pset7 buy

@app.route("/buy", methods=["GET", "POST"])
@login_required
def buy():
    """Buy shares of stock."""
    if request.method == "GET":
        return render_template("buy.html")

    # if user reached route via POST
    if request.method == "POST":
        # ensure symbol was submitted
        if not request.form.get("symbol") and request.form.get("number_stocks"):
            return apology("symbol required")

        else:
            #lookup the stock using the symbol and define vars
            details = lookup(request.form.get("symbol"))
            symbol = request.form.get("symbol")
            price = details["price"]
            quantity =  int(request.form.get("number_stocks"))
            total = price * quantity
            user = session["user_id"]


            #ensure the stock is valid
            if price == None:
                return apology("this stock is not valid")

            else:
                #get cost of stocks and deduct from balance in users account
                sum_req = round(price * quantity,2)
                balance = db.execute("SELECT cash FROM users WHERE id = :id", id = session["user_id"])
                balance = round(balance[0]['cash'])
                remaining = balance - sum_req

                if balance < sum_req:
                    return apology("You do not have sufficient funds for this transaction, please try again")

                else:
                    #insert transaction into 'transactions' table
                    db.execute ("UPDATE users SET cash = :cash WHERE id = :id", cash = remaining, id = session["user_id"])
                    db.execute ("INSERT INTO 'transactions' (users_id, symbol, number, price, date, total_cost) VALUES (user, symbol, quantity, price, datetime('now'), total)")

                    #check if stock is already in the 'portfolio' table
                    existing_symbol = db.execute ("SELECT symbol = :symbol, number = :number FROM 'users' WHERE users_id = :id", symbol = symbol, number = number, id = user)
                    #if so add new stock to existing quantity
                    if existing_symbol:
                        db.execute ("UPDATE 'portfolio' SET number = number + :quantity, current_value = :new_value where id = :id", quantity=quantity, new_value = (number +quantity)*price, id=user)

                    #if not insert new record
                    else:
                        db.execute ("INSERT INTO 'portfolio' (users_id, symbol, number, current_value) VALUES (users_id, symbol, number, current_values)")
                    #placeholder for now
                    return render_template("success.html")