package no.finntech.commons.constretto;

import java.util.HashMap;
import java.util.Map;
import java.util.concurrent.locks.ReentrantReadWriteLock;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.constretto.ConstrettoBuilder;
import org.constretto.ConstrettoConfiguration;
import org.springframework.core.io.DefaultResourceLoader;
import org.springframework.core.io.ResourceLoader;

/** Provides cache and convenience methods around ConstrettoConfigurations 
 * It is hardcoded to use Spring's DefaultResourceLoader.
 */
public final class ConstrettoConfigurationFactory {

    // Constants -----------------------------------------------------

    private static final ConstrettoConfigurationFactory INI_FILES
            = new ConstrettoConfigurationFactory(new IniFileConstrettoConfigurationFactory());
    private static final ConstrettoConfigurationFactory PROPERTIES 
            = new ConstrettoConfigurationFactory(new PropertiesConstrettoConfigurationFactory());

    private static final ResourceLoader LOADER = new DefaultResourceLoader();

    private static final Log LOG = LogFactory.getLog(ConstrettoConfigurationFactory.class);

    // Attributes ----------------------------------------------------

    private final Map<String,ConstrettoConfiguration> instances = new HashMap<String,ConstrettoConfiguration>();
    private final ReentrantReadWriteLock instancesLock = new ReentrantReadWriteLock();
    private final ConstrettoBuilderFactory builderFactory;

    // Static --------------------------------------------------------

    public static ConstrettoConfiguration iniFile(final String resource){
        return INI_FILES.configuration(resource);
    }

    public static ConstrettoConfiguration properties(final String resource){
        return PROPERTIES.configuration(resource);
    }

    // Constructors --------------------------------------------------

    private ConstrettoConfigurationFactory(final ConstrettoBuilderFactory builderFactory){
        this.builderFactory = builderFactory;
    }

    // Public --------------------------------------------------------

    // Package protected ---------------------------------------------

    // Protected -----------------------------------------------------

    // Private -------------------------------------------------------

    private ConstrettoConfiguration configuration(final String resource){
        ConstrettoConfiguration configuration = null;
        // Look for existing instances
        try{
            instancesLock.readLock().lock();
            LOG.trace("instances.get(" + resource + ")");
            configuration = instances.get(resource);
        }finally{
            instancesLock.readLock().unlock();
        }
        // construct a new instance
        if (null == configuration) {
            try{
                instancesLock.writeLock().lock();
                LOG.debug("creating configuration for " + resource);
                configuration = builderFactory.createConstrettoBuilder(resource).getConfiguration();
                instances.put(resource, configuration);
            }finally{
                instancesLock.writeLock().unlock();
            }
        }
        return configuration;
    }

    // Inner classes -------------------------------------------------
    
    private interface ConstrettoBuilderFactory{
        ConstrettoBuilder createConstrettoBuilder(String resource);
    }

    private static final class IniFileConstrettoConfigurationFactory implements ConstrettoBuilderFactory{
        @Override
        public ConstrettoBuilder createConstrettoBuilder(final String resource) {
            return new ConstrettoBuilder()
                .createIniFileConfigurationStore()
                .addResource(LOADER.getResource(resource))
                .done();
        }
    }

    private static final class PropertiesConstrettoConfigurationFactory implements ConstrettoBuilderFactory{
        @Override
        public ConstrettoBuilder createConstrettoBuilder(final String resource) {
            return new ConstrettoBuilder()
                .createPropertiesStore()
                .addResource(LOADER.getResource(resource))
                .done();
        }
    }
}