handle fully-qualified cask names, fixes #2235

form "<user>/<repo>/<cask>" may be used on cmdline, matching homebrew
- refactor Cask::Source::Tap into Cask::Source::Tapped, removing
  code, only handling unqualified cask names here now (ie no slash)
- create Cask::Source::TappedQualified, handling "<user>-<repo>/<cask>"
  form as before, and new form "<user>/<repo>/<cask>", for the case that
  the relevant tap already exists
- create Cask::Source::UntappedQualified, handling both command-line
  forms as above, but implicitly creating adding a new tap if it
  does not already exist
- add module Cask::QualifiedCaskName for utility functions on qualified
  Cask names

lib/cask.rb

@@ -19,6 +19,7 @@ require 'cask/link_checker'
 require 'cask/locations'
 require 'cask/pkg'
 require 'cask/pretty_listing'
+require 'cask/qualified_cask_name'
 require 'cask/scopes'
 require 'cask/source'
 require 'cask/system_command'

lib/cask/qualified_cask_name.rb

@@ -0,0 +1,49 @@
+module Cask::QualifiedCaskName
+  def self.repo_prefix
+    'homebrew-'
+  end
+
+  def self.user_regexp
+    # per https://github.com/Homebrew/homebrew/blob/4c7bc9ec3bca729c898ee347b6135ba692ee0274/Library/Homebrew/cmd/tap.rb#L121
+    %r{[a-z_\-]+}
+  end
+
+  def self.repo_regexp
+    # per https://github.com/Homebrew/homebrew/blob/4c7bc9ec3bca729c898ee347b6135ba692ee0274/Library/Homebrew/cmd/tap.rb#L121
+    %r{(?:#{repo_prefix})?\w+}
+  end
+
+  def self.cask_regexp
+    # per https://github.com/phinze/homebrew-cask/blob/04a8fa88c7b1d05adcd8307b9297e36f83ddbf5d/CONTRIBUTING.md#cask-name
+    %r{[a-z0-9\-]+}
+  end
+
+  def self.tap_regexp
+    %r{#{user_regexp}[/\-]#{repo_regexp}}
+  end
+
+  def self.qualified_cask_regexp
+    @qualified_cask_regexp ||= %r{#{tap_regexp}/#{cask_regexp}}
+  end
+
+  def self.parse(name)
+    return nil if ! name.kind_of?(String)
+    return nil if ! name.downcase.match(%r{^#{qualified_cask_regexp}$})
+    path_elements = name.downcase.split('/')
+    if path_elements.count == 2
+      # eg phinze-cask/google-chrome.
+      # Not certain this form is needed, but it was supported in the past.
+      cask = path_elements[1]
+      dash_elements = path_elements[0].split('-')
+      repo = dash_elements.pop
+      dash_elements.pop if dash_elements.count > 1 and dash_elements[-1] + '-' == repo_prefix
+      user = dash_elements.join('-')
+    else
+      # eg phinze/cask/google-chrome
+      # per https://github.com/Homebrew/homebrew/wiki/brew-tap
+      user, repo, cask = path_elements
+    end
+    repo.sub!(%r{^#{repo_prefix}}, '')
+    [user, repo, cask]
+  end
+end

lib/cask/source.rb

@@ -2,7 +2,9 @@ module Cask::Source; end
 
 require 'cask/source/gone'
 require 'cask/source/path'
-require 'cask/source/tap'
+require 'cask/source/tapped_qualified'
+require 'cask/source/untapped_qualified'
+require 'cask/source/tapped'
 require 'cask/source/uri'
 
 module Cask::Source
@@ -10,7 +12,9 @@ module Cask::Source
     [
       Cask::Source::URI,
       Cask::Source::Path,
-      Cask::Source::Tap,
+      Cask::Source::TappedQualified,
+      Cask::Source::UntappedQualified,
+      Cask::Source::Tapped,
       Cask::Source::Gone,
     ]
   end

lib/cask/source/tapped.rb

@@ -1,15 +1,10 @@
-class Cask::Source::Tap
+class Cask::Source::Tapped
   def self.me?(query)
     path_for_query(query).exist?
   end
 
   def self.path_for_query(query)
-    if query.include?('/')
-      cask_with_tap = query
-    else
-      cask_with_tap = Cask.all_titles.find { |t| t.split('/').last == query }
-    end
-
+    cask_with_tap = Cask.all_titles.find { |t| t.split('/').last == query }
     if cask_with_tap
       tap, cask = cask_with_tap.split('/')
       Cask.tapspath.join(tap, 'Casks', "#{cask}.rb")

lib/cask/source/tapped_qualified.rb

@@ -0,0 +1,13 @@
+require 'cask/source/tapped'
+
+class Cask::Source::TappedQualified < Cask::Source::Tapped
+  def self.me?(query)
+    !!Cask::QualifiedCaskName::parse(query) and path_for_query(query).exist?
+  end
+
+  def self.path_for_query(query)
+    user, repo, cask = Cask::QualifiedCaskName::parse(query)
+    tap = "#{user}-#{repo}"
+    Cask.tapspath.join(tap, 'Casks', "#{cask}.rb")
+  end
+end

lib/cask/source/untapped_qualified.rb

@@ -0,0 +1,14 @@
+require 'cask/source/tapped_qualified'
+require 'cmd/tap'
+
+class Cask::Source::UntappedQualified < Cask::Source::TappedQualified
+  def self.path_for_query(query)
+    user, repo, cask = Cask::QualifiedCaskName::parse(query)
+    tap = "#{user}-#{repo}"
+    unless Cask.tapspath.join(tap).exist?
+      ohai "Adding new tap '#{tap}'"
+      Homebrew.install_tap(user, repo)
+    end
+    Cask.tapspath.join(tap, 'Casks', "#{cask}.rb")
+  end
+end