class Expression {
	constructor(op, left, right) {
		this.op = op
		this.left = left
		this.right = right
	}
	
	eval() {
		return evalExpression(this)
	}
}

function evalExpression(expr) {
	let tempLeft
	let tempRight
	if (typeof(expr.left) === "object") { // Check if left type is another expression
		tempLeft = evalExpression(expr.left)
	} 
	else {
		tempLeft = expr.left
	}
	if (typeof(expr.right) === "object") { // Check if right type is another expression
		tempRight = evalExpression(expr.right)
	}
	else {
		tempRight = expr.right
	}
	if (typeof(tempLeft) === "number" & typeof(tempRight) === "number") { // Make sure both inputs are number
		if (expr.op === "+") {
			return tempLeft + tempRight
		}
		else if(expr.op === "-") {
			return tempLeft - tempRight
		}
		else if(expr.op === "*") {
			return tempLeft * tempRight
		}
		else if(expr.op === "/") {
			return tempLeft / tempRight
		}
		else { // Case for when there is no valid provided operator
			return "Invalid operator syntax"
		}
	}
	else { //Case for when the left or right are not numbers
		return "Invalid number syntax"
	}
}

exports.Expression = Expression;