#!/usr/bin/env ruby

class VersionNumber < Object
  include Comparable
  attr_accessor :major, :minor, :patchlevel, :project, :project_rev, :stability, :strict
  
  def initialize(version_string, strict=true)
    @strict = strict
    pieces = version_string.split(".")
    @major, @minor, pl = pieces[0].to_i, pieces[1].to_i, pieces[2]
    if /\A\d+\Z/.match pl
      @patchlevel = pl.to_i
    elsif /\A(\d+)(\D+)(\d+)\Z/.match pl
      @patchlevel, @stability, @project_rev = $~[1].to_i, $~[2].downcase, $~[3].to_i
      unless ["alpha","beta","rc"].include?(@stability)
        @project = @stability
        @stability = "beta"
      end
    elsif strict
      raise "Aiee! VersionNumber failed to initialize (from \"#{version_string}\")"
    else
      @patchlevel = nil
    end
  end
  
  
  def version_string
    "#{major}.#{minor}.#{patchlevel}#{project ? project : stability}#{project_rev}"
  end
  
  def svn_branch_name
    project ? project : "#{major}.#{minor}"
  end
  
  def to_s
    version_string
  end
  
  def ==(other)
    (other.respond_to? :major) &&
    (other.respond_to? :minor) &&
    (other.respond_to? :patchlevel) &&
    (other.respond_to? :project) &&
    (other.respond_to? :project_rev) &&
    (Integer(self.major) == Integer(other.major)) &&
    (Integer(self.minor) == Integer(other.minor)) &&
    (Integer(self.patchlevel) == Integer(other.patchlevel)) &&
    (self.project === other.project) &&
    (Integer(self.project_rev) == Integer(other.project_rev))
  end
  
  def <=>(other)
    digitTest = lambda {|x,y| (x && y) ? (x <=> y) : ((x && 1) || (y && -1)) }
    projectTest = lambda {|x,y| (x && y && (! x.empty?) ) ? 0 : ((x && 1) || (y && -1)) }
    majorResult = digitTest.call(Integer(self.major), Integer(other.major))
    if (majorResult != 0)
      return majorResult
    else
      minorResult = digitTest.call(Integer(self.minor), Integer(other.minor))
      if (minorResult != 0)
        return minorResult
      else
        patchResult = digitTest.call(Integer(self.patchlevel), Integer(other.patchlevel))
        if (patchResult != 0)
          return patchResult
        else
          projectResult = projectTest.call(self.project, other.project)
          if (projectResult && projectResult != 0)
            return projectResult
          else
            if strict and (self.project != other.project)
              raise Exception.new("Invalid comparison between versions - same major.minor.patchlevel, but different projects") 
            end
            projectRevResult = digitTest.call(self.project_rev, other.project_rev)
            return projectRevResult || 0
          end
        end
      end
    end
  end
  
  def eql?(other)
    other.instance_of? VersionNumber && other == self
  end
  
  def next_after_major_increment
    if (major < 1)
      VersionNumber.new("1.0.0")
    else
      VersionNumber.new("#{major + 1}.0.0")
    end
  end
  
  def next_after_minor_increment
    if (major < 1)
      VersionNumber.new("1.0.0")
    else
      VersionNumber.new("#{major}.#{minor.to_i+1}.0")
    end
  end
  
  alias :next_release_candidate :next_after_minor_increment
  
  def next_after_patchlevel_increment
    if (major < 1)
      VersionNumber.new("1.0.0")
    else
      VersionNumber.new("#{major}.#{minor}.#{patchlevel + 1}")
    end
  end
end

if (__FILE__==$0) then
  require 'test/unit'
  class TestVersionNumber < Test::Unit::TestCase
    def test_parsing
      v = VersionNumber.new("1.0.4facebook3")
      assert(v.major == 1)
      assert(v.minor == 0)
      assert(v.patchlevel == 4)
      assert(v.project === "facebook")
      assert(v.project_rev == 3)
    end

    def test_equal
      assert(VersionNumber.new("1.0.4rc3") == VersionNumber.new("1.0.4rc3"))
    end
    
    def test_inequality
      assert(VersionNumber.new("1.0.0") < VersionNumber.new("1.0.1"))
      assert(VersionNumber.new("1.0.1") > VersionNumber.new("1.0.0"))
      assert(VersionNumber.new("1.1.0") > VersionNumber.new("1.0.0"))
      assert(VersionNumber.new("2.0.0") > VersionNumber.new("1.1.1"))
      assert(VersionNumber.new("1.0.1") >= VersionNumber.new("1.0.1"))
      assert(VersionNumber.new("1.0.1") == VersionNumber.new("1.0.1"))
    end
  end
end