'use strict';

////////////////////////////////////////////////////////////////////////////////
/// @brief Replication management
///
/// @file
///
/// DISCLAIMER
///
/// Copyright 2012 triagens GmbH, Cologne, Germany
///
/// 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.
///
/// Copyright holder is triAGENS GmbH, Cologne, Germany
///
/// @author Jan Steemann
/// @author Copyright 2013, triAGENS GmbH, Cologne, Germany
////////////////////////////////////////////////////////////////////////////////

var internal = require("internal");
var endpointToURL = require("@arangodb/cluster/planner").endpointToURL;
var request = require("@arangodb/request").request;

var logger  = { };
var applier = { };

////////////////////////////////////////////////////////////////////////////////
/// @brief return the replication logger state
////////////////////////////////////////////////////////////////////////////////

logger.state = function () {
  return internal.getStateReplicationLogger();
};

////////////////////////////////////////////////////////////////////////////////
/// @brief return the tick ranges provided by the replication logger 
////////////////////////////////////////////////////////////////////////////////

logger.tickRanges = function () {
  return internal.tickRangesReplicationLogger();
};

////////////////////////////////////////////////////////////////////////////////
/// @brief return the first tick that can be provided by the replication logger
////////////////////////////////////////////////////////////////////////////////

logger.firstTick = function () {
  return internal.firstTickReplicationLogger();
};

////////////////////////////////////////////////////////////////////////////////
/// @brief starts the replication applier
////////////////////////////////////////////////////////////////////////////////

applier.start = function (initialTick, barrierId) {
  if (initialTick === undefined) {
    return internal.startReplicationApplier();
  }

  return internal.startReplicationApplier(initialTick, barrierId);
};

////////////////////////////////////////////////////////////////////////////////
/// @brief shuts down the replication applier
////////////////////////////////////////////////////////////////////////////////

applier.shutdown = applier.stop = function () {
  return internal.shutdownReplicationApplier();
};

////////////////////////////////////////////////////////////////////////////////
/// @brief return the replication applier state
////////////////////////////////////////////////////////////////////////////////

applier.state = function () {
  return internal.getStateReplicationApplier();
};

////////////////////////////////////////////////////////////////////////////////
/// @brief stop the applier and "forget" all configuration
////////////////////////////////////////////////////////////////////////////////

applier.forget = function () {
  return internal.forgetStateReplicationApplier();
};

////////////////////////////////////////////////////////////////////////////////
/// @brief returns the configuration of the replication applier
////////////////////////////////////////////////////////////////////////////////

applier.properties = function (config) {
  if (config === undefined) {
    return internal.configureReplicationApplier();
  }

  return internal.configureReplicationApplier(config);
};

////////////////////////////////////////////////////////////////////////////////
/// @brief performs a one-time synchronization with a remote endpoint
////////////////////////////////////////////////////////////////////////////////

function sync (config) {
  return internal.synchronizeReplication(config);
}

////////////////////////////////////////////////////////////////////////////////
/// @brief performs a one-time synchronization with a remote endpoint
////////////////////////////////////////////////////////////////////////////////

function syncCollection (collection, config) {
  config = config || { };
  config.restrictType = "include";
  config.restrictCollections = [ collection ];
  config.includeSystem = true;
  if (! config.hasOwnProperty('verbose')) {
    config.verbose = false;
  }

  return internal.synchronizeReplication(config);
}

////////////////////////////////////////////////////////////////////////////////
/// @brief sets up the replication (all-in-one function for initial
/// synchronization and continuous replication)
////////////////////////////////////////////////////////////////////////////////

function setupReplication (config) {
  config = config || { };
  if (! config.hasOwnProperty('autoStart')) {
    config.autoStart = true;
  }
  if (! config.hasOwnProperty('includeSystem')) {
    config.includeSystem = true;
  }
  if (! config.hasOwnProperty('verbose')) {
    config.verbose = false;
  }
  config.keepBarrier = true;

  try {
    // stop previous instance
    applier.stop();
  }
  catch (err) {
  }
  // remove existing configuration
  applier.forget();

  // run initial sync
  var result = internal.synchronizeReplication(config);

  // store applier configuration
  applier.properties(config);

  applier.start(result.lastLogTick, result.barrierId);
  return applier.state();
}

////////////////////////////////////////////////////////////////////////////////
/// @brief returns the server's id
////////////////////////////////////////////////////////////////////////////////

function serverId () {
  return internal.serverId();
}

////////////////////////////////////////////////////////////////////////////////
/// @brief finishes off a synchronization of a single collection
/// `collection` is the name of a collection on the other server that should
/// have been synchronized using syncCollection (incremental or not) 
/// recently. `from` is the tick as a string of that synchronization.
/// `config` can contain the following attributes:
///   - "endpoint": endpoint of the other server
/// If one ensures that there is a read transaction ongoing on that collection
/// on the other server, then this function is guaranteed to bring the two
/// collections in perfect sync, until that read transaction is aborted.
////////////////////////////////////////////////////////////////////////////////

var mType = { 
    REPLICATION_COLLECTION_CREATE: 2000,
    REPLICATION_COLLECTION_DROP: 2001,
    REPLICATION_COLLECTION_RENAME: 2002,
    REPLICATION_COLLECTION_CHANGE: 2003,

    REPLICATION_INDEX_CREATE: 2100,
    REPLICATION_INDEX_DROP: 2101,

    REPLICATION_TRANSACTION_START: 2200,
    REPLICATION_TRANSACTION_COMMIT: 2201,
    REPLICATION_TRANSACTION_ABORT: 2202,

    REPLICATION_MARKER_DOCUMENT: 2300,
    REPLICATION_MARKER_EDGE: 2301,
    REPLICATION_MARKER_REMOVE: 2302
  };

function syncCollectionFinalize(collname, collid, from, config) {
  var url = endpointToURL(config.endpoint) + "/_api/replication/logger-follow"
            + "?collection=" + collid + "&from=";

  var coll = require("internal").db[collid];

  var transactions = {};

  function apply(entry) {
    var todo;

    function tryPostpone(entry) {
      if (entry.tid !== "0") {
        todo = transactions[entry.tid];
        if (Array.isArray(todo)) {
          entry.tid = "0";
          todo.push(entry);
          return true;
        }
      }
      return false;
    }

    if (entry.type === mType.REPLICATION_MARKER_DOCUMENT) {
      if (tryPostpone(entry)) {
        return;
      }
      try {
        coll.insert(entry.data);
        return;
      }
      catch (err) {
      }
      coll.replace(entry.key, entry.data);
    } else if (entry.type === mType.REPLICATION_MARKER_EDGE) {
      if (tryPostpone(entry)) {
        return;
      }
      try {
        coll.insert(entry.data._from, entry.data._to, entry.data);
        return;
      }
      catch (err) {
      }
      coll.replace(entry.key, entry.data);
    } else if (entry.type === mType.REPLICATION_MARKER_REMOVE) {
      if (tryPostpone(entry)) {
        return;
      }
      coll.remove(entry.key);
    } else if (entry.type === mType.REPLICATION_TRANSACTION_START) {
      transactions[entry.tid] = [];
    } else if (entry.type === mType.REPLICATION_TRANSACTION_COMMIT) {
      todo = transactions[entry.tid];
      if (Array.isArray(todo)) {
        for (var i = 0; i < todo.length; i++) {
          apply(todo[i]);
        }
      }
      delete transactions[entry.tid];
    } else if (entry.type === mType.REPLICATION_TRANSACTION_ABORT) {
      delete transactions[entry.tid];
    } else if (entry.type === mType.REPLICATION_INDEX_CREATE) {
      coll.ensureIndex(entry.index);
    } else if (entry.type === mType.REPLICATION_INDEX_DROP) {
      coll.dropIndex(entry.id);
    } else if (entry.type === mType.REPLICATION_COLLECTION_CHANGE) {
      coll.properties(entry.collection);
    } else {
      // all else, including dropping and creating the collection
      throw "Found collection drop, create or rename marker.";
    }

  }

  while (true) {
    var chunk = request(url + from);
    if (chunk.statusCode !== 200 &&
        chunk.statusCode !== 204) {
      return {error: true, errorMessage: "could not contact leader",
              response: chunk};
    }
    if (chunk.statusCode === 204 || chunk.body.length === 0) {
      break;  // all done
    }

    var l = chunk.body.split("\n");
    l.pop();
    try {
      l = l.map(JSON.parse);
    }
    catch (err) {
      return {error: true, errorMessage: "could not parse body",
              response: chunk, exception: err};
    }

    console.log("Applying chunk:");
    try {
      for (var i = 0; i < l.length; i++) {
        apply(l[i]);
      }
    }
    catch (err2) {
      return {error: true, errorMessage: "could not replicate body ops",
              response: chunk, exception: err2};
    }
    if (chunk.headers["x-arango-replication-checkmore"] !== "true") {
      break;  // all done
    }

    from = chunk.headers["x-arango-replication-lastincluded"];
  }
  return {error: false};
}

exports.logger                 = logger;
exports.applier                = applier;
exports.sync                   = sync;
exports.syncCollection         = syncCollection;
exports.setupReplication       = setupReplication;
exports.serverId               = serverId;
exports.syncCollectionFinalize = syncCollectionFinalize;