values-aggregation

db.value.aggregate([
{$project:{ time:1,values:[{c:"$c"},{v:"$v"}]} },
{
   $project: {
      time:1,
      values2: {
         $map: {
            input: "$values",
            as: "pair",
            in: [{$ifNull:["$$pair.c","v-rep"]}, {$ifNull:["$$pair.v","c-rep"]}]
         }       
      }             
   } 
},
{
   $project: {
   time:1,
      values3: {
         $concatArrays: [{$arrayElemAt: ["$values2",0]}, {$arrayElemAt: ["$values2",1]}]
      }
   }
},
{
   $project: {
   time:1,
      values4: {
         $filter: {
            input: "$values3",
            as: "var",
            cond: {$and : [
               {$ne:["$$var","v-rep"]},
               {$ne:["$$var","c-rep"]}
            ]},
         }
      }
   }
},
{
   $group: { _id:{"time":"$time"},
      values5: {$push: "$values4"},
   }
}
])