package frontend.ast.exp;

import frontend.ast.Node;
import frontend.ast.NodeStack;
import frontend.ast.SyntaxType;
import frontend.lexer.TokenStream;
import frontend.lexer.TokenType;
import frontend.ast.token.TokenNode;
import error.Errors;

public class RelExp extends Node {
    public RelExp(TokenStream ts) {
        super(SyntaxType.REL_EXP, ts);
    }

    public void parse(Errors errors) {
        NodeStack stack = new NodeStack();
        while (true) {
            AddExp addexp = new AddExp(this.ts);
            addexp.parse(errors);
            stack.push(addexp);
            if (isRelOp()) {
                stack.push(new TokenNode(ts)); // relop
            } else {
                break;
            }
        }
        if (stack.size() == 1) {
            this.addChild((AddExp)stack.pop());
        } else {
            RelExp temp = this;
            while(stack.size() > 1) {
                RelExp rexp = new RelExp(this.ts);
                AddExp addexp = (AddExp)stack.pop();
                TokenNode relop = (TokenNode)stack.pop();
                temp.addChild(rexp);
                temp.addChild(relop);
                temp.addChild(addexp);
                temp = rexp;
            }
            temp.addChild((AddExp)stack.pop());
        }
    }

    public boolean isRelOp() {
        TokenType t = getCurrToken().getType();
        return t == TokenType.LSS || t == TokenType.GRE
                || t == TokenType.LEQ || t == TokenType.GEQ;
    }
}