module Byebug

  # Implements byebug "list" command.
  class ListCommand < Command

    register_setting_get(:autolist) do
      ListCommand.always_run
    end
    register_setting_set(:autolist) do |value|
      ListCommand.always_run = value
    end

    # Set default value
    Command.settings[:autolist] = 1

    def regexp
      /^\s* l(?:ist)? (?:\s*([-=])|\s+(.+))? $/x
    end

    def execute
      Byebug.source_reload if Command.settings[:autoreload]
      lines = LineCache::getlines @state.file, Command.settings[:autoreload]
      if !lines
        errmsg "No sourcefile available for #{@state.file}\n"
        return @state.previous_line
      end

      b, e = set_line_range(Command.settings[:listsize], lines.size)
      return @state.previous_line if b < 0

      print "[#{b}, #{e}] in #{@state.file}\n"
      @state.previous_line = display_list(b, e, lines, @state.line)
    end

    class << self
      def names
        %w(list)
      end

      def help(cmd)
        %{
          l[ist]\t\tlist forward
          l[ist] -\tlist backward
          l[ist] =\tlist current line
          l[ist] nn-mm\tlist given lines
          * NOTE - to turn on autolist, use 'set autolist'
        }
      end
    end

    private

      ##
      # Set line range to be printed by list
      #
      # @param listsize - number of lines to be printed
      # @param maxline - max line number that can be printed
      #
      def set_line_range(listsize, maxline)
        if !@match || !(@match[1] || @match[2])
          b = @state.previous_line ?
          @state.previous_line + listsize : @state.line - (listsize/2)
        elsif @match[1] == '-'
          b = if @state.previous_line
                if  @state.previous_line > 0
                  @state.previous_line - listsize
                else
                  @state.previous_line
                end
              else
                @state.line - (listsize/2)
              end
        elsif @match[1] == '='
          @state.previous_line = nil
          b = @state.line - (listsize/2)
        else
          b, e = @match[2].split(/[-,]/)
          if e
            b = b.to_i
            e = e.to_i
          else
            b = b.to_i - (listsize/2)
          end
        end

        if b > maxline
          errmsg "Invalid line range"
          return [ -1, -1 ]
        end

        b = [1, b].max
        e ||=  b + listsize - 1

        if e > maxline
          e = maxline
          b = e - listsize + 1
          b = [1, b].max
        end

        return [ b, e ]
      end

      ##
      # Show file lines in LINES from line B to line E where CURRENT is the
      # current line number. If we can show from B to E then we return B,
      # otherwise we return the previous line @state.previous_line.
      #
      def display_list(b, e, lines, current)
        width = e.to_s.size
        b.upto(e) do |n|
          if n > 0 && lines[n-1]
            if n == current
              print "=> %#{width}d: %s\n", n, lines[n-1].chomp
            else
              print "   %#{width}d: %s\n", n, lines[n-1].chomp
            end
          end
        end
        return e == lines.size ? @state.previous_line : b
      end
  end
end