defmodule Ash.DocIndex do
  @moduledoc """
  A module for configuring how a library is rendered in ash_hq.

  There is a small template syntax available in any documentation.
  The template syntax will link to the user's currently selected
  version for the relevant library.

  All templates should be wrapped in double curly braces, e.g `{{}}`.

  ## Links to other documentation

  `{{link:library:item_type:name}}`

  The only item_type currently supported is `guide`, so the name would be `category/name`

  For example:

  `{{link:ash:guide:Attributes}}` -> `<a href="/docs/guides/ash/topics/attributes.md">Attributes</a>`

  ## Mix dependencies

  `{{mix_dep:library}}`

  For example:

  `{{mix_dep:ash}}` -> `{:ash, "~> 1.5"}`
  """

  @type extension :: %{
          optional(:module) => module,
          optional(:target) => String.t(),
          optional(:default_for_target?) => boolean,
          :name => String.t(),
          :type => String.t()
        }

  @type guide :: %{
          name: String.t(),
          text: String.t(),
          category: String.t() | nil,
          route: String.t() | nil
        }

  @callback extensions() :: list(extension())
  @callback for_library() :: String.t()
  @callback guides() :: list(guide())
  @callback code_modules() :: [{String.t(), list(module())}]
  @callback default_guide() :: String.t()

  defmacro __using__(opts) do
    quote bind_quoted: [otp_app: opts[:otp_app], guides_from: opts[:guides_from]] do
      @behaviour Ash.DocIndex

      if guides_from do
        @impl Ash.DocIndex
        # sobelow_skip ["Traversal.FileModule"]
        def guides do
          unquote(otp_app)
          |> :code.priv_dir()
          |> Path.join(unquote(guides_from))
          |> Path.wildcard()
          |> Enum.map(fn path ->
            path
            |> Path.split()
            |> Enum.reverse()
            |> Enum.take(2)
            |> Enum.reverse()
            |> case do
              [category, file] ->
                %{
                  name: Ash.DocIndex.to_name(Path.rootname(file)),
                  category: Ash.DocIndex.to_name(category),
                  text: File.read!(path),
                  route: "#{Ash.DocIndex.to_path(category)}/#{Ash.DocIndex.to_path(file)}"
                }
            end
          end)
        end

        defoverridable guides: 0
      end
    end
  end

  def find_undocumented_items(doc_index) do
    Enum.each(doc_index.extensions(), fn extension ->
      Enum.each(
        extension.module.sections(),
        &find_undocumented_in_section(&1, [inspect(extension.module)])
      )
    end)
  end

  defp find_undocumented_in_section(section, path) do
    find_undocumented_in_schema(section.schema(), [section.name() | path])
    Enum.each(section.sections(), &find_undocumented_in_section(&1, [section.name() | path]))
    Enum.each(section.entities(), &find_undocumented_in_entity(&1, [section.name() | path]))
  end

  defp find_undocumented_in_entity(entity, path) do
    find_undocumented_in_schema(entity.schema(), [entity.name() | path])

    Enum.each(entity.entities(), fn {_key, entities} ->
      Enum.each(entities, &find_undocumented_in_entity(&1, [entity.name() | path]))
    end)
  end

  defp find_undocumented_in_schema(schema, path) do
    Enum.each(schema, fn {key, opts} ->
      if !opts[:links] do
        raise "Undocumented item #{Enum.reverse(path) |> Enum.join(".")}.#{key}"
      end
    end)
  end

  # sobelow_skip ["Traversal.FileModule"]
  def read!(app, path) do
    app
    |> :code.priv_dir()
    |> Path.join(path)
    |> File.read!()
  end

  def to_name(string) do
    string
    |> String.split(~r/[-_]/, trim: true)
    |> Enum.map_join(" ", &String.capitalize/1)
  end

  def to_path(string) do
    string
    |> String.split(~r/\s/, trim: true)
    |> Enum.join("-")
    |> String.downcase()
  end
end