defmodule BerrypodWeb.Helpers.SeoHelpers do
  @moduledoc """
  SEO-related helpers for generating structured data.
  """

  import Phoenix.Component, only: [assign: 3]
  alias Berrypod.Media

  @doc """
  Generates FAQPage JSON-LD schema from page blocks.

  Extracts FAQ items from any FAQ blocks on the page and builds a valid
  FAQPage schema. Returns nil if no FAQ blocks with valid content are found.

  ## Examples

      iex> faq_json_ld([%{"type" => "faq", "settings" => %{"items" => [...]}}])
      ~s({"@context":"https://schema.org","@type":"FAQPage",...})

  """
  def faq_json_ld(blocks) when is_list(blocks) do
    questions =
      blocks
      |> Enum.filter(&(&1["type"] == "faq"))
      |> Enum.flat_map(fn block ->
        (block["settings"] || %{})["items"] || []
      end)
      |> Enum.filter(fn item ->
        question = String.trim(item["question"] || "")
        answer = String.trim(item["answer"] || "")
        question != "" and answer != ""
      end)
      |> Enum.map(fn item ->
        %{
          "@type" => "Question",
          "name" => item["question"],
          "acceptedAnswer" => %{
            "@type" => "Answer",
            "text" => item["answer"]
          }
        }
      end)

    if questions != [] do
      %{
        "@context" => "https://schema.org",
        "@type" => "FAQPage",
        "mainEntity" => questions
      }
      |> Jason.encode!(escape: :html_safe)
    else
      nil
    end
  end

  def faq_json_ld(_), do: nil

  @doc """
  Assigns an og_image URL to the socket based on page-specific or default image.

  Priority: page-specific image > site-wide default > none
  """
  def assign_og_image(socket, page, base) do
    og_image_id = get_og_image_id(page)

    og_image =
      cond do
        og_image_id ->
          Media.get_image(og_image_id)

        true ->
          Media.get_default_og_image()
      end

    if og_image do
      url = og_image_url(og_image, base)
      assign(socket, :og_image, url)
    else
      socket
    end
  end

  defp get_og_image_id(nil), do: nil
  defp get_og_image_id(%{og_image_id: id}), do: id
  defp get_og_image_id(page) when is_map(page), do: page[:og_image_id]
  defp get_og_image_id(_), do: nil

  @doc """
  Generates a full URL for an OG image, preferring 1200px width for social sharing.

  Falls back to the largest available width if the image is smaller than 1200px.
  """
  def og_image_url(image, base) do
    path =
      if image.is_svg do
        "/image_cache/#{image.id}.webp"
      else
        widths = Berrypod.Images.Optimizer.applicable_widths(image.source_width)
        # Prefer 1200px or larger, otherwise use the largest available
        width = Enum.find(widths, List.last(widths), &(&1 >= 1200))

        "/image_cache/#{image.id}-#{width}.webp"
      end

    base <> path
  end
end