/* ***** BEGIN LICENSE BLOCK *****
 * Version: MPL 1.1/GPL 2.0/LGPL 2.1
 *
 * The contents of this file are subject to the Mozilla Public License Version
 * 1.1 (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.mozilla.org/MPL/
 *
 * Software distributed under the License is distributed on an "AS IS" basis,
 * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
 * for the specific language governing rights and limitations under the
 * License.
 *
 * The Original Code is Android Sync Client.
 *
 * The Initial Developer of the Original Code is
 * the Mozilla Foundation.
 * Portions created by the Initial Developer are Copyright (C) 2011
 * the Initial Developer. All Rights Reserved.
 *
 * Contributor(s):
 *  Richard Newman <rnewman@mozilla.com>
 *
 * Alternatively, the contents of this file may be used under the terms of
 * either the GNU General Public License Version 2 or later (the "GPL"), or
 * the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
 * in which case the provisions of the GPL or the LGPL are applicable instead
 * of those above. If you wish to allow use of your version of this file only
 * under the terms of either the GPL or the LGPL, and not to allow others to
 * use your version of this file under the terms of the MPL, indicate your
 * decision by deleting the provisions above and replace them with the notice
 * and other provisions required by the GPL or the LGPL. If you do not delete
 * the provisions above, a recipient may use your version of this file under
 * the terms of any one of the MPL, the GPL or the LGPL.
 *
 * ***** END LICENSE BLOCK ***** */

package org.mozilla.gecko.sync;

import java.io.IOException;
import java.io.UnsupportedEncodingException;

import org.json.simple.JSONObject;
import org.json.simple.parser.JSONParser;
import org.json.simple.parser.ParseException;
import org.mozilla.apache.commons.codec.binary.Base64;
import org.mozilla.gecko.sync.crypto.CryptoException;
import org.mozilla.gecko.sync.crypto.CryptoInfo;
import org.mozilla.gecko.sync.crypto.Cryptographer;
import org.mozilla.gecko.sync.crypto.KeyBundle;
import org.mozilla.gecko.sync.crypto.MissingCryptoInputException;
import org.mozilla.gecko.sync.crypto.NoKeyBundleException;
import org.mozilla.gecko.sync.repositories.domain.Record;

/**
 * A Sync crypto record has:
 *
 * * a collection of fields which are not encrypted (id and collection)
 * * a set of metadata fields (index, modified, ttl)
 * * a payload, which is encrypted and decrypted on request.
 *
 * The payload flips between being a blob of JSON with hmac/IV/ciphertext
 * attributes and the cleartext itself.
 *
 * Until there's some benefit to the abstraction, we're simply going to
 * call this CryptoRecord.
 *
 * @author rnewman
 *
 */
public class CryptoRecord extends Record {

  // JSON related constants.
  private static final String KEY_ID         = "id";
  private static final String KEY_COLLECTION = "collection";
  private static final String KEY_PAYLOAD    = "payload";
  private static final String KEY_MODIFIED   = "modified";
  private static final String KEY_SORTINDEX  = "sortindex";
  private static final String KEY_CIPHERTEXT = "ciphertext";
  private static final String KEY_HMAC       = "hmac";
  private static final String KEY_IV         = "IV";

  /**
   * Helper method for doing actual decryption.
   *
   * Input: JSONObject containing a valid payload (cipherText, IV, HMAC),
   * KeyBundle with keys for decryption. Output: byte[] clearText
   * @throws CryptoException
   * @throws UnsupportedEncodingException
   */
  private static byte[] decryptPayload(ExtendedJSONObject payload, KeyBundle keybundle) throws CryptoException, UnsupportedEncodingException {
    byte[] ciphertext = Base64.decodeBase64(((String) payload.get(KEY_CIPHERTEXT)).getBytes("UTF-8"));
    byte[] iv         = Base64.decodeBase64(((String) payload.get(KEY_IV)).getBytes("UTF-8"));
    byte[] hmac       = Utils.hex2Byte((String) payload.get(KEY_HMAC));
    return Cryptographer.decrypt(new CryptoInfo(ciphertext, iv, hmac, keybundle));
  }

  // The encrypted JSON body object.
  // The decrypted JSON body object. Fields are copied from `body`.

  public ExtendedJSONObject payload;
  public KeyBundle   keyBundle;

  /**
   * Don't forget to set cleartext or body!
   */
  public CryptoRecord() {
    super(null, null, 0, false);
  }

  public CryptoRecord(ExtendedJSONObject payload) {
    super(null, null, 0, false);
    if (payload == null) {
      throw new IllegalArgumentException(
          "No payload provided to CryptoRecord constructor.");
    }
    this.payload = payload;
  }

  public CryptoRecord(String jsonString) throws IOException, ParseException, NonObjectJSONException {
    this(ExtendedJSONObject.parseJSONObject(jsonString));
  }

  /**
   * Create a new CryptoRecord with the same metadata as an existing record.
   *
   * @param source
   */
  public CryptoRecord(Record source) {
    super(source.guid, source.collection, source.lastModified, source.deleted);
  }

  /**
   * Take a whole record as JSON -- i.e., something like
   *
   *   {"payload": "{...}", "id":"foobarbaz"}
   *
   * and turn it into a CryptoRecord object.
   *
   * @param jsonRecord
   * @return
   * @throws NonObjectJSONException
   * @throws ParseException
   * @throws IOException
   */
  public static CryptoRecord fromJSONRecord(String jsonRecord)
      throws ParseException, NonObjectJSONException, IOException {
    byte[] bytes = jsonRecord.getBytes("UTF-8");
    ExtendedJSONObject object = CryptoRecord.parseUTF8AsJSONObject(bytes);

    return CryptoRecord.fromJSONRecord(object);
  }

  // TODO: defensive programming.
  public static CryptoRecord fromJSONRecord(ExtendedJSONObject jsonRecord)
      throws IOException, ParseException, NonObjectJSONException {
    String id                  = (String) jsonRecord.get(KEY_ID);
    String collection          = (String) jsonRecord.get(KEY_COLLECTION);
    ExtendedJSONObject payload = jsonRecord.getJSONObject(KEY_PAYLOAD);
    CryptoRecord record = new CryptoRecord(payload);
    record.guid         = id;
    record.collection   = collection;
    if (jsonRecord.containsKey(KEY_MODIFIED)) {
      record.lastModified = jsonRecord.getTimestamp(KEY_MODIFIED);
    }
    if (jsonRecord.containsKey(KEY_SORTINDEX )) {
      record.sortIndex = jsonRecord.getLong(KEY_SORTINDEX);
    }
    // TODO: deleted?
    return record;
  }

  public void setKeyBundle(KeyBundle bundle) {
    this.keyBundle = bundle;
  }

  private static ExtendedJSONObject parseUTF8AsJSONObject(byte[] in)
      throws UnsupportedEncodingException, ParseException, NonObjectJSONException {
    Object obj = new JSONParser().parse(new String(in, "UTF-8"));
    if (obj instanceof JSONObject) {
      return new ExtendedJSONObject((JSONObject) obj);
    } else {
      throw new NonObjectJSONException(obj);
    }
  }

  public CryptoRecord decrypt() throws CryptoException, IOException, ParseException,
                       NonObjectJSONException {
    if (keyBundle == null) {
      throw new NoKeyBundleException();
    }

    // Check that payload contains all pieces for crypto.
    if (!payload.containsKey(KEY_CIPHERTEXT) ||
        !payload.containsKey(KEY_IV) ||
        !payload.containsKey(KEY_HMAC)) {
      throw new MissingCryptoInputException();
    }

    // There's no difference between handling the crypto/keys object and
    // anything else; we just get this.keyBundle from a different source.
    byte[] cleartext = decryptPayload(payload, keyBundle);
    payload = CryptoRecord.parseUTF8AsJSONObject(cleartext);
    return this;
  }

  public CryptoRecord encrypt() throws CryptoException, UnsupportedEncodingException {
    if (this.keyBundle == null) {
      throw new NoKeyBundleException();
    }
    String cleartext = payload.toJSONString();
    byte[] cleartextBytes = cleartext.getBytes("UTF-8");
    CryptoInfo info = new CryptoInfo(cleartextBytes, keyBundle);
    Cryptographer.encrypt(info);
    String message = new String(Base64.encodeBase64(info.getMessage()));
    String iv      = new String(Base64.encodeBase64(info.getIV()));
    String hmac    = Utils.byte2hex(info.getHMAC());
    ExtendedJSONObject ciphertext = new ExtendedJSONObject();
    ciphertext.put(KEY_CIPHERTEXT, message);
    ciphertext.put(KEY_HMAC, hmac);
    ciphertext.put(KEY_IV, iv);
    this.payload = ciphertext;
    return this;
  }

  @Override
  public void initFromPayload(CryptoRecord payload) {
    throw new IllegalStateException("Can't do this with a CryptoRecord.");
  }

  @Override
  public CryptoRecord getPayload() {
    throw new IllegalStateException("Can't do this with a CryptoRecord.");
  }

  // TODO: this only works with encrypted object, and has other limitations.
  public JSONObject toJSONObject() {
    ExtendedJSONObject o = new ExtendedJSONObject();
    o.put(KEY_PAYLOAD, payload.toJSONString());
    o.put(KEY_ID,      this.guid);
    return o.object;
  }

  @Override
  public String toJSONString() {
    return toJSONObject().toJSONString();
  }
}