class Byebug::DisplayCommand

def self.description
  <<-DESCRIPTION
    disp[lay][ <expression>]
    #{short_description}
    If <expression> specified, adds <expression> into display expression
    list. Otherwise, it lists all expressions.
  DESCRIPTION
end

def self.regexp
  /^\s* disp(?:lay)? (?:\s+ (.+))? \s*$/x
end

def self.short_description
  "Evaluates expressions every time the debugger stops"
end

def display_expression(exp)
  print pr("display.result", n: Byebug.displays.size,
                             exp: exp,
                             result: eval_expr(exp))
end

def eval_expr(expression)
  error_eval(expression).inspect
rescue StandardError
  "(undefined)"
end

def execute
  return print_display_expressions unless @match && @match[1]
  Byebug.displays.push [true, @match[1]]
  display_expression(@match[1])
end

def print_display_expressions
  result = prc("display.result", Byebug.displays) do |item, index|
    active, exp = item
    { n: index + 1, exp: exp, result: eval_expr(exp) } if active
  end
  print result
end