# frozen_string_literal: true

module RuboCop
  module Cop
    module Layout
      # This cop checks for Windows-style line endings in the source code.
      #
      # @example EnforcedStyle: native (default)
      #   # The `native` style means that CR+LF (Carriage Return + Line Feed) is
      #   # enforced on Windows, and LF is enforced on other platforms.
      #
      #   # bad
      #   puts 'Hello' # Return character is LF on Windows.
      #   puts 'Hello' # Return character is CR+LF on other than Windows.
      #
      #   # good
      #   puts 'Hello' # Return character is CR+LF on Windows.
      #   puts 'Hello' # Return character is LF on other than Windows.
      #
      # @example EnforcedStyle: lf
      #   # The `lf` style means that LF (Line Feed) is enforced on
      #   # all platforms.
      #
      #   # bad
      #   puts 'Hello' # Return character is CR+LF on all platfoms.
      #
      #   # good
      #   puts 'Hello' # Return character is LF on all platfoms.
      #
      # @example EnforcedStyle: crlf
      #   # The `crlf` style means that CR+LF (Carriage Return + Line Feed) is
      #   # enforced on all platforms.
      #
      #   # bad
      #   puts 'Hello' # Return character is LF on all platfoms.
      #
      #   # good
      #   puts 'Hello' # Return character is CR+LF on all platfoms.
      #
      class EndOfLine < Cop
        include ConfigurableEnforcedStyle
        include RangeHelp

        MSG_DETECTED = 'Carriage return character detected.'
        MSG_MISSING = 'Carriage return character missing.'

        def investigate(processed_source)
          last_line = last_line(processed_source)

          processed_source.raw_source.each_line.with_index do |line, index|
            break if index >= last_line

            msg = offense_message(line)
            next unless msg
            next if unimportant_missing_cr?(index, last_line, line)

            range =
              source_range(processed_source.buffer, index + 1, 0, line.length)
            add_offense(nil, location: range, message: msg)
            # Usually there will be carriage return characters on all or none
            # of the lines in a file, so we report only one offense.
            break
          end
        end

        # If there is no LF on the last line, we don't care if there's no CR.
        def unimportant_missing_cr?(index, last_line, line)
          style == :crlf && index == last_line - 1 && !/\n$/.match?(line)
        end

        def offense_message(line)
          effective_style = if style == :native
                              Platform.windows? ? :crlf : :lf
                            else
                              style
                            end
          case effective_style
          when :lf then MSG_DETECTED if line.end_with?("\r", "\r\n")
          else MSG_MISSING unless line.end_with?("\r\n")
          end
        end

        private

        def last_line(processed_source)
          last_token = processed_source.tokens.last
          last_token ? last_token.line : processed_source.lines.length
        end
      end
    end
  end
end
