Sales Data Analysis

You are given the content of a CSV file via standard input. The CSV file contains sales records, where each record represents a single transaction. The CSV file is expected to have at least two columns: Product Category and Sales.

Your task is to compute two things:

1. The total sales per product category. In other words, for each unique product category, sum all the sales.
2. The average sales per transaction, which is computed by \(\text{average} = \frac{\text{total sales}}{\text{number of transactions}}\).

If the CSV file does not contain both required columns or if the input is empty, your program should print an appropriate error message.

Note: The input is provided via standard input (stdin) and the output should be printed to standard output (stdout) as a JSON string with the following format:

{
  "total_sales_per_category": { ... },
  "average_sales_per_transaction": value
}

inputFormat

The input is provided via standard input and consists of CSV file content. The first line is the header which should include at least the following columns: Product Category and Sales. Each subsequent line represents a transaction with values separated by commas.

For example:

Product Category,Sales
Electronics,200
Electronics,300
Groceries,100
Groceries,150

outputFormat

If the input is valid, output a JSON string representing a dictionary with two keys:

• total_sales_per_category: an object where each key is a product category and its value is the total sales for that category.
• average_sales_per_transaction: a number representing the average sale per transaction.

If the CSV is missing required columns, or if the input is empty, print the corresponding error message.

## sample

Product Category,Sales
Electronics,200
Electronics,300
Groceries,100
Groceries,150

{"total_sales_per_category": {"Electronics": 500, "Groceries": 250}, "average_sales_per_transaction": 187.5}