1 files changed, 108 insertions, 0 deletions
diff --git a/lib/pleroma/mime.ex b/lib/pleroma/mime.ex
new file mode 100644
index 000000000..db8b7c742
--- /dev/null
+++ b/lib/pleroma/mime.ex
@@ -0,0 +1,108 @@
+defmodule Pleroma.MIME do
+  @moduledoc """
+  Returns the mime-type of a binary and optionally a normalized file-name.
+  """
+  @default "application/octet-stream"
+  @read_bytes 31
+
+  @spec file_mime_type(String.t()) ::
+          {:ok, content_type :: String.t(), filename :: String.t()} | {:error, any()} | :error
+  def file_mime_type(path, filename) do
+    with {:ok, content_type} <- file_mime_type(path),
+         filename <- fix_extension(filename, content_type) do
+      {:ok, content_type, filename}
+    end
+  end
+
+  @spec file_mime_type(String.t()) :: {:ok, String.t()} | {:error, any()} | :error
+  def file_mime_type(filename) do
+    File.open(filename, [:read], fn f ->
+      check_mime_type(IO.binread(f, @read_bytes))
+    end)
+  end
+
+  def bin_mime_type(binary, filename) do
+    with {:ok, content_type} <- bin_mime_type(binary),
+         filename <- fix_extension(filename, content_type) do
+      {:ok, content_type, filename}
+    end
+  end
+
+  @spec bin_mime_type(binary()) :: {:ok, String.t()} | :error
+  def bin_mime_type(<<head::binary-size(@read_bytes), _::binary>>) do
+    {:ok, check_mime_type(head)}
+  end
+
+  def mime_type(<<_::binary>>), do: {:ok, @default}
+
+  def bin_mime_type(_), do: :error
+
+  defp fix_extension(filename, content_type) do
+    parts = String.split(filename, ".")
+
+    new_filename =
+      if length(parts) > 1 do
+        Enum.drop(parts, -1) |> Enum.join(".")
+      else
+        Enum.join(parts)
+      end
+
+    cond do
+      content_type == "application/octet-stream" ->
+        filename
+
+      ext = List.first(MIME.extensions(content_type)) ->
+        new_filename <> "." <> ext
+
+      true ->
+        Enum.join([new_filename, String.split(content_type, "/") |> List.last()], ".")
+    end
+  end
+
+  defp check_mime_type(<<0x89, 0x50, 0x4E, 0x47, 0x0D, 0x0A, 0x1A, 0x0A, _::binary>>) do
+    "image/png"
+  end
+
+  defp check_mime_type(<<0x47, 0x49, 0x46, 0x38, _, 0x61, _::binary>>) do
+    "image/gif"
+  end
+
+  defp check_mime_type(<<0xFF, 0xD8, 0xFF, _::binary>>) do
+    "image/jpeg"
+  end
+
+  defp check_mime_type(<<0x1A, 0x45, 0xDF, 0xA3, _::binary>>) do
+    "video/webm"
+  end
+
+  defp check_mime_type(<<0x00, 0x00, 0x00, _, 0x66, 0x74, 0x79, 0x70, _::binary>>) do
+    "video/mp4"
+  end
+
+  defp check_mime_type(<<0x49, 0x44, 0x33, _::binary>>) do
+    "audio/mpeg"
+  end
+
+  defp check_mime_type(<<255, 251, _, 68, 0, 0, 0, 0, _::binary>>) do
+    "audio/mpeg"
+  end
+
+  defp check_mime_type(
+         <<0x4F, 0x67, 0x67, 0x53, 0x00, 0x02, 0x00, 0x00, _::size(160), 0x80, 0x74, 0x68, 0x65,
+           0x6F, 0x72, 0x61, _::binary>>
+       ) do
+    "video/ogg"
+  end
+
+  defp check_mime_type(<<0x4F, 0x67, 0x67, 0x53, 0x00, 0x02, 0x00, 0x00, _::binary>>) do
+    "audio/ogg"
+  end
+
+  defp check_mime_type(<<0x52, 0x49, 0x46, 0x46, _::binary>>) do
+    "audio/wav"
+  end
+
+  defp check_mime_type(_) do
+    @default
+  end
+end