import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileWriter;
import java.io.IOException;
import java.util.List;
import java.util.Scanner;

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() {
        File file = new File(ordersFilePath);
        if (!file.exists()) {
            System.err.println("File not found: " + ordersFilePath);
            return;
        }

        try (Scanner scanner = new Scanner(file)) {

            while (scanner.hasNextLine()) {
                String line = scanner.nextLine();

                if (line.isBlank()) {
                    continue;
                }

                try {
                    String[] parts = line.split(",");

                    if (parts.length != 3) {
                        throw new Exception("Invalid line structure");
                    }

                    int productID = Integer.parseInt(parts[0].trim());
                    int quantity = Integer.parseInt(parts[1].trim());
                    int discountPercent = Integer.parseInt(parts[2].trim());

                    if (productID <= 0 || quantity <= 0 || discountPercent < 0 || discountPercent > 99) {
                        throw new Exception("Values out of logical bounds");
                    }

                    Product matchedProduct = null;
                    for (Product p : productList) {
                        if (p.getProductID() == productID) {
                            matchedProduct = p;
                            break;
                        }
                    }

                    if (matchedProduct == null) {
                        throw new Exception("Product ID does not exist");
                    }

                    double subTotal = quantity * matchedProduct.getPrice();
                    double discountValue = subTotal * discountPercent / 100.0;
                    double finalCost = subTotal - discountValue;

                    totalQuantity += quantity;
                    totalFinalCost += finalCost;
                    totalDiscountValue += discountValue;

                } catch (Exception e) {
                    totalInvalidLines++;
                }
            }
        } catch (FileNotFoundException e) {
            System.err.println("Error opening file: " + e.getMessage());
        }
    }


    public void saveReport() {
        String report = "========= SALES REPORT =========\n" +
                "Total Quantity Sold: " + totalQuantity + "\n" +
                "Total Final Cost: $" + totalFinalCost + "\n" +
                "Total Discount Value: $" + totalDiscountValue + "\n" +
                "Invalid Rows: " + totalInvalidLines + "\n" +
                "================================";

        try {
            FileWriter writer = new FileWriter("report.txt");
            writer.write(report);
            writer.close();
        } catch (IOException e) {
            System.err.println("Error writing the report file");
        }
    }
}