From fee00469f61e14e7dd9503a7b3381a95eb49ad81 Mon Sep 17 00:00:00 2001
From: Adam Vandenberg <flangy@gmail.com>
Date: Tue, 28 Feb 2012 19:56:29 -0800
Subject: [PATCH] New external dependency implementation.

---
 Library/Homebrew/dependencies.rb | 138 +++++++++++++++++++++++++++++++
 1 file changed, 138 insertions(+)
 create mode 100644 Library/Homebrew/dependencies.rb

diff --git a/Library/Homebrew/dependencies.rb b/Library/Homebrew/dependencies.rb
new file mode 100644
index 0000000000..3d92d45e69
--- /dev/null
+++ b/Library/Homebrew/dependencies.rb
@@ -0,0 +1,138 @@
+## This file defines dependencies and requirements.
+##
+## A dependency is a formula that another formula needs to install.
+## A requirement is something other than a formula that another formula
+## needs to be present. This includes external language modules,
+## command-line tools in the path, or any arbitrary predicate.
+##
+## The `depends_on` method in the formula DSL is used to declare
+## dependencies and requirements.
+
+
+# This class is used by `depends_on` in the formula DSL to turn dependency
+# specifications into the proper kinds of dependencies and requirements.
+class DependencyCollector
+  # Define the languages that we can handle as external dependencies.
+  LANGUAGE_MODULES = [
+    :chicken, :jruby, :lua, :node, :perl, :python, :rbx, :ruby
+  ].freeze
+
+  attr_reader :deps, :external_deps
+
+  def initialize
+    @deps = Dependencies.new
+    @external_deps = []
+  end
+
+  def add spec
+    case spec
+    when String      then @deps << Dependency.new(spec)
+    when Formula     then @deps << Dependency.new(spec.name)
+    when Dependency  then @deps << spec
+    when Requirement then @external_deps << spec
+    when Hash
+      key, value = spec.shift
+      case value
+      when Array
+        @deps << Dependency.new(key, value)
+      when *LANGUAGE_MODULES
+        @external_deps << LanguageModuleDependency.new(key, value)
+      else
+        # :optional, :recommended, :build, :universal and "32bit" are predefined
+        @deps << Dependency.new(key, [value])
+      end
+    else
+      raise "Unsupported type #{spec.class} for #{spec}"
+    end
+  end
+end
+
+
+# A list of formula dependencies.
+class Dependencies < Array
+  def include? dependency_name
+    self.any?{|d| d.name == dependency_name}
+  end
+end
+
+
+# A dependency on another Homebrew formula.
+class Dependency
+  attr_reader :name, :tags
+
+  def initialize name, tags=nil
+    @name = name
+    tags = [] if tags == nil
+    @tags = tags.each {|s| s.to_s}
+  end
+
+  def to_s
+    @name
+  end
+
+  def ==(other_dep)
+    @name = other_dep.to_s
+  end
+
+  def options
+    @tags.select{|p|p.start_with? '--'}
+  end
+end
+
+
+# A base class for non-formula requirements needed by formulae.
+# A "fatal" requirement is one that will fail the build if it is not present.
+# By default, Requirements are non-fatal.
+class Requirement
+  def satisfied?; false; end
+  def fatal?; false; end
+  def message; ""; end
+end
+
+
+# A dependency on a language-specific module.
+class LanguageModuleDependency < Requirement
+  def initialize module_name, type
+    @module_name = module_name
+    @type = type
+  end
+
+  def fatal?; true; end
+
+  def satisfied?
+    quiet_system *the_test
+  end
+
+  def message; <<-EOS.undent
+    Unsatisfied dependency: #{@module_name}
+    Homebrew does not provide #{@type.to_s.capitalize} dependencies; install with:
+      #{command_line} #{@module_name}
+    EOS
+  end
+
+  def the_test
+    case @type
+      when :chicken then %W{/usr/bin/env csi -e (use #{@module_name})}
+      when :jruby then %W{/usr/bin/env jruby -rubygems -e require\ '#{@module_name}'}
+      when :lua then %W{/usr/bin/env luarocks show #{@module_name}}
+      when :node then %W{/usr/bin/env node -e require('#{@module_name}');}
+      when :perl then %W{/usr/bin/env perl -e use\ #{@module_name}}
+      when :python then %W{/usr/bin/env python -c import\ #{@module_name}}
+      when :ruby then %W{/usr/bin/env ruby -rubygems -e require\ '#{@module_name}'}
+      when :rbx then %W{/usr/bin/env rbx -rubygems -e require\ '#{@module_name}'}
+    end
+  end
+
+  def command_line
+    case @type
+      when :chicken then "chicken-install"
+      when :jruby   then "jruby -S gem install"
+      when :lua     then "luarocks install"
+      when :node    then "npm install"
+      when :perl    then "cpan -i"
+      when :python  then "easy_install"
+      when :rbx     then "rbx gem install"
+      when :ruby    then "gem install"
+    end
+  end
+end