module IRB::InputCompletor

def self.retrieve_completion_data(input, bind: IRB.conf[:MAIN_CONTEXT].workspace.binding, doc_namespace: false)
  case input
  # this regexp only matches the closing character because of irb's Reline.completer_quote_characters setting
  # details are described in: https://github.com/ruby/irb/pull/523
  when /^(.*["'`])\.([^.]*)$/
    # String
    receiver = $1
    message = $2
    if doc_namespace
      "String.#{message}"
    else
      candidates = String.instance_methods.collect{|m| m.to_s}
      select_message(receiver, message, candidates)
    end
  # this regexp only matches the closing character because of irb's Reline.completer_quote_characters setting
  # details are described in: https://github.com/ruby/irb/pull/523
  when /^(.*\/)\.([^.]*)$/
    # Regexp
    receiver = $1
    message = $2
    if doc_namespace
      "Regexp.#{message}"
    else
      candidates = Regexp.instance_methods.collect{|m| m.to_s}
      select_message(receiver, message, candidates)
    end
  when /^([^\]]*\])\.([^.]*)$/
    # Array
    receiver = $1
    message = $2
    if doc_namespace
      "Array.#{message}"
    else
      candidates = Array.instance_methods.collect{|m| m.to_s}
      select_message(receiver, message, candidates)
    end
  when /^([^\}]*\})\.([^.]*)$/
    # Proc or Hash
    receiver = $1
    message = $2
    if doc_namespace
      ["Proc.#{message}", "Hash.#{message}"]
    else
      proc_candidates = Proc.instance_methods.collect{|m| m.to_s}
      hash_candidates = Hash.instance_methods.collect{|m| m.to_s}
      select_message(receiver, message, proc_candidates | hash_candidates)
    end
  when /^(:[^:.]+)$/
    # Symbol
    if doc_namespace
      nil
    else
      sym = $1
      candidates = Symbol.all_symbols.collect do |s|
        s.inspect
      rescue EncodingError
        # ignore
      end
      candidates.grep(/^#{Regexp.quote(sym)}/)
    end
  when /^::([A-Z][^:\.\(\)]*)$/
    # Absolute Constant or class methods
    receiver = $1
    candidates = Object.constants.collect{|m| m.to_s}
    if doc_namespace
      candidates.find { |i| i == receiver }
    else
      candidates.grep(/^#{Regexp.quote(receiver)}/).collect{|e| "::" + e}
    end
  when /^([A-Z].*)::([^:.]*)$/
    # Constant or class methods
    receiver = $1
    message = $2
    if doc_namespace
      "#{receiver}::#{message}"
    else
      begin
        candidates = eval("#{receiver}.constants.collect{|m| m.to_s}", bind)
        candidates |= eval("#{receiver}.methods.collect{|m| m.to_s}", bind)
      rescue Exception
        candidates = []
      end
      select_message(receiver, message, candidates.sort, "::")
    end
  when /^(:[^:.]+)(\.|::)([^.]*)$/
    # Symbol
    receiver = $1
    sep = $2
    message = $3
    if doc_namespace
      "Symbol.#{message}"
    else
      candidates = Symbol.instance_methods.collect{|m| m.to_s}
      select_message(receiver, message, candidates, sep)
    end
  when /^(?<num>-?(?:0[dbo])?[0-9_]+(?:\.[0-9_]+)?(?:(?:[eE][+-]?[0-9]+)?i?|r)?)(?<sep>\.|::)(?<mes>[^.]*)$/
    # Numeric
    receiver = $~[:num]
    sep = $~[:sep]
    message = $~[:mes]
    begin
      instance = eval(receiver, bind)
      if doc_namespace
        "#{instance.class.name}.#{message}"
      else
        candidates = instance.methods.collect{|m| m.to_s}
        select_message(receiver, message, candidates, sep)
      end
    rescue Exception
      if doc_namespace
        nil
      else
        []
      end
    end
  when /^(-?0x[0-9a-fA-F_]+)(\.|::)([^.]*)$/
    # Numeric(0xFFFF)
    receiver = $1
    sep = $2
    message = $3
    begin
      instance = eval(receiver, bind)
      if doc_namespace
        "#{instance.class.name}.#{message}"
      else
        candidates = instance.methods.collect{|m| m.to_s}
        select_message(receiver, message, candidates, sep)
      end
    rescue Exception
      if doc_namespace
        nil
      else
        []
      end
    end
  when /^(\$[^.]*)$/
    # global var
    gvar = $1
    all_gvars = global_variables.collect{|m| m.to_s}
    if doc_namespace
      all_gvars.find{ |i| i == gvar }
    else
      all_gvars.grep(Regexp.new(Regexp.quote(gvar)))
    end
  when /^([^.:"].*)(\.|::)([^.]*)$/
    # variable.func or func.func
    receiver = $1
    sep = $2
    message = $3
    gv = bind.eval_global_variables.collect{|m| m.to_s}.push("true", "false", "nil")
    lv = bind.local_variables.collect{|m| m.to_s}
    iv = bind.eval_instance_variables.collect{|m| m.to_s}
    cv = bind.eval_class_constants.collect{|m| m.to_s}
    if (gv | lv | iv | cv).include?(receiver) or /^[A-Z]/ =~ receiver && /\./ !~ receiver
      # foo.func and foo is var. OR
      # foo::func and foo is var. OR
      # foo::Const and foo is var. OR
      # Foo::Bar.func
      begin
        candidates = []
        rec = eval(receiver, bind)
        if sep == "::" and rec.kind_of?(Module)
          candidates = rec.constants.collect{|m| m.to_s}
        end
        candidates |= rec.methods.collect{|m| m.to_s}
      rescue Exception
        candidates = []
      end
    else
      # func1.func2
      candidates = []
    end
    if doc_namespace
      rec_class = rec.is_a?(Module) ? rec : rec.class
      "#{rec_class.name}#{sep}#{candidates.find{ |i| i == message }}"
    else
      select_message(receiver, message, candidates, sep)
    end
  when /^\.([^.]*)$/
    # unknown(maybe String)
    receiver = ""
    message = $1
    candidates = String.instance_methods(true).collect{|m| m.to_s}
    if doc_namespace
      "String.#{candidates.find{ |i| i == message }}"
    else
      select_message(receiver, message, candidates.sort)
    end
  else
    if doc_namespace
      vars = (bind.local_variables | bind.eval_instance_variables).collect{|m| m.to_s}
      perfect_match_var = vars.find{|m| m.to_s == input}
      if perfect_match_var
        eval("#{perfect_match_var}.class.name", bind)
      else
        candidates = (bind.eval_methods | bind.eval_private_methods | bind.local_variables | bind.eval_instance_variables | bind.eval_class_constants).collect{|m| m.to_s}
        candidates |= ReservedWords
        candidates.find{ |i| i == input }
      end
    else
      candidates = (bind.eval_methods | bind.eval_private_methods | bind.local_variables | bind.eval_instance_variables | bind.eval_class_constants).collect{|m| m.to_s}
      candidates |= ReservedWords
      candidates.grep(/^#{Regexp.quote(input)}/).sort
    end
  end
end