module Travis::CLI

def command(name)
  const_name = command_name(name)
  constant   = CLI.const_get(const_name) if const_name =~ /^[A-Z][a-z]+$/ and const_defined? const_name
  if command? constant
    constant
  else
    $stderr.puts "unknown command #{name}"
    exit 1
  end
end

def command?(constant)
  constant.is_a? Class and constant < Command and not constant.abstract?
end

def command_name(name)
  case name
  when nil, '-h', '-?' then 'Help'
  when '-v'            then 'Version'
  when /^--/           then command_name(name[2..-1])
  else name.to_s.capitalize
  end
end

def commands
  CLI.constants.map { |n| try_const_get(n) }.select { |c| command? c }
end

def dummy_io
  return StringIO.new unless defined? IO::NULL and IO::NULL
  File.open(IO::NULL, 'w')
end

def preparse(unparsed, args = [], opts = {})
  case unparsed
  when Hash  then opts.merge! unparsed
  when Array then unparsed.each { |e| preparse(e, args, opts) }
  else args << unparsed.to_s
  end
  [args, opts]
end

def run(*args)
  args, opts = preparse(args)
  name       = args.shift unless args.empty?
  command    = command(name).new(opts)
  command.parse(args)
  command.execute
end

def silent
  stderr, $stderr = $stderr, dummy_io
  stdout, $stdout = $stdout, dummy_io
  yield
ensure
  $stderr = stderr if stderr
  $stdout = stdout if stdout
end

def try_const_get(name)
  CLI.const_get(name)
rescue Exception
end