'use strict';
  
  var bdd = require('../helpers/bdd-if');
  var should = require('should');
  var helpers = require('./_helpers');
  var Promise = require('bluebird');
  
  module.exports = function(dataSourceFactory, connectorCapabilities) {
    var TTL_PRECISION = connectorCapabilities.ttlPrecision;
  
    // Use ~1s for stores with precision of 1 ms,
    // about 3s for stores with precision of 1s.
    var INITIAL_TTL = Math.max(TTL_PRECISION + 1000, TTL_PRECISION * 3);
  
    // A small delay to allow the backend to process the request, run any
    // TTL/expire checks, etc. Use 1ms for backends supporting sub-10ms
    // resolution to ensure the delay is not too short..
    var SMALL_DELAY = Math.max(1, Math.floor(TTL_PRECISION / 10));
  
    var canQueryTtl = connectorCapabilities.canQueryTtl !== false;
  
    bdd.describeIf(canQueryTtl, 'ttl', function() {
      var CacheItem;
      beforeEach(function unpackContext() {
        CacheItem = helpers.givenCacheItem(dataSourceFactory);
      });
  
      it('gets TTL when key with unexpired TTL exists - Promise API',
      function() {
        return Promise.resolve(
            CacheItem.set('a-key', 'a-value', {ttl: INITIAL_TTL}))
          .delay(SMALL_DELAY)
          .then(function() { return CacheItem.ttl('a-key'); })
          .then(function(ttl) { ttl.should.be.within(1, INITIAL_TTL); });
      });
  
      it('gets TTL when key with unexpired TTL exists - Callback API',
      function(done) {
        CacheItem.set('a-key', 'a-value', {ttl: INITIAL_TTL}, function(err) {
          if (err) return done(err);
          CacheItem.ttl('a-key', function(err, ttl) {
            if (err) return done(err);
            ttl.should.be.within(1, INITIAL_TTL);
            done();
          });
        });
      });
  
      it('succeeds when key without TTL exists', function() {
        return CacheItem.set('a-key', 'a-value')
          .then(function() { return CacheItem.ttl('a-key'); })
          .then(function(ttl) { should.not.exist(ttl); });
      });
  
      it('fails when getting TTL for a key with expired TTL', function() {
        return Promise.resolve(
            CacheItem.set('expired-key', 'a-value', {ttl: TTL_PRECISION}))
          .delay(2 * TTL_PRECISION)
          .then(function() {
            return CacheItem.ttl('expired-key');
          })
          .then(
            function() { throw new Error('ttl() should have failed'); },
            function(err) {
              err.message.should.match(/expired-key/);
              err.should.have.property('statusCode', 404);
            });
      });
  
      it('fails when key does not exist', function() {
        return CacheItem.ttl('key-does-not-exist').then(
          function() { throw new Error('ttl() should have failed'); },
          function(err) {
            err.message.should.match(/key-does-not-exist/);
            err.should.have.property('statusCode', 404);
          });
      });
    });
  };