defmodule Exisbn do
require Integer
alias Exisbn.Regions
@moduledoc """
Documentation for `Exisbn`.
"""
@doc """
Takes an ISBN 10 code as string, returns its check digit.
## Examples
iex> Exisbn.isbn10_checkdigit("85-359-0277")
5
iex> Exisbn.isbn10_checkdigit("5-02-013850")
9
iex> Exisbn.isbn10_checkdigit("0str")
nil
"""
@spec isbn10_checkdigit(String.t()) :: nil | <<_::8>> | integer
def isbn10_checkdigit(isbn) when is_bitstring(isbn) do
if String.length(normalize(isbn)) in 8..10 do
nsum =
isbn
|> normalize()
|> String.slice(0..8)
|> String.split("", trim: true)
|> Enum.map(&to_int/1)
|> Enum.with_index()
|> Enum.map(fn {val, ind} ->
(10 - ind) * val
end)
|> Enum.reduce(&+/2)
digit = Integer.mod(11 - Integer.mod(nsum, 11), 11)
if digit == 10, do: "X", else: digit
else
nil
end
end
@doc """
Takes an ISBN 13 code as string, returns its check digit.
## Examples
iex> Exisbn.isbn13_checkdigit("978-5-12345-678")
1
iex> Exisbn.isbn13_checkdigit("978-0-306-40615")
7
iex> Exisbn.isbn13_checkdigit("0str")
nil
"""
@spec isbn13_checkdigit(binary) :: nil | integer
def isbn13_checkdigit(isbn) when is_bitstring(isbn) do
if String.length(normalize(isbn)) in 11..13 do
nsum =
isbn
|> normalize()
|> String.slice(0..11)
|> String.split("", trim: true)
|> Enum.map(&to_int/1)
|> Enum.with_index()
|> Enum.map(fn {val, ind} ->
if Integer.is_odd(ind), do: val * 3, else: val
end)
|> Enum.reduce(&+/2)
digit = 10 - Integer.mod(nsum, 10)
if digit == 10, do: 0, else: digit
else
nil
end
end
@doc """
Takes an ISBN (10 or 13) and checks its validity by its check digit
## Examples
iex> Exisbn.checkdigit_correct?("85-359-0277-5")
true
iex> Exisbn.checkdigit_correct?("978-5-12345-678-1")
true
iex> Exisbn.checkdigit_correct?("978-5-12345-678")
false
"""
@spec checkdigit_correct?(String.t()) :: boolean
def checkdigit_correct?(isbn) when is_bitstring(isbn) do
normalized = normalize(isbn)
digit =
if String.length(normalized) == 10 do
isbn10_checkdigit(normalized)
else
isbn13_checkdigit(normalized)
end
to_string(digit) == String.last(normalized)
end
@doc """
Takes an ISBN (10 or 13) and checks its validity by checking the checkdigit, length and characters.
## Examples
iex> Exisbn.valid?("978-5-12345-678-1")
true
iex> Exisbn.valid?("978-5-12345-678-1")
true
iex> Exisbn.valid?("978-5-12345-678")
false
iex> Exisbn.valid?("85-359-0277-5")
true
iex> Exisbn.valid?("85-359-0277")
false
"""
@spec valid?(String.t()) :: boolean
def valid?(isbn) do
Enum.all?([
correct_length?(isbn),
without_incorrect_chars?(isbn),
checkdigit_correct?(isbn)
])
end
@doc """
Takes an ISBN 10 and converts it to ISBN 13.
## Examples
iex> Exisbn.isbn10_to_13("85-359-0277-5")
"9788535902778"
iex> Exisbn.valid?("9788535902778")
true
iex> Exisbn.isbn10_to_13("0306406152")
"9780306406157"
iex> Exisbn.valid?("9780306406157")
true
iex> Exisbn.isbn10_to_13("0-19-853453123")
nil
"""
@spec isbn10_to_13(String.t()) :: String.t() | nil
def isbn10_to_13(isbn) when is_bitstring(isbn) do
if correct?(isbn) do
first_chars = "978#{String.slice(normalize(isbn), 0..8)}"
"#{first_chars}#{isbn13_checkdigit(first_chars)}"
else
nil
end
end
@doc """
Takes an ISBN 13 and converts it to ISBN 10.
## Examples
iex> Exisbn.isbn13_to_10("9788535902778")
"8535902775"
iex> Exisbn.valid?("8535902775")
true
iex> Exisbn.isbn13_to_10("9780306406157")
"0306406152"
iex> Exisbn.valid?("0306406152")
true
iex> Exisbn.isbn13_to_10("str")
nil
"""
@spec isbn13_to_10(String.t()) :: String.t() | nil
def isbn13_to_10(isbn) when is_bitstring(isbn) do
if correct?(isbn) do
first_chars =
isbn
|> normalize()
|> drop_chars(3)
|> String.slice(0..8)
"#{first_chars}#{isbn10_checkdigit(first_chars)}"
else
nil
end
end
@doc """
Takes an ISBN and returns its publisher zone.
## Examples
iex> Exisbn.publisher_zone("9788535902778")
"Brazil"
iex> Exisbn.publisher_zone("2-1234-5680-2")
"French language"
iex> Exisbn.publisher_zone("str")
nil
"""
@spec publisher_zone(String.t()) :: String.t() | nil
def publisher_zone(isbn) when is_bitstring(isbn) do
if correct?(isbn) do
prepared_isbn = if isbn10?(isbn), do: isbn10_to_13(isbn), else: normalize(isbn)
Map.get(fetch_info(prepared_isbn), "name")
else
nil
end
end
@doc """
Takes an ISBN and returns its prefix.
## Examples
iex> Exisbn.get_prefix("9788535902778")
"978-85"
iex> Exisbn.get_prefix("2-1234-5680-2")
"978-2"
iex> Exisbn.get_prefix("str")
nil
"""
@spec get_prefix(String.t()) :: String.t() | nil
def get_prefix(isbn) when is_bitstring(isbn) do
if correct?(isbn) do
prepared_isbn = if isbn10?(isbn), do: isbn10_to_13(isbn), else: normalize(isbn)
get_prefix(String.slice(prepared_isbn, 0..2), drop_chars(prepared_isbn, 3), 0)
else
nil
end
end
@doc """
Takes an ISBN and returns its checkdigit.
## Examples
iex> Exisbn.fetch_checkdigit("9788535902778")
8
iex> Exisbn.fetch_checkdigit("2-1234-5680-2")
2
iex> Exisbn.fetch_checkdigit("str")
nil
"""
@spec fetch_checkdigit(String.t()) :: String.t() | nil
def fetch_checkdigit(isbn) when is_bitstring(isbn) do
if correct?(isbn) do
to_int(String.last(isbn))
else
nil
end
end
defp normalize(isbn) do
isbn
|> String.split("", trim: true)
|> Enum.filter(fn ch -> is_digit(ch) || ch == "X" end)
|> Enum.join()
end
defp correct_length?(isbn) do
Enum.member?([10, 13, 17], String.length(isbn))
end
defp without_incorrect_chars?(isbn) do
isbn
|> normalize()
|> correct_length?()
end
defp isbn10?(isbn) do
length = isbn |> normalize() |> String.length()
length == 10
end
defp to_int(char) do
{number, _} = Integer.parse(char)
number
end
defp correct?(isbn) do
valid?(normalize(isbn))
end
defp drop_chars(str, amount) do
String.slice(str, amount..String.length(str))
end
defp is_digit(ch) do
Enum.member?(["0", "1", "2", "3", "4", "5", "6", "7", "8", "9"], ch)
end
defp get_prefix(prefix, body, search_length) do
search_prefix = "#{prefix}-#{String.slice(body, 0..search_length)}"
if Map.has_key?(Regions.dataset(), search_prefix) do
search_prefix
else
get_prefix(prefix, body, search_length + 1)
end
end
defp fetch_info(isbn) do
Map.get(Regions.dataset(), get_prefix(isbn))
end
end
