{-# LANGUAGE OverloadedStrings #-} module Data.ISBN.ISBN10 ( ISBN(..) , validateISBN10 -- * Validation Errors , ISBN10ValidationError(..) , renderISBN10ValidationError -- * Helpers , confirmISBN10CheckDigit , calculateISBN10CheckDigitValue , isbn10CharToNumericValue , numericValueToISBN10Char , isValidISBN10CheckDigit , isNumericCharacter , isISBN10 -- * Unsafe Coercion , unsafeToISBN10 ) where import Control.Monad import Data.Char import Data.Text ( Text ) import qualified Data.Text as Text import Data.ISBN.Types ( ISBN (ISBN10) ) -- | Used to safely create 'ISBN10' values represented by the 'ISBN' data type. -- Assumes that the 'Data.Text.Text' input is an ISBN-10 string, either with or -- without hyphens. -- -- Will return either a validated ISBN-10 or an 'ISBN10ValidationError', which can be -- rendered as a descriptive string using 'renderISBN10ValidationError'. -- -- /Examples:/ -- -- @ -- validateISBN10 "0-345-81602-1" == Right (ISBN10 "0345816021") -- validateISBN10 "0345816021" == Right (ISBN10 "0345816021") -- validateISBN10 "0-807-01429-X" == Right (ISBN10 "080701429X") -- validateISBN10 "0-345-816" == Left ISBN10InvalidInputLength -- validateISBN10 "X-345-81602-1" == Left ISBN10IllegalCharactersInBody -- validateISBN10 "0-345-81602-B" == Left ISBN10IllegalCharacterAsCheckDigit -- validateISBN10 "0-345-81602-3" == Left ISBN10InvalidCheckDigit -- @ validateISBN10 :: Text -> Either ISBN10ValidationError ISBN validateISBN10 input = do -- Make a copy of the text input before further manipulation to prevent -- space leaks if input text is a slice of a larger string let inputWithoutHyphens = Text.filter (/= '-') $ Text.copy input unless (Text.length inputWithoutHyphens == 10) $ Left ISBN10InvalidInputLength let invalidBodyCharacters = Text.filter (not . isNumericCharacter) (Text.init inputWithoutHyphens) unless (Text.length invalidBodyCharacters == 0) $ Left ISBN10IllegalCharactersInBody unless (isValidISBN10CheckDigit $ Text.last inputWithoutHyphens) $ Left ISBN10IllegalCharacterAsCheckDigit unless (confirmISBN10CheckDigit inputWithoutHyphens) $ Left ISBN10InvalidCheckDigit pure $ ISBN10 inputWithoutHyphens -- | Possible validation errors resulting from ISBN-10 validation. data ISBN10ValidationError = ISBN10InvalidInputLength -- ^ The length of the input string is not 10 characters, not counting hyphens | ISBN10IllegalCharactersInBody -- ^ The first nine characters of the ISBN-10 input contain non-numeric characters | ISBN10IllegalCharacterAsCheckDigit -- ^ The check digit of the ISBN-10 is not a valid character (@0-9@ or @\'X\'@) | ISBN10InvalidCheckDigit -- ^ The check digit is not valid for the given ISBN-10 deriving (Show, Eq) -- | Convert an 'ISBN10ValidationError' into a human-friendly error message. renderISBN10ValidationError :: ISBN10ValidationError -> Text renderISBN10ValidationError validationError = case validationError of ISBN10InvalidInputLength -> "An ISBN-10 must be 10 characters, not counting hyphens" ISBN10IllegalCharactersInBody -> "The first nine characters of an ISBN-10 must all be numbers" ISBN10IllegalCharacterAsCheckDigit -> "The last character of the supplied ISBN-10 must be a number or the letter 'X'" ISBN10InvalidCheckDigit -> "The supplied ISBN-10 is not valid" -- | Confirms that the check digit of an ISBN-10 is correct. Assumes that the -- input consists of 9 numeric characters followed by a legal check digit -- character (@0-9@ or @X@). -- -- /Examples:/ -- -- @ -- confirmISBN10CheckDigit "0345816021" == True -- confirmISBN10CheckDigit "080701429X" == True -- @ confirmISBN10CheckDigit :: Text -> Bool confirmISBN10CheckDigit isbn10 = calculateISBN10CheckDigitValue (Text.init isbn10) == isbn10CharToNumericValue (Text.last isbn10) -- | Calculates an ISBN-10 check digit value using the standard check digit -- calculation formula. Assumes that the input is 9 numeric characters. The -- check digit value can be any number in the range 0 to 10, the last of -- which is represented by the symbol \'X\' in an ISBN-10. -- -- See: -- -- /Examples:/ -- -- @ -- calculateISBN10CheckDigitValue "034581602" == 1 -- calculateISBN10CheckDigitValue "080701429" == 10 -- @ calculateISBN10CheckDigitValue :: Text -> Int calculateISBN10CheckDigitValue input = go 10 (Text.unpack input) 0 where go n charList acc = case charList of [] -> (11 - (acc `mod` 11)) `mod` 11 c:clist -> go (n - 1) clist (acc + isbn10CharToNumericValue c * n) -- | Converts an ISBN-10 character to a numeric value. Valid input characters -- include @0-9@ as well as @X@. isbn10CharToNumericValue :: Char -> Int isbn10CharToNumericValue 'X' = 10 isbn10CharToNumericValue c = digitToInt c -- | Converts a numeric value to an ISBN-10 character. Valid input values -- are the numbers from 0 to 10. numericValueToISBN10Char :: Int -> Char numericValueToISBN10Char 10 = 'X' numericValueToISBN10Char c = Text.head $ Text.pack $ show c -- | Validates a character as a valid ISBN-10 check digit character. ISBN-10 -- check digit characters include @0-9@ as well as the symbol @'X'@. The lowercase -- letter \'x\' is not considered valid. isValidISBN10CheckDigit :: Char -> Bool isValidISBN10CheckDigit char = char `elem` ("1234567890X" :: String) -- | Determines whether a character is numeric (e.g. in the range of @0-9@). isNumericCharacter :: Char -> Bool isNumericCharacter char = char `elem` ("1234567890" :: String) -- | Determines whether an 'ISBN' value is an ISBN-10. -- -- /Examples:/ -- -- @ -- isISBN10 (unsafeToISBN10 "0060899220") == True -- isISBN10 (unsafeToISBN13 "9780060899226") == False -- @ -- -- /Since: 1.1.0.0/ isISBN10 :: ISBN -> Bool isISBN10 (ISBN10 _) = True isISBN10 _ = False -- | Will create an 'ISBN10' value without any validation. unsafeToISBN10 :: Text -> ISBN unsafeToISBN10 = ISBN10