class ActionView::Template::Handlers::ERB

def self.call(template, source)
  new.call(template, source)
end

def call(template, source)
  # First, convert to BINARY, so in case the encoding is
  # wrong, we can still find an encoding tag
  # (<%# encoding %>) inside the String using a regular
  # expression
  template_source = source.b
  erb = template_source.gsub(ENCODING_TAG, "")
  encoding = $2
  erb.force_encoding valid_encoding(source.dup, encoding)
  # Always make sure we return a String in the default_internal
  erb.encode!
  # Strip trailing newlines from the template if enabled
  erb.chomp! if strip_trailing_newlines
  options = {
    escape: (self.class.escape_ignore_list.include? template.type),
    trim: (self.class.erb_trim_mode == "-")
  }
  if ActionView::Base.annotate_rendered_view_with_filenames && template.format == :html
    options[:preamble] = "@output_buffer.safe_append='<!-- BEGIN #{template.short_identifier} -->';"
    options[:postamble] = "@output_buffer.safe_append='<!-- END #{template.short_identifier} -->';@output_buffer"
  end
  self.class.erb_implementation.new(erb, options).src
end

def find_offset(compiled, source_tokens, error_column)
  compiled = StringScanner.new(compiled)
  passed_tokens = []
  while tok = source_tokens.shift
    tok_name, str = *tok
    case tok_name
    when :TEXT
      loop do
        break if compiled.match?(str)
        compiled.getch
      end
      raise LocationParsingError unless compiled.scan(str)
    when :CODE
      if compiled.pos > error_column
        raise LocationParsingError, "We went too far"
      end
      if compiled.pos + str.bytesize >= error_column
        offset = error_column - compiled.pos
        return passed_tokens.map(&:last).join.bytesize + offset
      else
        unless compiled.scan(str)
          raise LocationParsingError, "Couldn't find code snippet"
        end
      end
    when :OPEN
      next_tok = source_tokens.first.last
      loop do
        break if compiled.match?(next_tok)
        compiled.getch
      end
    when :CLOSE
      next_tok = source_tokens.first.last
      loop do
        break if compiled.match?(next_tok)
        compiled.getch
      end
    else
      raise LocationParsingError, "Not implemented: #{tok.first}"
    end
    passed_tokens << tok
  end
end

def handles_encoding?
  true
end

def supports_streaming?
  true
end

def translate_location(spot, backtrace_location, source)
  # Tokenize the source line
  tokens = ::ERB::Util.tokenize(source.lines[backtrace_location.lineno - 1])
  new_first_column = find_offset(spot[:snippet], tokens, spot[:first_column])
  lineno_delta = spot[:first_lineno] - backtrace_location.lineno
  spot[:first_lineno] -= lineno_delta
  spot[:last_lineno] -= lineno_delta
  column_delta = spot[:first_column] - new_first_column
  spot[:first_column] -= column_delta
  spot[:last_column] -= column_delta
  spot[:script_lines] = source.lines
  spot
rescue NotImplementedError, LocationParsingError
  nil
end

def valid_encoding(string, encoding)
  # If a magic encoding comment was found, tag the
  # String with this encoding. This is for a case
  # where the original String was assumed to be,
  # for instance, UTF-8, but a magic comment
  # proved otherwise
  string.force_encoding(encoding) if encoding
  # If the String is valid, return the encoding we found
  return string.encoding if string.valid_encoding?
  # Otherwise, raise an exception
  raise WrongEncodingError.new(string, string.encoding)
end