cf-list-aggregator

Aggregates content from lists.

Installation

  npm install cf-list-aggregator

Usage

var aggregate = createAggregator(listService, sectionService, articleService, { logger: logger })
aggregate(listId, dedupe, limit, section, function (err, results) {})

Types of list

There are two types of list:

### 1. Automatic

Automatic lists are used to auto-generate list content based on a number of properties:

• tags
• sections

For example (some properties omitted for brevity):

// This list will get all content with the Location tag "London"
{ type: 'auto'
, tags: [ { type: 'Location', tag: 'London' } ]
}

// Assuming the section "Reviews" has ID=123 and "Guides" has ID=456, this list
// will get all content from "Reviews", including any sub-sections and all content
// from "Guides", but nothing from "Guides" > "Premium".
{ type: 'auto'
, sections:
  [ { id: '123', includeSubSections: true }
  , { id: '456', includeSubSections: false }
  ]
}

### 2. Manual

Manual lists are lists where the contents are hand picked. The list object differs from the automatic list in that the contents are described in the items array property.

{ type: 'manual'
, items: []
}

Specifying manual list content

The most common and basic way to define a piece of manual list content is to provide the id of an item that exists in the crudService provided:

{ type: 'manual'
, items: [ { itemId: '123' }, isCustom: false, overrides: {} ]
}

Overriding item properties

Sometimes the item appearing in a list will need a slight modification for the context in which it will be used, perhaps a snappier title or a more appropriate image. In order to achieve this, the overrides property is used.

// The item ID=123 look like this:
{ _id: '123', title: 'Top 10 List Aggregation Modules' /* etc… */ }
// In order to select this item but give it a different image…
{ itemId: '123', isCustom: false, overrides: { image: 'http://diff.img/123' } }

All of the original item's content will be retrieved from the crudService and then the overrides will be applied.

Inserting custom items

Sometimes it is useful to inject an item that doesn't exist in the crudService. To do this, the item format is like so:

{ isCustom: true, properties: { title: 'A Custom Item', image: 'http://notinthe.db' /* etc… */ } }

Date based previewing

To create a list aggregator which allows searching from any date perspective, pass a date parameter into the options object like so:

var aggregate = createAggregator(listService, sectionService, articleService, { logger: logger, date: new Date() })

This aggregator instance now performs all operations based on this date.

Specifying fields to return

To specify fields to return from the query, use the fields option. This field can either be an object or an array - mongo is tolerant of either.

The default list is pretty minimal: [ "_id", "headline" ] so you will want to pass in the desired list every time. It is important to only specify the properties needed in order to minimise unnecessary database traffic.

  fields: { longTitle: 1, tags: 1 }

Or an array:

  fields: ['longTitle', 'tags']

Example:

var aggregate = createAggregator(listService, sectionService, articleService, { logger: logger, fields: { longTitle: 1 } })

Extending Query or Sort

If you need to add additional query or sorting to the default query you can pass additionalAutoQuery in options.

additionalAutoQuery is a function that is given the list and returns a function that takes { query: {}, options: {} } e.g

function additionalAutoQuery(list) {
  return function (q) {
    q.query.headline = 'News Flash'
    q.options.sort = { headline: -1 }
    return q
  }
}

Overriding prepareAutoQuery and prepareManualQuery

If your application needs to modify the queries that the list aggregator makes (need a custom sort function for automatic lists? override prepareAutoQuery) then override these functions.

Just pass in either prepareAutoQuery or prepareManualQuery as options to the list aggregator. The expected input and output for these functions is:

e.g

function prepareAutoQuery(list) {
  return { options: {}, query: {} }
}

function prepareManualQuery(list, IdType) {
  return { options: {}, query: {} }
}

Changlog

v.2.0.0

• The schema for lists that this module consumes is now totally different and not backwards compatible.
• crudService.idType is no longer required to be passed in. Make sure the version of save-mongodb in your application is >=0.0.12 so that it will properly reach into the _id: { $in: [] } query and conver to the appropriate id type.

v1.0.0

• The format for list.sections changed to account for functionality to include sub-sections. Previously the format was:

list.sections = [ 'id1', 'id2', 'id3' ]

This has changed to:

list.sections =
  [ { id: 'id1', includeSubSections: true }
  , { id: 'id2', includeSubSections: false }
  , { id: 'id3', includeSubSections: true }
  ]

Credits

Paul Serby follow me on twitter @serby

Licence

Licensed under the New BSD License