defmodule NLdoc.Conversion.Reader.Tiptap do
  @moduledoc """
  Reader for convert_elementing Tiptap elements to Spec Resources.
  """

  alias NLdoc.Conversion.Reader.Tiptap.{Attribute, Mark}

  alias NLdoc.Spec.{
    BlockQuotation,
    DefinitionDetails,
    DefinitionList,
    DefinitionTerm,
    Document,
    Heading,
    Image,
    Link,
    ListItem,
    OrderedList,
    Paragraph,
    Preformatted,
    Table,
    TableCell,
    TableHeader,
    TableRow,
    Text,
    UnorderedList
  }

  # TODO: Support descriptors

  # This defines functions to be generated in the for-loops below.
  #
  # This is a tuple in format:
  #   1. Element name in Tiptap.
  #   2. Struct from Spec.
  #   3. Attributes as keyword list in format {spec_attribute: tiptap_attribute}
  #      where spec_attribute is an atom and tiptap_attribute is a string.
  @element_mappings [
    {"doc", Document, [id: "id", assets: "assets"]},
    # TODO: Support attribute caption
    {"image", Image,
     [id: "id", source: "assetId", alternative_text: "alt", decorative: "isDecorative"]},
    # TODO: Support attributes cite, caption/footer
    {"blockquote", BlockQuotation, [id: "id"]},
    {"codeBlock", Preformatted, [id: "id"]},
    {"heading", Heading, [id: "id", level: "level"]},
    # TODO: Support attributes style type, reversed
    {"orderedList", OrderedList, [id: "id", start: "start"]},
    # TODO: Support attribute style type
    {"bulletList", UnorderedList, [id: "id"]},
    {"listItem", ListItem, [id: "id"]},
    # TODO: Support attribute caption
    {"table", Table, [id: "id"]},
    {"tableRow", TableRow, [id: "id"]},
    {"tableCell", TableCell, [id: "id", rowspan: "rowspan", colspan: "colspan"]},
    # TODO: Support attributes abbreviation, scope
    {"tableHeader", TableHeader, [id: "id", rowspan: "rowspan", colspan: "colspan"]},
    {"definitionList", DefinitionList, [id: "id"]},
    {"definitionTerm", DefinitionTerm, [id: "id"]},
    {"definitionDetails", DefinitionDetails, [id: "id"]},
    {"paragraph", Paragraph, [id: "id"]},

    # Custom cases, will generate &convert_element/1 functions that won't be used.
    # Used for setting the attributes.
    {"_text", Text, [id: "id"]},
    {"_link", Link, [id: "id", uri: "href", purpose: "purpose"]}
  ]

  @type tiptap_attribute_value :: String.t() | number() | boolean()
  @type tiptap_attribute :: {String.t(), tiptap_attribute_value()}

  @doc """
  Converts Tiptap document to a NLdoc document.
  """
  @spec convert(map()) :: Document.t()
  def convert(element = %{"type" => "doc"}),
    do: element |> convert_element() |> hd()

  @spec convert_element(map()) :: [NLdoc.Spec.object()]

  defp convert_element(%{"type" => "text", "text" => text, "marks" => marks})
       when is_binary(text) and text !== "" and is_list(marks),
       do: %Text{text: text} |> Mark.apply(marks) |> post_process()

  for {tiptap_type, struct_module, mappings} <- @element_mappings,
      not String.starts_with?(tiptap_type, "_") do
    if Map.has_key?(struct_module.__struct__(), :children) do
      defp convert_element(element = %{"type" => unquote(tiptap_type)}) do
        children =
          element
          |> Map.get("content", [])
          |> Enum.flat_map(&convert_element/1)

        %unquote(struct_module){}
        |> Map.put(:children, children)
        |> Attribute.apply(element |> Map.get("attrs", %{}), unquote(mappings))
        |> post_process()
      end
    else
      defp convert_element(element = %{"type" => unquote(tiptap_type)}),
        do:
          %unquote(struct_module){}
          |> Attribute.apply(element |> Map.get("attrs", %{}), unquote(mappings))
          |> post_process()
    end
  end

  # Unsupported element
  defp convert_element(_),
    do: []

  @spec post_process(t) :: [t] when t: term()
  defp post_process(%Image{source: nil}),
    do: []

  defp post_process(element),
    do: element |> List.wrap()
end