Merge pull request #227 from citizennet/arthur/negative-cents

Fix `Ocelot.Data.Currency` functions not working with negative `Cents` values

Author: arthurxavierx

package.json

@@ -1,6 +1,6 @@
 {
   "name": "purescript-ocelot",
-  "version": "0.33.1",
+  "version": "0.33.2",
   "private": true,
   "scripts": {
     "build-all": "make build",

src/Data/Currency.purs

@@ -14,6 +14,7 @@ import Data.Foldable (foldr)
 import Data.Int (fromString) as Int
 import Data.Maybe (Maybe(..), fromMaybe, isJust)
 import Data.Newtype (class Newtype, unwrap)
+import Data.Ord (abs)
 import Data.String (Pattern(..), Replacement(..), length, replaceAll, split, take, null)
 import Data.String.CodeUnits (toCharArray, fromCharArray)
 import Data.Tuple (Tuple(..), snd)
@@ -81,9 +82,11 @@ parseCentsFromDollarStr str = Cents <$> case split (Pattern ".") str of
 
   -- There is one decimal; truncate the cents to 2 places and
   -- add them to the dollars
-  [ dollars, cents ] ->
-    bigIntIs64Bit
-    =<< (+) <$> dollarsPlace dollars <*> BigInt.fromString (take 2 $ cents <> "0")
+  [ dollars, cents ] -> do
+    dollars' <- dollarsPlace dollars
+    cents' <- BigInt.fromString (take 2 $ cents <> "0")
+    let bigInt = if dollars' < zero then dollars' - cents' else dollars' + cents'
+    bigIntIs64Bit bigInt
 
   -- Unable to parse
   _ -> Nothing
@@ -115,8 +118,8 @@ parseCentsFromDollarStr str = Cents <$> case split (Pattern ".") str of
 -- in dollars.
 formatCentsToStrDollars :: Cents -> String
 formatCentsToStrDollars (Cents n)
-  | BigInt.toNumber n < 10.0  = "0.0" <> BigInt.toString n
-  | BigInt.toNumber n < 100.0 = "0." <> BigInt.toString n
+  | abs (BigInt.toNumber n) < 10.0  = (if n < zero then "-" else "") <> "0.0" <> BigInt.toString n
+  | abs (BigInt.toNumber n) < 100.0 = (if n < zero then "-" else "") <> "0." <> BigInt.toString n
   | otherwise = fromCharArray <<< snd $ foldr formatCentsToDollars' (Tuple 0 []) (chars n)
     where
       chars :: BigInt -> Array Char

test/Test/Data/Currency.purs

@@ -5,8 +5,10 @@ import Prelude
 import Ocelot.Data.Currency (Cents(..), formatCentsToStrDollars, parseCentsFromDollarStr, parseCentsFromMicroDollars)
 import Data.BigInt as BigInt
 import Data.Maybe (Maybe(..))
+import Test.QuickCheck ((===))
 import Test.Unit as Test.Unit
 import Test.Unit.Assert as Test.Unit.Assert
+import Test.Unit.QuickCheck as Test.Unit.QuickCheck
 
 suite :: Test.Unit.TestSuite
 suite = do
@@ -56,6 +58,11 @@ suite = do
           result = parseCentsFromDollarStr "1,234."
       Test.Unit.Assert.equal expect result
 
+    Test.Unit.test "parseCentsFromDollarStr -1,234.50" do
+      let expect = Just $ Cents $ BigInt.fromInt (-123450)
+          result = parseCentsFromDollarStr "-1,234.50"
+      Test.Unit.Assert.equal expect result
+
     Test.Unit.test "formatCentsToStrDollars 0.00" do
       let result = formatCentsToStrDollars $ Cents $ BigInt.fromInt 0
       Test.Unit.Assert.equal "0.00" result
@@ -71,3 +78,12 @@ suite = do
     Test.Unit.test "formatCentsToStrDollars 1,234.00" do
       let result = formatCentsToStrDollars $ Cents $ BigInt.fromInt 123400
       Test.Unit.Assert.equal "1,234.00" result
+
+    Test.Unit.test "formatCentsToStrDollars -1,234.50" do
+      let result = formatCentsToStrDollars $ Cents $ BigInt.fromInt (-123450)
+      Test.Unit.Assert.equal "-1,234.50" result
+
+    Test.Unit.test "Just cents === parseCentsFromDollarStr (formatCentsToStrDollars cents)" do
+      Test.Unit.QuickCheck.quickCheck \int -> do
+        let cents = Cents $ BigInt.fromInt int
+        Just cents === parseCentsFromDollarStr (formatCentsToStrDollars cents)