Add dumbest mixdown full of assumptions.

lib/balladina.rb

@@ -11,3 +11,4 @@
 require_relative "balladina/control_socket_listener"
 require_relative "balladina/track_coordinator"
 require_relative "balladina/board"
+require_relative "balladina/mixdown"

lib/balladina/mixdown.rb

@@ -0,0 +1,58 @@
+module Balladina
+  class Mixdown
+    def initialize(name, options = {})
+      @name        = name
+      @target_path = options.fetch(:target_path) { Configuration.mixdowns_path }
+    end
+
+    attr_reader :name, :target_path
+
+    def perform_on(tracks_clips)
+      create_temp_mixdown_path
+
+      tracks_clips.map { |track_name, clips|
+        join_clips track_name, clips
+      }.each { |track_path|
+        compress_track track_path
+      }
+
+      zip_tracks
+    ensure
+      FileUtils.rm_rf temp_mixdown_path
+    end
+
+    def join_clips(track_name, clips)
+      track_path = File.join(temp_mixdown_path, "#{track_name}.wav")
+      clip_paths = clips.join(" ")
+
+      `sox #{clip_paths} #{track_path}`
+
+      track_path
+    end
+
+    def compress_track(track_path)
+      mp3_path = track_path.sub(/\.wav$/, ".mp3")
+      `lame -V2 --quiet #{track_path} #{mp3_path}`
+      mp3_path
+    ensure
+      File.delete track_path
+    end
+
+    def zip_tracks
+      `cd #{temp_mixdown_path}/../; zip -r #{mixdown_zipfile_path} #{name}`
+      mixdown_zipfile_path
+    end
+
+    def create_temp_mixdown_path
+      FileUtils.mkdir_p temp_mixdown_path
+    end
+
+    def temp_mixdown_path
+      File.join Dir.tmpdir, "balladina-mixdowns", name
+    end
+
+    def mixdown_zipfile_path
+      File.join target_path, "#{name}.zip"
+    end
+  end
+end

spec/balladina/mixdown_spec.rb

@@ -0,0 +1,33 @@
+require_relative "../spec_helper"
+require "digest/md5"
+
+describe Balladina::Mixdown do
+  let(:clip_paths) {
+    Dir[File.expand_path("../fixtures/clips/*.wav", __dir__)]
+  }
+  let(:mixdown) {
+    File.expand_path("../fixtures/clips/mixdowns/my-crazy-mixdown.zip", __dir__)
+  }
+
+  let(:clips) { Hamster.set(clip_paths) }
+  let(:tmp_mixdowns) { Dir.tmpdir + "/balladina-mixdowns" }
+
+  subject { Balladina::Mixdown.new("my-crazy-mixdown", target_path: tmp_mixdowns) }
+
+  before do
+    FileUtils.mkdir_p tmp_mixdowns
+  end
+
+  after do
+    FileUtils.rm_rf tmp_mixdowns
+  end
+
+  it "joins a set of Tracks into a zipfile" do
+    zipped_path = subject.perform_on("track-1" => clips, "track-2" => clips)
+    expect(File.size(zipped_path)).to eq(File.size(mixdown))
+  end
+
+  def digest(path)
+    Digest::MD5.file path
+  end
+end