/*
    * Licensed to The Apereo Foundation under one or more contributor license
    * agreements. See the NOTICE file distributed with this work for additional
    * information regarding copyright ownership.
    *
    *
    * The Apereo Foundation licenses this file to you under the Educational
    * Community 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://opensource.org/licenses/ecl2.txt
   *
   * 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 org.opencastproject.urlsigning.utils;
  
  import org.opencastproject.urlsigning.common.Policy;
  
  import org.apache.commons.codec.binary.Base64;
  import org.joda.time.DateTime;
  import org.joda.time.DateTimeZone;
  import org.json.simple.JSONObject;
  import org.json.simple.parser.JSONParser;
  import org.json.simple.parser.ParseException;
  
  import java.nio.charset.StandardCharsets;
  import java.util.Map;
  import java.util.TreeMap;
  
  /**
   * A Utility class to encode / decode Policy files from and to Base 64 and Json.
   */
  public final class PolicyUtils {
    /** The JSON key for object that contains the date and ip conditions for the resource. */
    private static final String CONDITION_KEY = "Condition";
    /** The JSON key for the date and time the resource will become available. */
    private static final String DATE_GREATER_THAN_KEY = "DateGreaterThan";
    /** The JSON key for the date and time the resource will no longer be available. */
    private static final String DATE_LESS_THAN_KEY = "DateLessThan";
    /** The JSON key for the IP address of the acceptable client. */
    private static final String IP_ADDRESS_KEY = "IpAddress";
    /** The JSON key for the base url for the resource. */
    private static final String RESOURCE_KEY = "Resource";
    /** The JSON key for the main object of the policy. */
    private static final String STATEMENT_KEY = "Statement";
  
    private PolicyUtils() {
  
    }
  
    /**
     * Encode a {@link String} into Base 64 encoding
     *
     * @param value
     *          The {@link String} to encode into base 64 encoding
     * @return The {@link String} encoded into base 64.
     */
    public static String base64Encode(String value) {
      return Base64.encodeBase64URLSafeString(value.getBytes());
    }
  
    /**
     * Decode a {@link String} from Base 64 encoding
     *
     * @param value
     *          The {@link String} to encode into Base 64
     * @return The {@link String} decoded from base 64.
     */
    public static String base64Decode(String value) {
      return new String(Base64.decodeBase64(value), StandardCharsets.UTF_8);
    }
  
    /**
     * Get a {@link Policy} from JSON data.
     *
     * @param policyJson
     *          The {@link String} representation of the json.
     * @return A new {@link Policy} object populated from the JSON.
     */
    public static Policy fromJson(String policyJson) {
      JSONObject jsonPolicy = null;
      JSONParser jsonParser = new JSONParser();
      try {
        jsonPolicy = (JSONObject) jsonParser.parse(policyJson);
      } catch (ParseException e) {
        e.printStackTrace();
      }
      JSONObject statement = (JSONObject) jsonPolicy.get(STATEMENT_KEY);
      String resource = statement.get(RESOURCE_KEY).toString();
      JSONObject condition = (JSONObject) statement.get(CONDITION_KEY);
  
      final String lessThanString = condition.get(DATE_LESS_THAN_KEY).toString();
      final DateTime dateLessThan = new DateTime(Long.parseLong(lessThanString), DateTimeZone.UTC);
 
     final DateTime dateGreaterThan;
     Object greaterThanString = condition.get(DATE_GREATER_THAN_KEY);
     if (greaterThanString != null) {
       dateGreaterThan = new DateTime(Long.parseLong(greaterThanString.toString()), DateTimeZone.UTC);
     } else {
       dateGreaterThan = null;
     }
 
     return Policy.mkPolicyValidFromWithIP(resource, dateLessThan, dateGreaterThan,
             (String) condition.get(IP_ADDRESS_KEY));
   }
 
   /**
    * Render a {@link Policy} into JSON.
    *
    * @param policy
    *          The {@link Policy} to render into JSON.
    * @return The {@link JSONObject} representation of the {@link Policy}.
    */
   @SuppressWarnings("unchecked")
   public static JSONObject toJson(Policy policy) {
     JSONObject policyJSON = new JSONObject();
 
     Map<String, Object> conditions = new TreeMap<String, Object>();
     conditions.put(DATE_LESS_THAN_KEY, new Long(policy.getValidUntil().getMillis()));
     if (policy.getValidFrom().isPresent()) {
       conditions.put(DATE_GREATER_THAN_KEY, new Long(policy.getValidFrom().get().getMillis()));
     }
     if (policy.getClientIpAddress().isPresent()) {
       conditions.put(IP_ADDRESS_KEY, policy.getClientIpAddress().get().getHostAddress());
     }
     JSONObject conditionsJSON = new JSONObject();
     conditionsJSON.putAll(conditions);
 
     JSONObject statement = new JSONObject();
     statement.put(RESOURCE_KEY, policy.getResource());
     statement.put(CONDITION_KEY, conditions);
 
     policyJSON.put(STATEMENT_KEY, statement);
 
     return policyJSON;
   }
 
   /**
    * Create a {@link Policy} in Json format and Base 64 encoded.
    *
    * @param encodedPolicy
    *          The String representation of the {@link Policy} in Json format and encoded into Base 64
    * @return The {@link Policy} data
    */
   public static Policy fromBase64EncodedPolicy(String encodedPolicy) {
     String decodedPolicyString = base64Decode(encodedPolicy);
     return fromJson(decodedPolicyString);
   }
 
   /**
    * Create a {@link Policy} in Json format and Base 64 encoded.
    *
    * @param policy
    *          The String representation of the {@link Policy} in Json format and encoded into Base 64
    * @return The {@link Policy} data
    */
   public static String toBase64EncodedPolicy(Policy policy) {
     return base64Encode(PolicyUtils.toJson(policy).toJSONString());
   }
 
   /**
    * Get an encrypted version of a {@link Policy} to use as a signature.
    *
    * @param policy
    *          {@link Policy} that needs to be encrypted.
    * @param encryptionKey
    *          The key to use to encrypt the {@link Policy}.
    * @return An encrypted version of the {@link Policy} that is also Base64 encoded to make it safe to transmit as a
    *         query parameter.
    * @throws Exception
    *           Thrown if there is a problem encrypting or encoding the {@link Policy}
    */
   public static String getPolicySignature(Policy policy, String encryptionKey) throws Exception {
     return SHA256Util.digest(PolicyUtils.toJson(policy).toJSONString(), encryptionKey);
   }
 }