import java.util.ArrayList;
import java.util.List;
import java.util.Map;

public abstract class BinaryExpression extends BaseExpression {
    protected Expression exp1;
    protected Expression exp2;

    public BinaryExpression(Expression exp1, Expression exp2) {
        this.exp1 = exp1;
        this.exp2 = exp2;
    }

    public String toString() {
        return makeExpression(this.getPrefix(), this.exp1.toString(), this.exp2.toString(), this.getOperator());
    }

    public Expression assign(String var, Expression expression) {
        Expression returnExp1 = this.exp1;
        Expression returnExp2 = this.exp2;
        if (this.exp1.getVariables().contains(var)) {
            returnExp1 = expression.assign(var, expression);
        }

        if (this.exp2.getVariables().contains(var)) {
            returnExp2 = expression.assign(var, expression);
        }
        return this.newExpressionInstance(returnExp1, returnExp2);
    }

    public List<String> getVariables() {
        List<String> returnArray = new ArrayList<String>();
        List<String> exp2List = exp2.getVariables();

        returnArray.addAll(exp1.getVariables());
        returnArray.removeAll(exp2List);
        returnArray.addAll(exp2List);
        return returnArray;
    }

    public double evaluate(Map<String, Double> assignment) throws Exception {
        return this.doOperation(this.exp1.evaluate(assignment), this.exp2.evaluate(assignment));
    }

    public double evaluate() throws Exception {
        return this.doOperation(this.exp1.evaluate(), this.exp2.evaluate());
    }

    protected abstract double doOperation(double num1, double num2);

    protected abstract Expression newExpressionInstance(Expression exp1, Expression exp2);

    protected abstract String getOperator();
}