mitgliederverwaltung/lib/mv/membership/members_pdf.ex

defmodule Mv.Membership.MembersPDF do
  @moduledoc """
  Exports members to PDF using Typst templates and Imprintor.

  Uses the same data structure as `MemberExport.Build` and converts it
  to the format expected by the Typst template. No translations/Gettext
  in this module - labels come from the web layer.

  Ensures deterministic output by maintaining column and row order.

  Creates a temporary directory per request and copies the template there
  to avoid symlink issues and ensure isolation.
  """

  require Logger

  alias Mv.Config

  @template_filename "members_export.typ"
  @template_path "priv/pdf_templates/members_export.typ"

  @doc """
  Renders export data to PDF binary.

  - `export_data` - Map from `MemberExport.Build.build/3` with `columns`, `rows`, and `meta`

  Returns `{:ok, binary}` where binary is the PDF content, or `{:error, term}`.

  The PDF binary starts with "%PDF" (PDF magic bytes).

  Validates row count against configured limit before processing.
  """
  @spec render(map()) :: {:ok, binary()} | {:error, term()}
  def render(export_data) do
    row_count = length(export_data.rows)
    max_rows = Config.pdf_export_row_limit()

    if row_count > max_rows do
      Logger.warning("PDF export rejected: row count exceeds limit",
        row_count: row_count,
        max_rows: max_rows,
        error_type: :row_limit_exceeded
      )

      {:error, {:row_limit_exceeded, row_count, max_rows}}
    else
      Logger.info("Starting PDF export",
        row_count: row_count,
        column_count: length(export_data.columns)
      )

      create_and_use_temp_directory(export_data)
    end
  end

  defp create_and_use_temp_directory(export_data) do
    case create_temp_directory() do
      {:ok, temp_dir} ->
        try do
          with {:ok, template_content} <- load_template(),
               {:ok, _template_path} <- copy_template_to_temp(temp_dir, template_content),
               {:ok, template_data} <- convert_to_template_format(export_data),
               {:ok, config} <-
                 build_imprintor_config(template_content, template_data, temp_dir),
               {:ok, pdf_binary} <- compile_to_pdf(config) do
            Logger.info("PDF export completed successfully",
              row_count: length(export_data.rows)
            )

            {:ok, pdf_binary}
          else
            {:error, reason} = error ->
              Logger.error("PDF export failed",
                error: reason,
                error_type: :pdf_export_failed
              )

              error
          end
        after
          cleanup_temp_directory(temp_dir)
        end

      {:error, reason} = error ->
        Logger.error("Failed to create temp directory",
          error: reason,
          error_type: :temp_dir_creation_failed
        )

        error
    end
  end

  defp create_temp_directory do
    # Create unique temp directory per request
    temp_base = System.tmp_dir!()
    temp_dir = Path.join(temp_base, "mv_pdf_export_#{System.unique_integer([:positive])}")

    case File.mkdir_p(temp_dir) do
      :ok -> {:ok, temp_dir}
      {:error, reason} -> {:error, {:temp_dir_creation_failed, reason}}
    end
  end

  defp load_template do
    # Try multiple paths: compiled app path and source path (for tests/dev)
    template_paths = [
      Path.join(Application.app_dir(:mv, "priv"), "pdf_templates/#{@template_filename}"),
      Path.join([File.cwd!(), "priv", "pdf_templates", @template_filename])
    ]

    Enum.reduce_while(template_paths, nil, fn path, _acc ->
      case File.read(path) do
        {:ok, content} -> {:halt, {:ok, content}}
        {:error, _reason} -> {:cont, nil}
      end
    end)
    |> case do
      {:ok, content} -> {:ok, content}
      nil -> {:error, {:template_not_found, :enoent}}
    end
  end

  defp copy_template_to_temp(temp_dir, template_content) do
    # Write template to temp directory (no symlinks, actual file copy)
    template_path = Path.join(temp_dir, @template_filename)

    case File.write(template_path, template_content) do
      :ok -> {:ok, template_path}
      {:error, reason} -> {:error, {:template_copy_failed, reason}}
    end
  end

  defp cleanup_temp_directory(temp_dir) do
    # Clean up temp directory and all contents
    case File.rm_rf(temp_dir) do
      {:ok, _} ->
        :ok

      {:error, reason, _} ->
        Logger.warning("Failed to cleanup temp directory",
          temp_dir: temp_dir,
          error: reason
        )
    end
  end

  defp convert_to_template_format(export_data) do
    headers = Enum.map(export_data.columns, & &1.label)
    column_count = length(export_data.columns)

    meta = Map.get(export_data, :meta) || Map.get(export_data, "meta") || %{}

    generated_at =
      Map.get(meta, :generated_at) ||
        Map.get(meta, "generated_at") ||
        DateTime.utc_now() |> DateTime.to_iso8601()

    member_count =
      Map.get(meta, :member_count) ||
        Map.get(meta, "member_count") ||
        length(export_data.rows)

    template_data = %{
      "title" => "Mitglieder-Export",
      "generated_at" => generated_at,
      "column_count" => column_count,
      "headers" => headers,
      "rows" => export_data.rows,
      "columns" =>
        Enum.map(export_data.columns, fn col ->
          %{
            "key" => to_string(col.key),
            "kind" => to_string(col.kind),
            "label" => col.label
          }
        end),
      "meta" => %{
        "generated_at" => generated_at,
        "member_count" => member_count
      }
    }

    {:ok, template_data}
  end

  defp build_imprintor_config(template_content, template_data, root_directory) do
    # Imprintor.Config.new(source_document, inputs, options)
    # inputs: %{"elixir_data" => template_data} for sys.inputs.elixir_data in template
    # options: set root_directory to temp dir to ensure no symlink issues
    # extra_fonts: list of font file paths for Typst to use
    extra_fonts = get_extra_fonts()
    options = [root_directory: root_directory, extra_fonts: extra_fonts]

    config = Imprintor.Config.new(template_content, template_data, options)
    {:ok, config}
  end

  defp get_extra_fonts do
    # Try multiple paths: compiled app path and source path (for tests/dev)
    font_paths = [
      Path.join(Application.app_dir(:mv, "priv"), "fonts"),
      Path.join([File.cwd!(), "priv", "fonts"])
    ]

    Enum.reduce_while(font_paths, [], fn base_path, _acc ->
      case File.ls(base_path) do
        {:ok, files} ->
          fonts =
            files
            |> Enum.filter(&String.ends_with?(&1, ".ttf"))
            |> Enum.map(&Path.join(base_path, &1))
            |> Enum.sort()

          if fonts != [] do
            {:halt, fonts}
          else
            {:cont, []}
          end

        {:error, _reason} ->
          {:cont, []}
      end
    end)
    |> case do
      [] -> []
      fonts -> fonts
    end
  end

  defp compile_to_pdf(config) do
    case Imprintor.compile_to_pdf(config) do
      {:ok, pdf_binary} when is_binary(pdf_binary) ->
        # Verify PDF magic bytes
        if String.starts_with?(pdf_binary, "%PDF") do
          {:ok, pdf_binary}
        else
          Logger.error("PDF compilation returned invalid format",
            binary_start: String.slice(pdf_binary, 0, 20)
          )

          {:error, :invalid_pdf_format}
        end

      {:error, reason} ->
        Logger.error("PDF compilation failed",
          error: inspect(reason),
          error_type: :imprintor_compile_error
        )

        {:error, {:compile_error, reason}}

      other ->
        Logger.error("PDF compilation returned unexpected result",
          result: inspect(other),
          error_type: :unexpected_result
        )

        {:error, {:unexpected_result, other}}
    end
  rescue
    e ->
      Logger.error("PDF compilation raised exception",
        exception: inspect(e),
        error_type: :compile_exception
      )

      {:error, {:compile_exception, e}}
  end
end