/*
 * Copyright 2008 National Library of Sweden 
 * 
 * Licensed under the Apache License, Version 2.0 (the "License"); 
 * you may not use this file except in compliance with the License. 
 * You may obtain a copy of the License at 
 * 
 * 	http://www.apache.org/licenses/LICENSE-2.0 
 *  
 * Unless required by applicable law or agreed to in writing, software 
 * distributed  under the License is distributed on an "AS IS" BASIS, 
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 
 * See the License for the specific language governing permissions and 
 * limitations under the License.
 */

package se.kb.oai.pmh;

/**
 * Helper class that builds the URL:s that corresponds to the different requests to the 
 * OAI-PMH server.
 * 
 * @author Oskar Grenholm, National Library of Sweden
 */
public class QueryBuilder {

	private enum Verb { Identify, GetRecord, ListIdentifiers, ListMetadataFormats, ListRecords, ListSets }
	
	private static final String VERB = "verb";
	private static final String QUESTION_MARK = "?";
	private static final String AMPERSAND = "&";
	private static final String EQUAL_SIGN = "=";
	
	private static final String IDENTIFIER = "identifier";
	private static final String METADATA_PREFIX = "metadataPrefix";
	private static final String FROM = "from";
	private static final String UNTIL = "until";
	private static final String SET = "set";
	private static final String RESUMPTION_TOKEN = "resumptionToken";
	
	private String basesurl;
	private String extendedBasesurl;
	
	/**
	 * Creates a <code>QueryBuilder</code> for a specific OAI-PMH server.
	 * 
	 * @param baseurl the base URL to the OAI-PMH server
	 */
	public QueryBuilder(String baseurl) {
		this.basesurl = baseurl;
		this.extendedBasesurl = baseurl + QUESTION_MARK + VERB + EQUAL_SIGN;
	}
	
	/**
	 * Get the base URL.
	 * 
	 * @return the base URL
	 */
	public String getBaseUrl() {
		return basesurl;
	}

	/**
	 * Build the query for a <code>GetRecord</code> request.
	 * 
	 * @param identifier the identifier
	 * @param metadataPrefix the metadata prefix
	 * 
	 * @return the full query URL as a <code>String</code>
	 */
	public String buildGetRecordQuery(String identifier, String metadataPrefix) {
		StringBuffer buffer = new StringBuffer(extendedBasesurl);
		buffer.append(Verb.GetRecord);
		buffer.append(AMPERSAND).append(IDENTIFIER).append(EQUAL_SIGN).append(identifier);
		buffer.append(AMPERSAND).append(METADATA_PREFIX).append(EQUAL_SIGN).append(metadataPrefix);
		return buffer.toString();
	}
	
	/**
	 * Build the query for a <code>Identify</code> request.
	 * 
	 * @return the full query URL as a <code>String</code>
	 */
	public String buildIdentifyQuery() {
		StringBuffer buffer = new StringBuffer(extendedBasesurl);
		buffer.append(Verb.Identify);
		return buffer.toString();
	}
	
	/**
	 * Build the query for a <code>ListIdentifiers</code> request.
	 * 
	 * @param metadataPrefix which metadata format
     * @param from a start date, optional (may be <code>null</code>)
     * @param until a stop date, optional (may be <code>null</code>)
     * @param set a specific set, optional (may be <code>null</code>)
     * 
	 * @return the full query URL as a <code>String</code>
	 */
	public String buildListIdentifiersQuery(String metadataPrefix, String from, String until, String set) {
		StringBuffer buffer = new StringBuffer(extendedBasesurl);
		buffer.append(Verb.ListIdentifiers);
		buffer.append(AMPERSAND).append(METADATA_PREFIX).append(EQUAL_SIGN).append(metadataPrefix);
		if (from != null)
			buffer.append(AMPERSAND).append(FROM).append(EQUAL_SIGN).append(from);
		if (until != null)
			buffer.append(AMPERSAND).append(UNTIL).append(EQUAL_SIGN).append(until);
		if (set != null)
			buffer.append(AMPERSAND).append(SET).append(EQUAL_SIGN).append(set);
		return buffer.toString();
	}
	
	/**
	 * Build the query for an additional <code>ListIdentifiers</code> request 
	 * with a <code>ResumptionToken</code>. 
	 * 
	 * @param token a resumption token returned from a previous request
	 * @return the full query URL as a <code>String</code>
	 */
	public String buildListIdentifiersQuery(ResumptionToken token) {
		StringBuffer buffer = new StringBuffer(extendedBasesurl);
		buffer.append(Verb.ListIdentifiers);
		buffer.append(AMPERSAND).append(RESUMPTION_TOKEN).append(EQUAL_SIGN).append(token.getId());
		return buffer.toString();
	}
	
	/**
	 * Build the query for a <code>ListMetadtaFormats</code> request.
	 * 
	 * @param identifier the id, optional (may be <code>null</code>)
	 * 
	 * @return the full query URL as a <code>String</code>
	 */
	public String buildListMetadataFormatsQuery(String identifier) {
		StringBuffer buffer = new StringBuffer(extendedBasesurl);
		buffer.append(Verb.ListMetadataFormats);
		if (identifier != null)
			buffer.append(AMPERSAND).append(IDENTIFIER).append(EQUAL_SIGN).append(identifier);
		return buffer.toString();
	}
	
	/**
	 * Build the query for a <code>ListRecords</code> request.
	 * 
	 * @param metadataPrefix which metadata format
     * @param from a start date, optional (may be <code>null</code>)
     * @param until a stop date, optional (may be <code>null</code>)
     * @param set a specific set, optional (may be <code>null</code>)
	 * 
	 * @return the full query URL as a <code>String</code>
	 */
	public String buildListRecordsQuery(String metadataPrefix, String from, String until, String set) {
		StringBuffer buffer = new StringBuffer(extendedBasesurl);
		buffer.append(Verb.ListRecords);
		buffer.append(AMPERSAND).append(METADATA_PREFIX).append(EQUAL_SIGN).append(metadataPrefix);
		if (from != null)
			buffer.append(AMPERSAND).append(FROM).append(EQUAL_SIGN).append(from);
		if (until != null)
			buffer.append(AMPERSAND).append(UNTIL).append(EQUAL_SIGN).append(until);
		if (set != null)
			buffer.append(AMPERSAND).append(SET).append(EQUAL_SIGN).append(set);
		return buffer.toString();
	}
	
	/**
	 * Build the query for an additional <code>ListRecords</code> request 
	 * with a <code>ResumptionToken</code>. 
	 * 
	 * @param token a resumption token returned from a previous request
	 * @return the full query URL as a <code>String</code>
	 */
	public String buildListRecordsQuery(ResumptionToken token) {
		StringBuffer buffer = new StringBuffer(extendedBasesurl);
		buffer.append(Verb.ListRecords);
		buffer.append(AMPERSAND).append(RESUMPTION_TOKEN).append(EQUAL_SIGN).append(token.getId());
		return buffer.toString();
	}
	
	/**
	 * Build the query for a <code>ListSets</code> request.
	 * 
	 * @return the full query URL as a <code>String</code>
	 */
	public String buildListSetsQuery() {
		StringBuffer buffer = new StringBuffer(extendedBasesurl);
		buffer.append(Verb.ListSets);
		return buffer.toString();
	}
	
	/**
	 * Build the query for an additional <code>ListSets</code> request 
	 * with a <code>ResumptionToken</code>. 
	 * 
	 * @param token a resumption token returned from a previous request
	 * @return the full query URL as a <code>String</code>
	 */
	public String buildListSetsQuery(ResumptionToken token) {
		StringBuffer buffer = new StringBuffer(extendedBasesurl);
		buffer.append(Verb.ListSets);
		buffer.append(AMPERSAND).append(RESUMPTION_TOKEN).append(EQUAL_SIGN).append(token.getId());
		return buffer.toString();
	}
}