class ActionView::Template::Error

def annoted_source_code
  source_extract(4)
end

def file_name
  @template.identifier
end

def initialize(template, assigns, original_exception)
  @template, @assigns, @original_exception = template, assigns.dup, original_exception
  @backtrace = original_exception.backtrace
end

def line_number
  @line_number ||=
    if file_name
      regexp = /#{Regexp.escape File.basename(file_name)}:(\d+)/
      $1 if message =~ regexp || backtrace.find { |line| line =~ regexp }
    end
end

def message
  ActiveSupport::Deprecation.silence { original_exception.message }
end

def source_extract(indentation = 0)
  return unless num = line_number
  num = num.to_i
  source_code = @template.source.split("\n")
  start_on_line = [ num - SOURCE_CODE_RADIUS - 1, 0 ].max
  end_on_line   = [ num + SOURCE_CODE_RADIUS - 1, source_code.length].min
  indent = ' ' * indentation
  line_counter = start_on_line
  return unless source_code = source_code[start_on_line..end_on_line]
  source_code.sum do |line|
    line_counter += 1
    "#{indent}#{line_counter}: #{line}\n"
  end
end

def source_location
  if line_number
    "on line ##{line_number} of "
  else
    'in '
  end + file_name
end

def sub_template_message
  if @sub_templates
    "Trace of template inclusion: " +
    @sub_templates.collect { |template| template.inspect }.join(", ")
  else
    ""
  end
end

def sub_template_of(template_path)
  @sub_templates ||= []
  @sub_templates << template_path
end