GeoFeatureCollection.hs

{-# LANGUAGE NoImplicitPrelude #-}
{-# LANGUAGE OverloadedStrings #-}
{-# LANGUAGE TemplateHaskell   #-}
-------------------------------------------------------------------
-- |
-- Module       : Data.Geospatial.Internal.GeoFeature
-- Copyright    : (C) 2014-2019 HS-GeoJSON Project
-- License      : BSD-style (see the file LICENSE.md)
-- Maintainer   : Andrew Newman
--
-- See Section 2.3 /Feature Collection Objects/ of the GeoJSON spec
--
-------------------------------------------------------------------
module Data.Geospatial.Internal.GeoFeatureCollection (
    -- * Types
        GeoFeatureCollection(..)
    -- * Lenses
    ,   boundingbox
    ,   geofeatures
    ) where

import           Data.Geospatial.Internal.BasicTypes
import           Data.Geospatial.Internal.GeoFeature
import           Data.Geospatial.Internal.Geometry.Aeson

import           Control.Applicative                     ((<$>), (<*>))
import           Control.Lens                            (makeLenses)
import           Control.Monad                           (mzero)
import           Data.Aeson                              (FromJSON (..),
                                                          ToJSON (..),
                                                          Value (..), object,
                                                          (.:), (.:?), (.=))
import           Data.List                               ((++))
import           Data.Maybe                              (Maybe (..))
import qualified Data.Sequence                           as Sequence
import           Data.Text                               (Text)
import           Prelude                                 (Eq (..), Show, ($))

-- | See Section 2.3 /Feature Collection Objects/ of the GeoJSON spec
--
data GeoFeatureCollection a = GeoFeatureCollection
    {   _boundingbox :: Maybe BoundingBoxWithoutCRS
    ,   _geofeatures :: Sequence.Seq (GeoFeature a)
    } deriving (Show, Eq)

makeLenses ''GeoFeatureCollection

-- instances

-- | Decode FeatureCollection objects from GeoJSON
--
instance (FromJSON a) => FromJSON (GeoFeatureCollection a) where
--  parseJSON :: Value -> Parse a
    parseJSON (Object obj) = do
        objType <- obj .: ("type" :: Text)
        if objType /= ("FeatureCollection" :: Text)
            then
                mzero
            else
                GeoFeatureCollection
                    <$> obj .:? ("bbox" :: Text)
                    <*> obj .: ("features" :: Text)
    parseJSON _ = mzero

-- | Encode FeatureCollection objects to GeoJSON
--
instance (ToJSON a) => ToJSON (GeoFeatureCollection a) where
--  toJSON :: a -> Value
    toJSON (GeoFeatureCollection bbox' features) = object $ baseAttributes ++ optAttributes "bbox" bbox'
        where
            baseAttributes = ["type" .= ("FeatureCollection" :: Text), "features" .= features]