var _ = require('underscore');
var async = require('async');
var assert = require('assert');
var awssum = require('awssum');
var clone = require('clone');
var retry = require('retry');
var util = require('util');
var winston = require('winston');

var env = process.env;

if (typeof process.env.ACCESS_KEY_ID === 'undefined') {
  winston.error('You must specify an AWS Access Key ID.');
  process.exit(1);
}

if (typeof process.env.SECRET_ACCESS_KEY === 'undefined') {
  winston.error('You must specify an AWS Secret Access Key.');
  process.exit(1);
}

if (typeof process.env.ACCOUNT_ID === 'undefined') {
  winston.error('You must specifiy an AWS Account ID.');
  process.exit(1);
}

var accessKeyId = env.ACCESS_KEY_ID;
var secretAccessKey = env.SECRET_ACCESS_KEY;
var awsAccountId = env.ACCOUNT_ID;

var amazon = awssum.load('amazon/amazon');
var DynamoDB = awssum.load('amazon/dynamodb').DynamoDB;

var ddb = new DynamoDB({
  'accessKeyId': accessKeyId,
  'secretAccessKey': secretAccessKey,
  'region': amazon.US_EAST_1,
});

// prefix attributes with S (for String) or N (for Number)
var formatItem = function(item) {
  var itemToFormat = clone(item);
  _.map(itemToFormat, function(value, key, obj) {
    if (_.isString(value)) {
      obj[key] = {
        S: value
      };
    } else if (_.isNumber(value)) {
      obj[key] = {
        N: value.toString(),
      };
    } else {
      delete obj[key];
    }
  });
  return itemToFormat;
};

var importItem = function(formattedItem, tableName, callback) {
  if (!_.isNull(formattedItem)) {
    pendingItems.RequestItems[tableName].push({
      'PutRequest' : {
        'Item' : formattedItem,
      },
    });
  }
  if (pendingItems.RequestItems[tableName].length === 25 ||
      (pendingItems.RequestItems[tableName].length > 0 &&
       _.isNull(formattedItem))) {
    var operation = retry.operation({
      retries: 5,
      factor: 3,
      minTimeout: 5000,
      maxTimeout: 60 * 1000,
      randomize: true,
    });
    operation.attempt(function() {
      ddb.BatchWriteItem(pendingItems, function(err, response) {
        if (operation.retry(err)) {
          winston.warn(util.inspect(err));
          winston.warn('Retrying to import the items...');
        } else if (err) {
          winston.error('The import failed!');
          callback(operation.mainError());
        } else {
          if (_.isUndefined(response.Body.UnprocessedItems[tableName])) {
            pendingItems.RequestItems[tableName] = [];
          } else {
            // we are assuming that there are at most 24 unprocessed items
            pendingItems.RequestItems[tableName] =
              response.Body.UnprocessedItems[tableName];
          }
          callback(null);
        }
      });
    });
  } else {
    callback(null);
  }
};

var range2d = function(x, y) {
  var values = [];
  for (var i = 0; i < x; i++) {
    for (var j = 0; j < y; j++) {
      values.push([i, j]);
    }
  }
  return values;
}

// pending items are shared between calls to importItem
var pendingItems = {
  'RequestItems': {
    'myData': [],
  },
};

var pendingFunctions = _.map(range2d(10, 100), function(i) {
  return function(callback) {
    winston.debug('Preparing ' + JSON.stringify(i) + '...');
    var formattedItem = formatItem({appId: i[0], ts: i[1]});
    importItem(formattedItem, 'myData', callback);
  };
});

async.series(pendingFunctions, function(err) {
  if (err) {
    winston.error(util.inspect(err));
    process.exit(1);
  }
  // flush any remaining pending items
  async.whilst(function() {
    return pendingItems.RequestItems['myData'].length > 0;
  }, function(callback) {
    importItem(null, 'myData', callback);
  }, function(err) {
    if (err) {
      winston.error(util.inspect(err));
      process.exit(1);
    }
  });
});