import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.nio.charset.StandardCharsets;

public class ConfigReader {

    public static DownloadConfig readConfig(String fileName) {
        InputStream inputStream = ConfigReader.class.getClassLoader().getResourceAsStream(fileName);

        if (inputStream == null) {
            throw new IllegalArgumentException("Config file not found in resources: " + fileName);
        }

        String configFileName = null;
        int totalSizeMB = 0;
        int chunkCount = 0;
        int minStepDelayMs = 0;
        int maxStepDelayMs = 0;
        double minStepDownloadMB = 0;
        double maxStepDownloadMB = 0;

        try (BufferedReader reader = new BufferedReader(
                new InputStreamReader(inputStream, StandardCharsets.UTF_8))) {

            String line;
            while ((line = reader.readLine()) != null) {
                line = line.trim();

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

                String[] parts = line.split("=", 2);
                if (parts.length != 2) {
                    continue;
                }

                String key = parts[0].trim();
                String value = parts[1].trim();

                switch (key) {
                    case "fileName":
                        configFileName = value;
                        break;
                    case "totalSizeMB":
                        totalSizeMB = Integer.parseInt(value);
                        break;
                    case "chunkCount":
                        chunkCount = Integer.parseInt(value);
                        break;
                    case "minStepDelayMs":
                        minStepDelayMs = Integer.parseInt(value);
                        break;
                    case "maxStepDelayMs":
                        maxStepDelayMs = Integer.parseInt(value);
                        break;
                    case "minStepDownloadMB":
                        minStepDownloadMB = Double.parseDouble(value);
                        break;
                    case "maxStepDownloadMB":
                        maxStepDownloadMB = Double.parseDouble(value);
                        break;
                    default:
                        // Ignore unknown keys to keep parsing simple
                        break;
                }
            }

        } catch (IOException e) {
            throw new RuntimeException("Error reading config file: " + fileName, e);
        }

        return new DownloadConfig(
                configFileName,
                totalSizeMB,
                chunkCount,
                minStepDelayMs,
                maxStepDelayMs,
                minStepDownloadMB,
                maxStepDownloadMB
        );
    }
}