# frozen_string_literal: true

class Pry
  class Command
    class AmendLine < Pry::ClassCommand
      match(/amend-line(?: (-?\d+)(?:\.\.(-?\d+))?)?/)
      group 'Editing'
      description 'Amend a line of input in multi-line mode.'
      command_options interpolate: false, listing: 'amend-line'

      banner <<-'BANNER'
        Amend a line of input in multi-line mode. `amend-line N`, where the N represents
        line to replace. Can also specify a range of lines using `amend-line N..M`
        syntax. Passing "!" as replacement content deletes the line(s) instead.

        amend-line 1 puts 'new'    # replace line 1
        amend-line 1..4 !          # delete lines 1..4
        amend-line 3 >puts 'bye'   # insert before line 3
        amend-line puts 'appended' # no line number modifies immediately preceding line
      BANNER

      def process
        raise CommandError, "No input to amend." if eval_string.empty?

        eval_string.replace(amend_input)
        run "fix-indent"
        run "show-input"
      end

      private

      # @return [String] A new string with the amendments applied to it.
      def amend_input
        input_array = eval_string.each_line.to_a

        if arg_string == "!"
          delete_from_array(input_array, line_range)
        elsif arg_string.start_with?(">")
          insert_into_array(input_array, line_range)
        else
          replace_in_array(input_array, line_range)
        end

        input_array.join
      end

      def delete_from_array(array, range)
        array.slice!(range)
      end

      def insert_into_array(array, range)
        insert_slot = Array(range).first
        array.insert(insert_slot, arg_string[1..-1] << "\n")
      end

      def replace_in_array(array, range)
        array[range] = arg_string + "\n"
      end

      # @return [Fixnum] The number of lines currently in `eval_string` (the
      #   input buffer)
      def line_count
        eval_string.lines.count
      end

      # Returns the (one-indexed) start and end lines given by the user.
      # The lines in this range will be affected by the `amend-line`.
      # Returns `nil` if no lines were specified by the user.
      # @return [Array<Fixnum>, nil]
      def start_and_end_line_number
        start_line_number, end_line_number = args
        end_line_number ||= start_line_number.to_i

        [start_line_number.to_i, end_line_number.to_i] if start_line_number
      end

      # Takes two numbers that are 1-indexed, and returns a range (or
      # number) that is 0-indexed. 1-indexed means the first element is
      # identified by 1 rather than by 0 (as is the case for Ruby arrays).
      # @param [Fixnum] start_line_number One-indexed number.
      # @param [Fixnum] end_line_number One-indexed number.
      # @return [Range] The zero-indexed range.
      def zero_indexed_range_from_one_indexed_numbers(start_line_number, end_line_number)
        # FIXME: one_index_number is a horrible name for this method
        one_index_number(start_line_number)..one_index_number(end_line_number)
      end

      # The lines (or line) that will be modified by the `amend-line`.
      # @return [Range, Fixnum] The lines or line.
      def line_range
        start_line_number, end_line_number = start_and_end_line_number
        if start_line_number
          zero_indexed_range_from_one_indexed_numbers(start_line_number,
                                                      end_line_number)
        else
          line_count - 1
        end
      end
    end

    Pry::Commands.add_command(Pry::Command::AmendLine)
  end
end