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parser.ex
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defmodule Linkify.Parser do
@moduledoc """
Module to handle parsing the the input string.
"""
alias Linkify.Builder
@invalid_url ~r/(\.\.+)|(^(\d+\.){1,2}\d+$)/
@match_url ~r{^(?:\W*)?(?<url>(?:https?:\/\/)?[\w.-]+(?:\.[\w\.-]+)+[\w\-\._~%:\/?#[\]@!\$&'\(\)\*\+,;=.]+$)}u
@get_scheme_host ~r{^\W*(?<scheme>https?:\/\/)?(?:[^@\n]+\\w@)?(?<host>[^:#~\/\n?]+)}u
@match_hashtag ~r/^(?<tag>\#[[:word:]_]*[[:alpha:]_·][[:word:]_·\p{M}]*)/u
@match_skipped_tag ~r/^(?<tag>(a|code|pre)).*>*/
@delimiters ~r/[,.;:>?!]*$/
@prefix_extra [
"magnet:?",
"dweb://",
"dat://",
"gopher://",
"ipfs://",
"ipns://",
"irc://",
"ircs://",
"irc6://",
"mumble://",
"ssb://"
]
@tlds "./priv/tlds.txt"
|> File.read!()
|> String.split("\n", trim: true)
|> Enum.concat(["onion"])
|> MapSet.new()
@default_opts %{
url: true,
validate_tld: true
}
@doc """
Parse the given string, identifying items to link.
Parses the string, replacing the matching urls with an html link.
## Examples
iex> Linkify.Parser.parse("Check out google.com")
~s{Check out <a href="http://google.com">google.com</a>}
"""
@types [:url, :hashtag, :extra, :mention, :email]
def parse(input, opts \\ %{})
def parse(input, opts) when is_binary(input), do: {input, %{}} |> parse(opts) |> elem(0)
def parse(input, list) when is_list(list), do: parse(input, Enum.into(list, %{}))
def parse(input, opts) do
opts = Map.merge(@default_opts, opts)
{buffer, user_acc} = do_parse(input, opts, {"", [], :parsing})
if opts[:iodata] do
{buffer, user_acc}
else
{IO.iodata_to_binary(buffer), user_acc}
end
end
defp accumulate(acc, buffer),
do: [buffer | acc]
defp accumulate(acc, buffer, trailing),
do: [trailing, buffer | acc]
defp do_parse({"", user_acc}, _opts, {"", acc, _}),
do: {Enum.reverse(acc), user_acc}
defp do_parse(
{"<" <> text, user_acc},
%{hashtag: true} = opts,
{"#" <> _ = buffer, acc, :parsing}
) do
{buffer, user_acc} = link(buffer, opts, user_acc)
case Regex.run(@match_skipped_tag, text, capture: [:tag]) do
[tag] ->
text = String.trim_leading(text, tag)
do_parse({text, user_acc}, opts, {"", accumulate(acc, buffer, "<#{tag}"), :skip})
nil ->
do_parse({text, user_acc}, opts, {"<", acc, {:open, 1}})
end
end
defp do_parse({"<br" <> text, user_acc}, opts, {buffer, acc, :parsing}) do
{buffer, user_acc} = link(buffer, opts, user_acc)
do_parse({text, user_acc}, opts, {"", accumulate(acc, buffer, "<br"), {:open, 1}})
end
defp do_parse({"<a" <> text, user_acc}, opts, {buffer, acc, :parsing}),
do: do_parse({text, user_acc}, opts, {"", accumulate(acc, buffer, "<a"), :skip})
defp do_parse({"<pre" <> text, user_acc}, opts, {buffer, acc, :parsing}),
do: do_parse({text, user_acc}, opts, {"", accumulate(acc, buffer, "<pre"), :skip})
defp do_parse({"<code" <> text, user_acc}, opts, {buffer, acc, :parsing}),
do: do_parse({text, user_acc}, opts, {"", accumulate(acc, buffer, "<code"), :skip})
defp do_parse({"</a>" <> text, user_acc}, opts, {buffer, acc, :skip}),
do: do_parse({text, user_acc}, opts, {"", accumulate(acc, buffer, "</a>"), :parsing})
defp do_parse({"</pre>" <> text, user_acc}, opts, {buffer, acc, :skip}),
do: do_parse({text, user_acc}, opts, {"", accumulate(acc, buffer, "</pre>"), :parsing})
defp do_parse({"</code>" <> text, user_acc}, opts, {buffer, acc, :skip}),
do: do_parse({text, user_acc}, opts, {"", accumulate(acc, buffer, "</code>"), :parsing})
defp do_parse({"<" <> text, user_acc}, opts, {"", acc, :parsing}),
do: do_parse({text, user_acc}, opts, {"<", acc, {:open, 1}})
defp do_parse({">" <> text, user_acc}, opts, {buffer, acc, {:attrs, _level}}),
do: do_parse({text, user_acc}, opts, {"", accumulate(acc, buffer, ">"), :parsing})
defp do_parse({<<ch::8>> <> text, user_acc}, opts, {"", acc, {:attrs, level}}) do
do_parse({text, user_acc}, opts, {"", accumulate(acc, <<ch::8>>), {:attrs, level}})
end
defp do_parse({text, user_acc}, opts, {buffer, acc, {:open, level}}) do
do_parse({text, user_acc}, opts, {"", accumulate(acc, buffer), {:attrs, level}})
end
defp do_parse(
{<<char::bytes-size(1), text::binary>>, user_acc},
opts,
{buffer, acc, state}
)
when char in [" ", "\r", "\n"] do
{buffer, user_acc} = link(buffer, opts, user_acc)
do_parse(
{text, user_acc},
opts,
{"", accumulate(acc, buffer, char), state}
)
end
defp do_parse({<<ch::8>>, user_acc}, opts, {buffer, acc, state}) do
{buffer, user_acc} = link(buffer <> <<ch::8>>, opts, user_acc)
do_parse(
{"", user_acc},
opts,
{"", accumulate(acc, buffer), state}
)
end
defp do_parse({<<ch::8>> <> text, user_acc}, opts, {buffer, acc, state}),
do: do_parse({text, user_acc}, opts, {buffer <> <<ch::8>>, acc, state})
def check_and_link(:url, buffer, opts, _user_acc) do
if url?(buffer, opts) do
case @match_url |> Regex.run(buffer, capture: [:url]) |> hd() do
^buffer ->
link_url(buffer, opts)
url ->
link = link_url(url, opts)
restore_stripped_symbols(buffer, url, link)
end
else
:nomatch
end
end
def check_and_link(:email, buffer, opts, _user_acc) do
if email?(buffer, opts), do: link_email(buffer, opts), else: :nomatch
end
def check_and_link(:mention, buffer, opts, user_acc) do
buffer
|> match_mention
|> link_mention(buffer, opts, user_acc)
end
def check_and_link(:hashtag, buffer, opts, user_acc) do
buffer
|> match_hashtag
|> link_hashtag(buffer, opts, user_acc)
end
def check_and_link(:extra, "xmpp:" <> handle = buffer, opts, _user_acc) do
if email?(handle, opts), do: link_extra(buffer, opts), else: :nomatch
end
def check_and_link(:extra, buffer, opts, _user_acc) do
if String.starts_with?(buffer, @prefix_extra), do: link_extra(buffer, opts), else: :nomatch
end
defp maybe_strip_parens(buffer) do
trimmed = trim_leading_paren(buffer)
with :next <- parens_check_trailing(buffer),
:next <- parens_found_email(trimmed),
:next <- parens_found_url(trimmed),
%{path: path, query: query} = URI.parse(trimmed),
:next <- parens_in_query(query),
:next <- parens_found_path_separator(path),
:next <- parens_path_has_open_paren(path),
:next <- parens_check_balanced(trimmed) do
buffer |> trim_leading_paren |> trim_trailing_paren
else
:both -> buffer |> trim_leading_paren |> trim_trailing_paren
:leading_only -> buffer |> trim_leading_paren
:noop -> buffer
_ -> buffer
end
end
defp parens_check_trailing(buffer), do: (String.ends_with?(buffer, ")") && :next) || :noop
defp parens_found_email(trimmed),
do: (trim_trailing_paren(trimmed) |> email?(nil) && :both) || :next
defp parens_found_url(trimmed),
do: (trim_trailing_paren(trimmed) |> url?(nil) && :next) || :noop
defp parens_in_query(query), do: (is_nil(query) && :next) || :both
defp parens_found_path_separator(path), do: (String.contains?(path, "/") && :next) || :both
defp parens_path_has_open_paren(path), do: (String.contains?(path, "(") && :next) || :both
defp parens_check_balanced(trimmed) do
graphemes = String.graphemes(trimmed)
opencnt = graphemes |> Enum.count(fn x -> x == "(" end)
closecnt = graphemes |> Enum.count(fn x -> x == ")" end)
if opencnt == closecnt do
:leading_only
else
:next
end
end
defp trim_leading_paren(buffer),
do:
(String.starts_with?(buffer, "(") && String.slice(buffer, 1, String.length(buffer))) ||
buffer
defp trim_trailing_paren(buffer),
do:
(String.ends_with?(buffer, ")") && String.slice(buffer, 0, String.length(buffer) - 1)) ||
buffer
defp strip_punctuation(buffer), do: String.replace(buffer, @delimiters, "")
def url?(buffer, opts) do
valid_url?(buffer) && Regex.match?(@match_url, buffer) && valid_tld?(buffer, opts)
end
def email?(buffer, opts) do
# Note: In reality the local part can only be checked by the remote server
case Regex.run(~r/^(?<user>.*)@(?<host>[^@]+)$/, buffer, capture: [:user, :host]) do
[_user, hostname] -> valid_hostname?(hostname) && valid_tld?(hostname, opts)
_ -> false
end
end
defp valid_url?(url), do: !Regex.match?(@invalid_url, url)
@doc """
Validates a URL's TLD. Returns a boolean.
Will return `true` if `:validate_tld` option set to `false`.
Will skip validation and return `true` if `:validate_tld` set to `:no_scheme` and the url has a scheme.
"""
def valid_tld?(url, opts) do
[scheme, host] = Regex.run(@get_scheme_host, url, capture: [:scheme, :host])
cond do
opts[:validate_tld] == false ->
true
ip?(host) ->
true
# don't validate if scheme is present
opts[:validate_tld] == :no_scheme and scheme != "" ->
true
true ->
tld = host |> strip_punctuation() |> String.split(".") |> List.last()
MapSet.member?(@tlds, tld)
end
end
def safe_to_integer(string, base \\ 10) do
String.to_integer(string, base)
rescue
_ ->
nil
end
def ip?(buffer) do
case :inet.parse_strict_address(to_charlist(buffer)) do
{:error, _} -> false
{:ok, _} -> true
end
end
# IDN-compatible, ported from musl-libc's is_valid_hostname()
def valid_hostname?(hostname) do
hostname
|> String.to_charlist()
|> Enum.any?(fn s ->
!(s >= 0x80 || s in 0x30..0x39 || s in 0x41..0x5A || s in 0x61..0x7A || s in '.-')
end)
|> Kernel.!()
end
def match_mention(buffer) do
case Regex.run(~r/^@(?<user>[a-zA-Z\d_-]+)(@(?<host>[^@]+))?$/, buffer,
capture: [:user, :host]
) do
[user, ""] ->
"@" <> user
[user, hostname] ->
if valid_hostname?(hostname) && valid_tld?(hostname, []),
do: "@" <> user <> "@" <> hostname,
else: nil
_ ->
nil
end
end
def match_hashtag(buffer) do
case Regex.run(@match_hashtag, buffer, capture: [:tag]) do
[hashtag] -> hashtag
_ -> nil
end
end
def link_hashtag(nil, _buffer, _, _user_acc), do: :nomatch
def link_hashtag(hashtag, buffer, %{hashtag_handler: hashtag_handler} = opts, user_acc) do
hashtag
|> hashtag_handler.(buffer, opts, user_acc)
|> maybe_update_buffer(hashtag, buffer)
end
def link_hashtag(hashtag, buffer, opts, _user_acc) do
hashtag
|> Builder.create_hashtag_link(buffer, opts)
|> maybe_update_buffer(hashtag, buffer)
end
def link_mention(nil, _buffer, _, _user_acc), do: :nomatch
def link_mention(mention, buffer, %{mention_handler: mention_handler} = opts, user_acc) do
mention
|> mention_handler.(buffer, opts, user_acc)
|> maybe_update_buffer(mention, buffer)
end
def link_mention(mention, buffer, opts, _user_acc) do
mention
|> Builder.create_mention_link(buffer, opts)
|> maybe_update_buffer(mention, buffer)
end
defp maybe_update_buffer(out, match, buffer) when is_binary(out) do
maybe_update_buffer({out, nil}, match, buffer)
end
defp maybe_update_buffer({out, user_acc}, match, buffer)
when match != buffer and out != buffer do
out = String.replace(buffer, match, out)
{out, user_acc}
end
defp maybe_update_buffer(out, _match, _buffer), do: out
@doc false
def link_url(buffer, opts) do
Builder.create_link(buffer, opts)
end
@doc false
def link_email(buffer, opts) do
Builder.create_email_link(buffer, opts)
end
def link_extra(buffer, opts) do
Builder.create_extra_link(buffer, opts)
end
defp link(buffer, opts, user_acc) do
Enum.reduce_while(@types, {buffer, user_acc}, fn type, _ ->
if opts[type] == true do
check_and_link_reducer(type, buffer, opts, user_acc)
else
{:cont, {buffer, user_acc}}
end
end)
end
defp check_and_link_reducer(type, buffer, opts, user_acc) do
str =
buffer
|> String.split("<")
|> List.first()
|> strip_punctuation()
|> maybe_strip_parens()
case check_and_link(type, str, opts, user_acc) do
:nomatch ->
{:cont, {buffer, user_acc}}
{link, user_acc} ->
{:halt, {restore_stripped_symbols(buffer, str, link), user_acc}}
link ->
{:halt, {restore_stripped_symbols(buffer, str, link), user_acc}}
end
end
defp restore_stripped_symbols(buffer, buffer, link), do: link
defp restore_stripped_symbols(buffer, stripped_buffer, link) do
buffer
|> String.split(stripped_buffer)
|> Enum.intersperse(link)
end
end

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