var async = require('async');
var _ = require('underscore');

module.exports = {
  initialize: function(api, next){

    function nullOrErrorResult(err, result) {
      return (err || result === null || result.length === 0);
    }

    //returns a function which takes a callback(err, data)
    //callback:
    // - err will be null or contain an error if one occurs
    // - data will contain an object with:
    //   - 'timestamp': { class, queue, args }
    function getDelayedTaskSchedule(api) {
      return function(done) {
        var scheduler = api.resque.scheduler;
        var redis = scheduler.connection.redis;
        redis.zrangebyscore(scheduler.connection.key('delayed_queue_schedule'), '-inf', '+inf', function(err, items) {
          if (nullOrErrorResult(err, items)) {
            done(err, {});
          } else {
            async.reduce(items, {}, function(memo, timestamp, callback) {
              var key = scheduler.connection.key('delayed:' + timestamp);
              redis.lrange(key, 0, -1, function(err, jobs) {
                if(err) {
                  callback(err);
                } else {
                  var jobList = jobs.map(JSON.parse);
                  memo[timestamp] = jobList;
                  callback(null, memo);
                }
              });
            }, done);
          }
        });
      };
    }

    //returns a function which takes a callback(err, data)
    //callback:
    // - err will be null or contain an error if one occurs
    // - data will contain an object with:
    //  - 'queuename': [{ class, args }, ... ]
    function getQueuedTasks(api) {
      return function(done) {
        var scheduler = api.resque.scheduler;
        var redis = scheduler.connection.redis;
        redis.smembers(scheduler.connection.key('queues'), function(err, queues) {
          if(nullOrErrorResult(err, queues)) {
            done(err, {});
          } else {
            async.map(queues, function(queue, callback) {
              redis.lrange(scheduler.connection.key('queue:' + queue), 0, -1, function(err, items) {
                var result = {
                  name: queue,
                  items: []
                };
                if(!nullOrErrorResult(err, items)) {
                  for(var i = 0; i < items.length; i++) {
                    result.items.push(JSON.parse(items[i]));
                  }
                }
                callback(err, result);
              });
            }, function(err, queueObjects) {
              var result = {};
              for(var i = 0; i < queueObjects.length; i ++) {
                var queueItem = queueObjects[i];
                result[queueItem.name] = queueItem.items;
              }
              done(err, result);
            });
          }
        });
      };
    }

    //returns a function which takes a callback(err, data)
    //callback:
    // - err will be null or contain an error if one occurs
    // - data will contain an object with:
    //  - 'workername': 'idle' | { class, args }
    function getWorkerStatus(api) {
      return function(done) {
        var scheduler = api.resque.scheduler;
        var redis = scheduler.connection.redis;
        redis.smembers(scheduler.connection.key('workers'), function(err, workers) {
          if(nullOrErrorResult(err, workers)) {
            done(err, {});
          } else {
            async.map(workers, function(workerName, callback) {
              redis.get(scheduler.connection.key('worker:' + workerName), function(err, statusString) {
                if(err) {
                  callback(err);
                } else {
                  var result = {name: workerName};
                  if(statusString == null) {
                    result.status = 'idle';
                  } else {
                    var status = JSON.parse(statusString);
                    result.status = status.payload;
                  }
                  callback(null, result);
                }
              });
            }, function(err, workerItems) {
              var result = {};
              for(var i = 0; i < workerItems.length; i ++) {
                var workerItem = workerItems[i];
                result[workerItem.name] = workerItem.status;
              }
              done(err, result);
            });
          }
        });
      };
    }

    //returns a function which takes a callback(err, data)
    //callback:
    // - err will be null or contain an error if one occurs
    // - data will contain an object with:
    //  - 'jobName': {status: 'scheduled', at: timestamp, in: timeToTimestamp} |
    //               {status: 'running', running: 'workerName'} |
    //               {status: 'enqueued', queue: 'queueName'} |
    //               {status: 'dequeued'}
    function getStatusByJob(api) {
      return function(done) {
        var taskList = Object.keys(api.tasks.tasks);
        var result = {};
        for(var i = 0; i < taskList.length; i++) {
          result[taskList[i]] = { status: 'dequeued' };
        }
        async.parallel({
          schedule: getDelayedTaskSchedule(api),
          queuedTasks: getQueuedTasks(api),
          workers: getWorkerStatus(api)
        }, function(err, results) {
          if(err) {
            done(err, {});
          } else {
            _.each(results.schedule, function(jobs, timestamp) {
              var timeToTimestamp = timestamp - Math.round(new Date().getTime() / 1000);
              _.each(jobs, function(job) {
                result[job.class] = {status: 'scheduled', at: timestamp, in: timeToTimestamp};
              });
            });

            _.each(results.queuedTasks, function(jobs, queue) {
              _.each(jobs, function(job) {
                result[job.class] = {status: 'enqueued', queue: queue};
              });
            });

            _.each(results.workers, function(job, worker) {
              if(job === 'idle') {
                return;
              } else {
                result[job.class] = {status: 'running', running: worker};
              }
            });

            done(null, result);
          }
        });
      };
    }

    api.resqueHelper = {
      delayedSchedule: getDelayedTaskSchedule,
      queuedTasks: getQueuedTasks,
      workerStatus: getWorkerStatus,
      jobs: getStatusByJob
    };
    next();
  }
};