChar)) {
                    String identifier = "";

                    while (isAlpha(currentChar)) {
                        identifier += currentChar;

                        try {
                            currentChar = getNext();
                        } catch (Exception e) {
                            break;
                        }
                    }

                    cursorPosition -= 1;

                    Token token = new Token(TokenType.TOK_IDENTIFIER, identifier);

                    tokens.add(token);
                // 0..9
                } else if (isDigit(currentChar)) {
                    String identifier = "";

                    while (isDigit(currentChar)) {
                        identifier += currentChar;

                        try {
                            currentChar = getNext();
                        } catch (Exception e) {
                            break;
                        }
                    }

                    cursorPosition -= 1;

                    Token token = new Token(TokenType.TOK_IDENTIFIER, identifier);

                    tokens.add(token);
                }

                if (cursorPosition > code.length())
                    break;
            }
        } catch (Exception e) {
            System.out.println(e);
        }

        return tokens;
    }

    public char getNext() {
        cursorPosition += 1;

        return code.charAt(cursorPosition);
    }

    public boolean isWhitespace(char chr) {
        return chr == ' ' || chr == '\t' || chr == '\r' || chr == '\n';
    }

    /// = | + | ( | ) | [ | ]
    public boolean isSymbol(char chr) {
        return chr == '=' || chr == '+' || chr == '(' || chr == ')' || chr == '[' || chr == ']';
    }

    /// a .. z | A .. Z | _
    public boolean isAlpha(char chr) {
        return (chr >= 'a' && chr <= 'z') || (chr >= 'A' && chr <= 'Z') || chr == '_';
    }

    /// 0 .. 9
    public boolean isDigit(char chr) {
        return chr >= '0' && chr <= '9';
    }
}