require 'byebug/command'
require 'byebug/helpers/file'
require 'byebug/helpers/parse'

module Byebug
  #
  # List parts of the source code.
  #
  class ListCommand < Command
    include Helpers::FileHelper
    include Helpers::ParseHelper

    self.allow_in_post_mortem = true

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

    def self.description
      <<-EOD
        l[ist][[-=]][ nn-mm]

        #{short_description}

        Lists lines forward from current line or from the place where code was
        last listed. If "list-" is specified, lists backwards instead. If
        "list=" is specified, lists from current line regardless of where code
        was last listed. A line range can also be specified to list specific
        sections of code.
      EOD
    end

    def self.short_description
      'Lists lines of source code'
    end

    def execute
      msg = "No sourcefile available for #{frame.file}"
      raise(msg) unless File.exist?(frame.file)

      max_lines = n_lines(frame.file)
      b, e = range(@match[2], max_lines)
      raise('Invalid line range') unless valid_range?(b, e, max_lines)

      display_lines(b, e)

      processor.prev_line = b
    end

    private

    #
    # Line range to be printed by `list`.
    #
    # If <input> is set, range is parsed from it.
    #
    # Otherwise it's automatically chosen.
    #
    def range(input, max_line)
      size = [Setting[:listsize], max_line].min

      return set_range(size, max_line) unless input

      parse_range(input, size, max_line)
    end

    def valid_range?(first, last, max)
      first <= last && (1..max).cover?(first) && (1..max).cover?(last)
    end

    #
    # Set line range to be printed by list
    #
    # @param size - number of lines to be printed
    # @param max_line - max line number that can be printed
    #
    # @return first line number to list
    # @return last line number to list
    #
    def set_range(size, max_line)
      first = amend(lower(size, @match[1] || '+'), max_line - size + 1)

      [first, move(first, size - 1)]
    end

    def parse_range(input, size, max_line)
      first, err = get_int(lower_bound(input), 'List', 1, max_line)
      raise(err) unless first

      if upper_bound(input)
        last, err = get_int(upper_bound(input), 'List', 1, max_line)
        raise(err) unless last

        last = amend(last, max_line)
      else
        first -= (size / 2)
      end

      [first, last || move(first, size - 1)]
    end

    def amend(line, max_line)
      return 1 if line < 1

      [max_line, line].min
    end

    def lower(size, direction = '+')
      prev_line = processor.prev_line
      return frame.line - size / 2 if direction == '=' || prev_line.nil?

      move(prev_line, size, direction)
    end

    def move(line, size, direction = '+')
      line.send(direction, size)
    end

    #
    # Show a range of lines in the current file.
    #
    # @param min [Integer] Lower bound
    # @param max [Integer] Upper bound
    #
    def display_lines(min, max)
      puts "\n[#{min}, #{max}] in #{frame.file}"

      File.foreach(frame.file).with_index do |line, lineno|
        break if lineno + 1 > max
        next unless (min..max).cover?(lineno + 1)

        mark = lineno + 1 == frame.line ? '=> ' : '   '
        puts format("#{mark}%#{max.to_s.size}d: %s", lineno + 1, line)
      end
    end

    #
    # @param range [String] A string with an integer range format
    #
    # @return [String] The lower bound of the given range
    #
    def lower_bound(range)
      split_range(range)[0]
    end

    #
    # @param range [String] A string with an integer range format
    #
    # @return [String] The upper bound of the given range
    #
    def upper_bound(range)
      split_range(range)[1]
    end

    #
    # @param str [String] A string with an integer range format
    #
    # @return [Array] The upper & lower bounds of the given range
    #
    def split_range(str)
      str.split(/[-,]/)
    end
  end
end