1 files changed, 165 insertions, 0 deletions
diff --git a/trunk/lib/rubygems/dependency_list.rb b/trunk/lib/rubygems/dependency_list.rb
new file mode 100644
index 0000000000..a129743914
--- /dev/null
+++ b/trunk/lib/rubygems/dependency_list.rb
@@ -0,0 +1,165 @@
+#--
+# Copyright 2006 by Chad Fowler, Rich Kilmer, Jim Weirich and others.
+# All rights reserved.
+# See LICENSE.txt for permissions.
+#++
+
+require 'tsort'
+
+class Gem::DependencyList
+
+  include TSort
+
+  def self.from_source_index(src_index)
+    deps = new
+
+    src_index.each do |full_name, spec|
+      deps.add spec
+    end
+
+    deps
+  end
+
+  def initialize
+    @specs = []
+  end
+
+  # Adds +gemspecs+ to the dependency list.
+  def add(*gemspecs)
+    @specs.push(*gemspecs)
+  end
+
+  # Return a list of the specifications in the dependency list,
+  # sorted in order so that no spec in the list depends on a gem
+  # earlier in the list.
+  #
+  # This is useful when removing gems from a set of installed gems.
+  # By removing them in the returned order, you don't get into as
+  # many dependency issues.
+  #
+  # If there are circular dependencies (yuck!), then gems will be
+  # returned in order until only the circular dependents and anything
+  # they reference are left.  Then arbitrary gemspecs will be returned
+  # until the circular dependency is broken, after which gems will be
+  # returned in dependency order again.
+  def dependency_order
+    sorted = strongly_connected_components.flatten
+
+    result = []
+    seen = {}
+
+    sorted.each do |spec|
+      if index = seen[spec.name] then
+        if result[index].version < spec.version then
+          result[index] = spec
+        end
+      else
+        seen[spec.name] = result.length
+        result << spec
+      end
+    end
+
+    result.reverse
+  end
+
+  def find_name(full_name)
+    @specs.find { |spec| spec.full_name == full_name }
+  end
+
+  # Are all the dependencies in the list satisfied?
+  def ok?
+    @specs.all? do |spec|
+      spec.runtime_dependencies.all? do |dep|
+        @specs.find { |s| s.satisfies_requirement? dep }
+      end
+    end
+  end
+
+  # Is is ok to remove a gem from the dependency list?
+  #
+  # If removing the gemspec creates breaks a currently ok dependency,
+  # then it is NOT ok to remove the gem.
+  def ok_to_remove?(full_name)
+    gem_to_remove = find_name full_name
+
+    siblings = @specs.find_all { |s|
+      s.name == gem_to_remove.name &&
+        s.full_name != gem_to_remove.full_name
+    }
+
+    deps = []
+
+    @specs.each do |spec|
+      spec.dependencies.each do |dep|
+        deps << dep if gem_to_remove.satisfies_requirement?(dep)
+      end
+    end
+
+    deps.all? { |dep|
+      siblings.any? { |s|
+        s.satisfies_requirement? dep
+      }
+    }
+  end
+
+  def remove_by_name(full_name)
+    @specs.delete_if { |spec| spec.full_name == full_name }
+  end
+
+  # Return a hash of predecessors.  <tt>result[spec]</tt> is an
+  # Array of gemspecs that have a dependency satisfied by the named
+  # spec.
+  def spec_predecessors
+    result = Hash.new { |h,k| h[k] = [] }
+
+    specs = @specs.sort.reverse
+
+    specs.each do |spec|
+      specs.each do |other|
+        next if spec == other
+
+        other.dependencies.each do |dep|
+          if spec.satisfies_requirement? dep then
+            result[spec] << other
+          end
+        end
+      end
+    end
+
+    result
+  end
+
+  def tsort_each_node(&block)
+    @specs.each(&block)
+  end
+
+  def tsort_each_child(node, &block)
+    specs = @specs.sort.reverse
+
+    node.dependencies.each do |dep|
+      specs.each do |spec|
+        if spec.satisfies_requirement? dep then
+          begin
+            yield spec
+          rescue TSort::Cyclic
+          end
+          break
+        end
+      end
+    end
+  end
+
+  private
+
+  # Count the number of gemspecs in the list +specs+ that are not in
+  # +ignored+.
+  def active_count(specs, ignored)
+    result = 0
+    specs.each do |spec|
+      result += 1 unless ignored[spec.full_name]
+    end
+    result
+  end
+
+end
+