module Bundler::PubGrub::RubyGems

def parse_constraint(package, dep)
  range = parse_range(dep)
  Bundler::PubGrub::VersionConstraint.new(package, range: range)
end

def parse_range(dep)
  requirement_to_range(Gem::Requirement.new(dep))
end

def requirement_to_constraint(package, requirement)
  Bundler::PubGrub::VersionConstraint.new(package, range: requirement_to_range(requirement))
end

def requirement_to_range(requirement)
  ranges = requirement.requirements.map do |(op, ver)|
    case op
    when "~>"
      name = "~> #{ver}"
      bump = ver.class.new(ver.bump.to_s + ".A")
      VersionRange.new(name: name, min: ver, max: bump, include_min: true)
    when ">"
      VersionRange.new(min: ver)
    when ">="
      VersionRange.new(min: ver, include_min: true)
    when "<"
      VersionRange.new(max: ver)
    when "<="
      VersionRange.new(max: ver, include_max: true)
    when "="
      VersionRange.new(min: ver, max: ver, include_min: true, include_max: true)
    when "!="
      VersionRange.new(min: ver, max: ver, include_min: true, include_max: true).invert
    else
      raise "bad version specifier: #{op}"
    end
  end
  ranges.inject(&:intersect)
end