akkoma/lib/pleroma/helpers/media_helper.ex

# Pleroma: A lightweight social networking server
# Copyright © 2017-2020 Pleroma Authors <https://pleroma.social/>
# SPDX-License-Identifier: AGPL-3.0-only

defmodule Pleroma.Helpers.MediaHelper do
  @moduledoc """
  Handles common media-related operations.
  """

  @tmp_base "/tmp/pleroma-media_preview-pipe"

  def image_resize(url, options) do
    with executable when is_binary(executable) <- System.find_executable("convert"),
         {:ok, args} <- prepare_image_resize_args(options),
         url = Pleroma.Web.MediaProxy.url(url),
         {:ok, env} <- Pleroma.HTTP.get(url),
         {:ok, fifo_path} <- mkfifo()
    do
      run_fifo(fifo_path, env, executable, args)
    else
      nil -> {:error, {:convert, :command_not_found}}
      {:error, _} = error -> error
    end
  end

  defp prepare_image_resize_args(%{max_width: max_width, max_height: max_height} = options) do
    quality = options[:quality] || 85
    resize = Enum.join([max_width, "x", max_height, ">"])
    args = [
    "-interlace", "Plane",
    "-resize", resize,
    "-quality", to_string(quality),
    "jpg:-"
    ]
    {:ok, args}
  end

  defp prepare_image_resize_args(_), do: {:error, :missing_options}

  defp run_fifo(fifo_path, env, executable, args) do
    args = List.flatten([fifo_path, args])
    pid = Port.open({:spawn_executable, executable}, [:use_stdio, :stream, :exit_status, :binary, args: args])
    fifo = Port.open(to_charlist(fifo_path), [:eof, :binary, :stream, :out])
    true = Port.command(fifo, env.body)
    :erlang.port_close(fifo)
    loop_recv(pid)
  after
    File.rm(fifo_path)
  end

  defp mkfifo() do
    path = "#{@tmp_base}#{to_charlist(:erlang.phash2(self()))}"
    case System.cmd("mkfifo", [path]) do
      {_, 0} ->
        spawn(fifo_guard(path))
        {:ok, path}
      {_, err} ->
        {:error, {:fifo_failed, err}}
    end
  end

  defp fifo_guard(path) do
    pid = self()
    fn() ->
      ref = Process.monitor(pid)
      receive do
        {:DOWN, ^ref, :process, ^pid, _} ->
          File.rm(path)
      end
    end
  end

  defp loop_recv(pid) do
    loop_recv(pid, <<>>)
  end

  defp loop_recv(pid, acc) do
    receive do
      {^pid, {:data, data}} ->
        loop_recv(pid, acc <> data)
      {^pid, {:exit_status, 0}} ->
        {:ok, acc}
      {^pid, {:exit_status, status}} ->
        {:error, status}
     after
       5000 ->
         :erlang.port_close(pid)
         {:error, :timeout}
    end
  end
end