npm package: @sliit-foss/mongoose-aggregate-paginate-v2
Description: A cursor based custom aggregate pagination library for Mongoose with customizable labels.
Author: SLIIT FOSS
Latest version: 3.0.0

# @sliit-foss/mongoose-aggregate-paginate-v2

> A fork of the cursor based custom aggregate pagination library for [Mongoose](http://mongoosejs.com) with customizable labels

This is a fork of the [mongoose-aggregate-paginate-v2](https://www.npmjs.com/package/mongoose-aggregate-paginate-v2) package with the following changes:

- Added support for prepagination along with a custom pipeline. This allows for more complex queries to be paginated in a more efficient manner. (Prepagination is a feature that paginates the data at a given placeholder stage in the pipeline rather than at the end)

If you are looking for basic query pagination library without aggregate, use this one [mongoose-paginate-v2](https://github.com/aravindnc/mongoose-paginate-v2)

## Installation

```sh
npm install @sliit-foss/mongoose-aggregate-paginate-v2
```

## Usage

Adding the plugin to a schema,

```js
var mongoose = require("mongoose");
var aggregatePaginate = require("@sliit-foss/mongoose-aggregate-paginate-v2");

var mySchema = new mongoose.Schema({
  /* your schema definition */
});

mySchema.plugin(aggregatePaginate);

var myModel = mongoose.model("SampleModel", mySchema);
```

and then use model `aggregatePaginate` method,

```js
// as Promise

var myModel = require("/models/samplemodel");

const options = {
  page: 1,
  limit: 10
};

var myAggregate = myModel.aggregate();
myModel
  .aggregatePaginate(myAggregate, options)
  .then(function (results) {
    console.log(results);
  })
  .catch(function (err) {
    console.log(err);
  });
```

```js
// as Callback

var myModel = require('/models/samplemodel');

const options = {
    page: 1,
    limit: 10
};

var myAggregate = myModel.aggregate();
myModel.aggregatePaginate(myAggregate, options, function(err, results) {
	if(err) {
		console.err(err);
	else {
    	console.log(results);
	}
})
```

```js
// Execute pagination from aggregate
const myModel = require('/models/samplemodel');

const options = {
    page: 1,
    limit: 10
};

const myAggregate = myModel.aggregate();
myAggregate.paginateExec(options, function(err, results) {
	if(err) {
		console.err(err);
	else {
    	console.log(results);
	}
})
```

### Model.aggregatePaginate([aggregateQuery], [options], [callback])

Returns promise

**Parameters**

- `[aggregate-query]` {Object} - Aggregate Query criteria. [Documentation](https://docs.mongodb.com/manual/aggregation/)
- `[options]` {Object}
  - `[sort]` {Object | String} - Sort order. [Documentation](http://mongoosejs.com/docs/api.html#query_Query-sort)
  - `[offset=0]` {Number} - Use `offset` or `page` to set skip position
  - `[page]` {Number} - Current Page (Defaut: 1)
  - `[limit]` {Number} - Docs. per page (Default: 10).
  - `[customLabels]` {Object} - Developers can provide custom labels for manipulating the response data.
  - `[pagination]` {Boolean} - If `pagination` is set to false, it will return all docs without adding limit condition. (Default: True)
  - `[allowDiskUse]` {Bool} - To enable diskUse for bigger queries. (Default: False)
  - `[countQuery]` {Object} - Aggregate Query used to count the resultant documents. Can be used for bigger queries. (Default: `aggregate-query`)
  - `[useFacet]` {Bool} - To use facet operator instead of using two queries. This is the new default. (Default: true)
- `[callback(err, result)]` - (Optional) If specified the callback is called once pagination results are retrieved or when an error has occurred.

**Return value**

Promise fulfilled with object having properties:

- `docs` {Array} - Array of documents
- `totalDocs` {Number} - Total number of documents that match a query
- `limit` {Number} - Limit that was used
- `page` {Number} - Current page number
- `totalPages` {Number} - Total number of pages.
- `offset` {Number} - Only if specified or default `page`/`offset` values were used
- `hasPrevPage` {Bool} - Availability of prev page.
- `hasNextPage` {Bool} - Availability of next page.
- `prevPage` {Number} - Previous page number if available or NULL
- `nextPage` {Number} - Next page number if available or NULL
- `pagingCounter` {Number} - The starting sl. number of first document.
- `meta` {Object} - Object of pagination meta data (Default false).

Please note that the above properties can be renamed by setting customLabels attribute.

### Sample Usage

#### Return first 10 documents from 100

```javascript
const options = {
  page: 1,
  limit: 10
};

// Define your aggregate.
var aggregate = Model.aggregate();

Model.aggregatePaginate(aggregate, options)
  .then(function (result) {
    // result.docs
    // result.totalDocs = 100
    // result.limit = 10
    // result.page = 1
    // result.totalPages = 10
    // result.hasNextPage = true
    // result.nextPage = 2
    // result.hasPrevPage = false
    // result.prevPage = null
  })
  .catch(function (err) {
    console.log(err);
  });
```

### With custom return labels

Now developers can specify the return field names if they want. Below are the list of attributes whose name can be changed.

- totalDocs
- docs
- limit
- page
- nextPage
- prevPage
- totalPages
- hasNextPage
- hasPrevPage
- pagingCounter
- meta

You should pass the names of the properties you wish to changes using `customLabels` object in options. Labels are optional, you can pass the labels of what ever keys are you changing, others will use the default labels.

If you want to return paginate properties as a separate object then define `customLabels.meta`.

Same query with custom labels

```javascript

const myCustomLabels = {
  totalDocs: 'itemCount',
  docs: 'itemsList',
  limit: 'perPage',
  page: 'currentPage',
  nextPage: 'next',
  prevPage: 'prev',
  totalPages: 'pageCount',
  hasPrevPage: 'hasPrev',
  hasNextPage: 'hasNext',
  pagingCounter: 'pageCounter',
  meta: 'paginator'
};

const options = {
    page: 1,
    limit: 10,
    customLabels: myCustomLabels
};

// Define your aggregate.
var aggregate = Model.aggregate();

Model.aggregatePaginate(aggregate, options, function(err, result) {
if(!err) {
  // result.itemsList [here docs become itemsList]
  // result.itemCount = 100 [here totalDocs becomes itemCount]
  // result.perPage = 10 [here limit becomes perPage]
  // result.currentPage = 1 [here page becomes currentPage]
  // result.pageCount = 10 [here totalPages becomes pageCount]
  // result.next = 2 [here nextPage becomes next]
  // result.prev = null [here prevPage becomes prev]

  // result.hasNextPage = true [not changeable]
  // result.hasPrevPage = false [not changeable]
} else {
  console.log(err);
};
```

### Using `offset` and `limit`

```javascript
Model.aggregatePaginate(aggregate, { offset: 30, limit: 10 }, function (err, result) {
  // result
});
```

### Using `countQuery`

```javascript
// Define your aggregate query.
var aggregate = Model.aggregate();

// Define the count aggregate query. Can be different from `aggregate`
var countAggregate = Model.aggregate();

// Set the count aggregate query
const options = {
  countQuery: countAggregate
};

Model.aggregatePaginate(aggregate, options)
  .then(function (result) {
    // result
  })
  .catch(function (err) {
    console.log(err);
  });
```

### Using `prepagination`

```javascript
// Define your pipeline
const pipeline = [
  {
    $match: {
      status: "active"
    }
  },
  {
    $sort: {
      date: -1
    }
  },
  "__PREPAGINATE__",
  {
    $lookup: {
      from: "authors",
      localField: "author",
      foreignField: "_id",
      as: "author"
    }
  }
];
Model.aggregatePaginate(pipeline, options)
  .then(function (result) {
    // result
  })
  .catch(function (err) {
    console.log(err);
  });
```

### Global Options

If you want to set the pagination options globally across the model. Then you can do like below,

```js
let mongooseAggregatePaginate = require("mongoose-aggregate-paginate-v2");

let BookSchema = new mongoose.Schema({
  title: String,
  date: Date,
  author: {
    type: mongoose.Schema.ObjectId,
    ref: "Author"
  }
});

BookSchema.plugin(mongooseAggregatePaginate);

let Book = mongoose.model("Book", BookSchema);

// Like this.
Book.aggregatePaginate.options = {
  limit: 20
};
```

## Release Note

v1.0.7 - Upgrade to mongoose v8

v1.0.6 - Fixed exporting settings to global object.

v1.0.5 - Added `meta` attribute to return paginate meta data as a custom object.

v1.0.42 - Added optional `countQuery` parameter to specify separate count queries in case of bigger aggerate pipeline.

## License

[MIT](LICENSE)