/**
 * The Group Manager provides functions to manage groups in the database
 */

/*
 * 2011 Peter 'Pita' Martischka (Primary Technology Ltd)
 *
 * 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.
 */
 
var db = require("./DB").db;
var async = require("async");
var padManager = require("./PadManager");
var sessionManager = require("./SessionManager");
 
exports.deleteGroup = function(groupID, callback)
{
  var group;

  async.series([
    //ensure group exists 
    function (callback)
    {
      //try to get the group entry
      db.get("group:" + groupID, function (err, _group)
      {
        //error
        if(err) 
        {
          callback(err);
        }
        //group does not exist
        else if(_group == null)
        {
          callback({stop: "groupID does not exist"});
        }
        //group exists, everything is fine
        else
        {
          group = _group;
          callback();
        }
      });
    },
    //iterate trough all pads of this groups and delete them
    function(callback)
    {
      //collect all padIDs in an array, that allows us to use async.forEach
      var padIDs = [];
      for(var i in group.pads)
      {
        padIDs.push(i);
      }
      
      //loop trough all pads and delete them 
      async.forEach(padIDs, function(padID, callback)
      {
        padManager.getPad(padID, function(err, pad)
        {
          if(err) {callback(err); return}
          
          pad.remove(callback);
        });
      }, callback);
    },
    //iterate trough group2sessions and delete all sessions
    function(callback)
    {
      //try to get the group entry
      db.get("group2sessions:" + groupID, function (err, group2sessions)
      {
        if(err) {callback(err); return}
        
        //skip if there is no group2sessions entry
        if(group2sessions == null) {callback(); return}
        
        //collect all sessions in an array, that allows us to use async.forEach
        var sessions = [];
        for(var i in group2sessions.sessionsIDs)
        {
          sessions.push(i);
        }
        
        //loop trough all sessions and delete them 
        async.forEach(sessions, function(session, callback)
        {
          sessionManager.deleteSession(session, callback);
        }, callback);
      });
    },
    //remove group and group2sessions entry
    function(callback)
    {
      db.remove("group2sessions:" + groupID);
      db.remove("group:" + groupID);
      callback();
    }
  ], function(err)
  {
    callback(err);
  });
}
 
exports.doesGroupExist = function(groupID, callback)
{
  //try to get the group entry
  db.get("group:" + groupID, function (err, group)
  {
    callback(err, group != null);
  });
}

exports.createGroup = function(callback)
{
  //search for non existing groupID
  var groupID = "g." + randomString(16);
  
  //create the group
  db.set("group:" + groupID, {pads: {}});
  callback(null, {groupID: groupID});
}

exports.createGroupIfNotExistsFor = function(groupMapper, callback)
{
  //ensure mapper is optional
  if(typeof groupMapper != "string")
  {
    callback({stop: "groupMapper is no string"});
    return;
  }
  
  //try to get a group for this mapper
  db.get("mapper2group:"+groupMapper, function(err, groupID)
  {
     if(err)
     {
       callback(err);
       return;
     }
     
     //there is no group for this mapper, let's create a group
     if(groupID == null)
     {
       exports.createGroup(function(err, responseObj)
       {
         //check for errors
         if(err)
         {
           callback(err);
           return;
         }
         
         //create the mapper entry for this group
         db.set("mapper2group:"+groupMapper, responseObj.groupID);
         
         callback(null, responseObj);
       });
     }
     //there is a group for this mapper, let's return it
     else
     {
       callback(err, {groupID: groupID});
     }
  });
}

exports.createGroupPad = function(groupID, padName, text, callback)
{
  //create the padID
  var padID = groupID + "$" + padName;

  async.series([
    //ensure group exists 
    function (callback)
    {
      exports.doesGroupExist(groupID, function(err, exists)
      {
        //error
        if(err) 
        {
          callback(err);
        }
        //group does not exist
        else if(exists == false)
        {
          callback({stop: "groupID does not exist"});
        }
        //group exists, everything is fine
        else
        {
          callback();
        }
      });
    },
    //ensure pad does not exists
    function (callback)
    {
      padManager.doesPadExists(padID, function(err, exists)
      {
        //error
        if(err) 
        {
          callback(err);
        }
        //pad exists already
        else if(exists == true)
        {
          callback({stop: "padName does already exist"});
        }
        //pad does not exist, everything is fine
        else
        {
          callback();
        }
      });
    },
    //create the pad
    function (callback)
    {
      padManager.getPad(padID, text, function(err)
      {
        callback(err);
      });
    },
    //create an entry in the group for this pad
    function (callback)
    {
      db.setSub("group:" + groupID, ["pads", padID], 1);
      callback();
    }
  ], function(err)
  {
    callback(err, {padID: padID});
  });
}

exports.listPads = function(groupID, callback)
{
  exports.doesGroupExist(groupID, function(err, exists)
  {
    //error
    if(err) 
    {
      callback(err);
    }
    //group does not exist
    else if(exists == false)
    {
      callback({stop: "groupID does not exist"});
    }
    //group exists, let's get the pads
    else
    {
      db.getSub("group:" + groupID, ["pads"], function(err, pads)
      {
        callback(err, {padIDs: pads});
      });
    }
  });
}

/**
 * Generates a random String with the given length. Is needed to generate the Author Ids
 */
function randomString(len) 
{
  var chars = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz";
  var randomstring = '';
  for (var i = 0; i < len; i++)
  {
    var rnum = Math.floor(Math.random() * chars.length);
    randomstring += chars.substring(rnum, rnum + 1);
  }
  return randomstring;
}