Make snapshot generation aware of custom snapshot time on asciicast

app/services/asciicast_snapshot_updater.rb

@@ -1,6 +1,7 @@
 class AsciicastSnapshotUpdater
 
-  def update(asciicast, at_seconds = asciicast.duration / 2)
+  def update(asciicast, at_seconds = nil)
+    at_seconds ||= asciicast.snapshot_at || asciicast.duration / 2
     snapshot = generate_snapshot(asciicast, at_seconds)
     asciicast.update_attribute(:snapshot, snapshot)
   end

db/migrate/20141127112626_add_snapshot_at_to_asciicasts.rb

@@ -0,0 +1,5 @@
+class AddSnapshotAtToAsciicasts < ActiveRecord::Migration
+  def change
+    add_column :asciicasts, :snapshot_at, :float
+  end
+end

db/schema.rb

@@ -11,7 +11,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema.define(version: 20141005152615) do
+ActiveRecord::Schema.define(version: 20141127112626) do
 
   # These are extensions that must be enabled in order to support this database
   enable_extension "plpgsql"
@@ -52,6 +52,7 @@ ActiveRecord::Schema.define(version: 20141005152615) do
     t.string   "stdout_frames"
     t.string   "user_agent"
     t.string   "theme_name"
+    t.float    "snapshot_at"
   end
 
   add_index "asciicasts", ["created_at"], name: "index_asciicasts_on_created_at", using: :btree

spec/services/asciicast_snapshot_updater_spec.rb

@@ -5,11 +5,13 @@ describe AsciicastSnapshotUpdater do
   let(:updater) { described_class.new }
 
   describe '#update' do
-    let(:asciicast) { double('asciicast', :duration => 5.0, :stdout => stdout,
+    let(:asciicast) { double('asciicast', duration: 5.0, stdout: stdout,
-                                          :update_attribute => nil) }
+                                          update_attribute: nil,
+                                          snapshot_at: snapshot_at) }
     let(:stdout) { double('stdout') }
     let(:terminal) { double('terminal') }
     let(:film) { double('film', :snapshot_at => 'foo') }
+    let(:snapshot_at) { nil }
 
     subject { updater.update(asciicast) }
 
@@ -20,15 +22,25 @@ describe AsciicastSnapshotUpdater do
       subject
     end
 
-    it "generates the snapshot at half of asciicast's duration" do
-      expect(film).to have_received(:snapshot_at).with(2.5)
-    end
-
     it "updates asciicast's snapshot to the terminal's snapshot" do
       expect(asciicast).to have_received(:update_attribute).
         with(:snapshot, 'foo')
     end
 
+    context "when no snapshot time set on asciicast nor custom time given" do
+      it "generates the snapshot at half of asciicast's duration" do
+        expect(film).to have_received(:snapshot_at).with(2.5)
+      end
+    end
+
+    context "when snapshot time set on asciicast" do
+      let(:snapshot_at) { 2.0 }
+
+      it "generates the snapshot at half of asciicast's duration" do
+        expect(film).to have_received(:snapshot_at).with(2.0)
+      end
+    end
+
     context "when snapshot time given" do
       subject { updater.update(asciicast, 4.3) }