package org.simantics.scl.reflection;

import java.net.URL;
import java.util.Collection;
import java.util.HashMap;
import java.util.Map;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

import org.eclipse.core.internal.runtime.PlatformActivator;
import org.osgi.framework.Bundle;
import org.osgi.framework.Version;

public class OntologyVersions {

	private static final boolean PRINT = false;
	
	private static OntologyVersions INSTANCE;
	
	private final Pattern versionExtractPattern = Pattern.compile("^.*-(\\d+\\.\\d+)");

	private Map<String, String> unversionedToCurrent = new HashMap<String, String>();
	private Map<String, String> currentToUnversioned = new HashMap<String, String>();
	final private Pattern unversionedPattern;
	final private Pattern currentPattern;
	
	private OntologyVersions() {

		Map<String, Version> versions = new HashMap<String, Version>(); 
		
		if(PRINT) System.err.println("== Ontology report ==");
    	for(Bundle bundle : PlatformActivator.getContext().getBundles()) {
    		
    		URL url = bundle.getEntry("graph.tg");
    		if (url==null) continue;
    		try {
    			String name = (String) bundle.getHeaders().get("Bundle-Name");
    			Version osgiVersion = bundle.getVersion();
    			Version previous = versions.get(name);
    			if(previous == null || osgiVersion.compareTo(previous) > 0) versions.put(name, osgiVersion);
    			if(PRINT) System.err.println("found: " + name + ":" + osgiVersion);
    		} finally {
    		}
    		
    	}
    	
    	for(Map.Entry<String, Version> entry : versions.entrySet()) {
			int minor = entry.getValue().getMinor();
			int major = entry.getValue().getMajor();
			String unversioned = entry.getKey() + "-0.0";
			String versioned = entry.getKey() + "-" + major + "." + minor;
			unversionedToCurrent.put(unversioned, versioned);
			currentToUnversioned.put(versioned, unversioned);
			if(PRINT) System.err.println("latest: " + versioned);
    	}
    	
		if(PRINT) System.err.println("== Ontology report ends ==");
    	
    	unversionedPattern = Pattern.compile("(" + joinKeys(unversionedToCurrent) + ")");
    	currentPattern = Pattern.compile("(" + joinKeys(currentToUnversioned) + ")");
		
	}
	
	public static OntologyVersions getInstance() {
		if(INSTANCE == null) {
			INSTANCE = new OntologyVersions();
		}
		return INSTANCE;
	}

    private String joinKeys(Map<String,String> tokens) {
    	Collection<String> keys = tokens.keySet();
    	StringBuilder b = new StringBuilder();
    	boolean first = true;
    	for(String key : keys) {
    		if(!first) b.append("|");
    		first = false;
    		b.append(key);
    	}
    	return b.toString();
    }
    
    /*
     * Replaces all references to URIs with unversioned ontologies with current versions
     * e.g. http://www.simantics.org/Layer0-0.0 => http://www.simantics.org/Layer0-1.0
     * 
     * @param text Any string
     */
    public String currentVersion(String text) {
    	
    	Matcher matcher = unversionedPattern.matcher(text);

    	StringBuffer sb = new StringBuffer(text.length());
    	while(matcher.find()) {
    	    matcher.appendReplacement(sb, unversionedToCurrent.get(matcher.group(1)));
    	}
    	matcher.appendTail(sb);
    	return sb.toString();

    }
    
    /*
     * Replaces all references to URIs from current ontologies with unversioned ones
     * e.g. http://www.simantics.org/Layer0-1.0 => http://www.simantics.org/Layer0-0.0
     * 
     * @param text Any string
     */
    public String unversioned(String text) {
    	
    	Matcher matcher = currentPattern.matcher(text);

    	StringBuffer sb = new StringBuffer(text.length());
    	while(matcher.find()) {
    	    matcher.appendReplacement(sb, currentToUnversioned.get(matcher.group(1)));
    	}
    	matcher.appendTail(sb);
    	return sb.toString();

    }

    /**
     * Calculates the current version of the specified version-agnostic URI and
     * returns only the version part.
     * e.g. http://www.simantics.org/Layer0-0.0 => 1.1
     * 
     * @param text Any string
     */
    public String currentOntologyVersion(String ontologyURI) {
        String versionedURI = currentVersion(ontologyURI);
        Matcher m = versionExtractPattern.matcher(versionedURI);
        if (!m.matches())
            throw new IllegalArgumentException("Cannot extract version from ontology URI '" + ontologyURI + "' with pattern " + versionExtractPattern.pattern());
        return m.group(1);
    }
    
}