package com.onaro.sanscreen.client.help;

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

import javax.help.HelpSetException;

import org.apache.commons.lang3.StringUtils;
import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;

/**
 * This class provides help context IDs based on a help module
 * @author rnoel
 *
 */
public class HelpContextProvider implements IHelpContextProvider {
    private static final String SANSCREEN_CONTEXT_MAPPING_FILE_PATH = "contexts.properties"; //$NON-NLS-1$

    private static Logger logger = LogManager.getLogger(HelpContextProvider.class);

    /*
     * The help tools that IE uses generate non-human readable IDs.  So we have a separate mapping file that will
     * map our context IDs (human readable, dot notation to establish a hierarchy) to theirs.
     */
    private Properties contextsToTopicIds;
    
    /**
     * Constructor.
     * 
     * @param loader the class loader we'll use to find the help resources
     * @param path the path to the root of the help directory containing the HelpSet
     */
    public HelpContextProvider(ClassLoader loader, String helpPath) throws HelpSetException {
        contextsToTopicIds = new Properties();
        
        // Handle master help set that is located at the root where we don't want to add the
        // "/" to the path.
        String path = (StringUtils.isEmpty(helpPath) ? StringUtils.EMPTY : helpPath + "/"); //$NON-NLS-1$
        String propsFilePath = path +  SANSCREEN_CONTEXT_MAPPING_FILE_PATH;
        InputStream inStream = loader.getResourceAsStream(propsFilePath);
        Exception e = null;
        
        if(inStream == null) {
            throw new HelpSetException("Context mapping file '" + propsFilePath + "' not found."); //$NON-NLS-1$ //$NON-NLS-2$
        }
        try {
            contextsToTopicIds.load(inStream);
        }
        catch(IOException ioe) {
            e = ioe;
        }
        try {
            inStream.close();
        }
        catch(IOException ioe) {}
        
        if(e != null) {
            String message = e.getMessage();
            
            logger.error(message);
            throw new HelpSetException(message);
        }
    }
    
    /**
     * Returns the topic ID associated with the context ID or null if the context ID could not be found or was empty.
     * 
     * @param contextId the context ID
     * @return the topic ID associated with the context ID or null if the context ID could not be found or was empty.
     */
    public String getTopicId(String contextId) {
        String topicId = contextsToTopicIds.getProperty(contextId);
        
        return(StringUtils.isEmpty(topicId) ? null : topicId);
    }
    
    /**
     * Returns the closest topic ID associated with the context ID or null if the context ID could not be found or was empty.
     * 
     * @param contextId the context ID
     * @return the closest topic ID associated with the context ID or null if the context ID could not be found or was empty.
     */
    public String getClosestTopicId(String contextId) {
        while(StringUtils.isNotEmpty(contextId)) {
            String topicId = getTopicId(contextId);
            
            if(topicId != null) {
                return(topicId);
            }
            int dotNdx = contextId.lastIndexOf('.');
            
            // If no more parts to strip off, return null
            if(dotNdx < 0) {
                break;
            }
            // Strip off last part of context and try again
            contextId = contextId.substring(0, dotNdx);
        }
        return(null);
    }
}