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// Logic MUST BE identical to the synchronous way:
// https://gist.github.com/melissamarima/2b9e8594892103dbc02c
var mongoose = require('mongoose');
var collectionASchema = new mongoose.Schema({field1: Number, field2: Number});
var collectionBSchema = new mongoose.Schema({field1: Number, field2: Number});
collectionASchema.index({field1: 1});
collectionBSchema.index({field1: -1});
mongoose.model('collectionA', collectionASchema);
mongoose.model('collectionB', collectionBSchema);
collectionBSchema.methods.addToCollectionB = function(cb){
// `this` is the newDocB
var newDocB = this;
var collectionA = mongoose.model("collectionA");
// set up the recursive promise loop
// returns nothing -- should break out of this recursion at the end
function promiseRecursion(){
// 2. Get the current collection A's first element
var colAFirstGetPromise = collectionA.find({}).sort({price:1}).limit(1).exec();
colAFirstGetPromise.then(function (collectionADocsArray){
var docA = collectionADocsArray[0];
// 3. check loop condition, break out of loop if satisfied
if (docA.field2 <= 0){
return; // EXISTS LOOP! TODO: make sure this breaks out of the loop
}
// 4. check which of the two ways to modify newDocB
if (docA.field1 <= 0){
// 6. one other way breaks out of the loop
newDocB.field1 = 0;
return; // EXISTS LOOP! TODO: make sure this breaks out of the loop
}
// else .. 5. one way removes docA from collectionA
newDocB.field1 -= docA.field1;
return collectionA.findByIdAndRemove(docA.id).exec();
}).then(function(doc){
// doc A should be removed at this point
// 7. if collectionA is empty, break out of the loop
return collectionA.find().exec();
}).then(function(collectionADocsArray){
if (collectionADocsArray.length == 0){
return; // EXISTS LOOP! TODO: make sure this breaks out of the loop
}
// 8. loads the new docA and continues to the next loop
return colAFirstGetPromise;
}).then(function (collectionADocsArray){
docA = collectionADocsArray[0];
// loop back
return promiseRecursion();
// handles error for all the promises above
}, function(err){
return err;
});
} // end of promiseRecursion();
// START HERE!!!!!!!!! THIS IS THE FIRST STEP
// 1. If collection A is empty, push newDocB onto collection B, and stop
collectionA.find(function(err, collectionADocsArray){
if (err){return err;}
if (collectionADocsArray.length == 0){
newDocB.save(cb); // saves newDocB to collectionB
return; // ends addToCollectionB()
}
promiseRecursion();
// 9. Loop is done, check if newDocB needs to be saved
//TODO: QUESTION QUESTION!!!!!!!!!!
// Was the newDocB modified in promiseRecursion() the same as the one below???
if (newDocB.field1 >= 0){
newDocB.save(cb); // saves newDocB to collectionB
return; // ends addToCollectionB()
}
});
}
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