163 lines
4.2 KiB
Elixir
163 lines
4.2 KiB
Elixir
defmodule Frenzy.Pipeline.ScrapeStage do
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require Logger
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alias Frenzy.Network
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alias Frenzy.Pipeline.Stage
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@behaviour Stage
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@impl Stage
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def apply(opts, %{url: url} = item_params) do
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case get_article_content(url, opts) do
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{:ok, content} ->
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{:ok, %{item_params | content: content}}
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{:error, reason} ->
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Logger.warn("Unable to get article content for #{url}: #{reason}")
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{:ok, item_params}
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end
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end
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@impl Stage
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def validate_opts(opts) when is_map(opts) do
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opts =
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case opts["extractor"] do
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nil ->
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{:ok, Map.put(opts, "extractor", "builtin")}
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extractor when not is_binary(extractor) ->
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{:error, "extractor must be a string"}
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"builtin" ->
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{:ok, opts}
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extractor ->
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try do
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String.to_existing_atom("Elixir." <> extractor)
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{:ok, opts}
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rescue
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ArgumentError ->
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{:error, "extractor must be \"builtin\" or a module that exists"}
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end
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end
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case opts do
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{:ok, opts} ->
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case opts["convert_to_data_uris"] do
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nil ->
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{:ok, Map.put(opts, "convert_to_data_uris", true)}
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value when is_boolean(value) ->
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{:ok, opts}
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_ ->
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{:error, "convert_to_data_uris must be a boolean"}
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end
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_ ->
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opts
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end
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end
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@impl Stage
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def validate_opts(_), do: {:error, "options must be a map"}
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@impl Stage
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def default_opts(), do: %{}
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@spec get_article_content(String.t(), map()) :: {:ok, String.t()} | {:error, String.t()}
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defp get_article_content(url, opts) when is_binary(url) and url != "" do
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Logger.debug("Getting article from #{url}")
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url
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|> Network.http_get()
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|> case do
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{:ok, response} ->
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handle_response(url, response, opts)
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{:error, reason} ->
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{:error, "Couldn't scrape article: #{reason}"}
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end
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end
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defp get_article_content(_url, _opts), do: {:error, "URL must be a non-empty string"}
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@spec handle_response(String.t(), Mojito.Response.t(), map()) ::
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{:ok, String.t()} | {:error, String.t()}
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defp handle_response(url, %Mojito.Response{body: body}, opts) do
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case opts["extractor"] do
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"builtin" ->
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{:ok, Readability.article(body)}
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module_name ->
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html_tree = Floki.parse(body)
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apply(String.to_existing_atom("Elixir." <> module_name), :extract, [html_tree])
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end
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|> case do
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{:ok, html} ->
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convert_to_data_uris =
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case opts["convert_to_data_uris"] do
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nil -> true
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value -> value
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end
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html = Floki.map(html, rewrite_image_urls(convert_to_data_uris, URI.parse(url)))
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case opts["extractor"] do
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"builtin" ->
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{:ok, Readability.readable_html(html)}
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_ ->
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{:ok, Floki.raw_html(html)}
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end
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res ->
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res
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end
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end
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# Generates a helper function for the article with the given URI that takes an HTML element and,
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# if it's an <img> element whose src attribute does not have a hostname, adds the hostname and
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# scheme to the element.
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defp rewrite_image_urls(convert_to_data_uris, site_uri) do
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fn
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{"img", attrs} ->
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new_attrs =
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Enum.map(attrs, fn
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{"src", src} ->
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{"src", image_to_data_uri(src, site_uri, convert_to_data_uris)}
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attr ->
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attr
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end)
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{"img", new_attrs}
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elem ->
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elem
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end
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end
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@content_type_allowlist ["image/jpeg", "image/png", "image/heic", "image/heif", "image/tiff"]
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# convert images to data URIs so that they're stored by clients as part of the body
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defp image_to_data_uri(src, site_uri, true) do
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absolute_url = URI.merge(site_uri, src) |> to_string()
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case Network.http_get(absolute_url) do
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{:ok, %Mojito.Response{body: body, headers: headers}} ->
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{"Content-Type", content_type} =
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Enum.find(headers, fn {header, _value} -> header == "Content-Type" end)
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if content_type in @content_type_allowlist do
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"data:#{content_type};base64,#{Base.encode64(body)}"
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else
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src
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end
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_ ->
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src
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end
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end
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defp image_to_data_uri(src, _site_uri, false), do: src
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end
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