serve images, not HTML

lib/labelmaker_web/constants.ex

@@ -0,0 +1,37 @@
+defmodule LabelmakerWeb.Constants do
+  @defaults %{
+    "label" => "Labelmaker",
+    "font" => "Helvetica",
+    "color" => "black",
+    "size" => "24"
+  }
+
+  @permitted_keys Map.keys(@defaults)
+
+  @colors System.cmd("magick", ["-list", "color"])
+          |> elem(0)
+          |> String.split("\n")
+          # drop header stuff
+          |> Enum.drop(5)
+          |> Enum.map(fn color_info -> color_info |> String.split() |> List.first() end)
+
+  @fonts System.cmd("magick", ["-list", "font"])
+         |> elem(0)
+         |> String.split("\n")
+         |> Enum.filter(&String.starts_with?(&1, "  Font:"))
+         |> Enum.reject(&String.starts_with?(&1, "  Font: ."))
+         |> Enum.map(&String.trim_leading(&1, "  Font: "))
+
+  @sizes 8..72
+         |> Enum.to_list()
+         |> Enum.take_every(4)
+         |> Enum.map(&Integer.to_string/1)
+
+  def defaults, do: @defaults
+  def permitted_keys, do: @permitted_keys
+  def colors, do: @colors
+  def color_count, do: @colors |> length()
+  def fonts, do: @fonts
+  def font_count, do: @fonts |> length()
+  def sizes, do: @sizes
+end

lib/labelmaker_web/controllers/label_controller.ex

@@ -0,0 +1,48 @@
+defmodule LabelmakerWeb.LabelController do
+  use LabelmakerWeb, :controller
+  alias LabelmakerWeb.Constants
+
+  @label_dir Path.join(:code.priv_dir(:labelmaker), "static/labels")
+  File.mkdir_p!(@label_dir)
+
+  def show(conn, params) do
+    options =
+      Constants.defaults()
+      |> Map.merge(params)
+      |> Map.take(Constants.permitted_keys())
+
+    filename =
+      options
+      |> inspect()
+      |> (fn str -> :crypto.hash(:sha256, str) end).()
+      |> Base.encode16(case: :lower)
+
+    filename = filename <> ".png"
+    filepath = Path.join(@label_dir, filename)
+
+    unless File.exists?(filepath) do
+      generate_image(options, filepath)
+    end
+
+    conn
+    |> put_resp_content_type("image/png")
+    |> send_file(200, filepath)
+  end
+
+  defp generate_image(options, filepath) do
+    args = [
+      "-background",
+      "none",
+      "-fill",
+      options["color"],
+      "-pointsize",
+      options["size"],
+      "-font",
+      options["font"],
+      "label:#{options["label"]}",
+      filepath
+    ]
+
+    {_, 0} = System.cmd("magick", args)
+  end
+end

lib/labelmaker_web/router.ex

@@ -24,7 +24,8 @@ defmodule LabelmakerWeb.Router do
     pipe_through :browser
 
     live "/", Home
-    live "/:label", Label
+    get "/:label", LabelController, :show
+    # live "/:label", Label
   end
 
   # Other scopes may use custom stacks.