import java.io.BufferedReader;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
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()
    {

        try (BufferedReader reader = new BufferedReader(new FileReader(ordersFilePath)))
        {
            String line;
            while ((line = reader.readLine()) != null)
            {
                String[] parts = line.split(",");
                if (parts.length != 3)
                {
                    totalInvalidLines++;
                    continue;
                }

                try
                {
                    int id = Integer.parseInt(parts[0]);
                    int quantity = Integer.parseInt(parts[1]);
                    int discountPercent = Integer.parseInt(parts[2]);
                    if (id <= 0 || quantity <= 0 || discountPercent < 0 || discountPercent > 99) {
                        totalInvalidLines++;
                        continue;
                    }
                    Product product = findProductById(id);
                    if (product == null)
                    {
                        totalInvalidLines++;
                        continue;
                    }

                    double subtotal = quantity * product.getPrice();
                    double discountValue = subtotal * discountPercent / 100.0;
                    double finalCost = subtotal - discountValue;
                    totalQuantity += quantity;
                    totalFinalCost += finalCost;
                    totalDiscountValue += discountValue;
                }
                catch (NumberFormatException e)
                {
                    totalInvalidLines++;
                }
            }
        }
        catch (IOException e)
        {
            System.err.println("Error reading order file: " + e.getMessage());
        }
    }

    private Product findProductById(int id) {
        for (Product p : productList) {
            if (p.getProductID() == id) {
                return p;
            }
        }
        return null;
    }

    public void saveReport()
    {
        String report = String.format(
                "========= SALES REPORT =========\n" +
                        "Total Quantity Sold: %d\n" +
                        "Total Final Cost: $%.2f\n" +
                        "Total Discount Value: $%.2f\n" +
                        "Invalid Rows: %d\n" +
                        "================================\n",
                totalQuantity,
                totalFinalCost,
                totalDiscountValue,
                totalInvalidLines
        );
        try (FileWriter writer = new FileWriter("report.txt"))
        {
            writer.write(report);
        }
        catch (IOException e)
        {
            System.err.println("Error saving report: " + e.getMessage());
        }
    }
}