import java.io.*;
import java.util.List;

public class ReportGenerator {

    private final String ordersFilePath;
    private final List<Product> productList;

    private double totalFinalCost;
    private int totalQuantity;
    private double totalDiscountValue;
    private int totalInvalidLines;

    public ReportGenerator(String ordersFilePath, List<Product> productList) {
        this.ordersFilePath = ordersFilePath;
        this.productList = productList;
    }

    public void processFile()
    {
        // TODO:
        // 1. Open the order details CSV file
        // 2. Read the file line by line
        // 3. Split each line using comma delimiter
        //      (each line is guaranteed to contain exactly two commas)
        // 4. Each line contains exactly 3 values in the format:
        //      [productId],[quantity],[discountPercent]
        // 5. Attempt to convert values:
        //      - productId -> int
        //      - quantity -> int
        //      - discountPercent -> int
        //    NOTE:
        //      - quantity and discountPercent may contain invalid characters
        //        (e.g., letters instead of numbers).
        //      - If parsing any value fails (NumberFormatException),
        //        the entire line must be considered invalid.
        //      - Use try-catch blocks and exception handling to safely
        //        handle parsing and validation errors without stopping
        //        the processing of the remaining lines.
        // 6. Validate parsed values:
        //      - productId must be greater than 0
        //      - quantity must be greater than 0
        //      - discountPercent must be between 0 and 99 inclusive
        // 7. Look for a Product in productList that matches productId
        // 8. If no Product with that ID exists in the catalog,
        //      the entire line is considered invalid
        // 9. If all values are valid and the product exists, calculate:
        //      subtotal = quantity * product price
        //      discountValue = subtotal * discountPercent / 100
        //      finalCost = subtotal - discountValue
        // 10. Update report totals:
        //      - totalQuantity += quantity
        //      - totalFinalCost += finalCost
        //      - totalDiscountValue += discountValue
        // 11. If any parsing error, validation failure, or missing product occurs:
        //      - increment totalInvalidLines
        //      - skip the line and continue processing the next line
        // 12. Close all file resources



        try (FileReader fileReader = new FileReader(ordersFilePath)) {
            BufferedReader bufferedReader = new BufferedReader(fileReader);
            String line;
            while ((line = bufferedReader.readLine()) != null) {
                String[] fields = line.split(",");
                try {
                    int productId_rd = Integer.parseInt(fields[0]);
                    int quantity_rd = Integer.parseInt(fields[1]);
                    int discountPercent_rd = Integer.parseInt(fields[2]);

                    if ((productId_rd <= 0)||(quantity_rd <= 0)||(discountPercent_rd < 0)||(discountPercent_rd > 99)) {
                        totalInvalidLines++;
                        continue;
                    }

                    boolean isTheId = false;

                    for (Product p : productList) {
                        if (p.getProductID() == productId_rd) {
                            double subtotal = quantity_rd * p.getPrice();
                            double discountValue = subtotal * discountPercent_rd / 100;
                            double finalCost = subtotal - discountValue;
                            totalFinalCost += finalCost;
                            totalQuantity += quantity_rd;
                            totalDiscountValue += discountValue;
                            isTheId = true;
                            break;
                        }
                    }

                    if (!isTheId) {
                        totalInvalidLines++;
                    }
                }
                catch (NumberFormatException e) {
                    totalInvalidLines++;
                }
            }
            bufferedReader.close();
        }
        catch (IOException e) {
            System.out.println("Can't read " + ordersFilePath);
            System.out.println(e.getMessage());
        }


    }

    public void saveReport()
    {
        // TODO:
        // 1. Build a formatted report string
        // 2. Include:
        //      - total quantity
        //      - total final cost
        //      - total discount value
        //      - total invalid lines
        // 3. Create/open output report file (name it report.txt)
        // 4. Write report string into file
        // 5. Handle file writing exceptions
        // 6. Close writer resources

        /* Example Structure
        ========= SALES REPORT =========
        Total Quantity Sold: 42
        Total Final Cost: $1520.75
        Total Discount Value: $230.50
        Invalid Rows: 3
        ================================
        */

        String report_format = "========= SALES REPORT =========\nTotal Quantity Sold: %d\nTotal Final Cost: %.4f\nTotal Discount Value: %.4f\nInvalid Rows: %d\n================================\n";
        String report_str = String.format(report_format, totalQuantity, totalFinalCost, totalDiscountValue, totalInvalidLines);

        try (FileWriter fw = new FileWriter("report.txt", true)) {
            BufferedWriter bw = new BufferedWriter(fw);
            bw.write(report_str);
            bw.close();
        }
        catch (IOException e) {
            System.out.println(e.getMessage());
        }
    }
}