From e1d8dfbab672d2f19ecf0c3af8f7e0f3f2385858 Mon Sep 17 00:00:00 2001
From: Josh Holtrop <jholtrop@gmail.com>
Date: Thu, 16 Feb 2017 18:09:02 -0500
Subject: [PATCH] add JobSet class

---
 lib/rscons.rb         |  1 +
 lib/rscons/job_set.rb | 56 +++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 57 insertions(+)
 create mode 100644 lib/rscons/job_set.rb

diff --git a/lib/rscons.rb b/lib/rscons.rb
index a7e8f08..c760982 100644
--- a/lib/rscons.rb
+++ b/lib/rscons.rb
@@ -2,6 +2,7 @@ require_relative "rscons/build_target"
 require_relative "rscons/builder"
 require_relative "rscons/cache"
 require_relative "rscons/environment"
+require_relative "rscons/job_set"
 require_relative "rscons/varset"
 require_relative "rscons/version"
 
diff --git a/lib/rscons/job_set.rb b/lib/rscons/job_set.rb
new file mode 100644
index 0000000..76de53e
--- /dev/null
+++ b/lib/rscons/job_set.rb
@@ -0,0 +1,56 @@
+require "set"
+
+module Rscons
+  # Class to keep track of a set of jobs that need to be performed.
+  class JobSet
+
+    # Create a JobSet
+    def initialize
+      @jobs = {}
+    end
+
+    # Add a job to the JobSet.
+    #
+    # @param target [Symbol, String]
+    #   Build target name.
+    # @param builder [Builder]
+    #   The {Builder} to use to build the target.
+    # @param sources [Array<String>]
+    #   Source file name(s).
+    # @param vars [Hash]
+    #   Construction variable overrides.
+    def add_job(builder, target, sources, vars)
+      @jobs[target] = {
+        builder: builder,
+        target: target,
+        sources: sources,
+        vars: vars,
+      }
+    end
+
+    # Get the next job that is ready to run from the JobSet.
+    #
+    # This method will remove the job from the JobSet.
+    #
+    # @return [nil, Hash]
+    #   The next job to run.
+    def get_next_job_to_run
+      if @jobs.size > 0
+        evaluated_targets = Set.new
+        attempt = lambda do |target|
+          evaluated_targets << target
+          @jobs[target][:sources].each do |src|
+            if @jobs.include?(src) and not evaluated_targets.include?(src)
+              return attempt[src]
+            end
+          end
+          job = @jobs[target].merge(target: target)
+          @jobs.delete(target)
+          return job
+        end
+        attempt[@jobs.first.first]
+      end
+    end
+
+  end
+end