# Mongoid Geospatial

A Mongoid Extension that simplifies the use of MongoDB spatial features.

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## Quick Start

This gem focuses on (making helpers for) MongoDB's spatial features using Mongoid 5, 6 and 7.

```ruby
# Gemfile
gem 'mongoid-geospatial'
```

A `Place` to illustrate `Point`, `Line` and `Polygon`

```ruby
class Place
  include Mongoid::Document

  # Include the module
  include Mongoid::Geospatial

  # Just like mongoid,
  field :name,     type: String

  # define your field, but choose a geometry type:
  field :location, type: Point
  field :route,    type: LineString
  field :area,     type: Polygon

  # To query on your points, don't forget to index:
  # You may use a method:
  sphere_index :location  # 2dsphere
  # or
  spatial_index :location # 2d

  # Or use a helper directly on the `field`:
  field :location, type: Point, spatial: true  # 2d
  # or
  field :location, type: Point, sphere: true   # 2dsphere
end
```

Generate indexes on MongoDB via rake:

```
rake db:mongoid:create_indexes
```

Or programatically:

```ruby
Place.create_indexes
```

## Points

This gem defines a specific `Point` class under the Mongoid::Geospatial namespace. Make sure to use `type: ::Mongoid::Geospatial::Point` to avoid name errors or collisions with other `Point` classes you might already have defined `NameError`s.

Currently, MongoDB supports query operations on 2D points only, so that's what this lib does. All geometries apart from points are just arrays in the database. Here's is how you can input a point as:

- longitude latitude array in that order - [long,lat] ([x, y])
- an unordered hash with latitude key(:lat, :latitude) and a longitude key(:lon, :long, :lng, :longitude)
- an ordered hash with longitude as the first item and latitude as the second item; this hash does not have include the latitude and longitude keys
- anything with the a method #to_xy or #to_lng_lat that converts itself to [long, lat] array

_Note: the convention of having longitude as the first coordinate may vary for other libraries. For instance, Google Maps often refer to "LatLng". Make sure you keep those differences in mind. See below for how to configure this library for LatLng._

We store data in the DB as a [x, y] array then reformat when it is returned to you

```ruby
cafe = Place.create(
  name: 'Café Rider',
  location: {:lat => 44.106667, :lng => -73.935833},
  # or
  location: {latitude: 40.703056, longitude: -74.026667}
  #...
```

Now to access this spatial information we can do this

```ruby
cafe.location  # => [-74.026667, 40.703056]
```

If you need a hash

```ruby
cafe.location.to_hsh   # => { x: -74.026667, y: 40.703056 }
```

Commonly used

```ruby
cafe.location.to_lat_lon   # => { lat: 40.703056, lon: -74.026667 }
```

If you are using GeoRuby or RGeo

```ruby
cafe.location.to_geo   # => GeoRuby::Point

cafe.location.to_rgeo  # => RGeo::Point
```

Conventions:

This lib uses #x and #y everywhere.
It's shorter than lat or lng or another variation that also confuses.
A point is a 2D mathematical notation, longitude/latitude is when you use that notation to map an sphere. In other words: all longitudes are 'xs' where not all 'xs' are longitudes.

Distance and other geometrical calculations are delegated to the external library of your choice. More info about using RGeo or GeoRuby below. Some built in helpers for mongoid queries:

```ruby
# Returns middle point + radius
# Useful to search #within_circle
cafe.location.radius(5)        # [[-74.., 40..], 5]
cafe.location.radius_sphere(5) # [[-74.., 40..], 0.00048..]

# Returns hash if needed
cafe.location.to_hsh              # {:x => -74.., :y => 40..}
cafe.location.to_hsh(:lon, :lat)  # {:lon => -74.., :lat => 40..}
```

And for polygons and lines:

```ruby
house.area.bbox    # Returns polygon bounding_box (envelope)
house.area.center  # Returns calculate middle point
```

## Model Setup

You can create Point, Line, Circle, Box and Polygon on your models:

```ruby
class CrazyGeom
  include Mongoid::Document
  include Mongoid::Geospatial

  field :location,  type: Point, spatial: true, delegate: true

  field :route,     type: Line
  field :area,      type: Polygon

  field :square,    type: Box
  field :around,    type: Circle

  # default mongodb options
  spatial_index :location, {bit: 24, min: -180, max: 180}

  # query by location
  spatial_scope :location
end
```

## Helpers

You can use `spatial: true` to add a '2d' index automatically,
No need for `spatial_index :location`:

```ruby
field :location,  type: Point, spatial: true
```

And you can use `sphere: true` to add a '2dsphere' index automatically, no need for `spatial_sphere :location`:

```ruby
field :location,  type: Point, sphere: true
```

You can delegate some point methods to the instance itself:

```ruby
field :location,  type: Point, delegate: true
```

Now instead of `instance.location.x` you may call `instance.x`.

## Geometry

You can also store Circle, Box, Line (LineString) and Polygons.
Some helper methods are available to them:

```ruby
# Returns a geometry bounding box
# Useful to query #within_geometry
polygon.bbox
polygon.bounding_box

# Returns a geometry calculated middle point
# Useful to query for #near
polygon.center

# Returns middle point + radius
# Useful to search #within_circle
polygon.radius(5)        # [[1.0, 1.0], 5]
polygon.radius_sphere(5) # [[1.0, 1.0], 0.00048..]
```

## Query

You can use Geometry instance directly on any query:

### near

```ruby
Bar.near(location: person.house)
Bar.where(:location.near => person.house)
```

### near_sphere

```ruby
Bar.near_sphere(location: person.house)
Bar.where(:location.near_sphere => person.house)
```

### nearby

You can add a `spatial_scope` on your models. So you can query:

```ruby
Bar.nearby(my.location)
```

instead of

```ruby
Bar.near(location: my.location)
```

Good when you're drunk. Just add to your model:

```ruby
spatial_scope :<field>
```

### geo_near

The `geo_near` class method provides a more powerful way to query for documents based on proximity,
using MongoDB's `$geoNear` aggregation pipeline stage. This method allows for more complex
options and returns the distance to each matched document.

```ruby
# Find places near [10, 20], using spherical calculations, up to 5km away,
# and get the distance.
# The :distanceField option specifies the name of the field that will contain the distance.
# The :limit option is applied as a separate $limit stage in the aggregation.
Place.geo_near(:location, [10, 20],
               spherical: true,
               maxDistance: 5000, # 5 kilometers in meters for spherical queries
               distanceField: 'dist.calculated', # Default is 'distance'
               query: { category: 'restaurant' }, # Optional: filter documents before geoNear
               limit: 10)

# Iterate over results
Place.geo_near(:location, [10, 20], spherical: true).each do |place|
  # 'place.distance' will be available if distanceField was 'distance' (the default)
  # or 'place.dist_calculated' if distanceField was 'dist.calculated'
  puts "#{place.name} is #{place.distance || place.dist_calculated} meters away."
end
```

Key features and options for `geo_near`:

- `:spherical` (Boolean): If `true`, calculates distances using spherical geometry. Defaults to `false`.
- `:distanceField` (String): Name of the output field for the calculated distance. Defaults to `'distance'`.
- `:maxDistance` (Numeric): Maximum distance from the center point. (Meters for spherical, units of coordinates for planar).
- `:minDistance` (Numeric): Minimum distance from the center point.
- `:query` (Hash): A query to filter documents _before_ the `$geoNear` stage.
- `:limit` (Integer): Maximum number of documents to return (applied as a separate `$limit` stage).
- `:distanceMultiplier` (Numeric): A factor to multiply all distances.
- `:includeLocs` (String): Name of an output field that will contain the exact location on the document used for the distance calculation. Useful for multi-location fields or complex GeoJSON geometries.

The `geo_near` method returns an array of instantiated Mongoid documents, with the `distanceField` and `includeLocs` field (if specified) available as dynamic attributes on each model instance.

- within_polygon

```ruby
Bar.within_polygon(location: [[[x,y],...[x,y]]])
# or with a bbox
Bar.within_polygon(location: street.bbox)
```

- intersects_line
- intersects_point
- intersects_polygon

## External Libraries

We currently support GeoRuby and RGeo.
If you require one of those, a #to_geo and #to_rgeo, respectivelly,
method(s) will be available to all spatial fields, returning the
external library corresponding object.

### Use RGeo?

<https://github.com/dazuma/rgeo>

RGeo is a Ruby wrapper for Proj/GEOS.
It's perfect when you need to work with complex calculations and projections.
It'll require more stuff installed to compile/work.

### Use GeoRuby?

<https://github.com/nofxx/georuby>

GeoRuby is a pure Ruby Geometry Library.
It's perfect if you want simple calculations and/or keep your stack in pure ruby.
Albeit not full featured in maths it has a handful of methods and good import/export helpers.

### Example

```ruby
class Person
  include Mongoid::Document
  include Mongoid::Geospatial

  field :location, type: Point
end

me = Person.new(location: [8, 8])

# Example with GeoRuby
point.class # Mongoid::Geospatial::Point
point.to_geo.class # GeoRuby::SimpleFeatures::Point

# Example with RGeo
point.class # Mongoid::Geospatial::Point
point.to_rgeo.class # RGeo::Geographic::SphericalPointImpl
```

## Configure

Assemble it as you need (use a initializer file):

With RGeo

```ruby
Mongoid::Geospatial.with_rgeo!
# Optional
# Mongoid::Geospatial.factory = RGeo::Geographic.spherical_factory
```

With GeoRuby

```ruby
Mongoid::Geospatial.with_georuby!
```

By default the convention of this library is LngLat, configure it for LatLng as follows.

```ruby
Mongoid::Geospatial.configure do |config|
  config.point.x = Mongoid::Geospatial.lat_symbols
  config.point.y = Mongoid::Geospatial.lng_symbols
end
```

You will need to manually migrate any existing `Point` data if you change configuration in an existing system.

## This Fork

This fork is not backwards compatible with 'mongoid_spacial'.
This fork delegates calculations to external libs.

Change in your models:

```ruby
include Mongoid::Spacial::Document
```

to

```ruby
include Mongoid::Geospatial
```

And for the fields:

```ruby
field :source,  type: Array,    spacial: true
```

to

```ruby
field :source,  type: Point,    spatial: true # or sphere: true
```

Beware the 't' and 'c' issue. It's spaTial.

## Troubleshooting

**Mongo::OperationFailure: can't find special index: 2d**

Indexes need to be created. Execute command:

```
rake db:mongoid:create_indexes
```

Programatically

```
Model.create_indexes
```

## Contributing

See [CONTRIBUTING](CONTRIBUTING.md).

## License

Copyright (c) 2009-2017 Mongoid Geospatial Authors

MIT License, see [MIT-LICENSE](MIT-LICENSE).