Export participants to different formats

* CSV
* PDF (requires Python dependency `weasyprint`)
* ODS (requires Python dependency `pyexcel_ods3`)

Signed-off-by: Thomas Citharel <tcit@tcit.fr>

lib/service/export/participants/csv.ex

@@ -0,0 +1,100 @@
+defmodule Mobilizon.Service.Export.Participants.CSV do
+  @moduledoc """
+  Export a list of participants to CSV
+  """
+
+  alias Mobilizon.Events
+  alias Mobilizon.Events.Event
+  alias Mobilizon.Export
+  alias Mobilizon.Storage.Repo
+  alias Mobilizon.Web.Gettext
+  import Mobilizon.Web.Gettext, only: [gettext: 2]
+
+  import Mobilizon.Service.Export.Participants.Common,
+    only: [save_upload: 5, columns: 0, to_list: 1, clean_exports: 2, export_enabled?: 1]
+
+  @upload_path "uploads/exports/csv/"
+
+  @extension "csv"
+
+  def extension do
+    @extension
+  end
+
+  @spec export(Event.t(), Keyword.t()) ::
+          {:ok, String.t()} | {:error, :failed_to_save_upload | :export_dependency_not_installed}
+  def export(%Event{id: event_id} = event, options \\ []) do
+    if ready?() do
+      filename = "#{ShortUUID.encode!(Ecto.UUID.generate())}.csv"
+      full_path = @upload_path <> filename
+
+      file = File.open!(full_path, [:write, :utf8])
+
+      case Repo.transaction(
+             fn ->
+               event_id
+               |> Events.participant_for_event_export_query(Keyword.get(options, :roles, []))
+               |> Repo.stream()
+               |> Stream.map(&to_list/1)
+               |> NimbleCSV.RFC4180.dump_to_iodata()
+               |> (fn stream -> Stream.concat([Enum.join(columns(), ","), "\n"], stream) end).()
+               |> Stream.each(fn line -> IO.write(file, line) end)
+               |> Stream.run()
+
+               with {:error, err} <- save_csv_upload(full_path, filename, event) do
+                 Repo.rollback(err)
+               end
+             end,
+             timeout: :infinity
+           ) do
+        {:error, _err} ->
+          File.rm!(full_path)
+          {:error, :failed_to_save_upload}
+
+        {:ok, _ok} ->
+          {:ok, filename}
+      end
+    else
+      {:error, :export_dependency_not_installed}
+    end
+  end
+
+  @spec save_csv_upload(String.t(), String.t(), Event.t()) ::
+          {:ok, Export.t()} | {:error, atom() | Ecto.Changeset.t()}
+  defp save_csv_upload(full_path, filename, %Event{id: event_id, title: title}) do
+    Gettext.gettext_comment(
+      "File name template for exported list of participants. Should NOT contain spaces. Make sure the output is going to be something standardized that is acceptable as a file name on most systems."
+    )
+
+    save_upload(
+      full_path,
+      filename,
+      to_string(event_id),
+      gettext("%{event}_participants", event: title) <> ".csv",
+      "csv"
+    )
+  end
+
+  @doc """
+  Clean outdated files in export folder
+  """
+  @spec clean_exports :: :ok
+  def clean_exports do
+    clean_exports("csv", @upload_path)
+  end
+
+  @spec dependencies_ok? :: boolean
+  def dependencies_ok? do
+    true
+  end
+
+  @spec enabled? :: boolean
+  def enabled? do
+    export_enabled?(__MODULE__)
+  end
+
+  @spec ready? :: boolean
+  def ready? do
+    enabled?() && dependencies_ok?()
+  end
+end