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Library that provides client access to the FIT-Connect api-endpoints for sending, subscribing and routing
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package dev.fitko.fitconnect.client.bootstrap;

import dev.fitko.fitconnect.api.config.ApplicationConfig;
import dev.fitko.fitconnect.api.config.defaults.Environments;
import dev.fitko.fitconnect.api.config.Environment;
import dev.fitko.fitconnect.api.config.EnvironmentName;
import dev.fitko.fitconnect.api.exceptions.client.FitConnectInitialisationException;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.yaml.snakeyaml.Yaml;
import org.yaml.snakeyaml.error.YAMLException;
import org.yaml.snakeyaml.introspector.BeanAccess;

import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.InvalidPathException;
import java.nio.file.Path;
import java.util.Map;

public final class ApplicationConfigLoader {

    private static final Logger LOGGER = LoggerFactory.getLogger(ApplicationConfigLoader.class);
    private static final String CONFIG_ENV_KEY_NAME = "FIT_CONNECT_CONFIG";

    private ApplicationConfigLoader() {
    }

    /**
     * Load ApplicationConfig from path.
     *
     * @param configPath path to config file
     * @return ApplicationConfig
     * @throws FitConnectInitialisationException if the config file could not be loaded
     */
    public static ApplicationConfig loadConfigFromPath(final Path configPath) {
        try {
            return loadConfigFromYamlString(Files.readString(configPath));
        } catch (final IOException | YAMLException | NullPointerException e) {
            LOGGER.error("config file could not be loaded from path {}", configPath);
            throw new FitConnectInitialisationException(e.getMessage(), e);
        }
    }

    /**
     * Load ApplicationConfig from FIT_CONNECT_CONFIG environment variable.
     * Make sure this variable is set and points to a config.yaml.
     *
     * @return ApplicationConfig
     * @throws FitConnectInitialisationException if the config file could not be loaded
     */
    public static ApplicationConfig loadConfigFromEnvironment() {
        final Path configPath = getPathFromEnvironment();
        return loadConfigFromPath(configPath);
    }

    /**
     * Load ApplicationConfig from yaml string.
     *
     * @param configYaml string content of the yaml config file
     * @return ApplicationConfig
     */
    public static ApplicationConfig loadConfigFromYamlString(final String configYaml) {
        return mergeConfigEnvironmentsWithSdkDefaults(initNewYaml().loadAs(configYaml, ApplicationConfig.class));
    }

    /**
     * Merge the configured default environments with the config from user.
     *
     * @param config loaded config with user overrides
     * @return application config that contains default environments, overrides of the defaults  user specific environments
     */
    private static ApplicationConfig mergeConfigEnvironmentsWithSdkDefaults(final ApplicationConfig config) {

        final Map sdkEnvironments = Environments.getEnvironmentsAsMap();

        config.getEnvironments().forEach((key, value) -> {
            if (sdkEnvironments.containsKey(key)) {
                sdkEnvironments.put(key, value.merge(sdkEnvironments.get(key)));
            } else {
                sdkEnvironments.put(key, value);
            }
        });

        return config.withEnvironments(sdkEnvironments);
    }

    private static Path getPathFromEnvironment() {
        try {
            return Path.of(System.getenv(CONFIG_ENV_KEY_NAME));
        } catch (final NullPointerException | InvalidPathException e) {
            LOGGER.warn("Environment variable {} could not be loaded", CONFIG_ENV_KEY_NAME);
            throw new FitConnectInitialisationException(e.getMessage(), e);
        }
    }

    private static Yaml initNewYaml() {
        final Yaml yaml = new Yaml();
        yaml.setBeanAccess(BeanAccess.FIELD);
        return yaml;
    }
}