-- Copyright 2020 United States Government as represented by the Administrator
-- of the National Aeronautics and Space Administration. All Rights Reserved.
--
-- Disclaimers
--
-- No Warranty: THE SUBJECT SOFTWARE IS PROVIDED "AS IS" WITHOUT ANY WARRANTY
-- OF ANY KIND, EITHER EXPRESSED, IMPLIED, OR STATUTORY, INCLUDING, BUT NOT
-- LIMITED TO, ANY WARRANTY THAT THE SUBJECT SOFTWARE WILL CONFORM TO
-- SPECIFICATIONS, ANY IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS FOR A
-- PARTICULAR PURPOSE, OR FREEDOM FROM INFRINGEMENT, ANY WARRANTY THAT THE
-- SUBJECT SOFTWARE WILL BE ERROR FREE, OR ANY WARRANTY THAT DOCUMENTATION, IF
-- PROVIDED, WILL CONFORM TO THE SUBJECT SOFTWARE. THIS AGREEMENT DOES NOT, IN
-- ANY MANNER, CONSTITUTE AN ENDORSEMENT BY GOVERNMENT AGENCY OR ANY PRIOR
-- RECIPIENT OF ANY RESULTS, RESULTING DESIGNS, HARDWARE, SOFTWARE PRODUCTS OR
-- ANY OTHER APPLICATIONS RESULTING FROM USE OF THE SUBJECT SOFTWARE. FURTHER,
-- GOVERNMENT AGENCY DISCLAIMS ALL WARRANTIES AND LIABILITIES REGARDING
-- THIRD-PARTY SOFTWARE, IF PRESENT IN THE ORIGINAL SOFTWARE, AND DISTRIBUTES
-- IT "AS IS."
--
-- Waiver and Indemnity: RECIPIENT AGREES TO WAIVE ANY AND ALL CLAIMS AGAINST
-- THE UNITED STATES GOVERNMENT, ITS CONTRACTORS AND SUBCONTRACTORS, AS WELL AS
-- ANY PRIOR RECIPIENT. IF RECIPIENT'S USE OF THE SUBJECT SOFTWARE RESULTS IN
-- ANY LIABILITIES, DEMANDS, DAMAGES, EXPENSES OR LOSSES ARISING FROM SUCH USE,
-- INCLUDING ANY DAMAGES FROM PRODUCTS BASED ON, OR RESULTING FROM, RECIPIENT'S
-- USE OF THE SUBJECT SOFTWARE, RECIPIENT SHALL INDEMNIFY AND HOLD HARMLESS THE
-- UNITED STATES GOVERNMENT, ITS CONTRACTORS AND SUBCONTRACTORS, AS WELL AS ANY
-- PRIOR RECIPIENT, TO THE EXTENT PERMITTED BY LAW. RECIPIENT'S SOLE REMEDY
-- FOR ANY SUCH MATTER SHALL BE THE IMMEDIATE, UNILATERAL TERMINATION OF THIS
-- AGREEMENT.
--
-- | Auxiliary functions for working with values of type 'String'.
module Data.String.Extra
    (
      -- * Safe I/O
      safeReadFile

      -- * String sanitization
    , sanitizeLCIdentifier
    , sanitizeUCIdentifier
    )
  where

-- External imports
import Control.Exception ( catch )
import Data.Char         ( toLower, toUpper )
import System.IO.Error   ( isDoesNotExistError )

-- * Safe I/O

-- | Safely read a file into a 'String', returning a 'Left' error message if
-- the file cannot be opened.

-- This function could also be placed in System.IO. However, we decide to
-- include it in this module for symmetry with an analogous function for
-- ByteString, included in Data.ByteString.Extra.
safeReadFile :: FilePath -> IO (Either String String)
safeReadFile :: String -> IO (Either String String)
safeReadFile String
fp =
  forall e a. Exception e => IO a -> (e -> IO a) -> IO a
catch (forall (m :: * -> *) a. Monad m => a -> m a
return forall (f :: * -> *) a b. Functor f => (a -> b) -> f a -> f b
<$> String -> IO String
readFile String
fp) forall a b. (a -> b) -> a -> b
$ \IOError
e ->
    if IOError -> Bool
isDoesNotExistError IOError
e
      then forall (m :: * -> *) a. Monad m => a -> m a
return forall a b. (a -> b) -> a -> b
$ forall a b. a -> Either a b
Left forall a b. (a -> b) -> a -> b
$ String -> String
strStringFileNotFound String
fp
      else forall (m :: * -> *) a. Monad m => a -> m a
return forall a b. (a -> b) -> a -> b
$ forall a b. a -> Either a b
Left forall a b. (a -> b) -> a -> b
$ String -> String
strStringCannotOpenFile String
fp

-- ** Error messages

-- | File-not-found message.
strStringFileNotFound :: FilePath -> String
strStringFileNotFound :: String -> String
strStringFileNotFound String
fp = String
"File not found: " forall a. [a] -> [a] -> [a]
++ String
fp

-- | Cannot-open-file message.
strStringCannotOpenFile :: FilePath -> String
strStringCannotOpenFile :: String -> String
strStringCannotOpenFile String
fp = String
"Error opening file: " forall a. [a] -> [a] -> [a]
++ String
fp

-- * Sanitization

-- | Remove extraneous characters from an identifier and make the starting
-- character lowercase.
--
-- This function currently replaces hyphens with underscores.
sanitizeLCIdentifier :: String -> String
sanitizeLCIdentifier :: String -> String
sanitizeLCIdentifier = String -> String
headToLower forall b c a. (b -> c) -> (a -> b) -> a -> c
. forall a b. (a -> b) -> [a] -> [b]
map Char -> Char
sanitizeCharacter
  where
    sanitizeCharacter :: Char -> Char
sanitizeCharacter Char
'-' = Char
'_'
    sanitizeCharacter Char
x   = Char
x

    headToLower :: [Char] -> [Char]
    headToLower :: String -> String
headToLower []     = []
    headToLower (Char
x:String
xs) = Char -> Char
toLower Char
x forall a. a -> [a] -> [a]
: String
xs

-- | Remove extraneous characters from an identifier and make the starting
-- character uppercase.
--
-- This function currently replaces hyphens with underscores.
sanitizeUCIdentifier :: String -> String
sanitizeUCIdentifier :: String -> String
sanitizeUCIdentifier = String -> String
headToUpper forall b c a. (b -> c) -> (a -> b) -> a -> c
. forall a b. (a -> b) -> [a] -> [b]
map Char -> Char
sanitizeCharacter
  where
    sanitizeCharacter :: Char -> Char
sanitizeCharacter Char
'-' = Char
'_'
    sanitizeCharacter Char
x   = Char
x

    headToUpper :: [Char] -> [Char]
    headToUpper :: String -> String
headToUpper []     = []
    headToUpper (Char
x:String
xs) = Char -> Char
toUpper Char
x forall a. a -> [a] -> [a]
: String
xs