From 4399097564c041838140225f30dcda7f92caa88a Mon Sep 17 00:00:00 2001
From: Joris
Date: Wed, 10 May 2017 10:29:30 +0200
Subject: Add tests for purescript number and parser utilities

---
 js/src/Parser.purs | 76 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 76 insertions(+)
 create mode 100644 js/src/Parser.purs

(limited to 'js/src/Parser.purs')

diff --git a/js/src/Parser.purs b/js/src/Parser.purs
new file mode 100644
index 0000000..cad9f1b
--- /dev/null
+++ b/js/src/Parser.purs
@@ -0,0 +1,76 @@
+module Parser
+  ( TextWithNumber
+  , textWithNumber
+  , number
+  ) where
+
+import Control.Alt ((<|>))
+import Data.Array as Array
+import Data.Char as Char
+import Data.Either (Either(Right))
+import Data.Int as Int
+import Data.Maybe (fromMaybe) as Maybe
+import Data.Maybe (Maybe(Just, Nothing))
+import Data.String as String
+import Prelude
+import Text.Parsing.Parser (Parser)
+import Text.Parsing.Parser (runParser) as Parser
+import Text.Parsing.Parser.Combinators (optionMaybe) as Parser
+import Text.Parsing.Parser.String (satisfy, anyChar, string, eof) as Parser
+
+type TextWithNumber =
+  { begin :: String
+  , number :: Number
+  , end :: String
+  }
+
+textWithNumber :: String -> Maybe TextWithNumber
+textWithNumber input =
+  case Parser.runParser input textWithNumberParser of
+    Right x -> Just x
+    _ -> Nothing
+
+number :: String -> Maybe Number
+number input =
+  case Parser.runParser input (numberParser <* Parser.eof) of
+    Right x -> Just x
+    _ -> Nothing
+
+textWithNumberParser :: Parser String TextWithNumber
+textWithNumberParser = do
+  begin <- String.fromCharArray <$> Array.many notDigit
+  num <- numberParser
+  end <- String.fromCharArray <$> Array.many Parser.anyChar
+  pure { begin: begin, number: num, end: end }
+
+numberFromIntArray :: Array Int -> Int
+numberFromIntArray xs =
+  Array.range 0 (Array.length xs - 1)
+    # map (Int.pow 10)
+    # Array.reverse
+    # Array.zipWith (*) xs
+    # Array.foldl (+) 0
+
+notDigit :: Parser String Char
+notDigit = Parser.satisfy (not <<< isDigit)
+
+numberParser :: Parser String Number
+numberParser = do
+  whole <- numberFromIntArray <$> Array.some digit
+  decimal <- Parser.optionMaybe $ do
+    _ <- Parser.string "," <|> Parser.string "."
+    digits <- Array.some digit
+    let decimals = numberFromIntArray digits
+    pure $ Int.toNumber decimals / Int.toNumber (Int.pow 10 (Array.length digits))
+  pure (Int.toNumber whole + Maybe.fromMaybe 0.0 decimal)
+
+digit :: Parser String Int
+digit = map (\c -> Char.toCharCode c - zeroCode) $ Parser.satisfy isDigit
+
+isDigit :: Char -> Boolean
+isDigit char =
+  let code = Char.toCharCode char
+  in  code >= zeroCode && code <= zeroCode + 9
+
+zeroCode :: Int
+zeroCode = 48
-- 
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