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@jarnaldich
Last active Mar 26, 2022
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[ETL in Haskell] Enrich a geojson file with attributes coming from an .xml #haskell #xml #geojson
#!/usr/bin/env stack
{-
stack
--install-ghc runghc
--package aeson
--package lens-aeson
--package xml-lens
-}
{-# Language OverloadedStrings #-}
import Control.Monad.Reader
import qualified Data.Text as T
import qualified Data.Text.IO as T
import qualified Data.ByteString.Lazy.Char8 as LB8
import qualified Data.Map as Map
import qualified Data.Vector as V
import Data.Scientific (Scientific)
import qualified Data.Aeson as Json
import Data.Aeson.Lens
import qualified Text.XML as XML
import Text.XML.Lens
records :: Reader XML.Document [(T.Text, Scientific)]
records =
let
field name = nodes . folded . _Element . named "field" . attributeIs "name" name
in do
magnify (root . named "Root" ./ named "data" ./ named "record") $ do
record <- ask
let name = record ^? (field "Country or Area" . attr "key")
let year = record ^? (field "Year" . text)
let val = record ^? (field "Value" . text)
return $ case (name, year, val) of
(Just key, Just "2020", Just val) -> [ (key, read $ T.unpack val) ]
_ -> []
features :: Map.Map T.Text Scientific -> Reader Json.Value [ Json.Value ]
features popMap = do
magnify (key "features" . values) $ do
feature <- ask
let Just id = feature ^? (key "id" . _String)
return $ case (Map.lookup id popMap) of
Just pop -> [ feature & key "properties" . _Object . at "pop2020" ?~ Json.Number pop ]
_ -> [ feature ]
main = do
xml <- XML.readFile XML.def "population.xml"
let pop2020Map = Map.fromList $ runReader records xml
jsonBytes <- LB8.readFile "countries.geo.json"
let Just json = Json.decode jsonBytes :: Maybe Json.Value
let featureList = runReader (features pop2020Map) json :: [ Json.Value ]
let newJson = json & key "features" .~ (Json.Array $ V.fromList featureList)
LB8.writeFile "countriesWithPopulation.geo.json" $ Json.encode newJson
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