Initial commit

lib/iban_ex/validator/validator.ex

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+defmodule IbanEx.Validator do
+  alias IbanEx.{Country, Parser}
+  alias IbanEx.Validator.Replacements
+  import IbanEx.Commons, only: [normalize: 1]
+
+  @spec validate(String.t()) :: {:ok, String.t()} | {:error}
+  def validate(iban) do
+    cond do
+      iban_violates_format?(iban) ->
+        {:error, :invalid_format}
+
+      iban_unsupported_country?(iban) ->
+        {:error, :unsupported_country_code}
+
+      iban_violates_length?(iban) ->
+        {:error, :invalid_length}
+
+      iban_violates_country_rule?(iban) ->
+        {:error, :invalid_format}
+
+      iban_violates_checksum?(iban) ->
+        {:error, :invalid_checksum}
+
+      true ->
+        {:ok, normalize(iban)}
+    end
+  end
+
+  @spec size(String.t()) :: non_neg_integer()
+  defp size(iban) do
+    iban
+    |> normalize()
+    |> String.length()
+  end
+
+  # - Check whether a given IBAN violates the required format.
+  @spec iban_violates_format?(String.t()) :: boolean
+  defp iban_violates_format?(iban),
+    do: Regex.match?(~r/[^A-Z0-9]/i, normalize(iban))
+
+  # - Check whether a given IBAN violates the supported countries.
+  @spec iban_unsupported_country?(String.t()) :: boolean
+  defp iban_unsupported_country?(iban) do
+    supported? =
+      iban
+      |> Parser.country_code()
+      |> Country.is_country_code_supported?()
+
+    !supported?
+  end
+
+  # - Check whether a given IBAN violates the required length.
+  @spec iban_violates_length?(String.t()) :: boolean
+  defp iban_violates_length?(iban) do
+    with country_code <- Parser.country_code(iban),
+         country_module <- Country.country_module(country_code) do
+      size(iban) != country_module.size()
+    else
+      {:error, _} -> true
+    end
+  end
+
+  # - Check whether a given IBAN violates the country rules.
+  @spec iban_violates_country_rule?(String.t()) :: boolean
+  defp iban_violates_country_rule?(iban) do
+    with country_code <- Parser.country_code(iban),
+         bban <- Parser.bban(iban),
+         country_module <- Country.country_module(country_code),
+         rule <- country_module.rule() do
+      !Regex.match?(rule, bban)
+    else
+      {:error, _} -> true
+    end
+  end
+
+  # - Check whether a given IBAN violates the required checksum.
+  @spec iban_violates_checksum?(String.t()) :: boolean
+  defp iban_violates_checksum?(iban) do
+    check_sum_base = Parser.bban(iban) <> Parser.country_code(iban) <> "00"
+
+    replacements = Replacements.replacements()
+
+    remainder =
+      for(<<c <- check_sum_base>>, into: "", do: replacements[<<c>>] || <<c>>)
+      |> String.to_integer()
+      |> rem(97)
+
+    checksum =
+      (98 - remainder)
+      |> Integer.to_string()
+      |> String.pad_leading(2, "0")
+
+    checksum !== Parser.check_digits(iban)
+  end
+end