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Core Java client library for ChainTest framework
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package com.aventstack.chaintest.conf;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.io.IOException;
import java.io.InputStream;
import java.util.HashMap;
import java.util.Map;
import java.util.Properties;

/**
 * ChainTest allows you to load externalized configuration from properties files,
 * environment variables and system properties using the following order:
 *
 * 
 *     application.properties
 *     application-test.properties
 *     test.properties
 *     config.properties
 *     chaintest.properties
 *     OS environment variables
 *     System.getProperties()
 * 
 */
public class Configuration {

    private static final Logger log = LoggerFactory.getLogger(Configuration.class);
    private static final String APP_NAME = "chaintest";
    private static final String[] RESOURCES = new String[] {
            "application.properties",
            "application-test.properties",
            "test.properties",
            "config.properties",
            "chaintest.properties"
    };

    private final Map _config = new HashMap<>();

    public String get(final String prop) {
        return _config.get(prop);
    }

    public Map getConfig() {
        return _config;
    }

    public void load() throws IOException {
        log.trace("Starting load externalized configuration");
        for (final String resource : RESOURCES) {
            loadFromClasspathResource(resource);
        }

        System.getenv().forEach((k, v) -> {
            if (k.startsWith(APP_NAME)) {
                log.trace("Adding environment property {} to configuration", k);
                _config.put(k, v);
            }
        });

        loadFromProperties(System.getProperties());
    }

    public void loadFromClasspathResource(final String resource) throws IOException {
        log.trace("Loading configuration from resource {}", resource);
        final Properties properties = new Properties();
        try (final InputStream is = Thread.currentThread().getContextClassLoader().getResourceAsStream(resource)) {
            if (is != null) {
                properties.load(is);
                loadFromProperties(properties);
            }
        }
        log.trace("Configuration entries after loading from resource {}: {}", resource, _config);
    }

    public void loadFromProperties(final Properties properties) {
        properties.forEach((key, value) -> {
            if (key.toString().startsWith(APP_NAME)) {
                _config.put(key.toString(), value.toString());
            }
        });
    }

}