using camelCase for mapping from JSON with Purescript

example.purs

{-
  Author    | Tim Dysinger <tim@dysinger.net>
  Copyright | WTFPL 2.0 http://www.gnu.org/licenses/license-list.html#WTFPL
-}

module Main where

import Control.Monad.Eff
import Data.Array
import Data.Foreign
import Debug.Trace

{- GOAL: Take an example Amazon API response & use it in PS.  Amazon
uses "PascalCase" in it's Webservice API.  This breaks Purescript's
mapping to record attributes.  Purescript uses PascalCase for data
types and camelCase for functions & attributes. -}

foreign import data AWS :: !

foreign import amazonWebServiceRegions
  """
  function amazonWebServiceRegions() {
    return {
      "Regions": [
        {
          "Endpoint": "ec2.eu-west-1.amazonaws.com",
          "RegionName": "eu-west-1"
        },
        {
          "Endpoint": "ec2.sa-east-1.amazonaws.com",
          "RegionName": "sa-east-1"
        },
        {
          "Endpoint": "ec2.us-east-1.amazonaws.com",
          "RegionName": "us-east-1"
        },
        {
          "Endpoint": "ec2.ap-northeast-1.amazonaws.com",
          "RegionName": "ap-northeast-1"
        },
        {
          "Endpoint": "ec2.us-west-2.amazonaws.com",
          "RegionName": "us-west-2"
        },
        {
          "Endpoint": "ec2.us-west-1.amazonaws.com",
          "RegionName": "us-west-1"
        },
        {
          "Endpoint": "ec2.ap-southeast-1.amazonaws.com",
          "RegionName": "ap-southeast-1"
        },
        {
          "Endpoint": "ec2.ap-southeast-2.amazonaws.com",
          "RegionName": "ap-southeast-2"
        }
      ]
    }
  }
  """
  :: forall e. Eff (aws :: AWS | e) Foreign

foreign import camelCase
  """
  var us = require('underscore');
  var cc = require('change-case');
  function camelCase(obj) {
    if ( us.isArray(obj) ) {
      return us.map(obj, camelCase);
    } else if ( us.isObject(obj) ) {
      return us.reduce(us.pairs(obj), function(m, p) {
        m[cc.camelCase(p[0])] = camelCase(p[1]);
        return m;
      }, {});
    } else {
      return obj;
    }
  }
  """
  :: Foreign -> Foreign

main = do
  rs <- amazonWebServiceRegions >>= return <<< unsafeFromForeign <<< camelCase
  print $ map (\r -> r.regionName :: String) rs.regions

-- prints ["eu-west-1","sa-east-1","us-east-1","ap-northeast-1","us-west-2","us-west-1","ap-southeast-1","ap-southeast-2"]