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geo
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Encodes and decodes WKB, WKT, and GeoJSON formats.
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lib/geo/geo_json.ex
defmodule Geo.JSON do
alias Geo.Geometry
use Jazz
@moduledoc """
Converts to and from GeoJSON
```
json = "{ \"type\": \"Point\", \"coordinates\": [100.0, 0.0] }"
geom = Geo.JSON.decode(json)
Geo.Geometry[type: :point, coordinates: [100.0, 0.0], srid: nil]
Geo.JSON.encode(geom)
"{ \"type\": \"Point\", \"coordinates\": [100.0, 0.0] }"
```
"""
@doc """
Takes a GeoJSON string and returns a Geo.Geometry struct or list of Geo.Geometry
"""
def decode(geo_json) do
decoded_json = JSON.decode!(geo_json, keys: :atoms)
case Map.has_key?(decoded_json, :geometries) do
true ->
Enum.map(decoded_json.geometries,
fn(x) -> %Geometry{ type: decode_type(x.type), coordinates: x.coordinates } end)
false ->
%Geometry{ type: decode_type(decoded_json.type), coordinates: decoded_json.coordinates }
end
end
@doc """
Takes a Geo.Geometry struct or a list of Geo.Geometry and returns a geoJSON string
"""
def encode(geom) when is_list(geom) do
JSON.encode!(%{
type: "GeometryCollection",
geometries: Enum.map(geom, fn(x) -> %{ type: encode_type(x.type), coordinates: x.coordinates } end)
})
end
def encode(geom) do
JSON.encode!(%{ type: encode_type(geom.type), coordinates: geom.coordinates })
end
defp decode_type(geo_json_type) do
case geo_json_type do
"Point" ->
:point
"LineString" ->
:line_string
"Polygon" ->
:polygon
"MultiPoint" ->
:multi_point
"MultiLineString" ->
:multi_line_string
"MultiPolygon" ->
:multi_polygon
_ ->
:geometry_collection
end
end
defp encode_type(geom_type) do
case geom_type do
:point ->
"Point"
:line_string ->
"LineString"
:polygon ->
"Polygon"
:multi_point ->
"MultiPoint"
:multi_line_string ->
"MultiLineString"
:multi_polygon ->
"MultiPolygon"
_ ->
"GeometryCollection"
end
end
end