1 files changed, 75 insertions, 0 deletions
diff --git a/lib/bundler/version_ranges.rb b/lib/bundler/version_ranges.rb
new file mode 100644
index 0000000000..1ee8440edd
--- /dev/null
+++ b/lib/bundler/version_ranges.rb
@@ -0,0 +1,75 @@
+# frozen_string_literal: true
+module Bundler
+  module VersionRanges
+    NEq = Struct.new(:version)
+    ReqR = Struct.new(:left, :right)
+    class ReqR
+      Endpoint = Struct.new(:version, :inclusive)
+      def to_s
+        "#{left.inclusive ? "[" : "("}#{left.version}, #{right.version}#{right.inclusive ? "]" : ")"}"
+      end
+      INFINITY = Object.new.freeze
+      ZERO = Gem::Version.new("0.a")
+
+      def cover?(v)
+        return false if left.inclusive && left.version > v
+        return false if !left.inclusive && left.version >= v
+
+        if right.version != INFINITY
+          return false if right.inclusive && right.version < v
+          return false if !right.inclusive && right.version <= v
+        end
+
+        true
+      end
+
+      def empty?
+        left.version == right.version && !(left.inclusive && right.inclusive)
+      end
+
+      def single?
+        left.version == right.version
+      end
+
+      UNIVERSAL = ReqR.new(ReqR::Endpoint.new(Gem::Version.new("0.a"), true), ReqR::Endpoint.new(ReqR::INFINITY, false)).freeze
+    end
+
+    def self.for_many(requirements)
+      requirements = requirements.map(&:requirements).flatten(1).map {|r| r.join(" ") }
+      requirements << ">= 0.a" if requirements.empty?
+      requirement = Gem::Requirement.new(requirements)
+      self.for(requirement)
+    end
+
+    def self.for(requirement)
+      ranges = requirement.requirements.map do |op, v|
+        case op
+        when "=" then ReqR.new(ReqR::Endpoint.new(v, true), ReqR::Endpoint.new(v, true))
+        when "!=" then NEq.new(v)
+        when ">=" then ReqR.new(ReqR::Endpoint.new(v, true), ReqR::Endpoint.new(ReqR::INFINITY, false))
+        when ">" then ReqR.new(ReqR::Endpoint.new(v, false), ReqR::Endpoint.new(ReqR::INFINITY, false))
+        when "<" then ReqR.new(ReqR::Endpoint.new(ReqR::ZERO, true), ReqR::Endpoint.new(v, false))
+        when "<=" then ReqR.new(ReqR::Endpoint.new(ReqR::ZERO, true), ReqR::Endpoint.new(v, true))
+        when "~>" then ReqR.new(ReqR::Endpoint.new(v, true), ReqR::Endpoint.new(v.bump, false))
+        else raise "unknown version op #{op} in requirement #{requirement}"
+        end
+      end.uniq
+      ranges, neqs = ranges.partition {|r| !r.is_a?(NEq) }
+
+      [ranges.sort_by {|range| [range.left.version, range.left.inclusive ? 0 : 1] }, neqs.map(&:version)]
+    end
+
+    def self.empty?(ranges, neqs)
+      !ranges.reduce(ReqR::UNIVERSAL) do |last_range, curr_range|
+        next false unless last_range
+        next false if curr_range.single? && neqs.include?(curr_range.left.version)
+        next curr_range if last_range.right.version == ReqR::INFINITY
+        case last_range.right.version <=> curr_range.left.version
+        when 1 then next curr_range
+        when 0 then next(last_range.right.inclusive && curr_range.left.inclusive && !neqs.include?(curr_range.left.version) && curr_range)
+        when -1 then next false
+        end
+      end
+    end
+  end
+end