Defined the Instagram service.

(The account namespace is a little irregular, but I think it covers the prominent special cases.)
Shifted titles in the spec so errors make more sense.
Closes #9.

lib/services/instagram_service.rb

@@ -0,0 +1,44 @@
+class InstagramService < Service
+  def self.handles?(uri)
+    # Exclude help.instagram.com, blog.instagram.com, etc.
+    uri.host =~ /^instagram.com$/
+  end
+
+  def self.shortname
+    :instagram
+  end
+
+  def display_name
+    "#{account} on Instagram"
+  end
+
+  def account
+    /^\/(?<account>[\w-]+)/ =~ @uri.path
+
+
+    @exclude = ['p', 'popular', 'developer', 'press', 'about']
+    if @exclude.any? {|stopword| account == stopword}
+      account = nil
+    end
+
+    account
+  end
+
+  def service_url_example
+    "http://instagram.com/username"
+  end
+
+  def service_url_canonical
+    "http://instagram.com/#{account}"
+  end
+
+  private
+
+  def fetch_details
+    {
+      :account => account,
+    }
+  end
+end
+
+Service.register(:instagram, InstagramService)

spec/models/service_spec.rb

@@ -7,7 +7,7 @@
     unknown.should be_nil
   end
 
-  describe "Twitter plugin" do
+  describe "definition for Twitter" do
 
     it "should be chosen for Twitter URLs" do
       service = Service.find_by_url("http://twitter.com/usagov")
@@ -25,15 +25,15 @@
     end
   end
 
-  describe "Facebook plugin" do
+  describe "definition for Facebook" do
 
     it "should be chosen for Facebook URLs" do
       service = Service.find_by_url("http://facebook.com/USAgov")
       service.shortname.should == :facebook
     end
   end
 
-  describe "Youtube plugin" do
+  describe "definition for Youtube" do
 
     it "should be chosen for Youtube URLs" do
       service = Service.find_by_url("http://www.youtube.com/USGovernment")
@@ -46,7 +46,7 @@
     end
   end
 
-  describe "Flickr plugin" do
+  describe "definition for Flickr" do
 
     it "should be chosen for Flickr URLs" do
       service = Service.find_by_url("http://www.flickr.com/groups/usagov/")
@@ -78,7 +78,7 @@
     end
   end
 
-  describe "Slideshare plugin" do
+  describe "definition for Slideshare" do
 
     it "should be chosen for Slideshare URLs" do
       service = Service.find_by_url("http://www.slideshare.net/nasa")
@@ -94,7 +94,7 @@
     end
   end
 
-  describe "Pinterest plugin" do
+  describe "definition for Pinterest" do
     it "should be chosen for Pinterest URLs" do
       service = Service.find_by_url("http://pinterest.com/michelleobama/")
       service.shortname.should == :pinterest
@@ -105,4 +105,32 @@
       service.account.should == 'michelleobama'
     end
   end
+
+  describe "definition for Instagram" do
+    it "should be chosen for Instagram URLs" do
+      service = Service.find_by_url("http://instagram.com/morgantown_wv/")
+      service.shortname.should == :instagram
+    end
+
+    it "should pick out the correct account name" do
+      service = Service.find_by_url("http://instagram.com/morgantown_wv/")
+      service.shortname.should == :instagram
+      service.account.should == 'morgantown_wv'
+
+      service = Service.find_by_url("http://instagram.com/cityofdetroit#")
+      service.shortname.should == :instagram
+      service.account.should == 'cityofdetroit'
+    end
+
+    it "should ignore system URLs" do
+      service = Service.find_by_url("http://instagram.com/about/us/")
+      service.account.should be_nil
+
+      service = Service.find_by_url("http://instagram.com/press/")
+      service.account.should be_nil
+
+      service = Service.find_by_url("http://blog.instagram.com/")
+      service.should be_nil
+    end
+  end
 end