/*
 * Copyright @ 2013 CurisTEC, S.A.S. All Rights Reserved.
 */
package net.curisit.securis.utils;

import java.io.IOException;
import java.io.InputStream;
import java.text.MessageFormat;
import java.util.ArrayList;
import java.util.List;
import java.util.Properties;

import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;

/**
 * Config
 * <p>
 * Class that loads and serves global config parameters from a classpath properties file
 * and, as a fallback, from environment variables.
 *
 * Initialization:
 *  - Static initializer loads {@link #KEY_CONFIG_FILE} from classpath (fails hard if missing).
 *
 * Accessors:
 *  - {@link #get(String)} / {@link #get(String, String)}
 *  - Integer variants: {@link #getInt(String)} / {@link #getInt(String, int)}
 *  - Namespaced helpers: by prefix/domain, and sequential lists via {@link #getListByPrefix(String)}.
 *
 * Thread-safety: static-only utility; internal state is read-only after init.
 * 
 * @author JRA
 * Last reviewed by JRA on Oct 5, 2025.
 */
public class Config {

    private static final Logger LOG = LogManager.getLogger(Config.class);

    /**
     * Resource path of the application properties file (in classpath).
     * E.g. "/securis-server.properties".
     */
    public static final String KEY_CONFIG_FILE = "/securis-server.properties";

    private static Properties params = null;

    static {
        try {
            loadParameters(KEY_CONFIG_FILE);
        } catch (IOException e) {
            LOG.error("Config file {} was not found in classpath", KEY_CONFIG_FILE);
            System.exit(-2);
        }
    }

    /**
     * loadParameters
     * <p>
     * Loads application global parameters from a classpath resource.
     *
     * @param resource Classpath location (e.g. "/resource/cp-securis.conf").
     * @throws IOException If the resource cannot be found or read.
     */
    public static void loadParameters(String resource) throws IOException {

        LOG.debug("Loading params from " + resource);
        InputStream fileis = Params.class.getResourceAsStream(resource);

        params = new Properties();
        try {
            params.load(fileis);
            LOG.debug("Params loaded OK from {}", resource);
        } catch (IOException e) {
            LOG.error("Error loading config file: " + e);
            params = null;
            throw e;
        }
    }

    /**
     * getByDomain
     * <p>
     * Convenience accessor for domain-suffixed parameters (param.domain).
     *
     * @param domain     Domain suffix.
     * @param paramname  Base parameter name.
     * @return String value or null if not present.
     */
    public static String getByDomain(String domain, String paramname) {
        return getByDomain(domain, paramname, null);
    }

    /**
     * getByPrefix
     * <p>
     * Returns parameter value from "{prefix}.{param}" or falls back to the plain "{param}".
     *
     * @param prefix    Namespace prefix.
     * @param paramname Parameter name.
     * @return Resolved value or null.
     */
    public static String getByPrefix(String prefix, String paramname) {
        return get(prefix + "." + paramname, get(paramname));
    }

    /**
     * getByPrefix
     * <p>
     * Returns parameter value from "{prefix}.{param}" or provided default (which itself
     * falls back to "{param}" or its default).
     *
     * @param prefix     Namespace prefix.
     * @param paramname  Parameter name.
     * @param defaultVal Default value if none resolved.
     * @return Resolved value.
     */
    public static String getByPrefix(String prefix, String paramname, String defaultVal) {
        return get(prefix + "." + paramname, get(paramname, defaultVal));
    }

    /**
     * getByDomain
     * <p>
     * Returns value from "{param}.{domain}" or provided default.
     *
     * @param domain     domain suffix.
     * @param paramname  base name.
     * @param defaultval fallback if not found.
     * @return resolved string.
     */
    public static String getByDomain(String domain, String paramname, String defaultval) {
        return get(paramname + "." + domain, defaultval);
    }

    /**
     * getIntByDomain
     * <p>
     * Integer variant of {@link #getByDomain(String, String)} with fallback to plain param.
     */
    public static int getIntByDomain(String domain, String paramname) {
        return getInt(paramname + "." + domain, getInt(paramname));
    }

    /**
     * getIntByDomain
     * <p>
     * Integer variant returning provided default when missing.
     */
    public static int getIntByDomain(String domain, String paramname, int defaultval) {
        return getInt(paramname + "." + domain, defaultval);
    }

    /**
     * getListByPrefix
     * <p>
     * Reads sequential properties using numeric suffixes starting from 0 and stops on first gap.
     * Example:
     *  securis.sort.comparator.0=...
     *  securis.sort.comparator.1=...
     *  ...
     *
     * @param prefix Base prefix (e.g. "securis.sort.comparator").
     * @return Ordered list of values until first missing index.
     */
    public static List<String> getListByPrefix(String prefix) {
        List<String> list = new ArrayList<String>();
        String tpl = prefix + ".{0}";
        int i = 0;
        String value = get(MessageFormat.format(tpl, i++));
        while (value != null) {
            list.add(value);
            value = get(MessageFormat.format(tpl, i++));
        }
        return list;
    }

    /**
     * get
     * <p>
     * Get a parameter value from the loaded properties or environment variables.
     *
     * @param paramname Parameter key.
     * @return Value or null if not found anywhere.
     */
    public static String get(String paramname) {

        assert (params != null) : "Parameters have not been loaded. Call method loadParameters(resource) before use Params.";

        String value = params.getProperty(paramname);
        if (value == null)
            value = System.getenv(paramname);
        return value;
    }

    /**
     * get
     * <p>
     * Returns parameter value or default if missing.
     *
     * @param paramname Key.
     * @param defaultval Default fallback.
     * @return value or default.
     */
    public static String get(String paramname, String defaultval) {
        String value = get(paramname);
        return (value == null ? defaultval : value);
    }

    /**
     * getInt
     * <p>
     * Integer accessor, returns -1 if missing.
     *
     * @param paramname Key.
     * @return Parsed integer or -1.
     */
    public static int getInt(String paramname) {
        String value = get(paramname);
        return (value == null ? -1 : Integer.parseInt(value));
    }

    /**
     * getInt
     * <p>
     * Integer accessor, returns provided default when missing.
     *
     * @param paramname Key.
     * @param defaultval Default fallback.
     * @return Parsed integer or default.
     */
    public static int getInt(String paramname, int defaultval) {
        String value = get(paramname);
        return (value == null ? defaultval : Integer.parseInt(value));
    }

    /**
     * KEYS
     * <p>
     * Strongly-typed keys used across the application.
     */
    public static class KEYS {

        public static final String SERVER_HOSTNAME = "license.server.hostname";

        public static final String SERVER_PORT = "license.server.port";
        public static final String SERVER_SSL_PORT = "license.server.ssl.port";

        public static final String KEYSTORE_PATH = "ssl.keystore.path";
        public static final String KEYSTORE_TYPE = "ssl.keystore.type";
        public static final String KEYSTORE_PASSWORD = "ssl.keystore.password";
        public static final String KEYSTORE_ALIAS = "ssl.keystore.alias";

        public static final String MAILGUN_DOMAIN = "mailgun.domain";
        public static final String MAILGUN_API_KEY = "mailgun.api.key";
        public static final String EMAIL_FROM_ADDRESS = "email.from.address";
        public static final String EMAIL_LIC_DEFAULT_SUBJECT = "email.lic.default.subject";
    }
}