{-# LANGUAGE OverloadedStrings #-} module Data.ISBN.ISBN13 ( ISBN(..) , validateISBN13 -- * Validation Errors , renderISBN13ValidationError , ISBN13ValidationError(..) -- * Helpers , confirmISBN13CheckDigit , calculateISBN13CheckDigitValue , numericValueToISBN13Char , isISBN13 -- * Unsafe Coercion , unsafeToISBN13 ) where import Control.Monad import Data.Char import Data.Text ( Text ) import qualified Data.Text as Text import Data.ISBN.Types ( ISBN (ISBN13) ) -- | Used to safely create 'ISBN13' values represented by the 'ISBN' data type. -- Assumes that the 'Data.Text.Text' input is an ISBN-13 string, either with or -- without hyphens. -- -- Will return either a validated ISBN-13 or an 'ISBN13ValidationError', which can be -- rendered as a descriptive string using 'renderISBN13ValidationError'. -- -- /Examples:/ -- -- @ -- validateISBN13 "9780345816023" == Right (ISBN13 "9780345816023") -- validateISBN13 "9780807014295" == Right (ISBN13 "9780807014295") -- validateISBN13 "9780306406157" == Right (ISBN13 "9780306406157") -- validateISBN13 "978-0-306-40615-7" == Right (ISBN13 "9780306406157") -- validateISBN13 "9780345816029" == Left ISBN13InvalidCheckDigit -- validateISBN13 "9780807014299" == Left ISBN13InvalidCheckDigit -- validateISBN13 "00000000000000" == Left ISBN13InvalidInputLength -- validateISBN13 "0X00000000000" == Left ISBN13IllegalCharactersInInput -- @ validateISBN13 :: Text -> Either ISBN13ValidationError ISBN validateISBN13 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 == 13) $ Left ISBN13InvalidInputLength let illegalCharacters = Text.filter (not . isNumericCharacter) inputWithoutHyphens unless (Text.length illegalCharacters == 0) $ Left ISBN13IllegalCharactersInInput unless (confirmISBN13CheckDigit inputWithoutHyphens) $ Left ISBN13InvalidCheckDigit pure $ ISBN13 inputWithoutHyphens -- | Possible validation errors resulting from ISBN-13 validation. data ISBN13ValidationError = ISBN13InvalidInputLength -- ^ The length of the input string is not 13 characters, not counting hyphens | ISBN13IllegalCharactersInInput -- ^ The ISBN-13 input contains non-numeric characters | ISBN13InvalidCheckDigit -- ^ The check digit is not valid for the given ISBN-13 deriving (Show, Eq) -- | Convert an 'ISBN13ValidationError' into a human-friendly error message. renderISBN13ValidationError :: ISBN13ValidationError -> Text renderISBN13ValidationError validationError = case validationError of ISBN13InvalidInputLength -> "An ISBN-13 must be 13 characters, not counting hyphens" ISBN13IllegalCharactersInInput -> "Every non-hyphen character of an ISBN-13 must be a number" ISBN13InvalidCheckDigit -> "The supplied ISBN-13 is not valid" -- | Determines whether a character is numeric (e.g. in the range of @0-9@). isNumericCharacter :: Char -> Bool isNumericCharacter char = char `elem` ("1234567890" :: String) -- | Confirms that the check digit of an ISBN-13 is correct. Assumes that the -- input consists of 12 numeric characters followed by a legal check digit -- character (@0-9@). -- -- /Examples:/ -- -- @ -- confirmISBN13CheckDigit "9780306406157" == True -- confirmISBN13CheckDigit "9780345816029" == False -- @ confirmISBN13CheckDigit :: Text -> Bool confirmISBN13CheckDigit isbn13 = calculateISBN13CheckDigitValue (Text.init isbn13) == isbn13CharToNumericValue (Text.last isbn13) -- | Calculates an ISBN-13 check digit value using the standard check digit -- calculation formula. Assumes that the input is 12 numeric characters. The -- check digit value will be a number from 0 to 9. -- -- See: -- -- /Examples:/ -- -- @ -- calculateISBN13CheckDigitValue "978030640615" == 7 -- calculateISBN13CheckDigitValue "978151915024" == 0 -- @ calculateISBN13CheckDigitValue :: Text -> Int calculateISBN13CheckDigitValue input = go 1 (Text.unpack input) 0 where go w charList acc = case charList of [] -> (10 - (acc `mod` 10)) `mod` 10 c:clist -> go ((w + 2) `mod` 4) clist (acc + w * isbn13CharToNumericValue c) -- | Converts an ISBN-13 character to a numeric value. Valid input characters -- include @0-9@ as well as @X@. isbn13CharToNumericValue :: Char -> Int isbn13CharToNumericValue = digitToInt -- | Converts a numeric value to an ISBN-13 character. Valid input values -- are the numbers from 0 to 10. numericValueToISBN13Char :: Int -> Char numericValueToISBN13Char c = Text.head $ Text.pack $ show c -- | Determines whether an 'ISBN' value is an ISBN-13. -- -- /Examples:/ -- -- @ -- isISBN13 (unsafeToISBN10 "0060899220") == False -- isISBN13 (unsafeToISBN13 "9780060899226") == True -- @ -- -- /Since: 1.1.0.0/ isISBN13 :: ISBN -> Bool isISBN13 (ISBN13 _) = True isISBN13 _ = False -- | Will create an 'ISBN13' value without any validation. unsafeToISBN13 :: Text -> ISBN unsafeToISBN13 = ISBN13