mobilizon/lib/service/rich_media/favicon.ex

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Elixir
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defmodule Mobilizon.Service.RichMedia.Favicon do
@moduledoc """
Module to fetch favicon information from a website
Taken and adapted from https://github.com/ricn/favicon
"""
require Logger
alias Mobilizon.Config
@options [
max_body: 2_000_000,
timeout: 10_000,
recv_timeout: 20_000,
follow_redirect: true,
ssl: [{:versions, [:"tlsv1.2"]}]
]
@spec fetch(String.t(), Enum.t()) :: {:ok, String.t()} | {:error, any()}
def fetch(url, options \\ []) do
user_agent = Keyword.get(options, :user_agent, Config.instance_user_agent())
headers = [{"User-Agent", user_agent}]
case Tesla.get(url, headers: headers, opts: @options) do
{:ok, %{status: code, body: body}} when code in 200..299 ->
find_favicon_url(url, body, headers)
{:ok, %{}} ->
{:error, "Error while fetching the page"}
{:error, err} ->
{:error, err}
end
end
@spec find_favicon_url(String.t(), String.t(), Enum.t()) :: {:ok, String.t()} | {:error, any()}
defp find_favicon_url(url, body, headers) do
Logger.debug("finding favicon URL for #{url}")
case find_favicon_link_tag(body) do
{:ok, tag} ->
Logger.debug("Found link #{inspect(tag)}")
{"link", attrs, _} = tag
{"href", path} =
Enum.find(attrs, fn {name, _} ->
name == "href"
end)
{:ok, format_url(url, path)}
_ ->
find_favicon_in_root(url, headers)
end
end
@spec format_url(String.t(), String.t()) :: String.t()
defp format_url(url, path) do
url
|> URI.parse()
|> URI.merge(path)
|> to_string()
end
@spec find_favicon_link_tag(String.t()) :: {:ok, tuple()} | {:error, any()}
defp find_favicon_link_tag(html) do
with {:ok, html} <- Floki.parse_document(html),
links <- Floki.find(html, "link"),
{:link, link} when not is_nil(link) <-
{:link,
Enum.find(links, fn {"link", attrs, _} ->
Enum.any?(attrs, fn {name, value} ->
name == "rel" && String.contains?(value, "icon") &&
!String.contains?(value, "-icon-")
end)
end)} do
{:ok, link}
else
{:link, nil} -> {:error, "No link found"}
err -> err
end
end
@spec find_favicon_in_root(String.t(), Enum.t()) :: {:ok, String.t()} | {:error, any()}
defp find_favicon_in_root(url, headers) do
uri = URI.parse(url)
favicon_url = "#{uri.scheme}://#{uri.host}/favicon.ico"
case Tesla.head(favicon_url, headers: headers, opts: @options) do
{:ok, %{status: code}} when code in 200..299 ->
{:ok, favicon_url}
{:ok, %{}} ->
{:error, "Error while doing a HEAD request on the favicon"}
{:error, err} ->
{:error, err}
end
end
end