defmodule Urlpreview.Parser do

  @doc """
  Parses the given html body and returns meta data relevant to the html

  ## Examples

      iex> Urlpreview.Parser.parse(%{ body: File.read!("fixtures/general_page.html"), url: "https://www.test-site.com" })
      {:ok, %{
        real_url: "https://www.test-site.com",
        url: "https://www.test-site.com",
        description: "This is the meta description",
        images: [
          "https://www.test-site.com/itemprop_image.png",
          "https://www.test-site.com/itemprop_image2.png"
        ],
        title: "My Test Site"
      }}

  """
  def parse(%{body: body, url: url}) do
    {:ok, %{
        title: get_title(body),
        description: get_description(body),
        images: get_images(body) |> add_images_base_url(url),
        url: url,
        real_url: get_real_url(body, url)
      }}
  end

  defp get_real_url(html, url) do
    Floki.attribute(html, "meta[property=\"og:url\"]", "content") ++ [url]
      |> remove_empty_list_items
      |> Enum.at(0)
  end

  defp add_images_base_url(image_urls, base_url) do
    parsed_url = Fuzzyurl.from_string(base_url)
    Enum.map(image_urls, fn(x) ->
      x |> append_protocol_and_host(parsed_url)
    end)
  end

  defp append_protocol_and_host(url, parsed_url) do
    if !Regex.match?(~r/^(http:\/\/|https:\/\/)/, url) do
      if !Regex.match?(~r/^\/\//, url) do
        if String.at(url, 0) == "/" do
          "#{parsed_url.protocol}://#{parsed_url.hostname}#{url}"
        else
          "#{parsed_url.protocol}://#{parsed_url.hostname}/#{url}"
        end
      else
        "#{parsed_url.protocol}:#{url}"
      end
    else
      url
    end
  end

  defp get_description(html) do
    Floki.attribute(html, "meta[property=\"og:description\"]", "content") ++
      Floki.attribute(html, "meta[name=\"description\"]", "content")
      |> remove_empty_list_items
      |> Enum.at(0)
  end

  defp get_title(html) do
    Floki.attribute(html, "meta[property=\"og:site_name\"]", "content") ++
      [Floki.find(html, "title") |> Floki.text]
      |> remove_empty_list_items
      |> Enum.at(0)
  end

  defp get_images(html) do
    Floki.attribute(html, "meta[property=\"og:image\"]", "content") ++
      Floki.attribute(html, "meta[property=\"twitter:image\"]", "content") ++
      Floki.attribute(html, "meta[itemprop='image']", "content")
      |> remove_empty_list_items
  end

  defp remove_empty_list_items(list) do
    Enum.filter(list, fn(x) -> x != nil and x != "" end)
  end
end