From 899d2078deb21448b4573e015572d4ddfba22504 Mon Sep 17 00:00:00 2001
From: aidewoode <aidewoode@gmail.com>
Date: Thu, 6 Jun 2024 15:19:00 +0800
Subject: [PATCH] Parse Ogg duration and bitrate lazily

Co-authored-by: obskyr <powpowd@gmail.com>
---
 README.md                   | 10 +++++++---
 lib/wahwah/helper.rb        |  8 ++------
 lib/wahwah/ogg_tag.rb       | 16 ++++++++++++++--
 lib/wahwah/tag.rb           |  4 ++--
 test/wahwah/ogg_tag_test.rb | 22 ++++++++++++++++++++++
 5 files changed, 47 insertions(+), 13 deletions(-)

diff --git a/README.md b/README.md
index 15b2fa5..b66a84b 100644
--- a/README.md
+++ b/README.md
@@ -36,10 +36,15 @@ WahWah is so easy to use.
 ```ruby
 require "wahwah"
 
-# Get metadata from an audio file
-
+# Get metadata from an audio file path
 tag = WahWah.open("/files/example.wav")
 
+# Or from IO like object
+File.open("/files/example.wav") do |file|
+  tag = WahWah.open(file)
+end
+
+# Supported attributes
 tag.title       # => "song title"
 tag.artist      # => "artist name"
 tag.album       # => "album name"
@@ -62,6 +67,5 @@ tag.images      # => [{ :type => :cover_front, :mime_type => 'image/jpeg', :data
 
 
 # Get all support formats
-
 WahWah.support_formats # => ["mp3", "ogg", "oga", "opus", "wav", "flac", "wma", "m4a"]
 ```
diff --git a/lib/wahwah/helper.rb b/lib/wahwah/helper.rb
index d2f0aac..98392d4 100644
--- a/lib/wahwah/helper.rb
+++ b/lib/wahwah/helper.rb
@@ -28,14 +28,10 @@ def self.split_with_terminator(string, terminator_size)
     def self.file_format(io)
       if io.respond_to?(:path) && io.path && !io.path.empty?
         file_format = file_format_from_extension io.path
-        # Using OpenURI, the file *has* a path, but it's without an extension.
-        # To support that case, we fall back on signature detection.
-        file_format = file_format_from_signature io if file_format.empty?
-      else
-        file_format = file_format_from_signature io
+        return file_format unless file_format.nil? || file_format.empty?
       end
 
-      file_format
+      file_format_from_signature io
     end
 
     def self.byte_string_to_guid(byte_string)
diff --git a/lib/wahwah/ogg_tag.rb b/lib/wahwah/ogg_tag.rb
index 6e993fd..c8b5151 100644
--- a/lib/wahwah/ogg_tag.rb
+++ b/lib/wahwah/ogg_tag.rb
@@ -17,6 +17,20 @@ class OggTag < Tag
       :sample_rate,
       :lyrics
 
+    # Oggs require reading to the end of the file in order to calculate their
+    # duration (as it's not stored in any header or metadata). Thus, if the
+    # IO like object supplied to WahWah is a streaming download, getting the
+    # duration would download the entire audio file, which may not be
+    # desirable. Making it lazy in this manner allows the user to avoid that.
+    def duration
+      @duration ||= parse_duration
+    end
+
+    # Requires duration to calculate, so lazy as well.
+    def bitrate
+      @bitrate ||= parse_bitrate
+    end
+
     private
 
     def packets
@@ -41,8 +55,6 @@ def parse
         Ogg::FlacTag.new(identification_packet, comment_packet)
       end
 
-      @duration = parse_duration
-      @bitrate = parse_bitrate
       @bit_depth = parse_bit_depth
     end
 
diff --git a/lib/wahwah/tag.rb b/lib/wahwah/tag.rb
index 3e95151..b89ad44 100644
--- a/lib/wahwah/tag.rb
+++ b/lib/wahwah/tag.rb
@@ -3,7 +3,7 @@
 module WahWah
   class Tag
     INTEGER_ATTRIBUTES = %i[disc disc_total track track_total]
-    INSPECT_ATTRIBUTES = %i[title artist album albumartist composer track track_total genre year disc disc_total duration bitrate sample_rate bit_depth]
+    INSPECT_ATTRIBUTES = %i[title artist album albumartist composer track track_total genre year disc disc_total]
 
     attr_reader(
       :title,
@@ -51,7 +51,7 @@ def inspect
     def images
       return @images_data if @images_data.empty?
 
-      @images_data.map do |data|
+      @images ||= @images_data.map do |data|
         parse_image_data(data)
       end
     end
diff --git a/test/wahwah/ogg_tag_test.rb b/test/wahwah/ogg_tag_test.rb
index f8887d4..fa2b686 100644
--- a/test/wahwah/ogg_tag_test.rb
+++ b/test/wahwah/ogg_tag_test.rb
@@ -68,4 +68,26 @@ def test_flac_tag_file
       assert_equal "I'm feeling tragic like I'm Marlon Brando", tag.lyrics
     end
   end
+
+  def test_lazy_duration
+    File.open("test/files/vorbis_tag.ogg", "rb") do |file|
+      tag = WahWah::OggTag.new(file)
+      assert tag.instance_variable_get(:@file_io).pos < file.size
+      assert_nil tag.instance_variable_get(:@duration)
+
+      tag.duration
+      assert_equal 8.0, tag.instance_variable_get(:@duration)
+    end
+  end
+
+  def test_lazy_bitrate
+    File.open("test/files/vorbis_tag.ogg", "rb") do |file|
+      tag = WahWah::OggTag.new(file)
+      assert tag.instance_variable_get(:@file_io).pos < file.size
+      assert_nil tag.instance_variable_get(:@bitrate)
+
+      tag.bitrate
+      assert_equal 192, tag.instance_variable_get(:@bitrate)
+    end
+  end
 end