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IBM Data Merge Utility - a template based transformation and enrichment engine
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/*
 * 
 * Copyright 2015-2017 IBM
 * 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 com.ibm.util.merge.template.directive.enrich.provider;

import java.net.MalformedURLException;
import java.net.URL;
import java.util.List;

import com.cloudant.client.api.ClientBuilder;
import com.cloudant.client.api.CloudantClient;
import com.cloudant.client.api.Database;
import com.cloudant.client.org.lightcouch.CouchDbException;
import com.ibm.util.merge.Config;
import com.ibm.util.merge.data.DataElement;
import com.ibm.util.merge.data.DataList;
import com.ibm.util.merge.data.parser.DataProxyJson;
import com.ibm.util.merge.exception.Merge500;
import com.ibm.util.merge.exception.MergeException;
import com.ibm.util.merge.template.content.Content;
import com.ibm.util.merge.template.content.TagSegment;
import com.ibm.util.merge.template.directive.Enrich;

/**
 * A Cloudant provider that fetches documents from a Cloudant Database
 * Provide Parameters usage
 * 
 * 		String command - A Cloudant query JSON object, can contain replace tags
 * 		int parseAs - Not Applicable
 * 		
Wrapper wrapper - Wrapper for tags in command
 * 		HashMap<String,String> replace - The Replace HashMap used to process tags in command
 * 		Merger context - Merger managing the merge
 * 
 * Configuration Environment Variables
 * 
 * 		{SourceName}.URL - The database connection URL 
 * 		{SourceName}.USER - The database User ID
 * 		{SourceName}.PW - The database Password
 * 
 *   
 * @author Mike Storey
 */
public class CloudantProvider implements ProviderInterface {
	private static final ProviderMeta meta = new ProviderMeta(
			"Database",
			"The following environment variables are expected: /n"
			+ "{SourceName}.URL - The database connection URL/n"
			+ "{SourceName}.USER - The database User ID/n"
			+ "{SourceName}.PW - The database Password", 
			"A cloudant Query JSON string - Replace Tags are supported and jSon encoded",
			"N/A",
			"This provider always returns a List of Objects");
	
	private transient CloudantClient cloudant = null;
	private transient Database db = null;
	private transient DataProxyJson proxy = new DataProxyJson();
	private transient final String source;
	private transient final String parameter;
	
	/**
	 * Instantiate the provider and get the database connection
	 * @param source The Source environment name
	 * @param parameter The cloudant database name
	 */
	public CloudantProvider(String source, String parameter) {
		this.source = source;
		this.parameter = parameter;
	}
	
	private void connect(Config config) throws MergeException {
		// implements lazy connection
		if (db != null) 	return;
		
		// Get the credentials
		String user = "";
		String pw = "";
		String url = "";
		try {
			url = config.getEnv(source + ".URL");
			user = config.getEnv(source + ".USER");
			pw = config.getEnv(source + ".PW");
		} catch (MergeException e) {
			throw new Merge500("Malformed or Missing Cloudant Source Credentials found for:" + source + ":" + url + ":" + user + ":" + pw);
		}
		
		try {
			// Get the connection
			this.cloudant = ClientBuilder
					.url(new URL(url))
					.username(user)
					.password(pw)
					.gsonBuilder(proxy.getBuilder())
					.build();
			// Get the database object
			db = cloudant.database(parameter, false);
		} catch (CouchDbException e) {
			throw new Merge500("Unable to connect to Cloudant repository:" + url + ":" + user + ":" + pw + ":" + parameter + ":" + e.getMessage());
		} catch (MalformedURLException e) {
			throw new Merge500("Invalid URL for provider :" + source + ":" + parameter + "Message:" + e.getMessage());
		}
		
	}
	
	@Override
	public DataElement provide(Enrich context) throws MergeException {
		connect(context.getConfig());
		Content query = new Content(context.getTemplate().getWrapper(), context.getEnrichCommand(), TagSegment.ENCODE_JSON);
		query.replace(context.getTemplate().getReplaceStack(), false, context.getConfig().getNestLimit());
		
		List results;
		
		results = db.findByIndex(query.getValue(), DataElement.class);
		
		DataList reply = new DataList();
		for (DataElement doc : results) {
			reply.add(doc);
		}
		return reply;
	}
	
	@Override
	public void close() {
		// Nothing to do - I think..... need Cloudant Help
		return;
	}
	
	@Override
	public ProviderMeta getMetaInfo() {
		return CloudantProvider.meta;
	}
	
}