add SoundFile::Wav and SoundFile::Mp3

lib/scissor/sound_file.rb

@@ -4,44 +4,66 @@
 
 module Scissor
   class SoundFile
-    SUPPORTED_FORMATS = %w/mp3 wav/
+    class Mp3 < SoundFile
+      def length
+        info.length
+      end
 
-    class Error < StandardError; end
-    class UnknownFormat < Error; end
+      def mono?
+        info.channel_mode == 'Single Channel'
+      end
 
-    def initialize(filename)
-      @filename = Pathname.new(filename)
-      @ext = @filename.extname.sub(/^\./, '').downcase
+      private
 
-      unless SUPPORTED_FORMATS.include?(@ext)
-        raise UnknownFormat
+      def info
+        @info ||= Mp3Info.new(@filename.to_s)
       end
     end
 
-    def length
-      case @ext
-      when 'mp3'
-        Mp3Info.new(@filename.to_s).length
-      when 'wav'
-        riff = Riff::Reader.open(@filename ,"r")
-        data = riff.root_chunk['data']
-        fmt = riff.root_chunk['fmt ']
-
+    class Wav < SoundFile
+      def length
         data.length / fmt.body.unpack('s2i2')[3].to_f
       end
+
+      def mono?
+        fmt.body.unpack('s2')[1] == 1
+      end
+
+      private
+
+      def riff
+        @riff ||= Riff::Reader.open(@filename ,"r")
+      end
+
+      def data
+        @data ||= riff.root_chunk['data']
+      end
+
+      def fmt
+        @fmt ||= riff.root_chunk['fmt ']
+      end
     end
 
-    def mono?
-      case @ext
-      when 'mp3'
-        Mp3Info.new(@filename.to_s).channel_mode == 'Single Channel'
-      when 'wav'
-        riff = Riff::Reader.open(@filename ,"r")
-        data = riff.root_chunk['data']
-        fmt = riff.root_chunk['fmt ']
+    SUPPORTED_FORMATS = {
+      :mp3 => Mp3,
+      :wav => Wav
+    }
 
-        fmt.body.unpack('s2')[1] == 1
+    class Error < StandardError; end
+    class UnknownFormat < Error; end
+
+    def self.new_from_filename(filename)
+      ext = filename.extname.sub(/^\./, '').downcase
+
+      unless klass = SUPPORTED_FORMATS[ext.to_sym]
+        raise UnknownFormat
       end
+
+      klass.new(filename)
+    end
+
+    def initialize(filename)
+      @filename = Pathname.new(filename)
     end
   end
 end

lib/scissor/tape.rb

@@ -17,7 +17,7 @@ def initialize(filename = nil)
         @fragments << Fragment.new(
           filename,
           0,
-          SoundFile.new(filename).length)
+          SoundFile.new_from_filename(filename).length)
       end
     end
 

lib/scissor/writer.rb

@@ -154,7 +154,7 @@ def run_command(cmd)
     private
 
     def mono?(filename)
-      SoundFile.new(filename).mono?
+      SoundFile.new_from_filename(filename).mono?
     end
   end
 end

spec/sound_file_spec.rb

@@ -7,16 +7,16 @@
 
 describe Scissor::SoundFile do
   before do
-    @mp3 = Scissor::SoundFile.new(fixture('sample.mp3'))
-    @wav = Scissor::SoundFile.new(fixture('sine.wav'))
+    @mp3 = Scissor::SoundFile.new_from_filename(fixture('sample.mp3'))
+    @wav = Scissor::SoundFile.new_from_filename(fixture('sine.wav'))
   end
 
   after do
   end
 
   it "raise error if unknown file format" do
     lambda {
-      Scissor::SoundFile.new(fixture('foo.bar'))
+      Scissor::SoundFile.new_from_filename(fixture('foo.bar'))
     }.should raise_error(Scissor::SoundFile::UnknownFormat)
   end
 
@@ -30,7 +30,7 @@
       @mp3.should be_mono
       @wav.should_not be_mono
 
-      Scissor::SoundFile.new(fixture('mono.wav')).should be_mono
+      Scissor::SoundFile.new_from_filename(fixture('mono.wav')).should be_mono
     end
   end
 end