metadata: add CLI script for printing image metadata

Add a utility script for printing image metadata from the command line.

Usage: `bin/lsmetadata 1.jpg 2.jpg`

app/logical/media_file.rb

@@ -6,6 +6,8 @@
 # supported by a File.
 class MediaFile
   extend Memoist
+  include ActiveModel::Serializers::JSON
+
   attr_accessor :file
 
   # delegate all File methods to `file`.
@@ -168,5 +170,18 @@ class MediaFile
     nil
   end
 
+  def attributes
+    {
+      path: path,
+      width: width,
+      height: height,
+      file_ext: file_ext,
+      file_size: file_size,
+      md5: md5,
+      is_corrupt?: is_corrupt?,
+      metadata: metadata
+    }.stringify_keys
+  end
+
   memoize :file_ext, :file_size, :md5, :metadata
 end

bin/lsmetadata

@@ -0,0 +1,25 @@
+#!/usr/bin/env ruby
+
+# List metadata for given image and video files in JSON format.
+#
+# Usage:
+#
+#   bin/lsmetadata 1.jpg | jq        # list file
+#   bin/lsmetadata | jq              # list all files in current directory
+#   bin/lsmetadata images/ | jq      # list directory
+#   bin/lsmetadata images/**/* | jq  # list directory recursively
+#
+#   # Run from Docker without having to install Danbooru
+#   docker run -rm -it -v $PWD:/mnt ghcr.io/danbooru/danbooru bin/lsmetadata /mnt/images/**/* | jq
+
+APP_PATH = File.expand_path('../config/application', __dir__)
+require_relative "../config/environment"
+
+files = ARGV
+files = [Dir.pwd] if files.empty?
+files.map! { |file| File.directory?(file) ? Dir[file + "/*"] : file }.flatten!
+files.reject! { |file| File.directory?(file) }
+
+files.each do |filename|
+  puts MediaFile.open(filename).to_json
+end