1 files changed, 65 insertions, 0 deletions
diff --git a/lib/semver.rb b/lib/semver.rb
new file mode 100644
index 000000000..ef9435abd
--- /dev/null
+++ b/lib/semver.rb
@@ -0,0 +1,65 @@
+class SemVer
+  VERSION = /^v?(\d+)\.(\d+)\.(\d+)([A-Za-z][0-9A-Za-z-]*|)$/
+  SIMPLE_RANGE = /^v?(\d+|[xX])(?:\.(\d+|[xX])(?:\.(\d+|[xX]))?)?$/
+
+  include Comparable
+
+  def self.valid?(ver)
+    VERSION =~ ver
+  end
+
+  def self.find_matching(pattern, versions)
+    versions.select { |v| v.matched_by?("#{pattern}") }.sort.last
+  end
+
+  attr_reader :major, :minor, :tiny, :special
+
+  def initialize(ver)
+    unless SemVer.valid?(ver)
+      raise ArgumentError.new("Invalid version string '#{ver}'!")
+    end
+
+    @major, @minor, @tiny, @special = VERSION.match(ver).captures.map do |x|
+      # Because Kernel#Integer tries to interpret hex and octal strings, which
+      # we specifically do not want, and which cannot be overridden in 1.8.7.
+      Float(x).to_i rescue x
+    end
+  end
+
+  def <=>(other)
+    other = SemVer.new("#{other}") unless other.is_a? SemVer
+    return self.major <=> other.major unless self.major == other.major
+    return self.minor <=> other.minor unless self.minor == other.minor
+    return self.tiny  <=> other.tiny  unless self.tiny  == other.tiny
+
+    return 0  if self.special  == other.special
+    return 1  if self.special  == ''
+    return -1 if other.special == ''
+
+    return self.special <=> other.special
+  end
+
+  def matched_by?(pattern)
+    # For the time being, this is restricted to exact version matches and
+    # simple range patterns.  In the future, we should implement some or all of
+    # the comparison operators here:
+    # https://github.com/isaacs/node-semver/blob/d474801/semver.js#L340
+
+    case pattern
+    when SIMPLE_RANGE
+      pattern = SIMPLE_RANGE.match(pattern).captures
+      pattern[1] = @minor unless pattern[1] && pattern[1] !~ /x/i
+      pattern[2] = @tiny  unless pattern[2] && pattern[2] !~ /x/i
+      [@major, @minor, @tiny] == pattern.map { |x| x.to_i }
+    when VERSION
+      self == SemVer.new(pattern)
+    else
+      false
+    end
+  end
+
+  def inspect
+    "v#{@major}.#{@minor}.#{@tiny}#{@special}"
+  end
+  alias :to_s :inspect
+end