image saving with basic error handling

lib/plantid_discord_bot/cogs/plantnet.ex

@@ -1,8 +1,8 @@
 defmodule PlantIdDiscordBot.Cog.PlantNet do
   use Nostrum.Consumer
-  # alias PlantIdDiscordBot.Cog.PlantNet
   alias PlantIdDiscordBot.RateLimiter
   alias PlantIdDiscordBot.PlantNet.Parser
+  alias PlantIdDiscordBot.FileServer.File
 
   @api Application.compile_env(:plantid_discord_bot, :api)
 
@@ -26,18 +26,40 @@ defmodule PlantIdDiscordBot.Cog.PlantNet do
       {:ok, _} ->
         do_identification(interaction)
     end
-
-    # TODO increase on success (failed id or otherwise)
-    # RateLimiter.increase_counter(guild_id)
   end
 
   defp do_identification(interaction) do
     attachment_urls = get_attachment_urls(interaction)
     original_images = get_original_images(attachment_urls)
 
+    try do
+      Enum.each(attachment_urls, fn url ->
+        binary = File.download_file!(url)
+        File.save_file!(binary)
+      end)
+    rescue
+      e in RuntimeError ->
+        # Logger.error("An error occurred while processing the images.")
+
+        @api.create_interaction_response(interaction, %{
+          type: 4,
+          data: %{
+            content:
+              "An error occurred while processing the images." <> "\n\nReason:\n#{e.message}"
+          }
+        })
+    end
+
+    # TODO call PlantNet API and get response, with error handling
+
+    # TODO pass this response to the parser as below, with error handling
+
     # temp data
     response_message = Parser.parse(@plantnet_raw_response)
 
+    # TODO increase on success (failed id or otherwise)
+    # RateLimiter.increase_counter(guild_id)
+
     @api.create_interaction_response(interaction, %{
       type: 4,
       data: %{content: response_message <> "\n#{original_images}"}

lib/plantid_discord_bot/file_server/file.ex

@@ -0,0 +1,36 @@
+defmodule PlantIdDiscordBot.FileServer.File do
+  @moduledoc """
+  File utilities
+  """
+  alias PlantIdDiscordBot.FileServer.ImageConverter
+
+  @image_path Application.compile_env(:plantid_discord_bot, :image_path)
+
+  @doc """
+  Downloads a file from the given URL. Throws an error if unsuccessful.
+  """
+  @spec download_file!(String.t()) :: binary
+  def download_file!(url) do
+    HTTPoison.get!(url)
+    |> Map.get(:body)
+  end
+
+  @spec save_file!(binary) :: :ok
+  def save_file!(binary) do
+    File.mkdir_p!(@image_path)
+
+    jpg_binary = ImageConverter.to_jpg!(binary)
+
+    generate_unique_filename("jpg")
+    |> File.write!(binary)
+  end
+
+  @doc """
+  Generates a unique filename with the given file extension.
+  """
+  @spec generate_unique_filename(String.t()) :: String.t()
+  def generate_unique_filename(file_extension) do
+    filename = :crypto.strong_rand_bytes(8) |> Base.encode16()
+    Path.join(@image_path, "#{filename}.#{file_extension}")
+  end
+end

lib/plantid_discord_bot/file_server/image_converter.ex

@@ -0,0 +1,19 @@
+defmodule PlantIdDiscordBot.FileServer.ImageConverter do
+  @moduledoc """
+  Image conversion utilities
+  """
+  alias PlantIdDiscordBot.FileServer.MimeTypes
+
+  def to_jpg!(binary) do
+    case MimeTypes.detect_mime_type(binary) do
+      {:error, message} -> raise RuntimeError, message
+      "image/jpeg" -> binary
+      _ -> do_to_jpg(binary)
+    end
+  end
+
+  defp do_to_jpg(binary) do
+    Image.from_binary!(binary)
+    |> Image.write!(:memory, suffix: ".jpg")
+  end
+end

lib/plantid_discord_bot/file_server/mime_types.ex

@@ -0,0 +1,17 @@
+defmodule PlantIdDiscordBot.FileServer.MimeTypes do
+  @moduledoc """
+  Mime type utilities
+  """
+
+  @doc """
+  Detect the mime type of a binary
+  """
+  @spec detect_mime_type(binary) :: String.t()
+  def detect_mime_type(<<0x52, 0x49, 0x46, 0x46, _::binary>>), do: "image/webp"
+  def detect_mime_type(<<0xFF, 0xD8, 0xFF, _::binary>>), do: "image/jpeg"
+  def detect_mime_type(<<0x89, 0x50, 0x4E, 0x47, _::binary>>), do: "image/png"
+  def detect_mime_type(<<0x47, 0x49, 0x46, 0x38, _::binary>>), do: "image/gif"
+  def detect_mime_type(<<0x42, 0x4D, _::binary>>), do: "image/bmp"
+  def detect_mime_type(<<0x49, 0x49, 0x2A, 0x00, _::binary>>), do: "image/tiff"
+  def detect_mime_type(_), do: {:error, "Unsupported file type"}
+end

lib/plantid_discord_bot/plantnet/parser.ex

@@ -36,14 +36,14 @@ defmodule PlantIdDiscordBot.PlantNet.Parser do
   @spec parse(String.t()) :: map()
   def parse(response) do
     response
-    |> to_map()
+    |> to_map!()
     |> filter_by_score()
     |> add_external_urls()
     |> generate_response_message()
   end
 
-  @spec to_map(String.t()) :: map()
-  def to_map(response), do: Jason.decode!(response)
+  @spec to_map!(String.t()) :: map()
+  def to_map!(response), do: Jason.decode!(response)
 
   @doc """
   Filters the data by score. Data is a parsed response from the PlantNet API.