require 'facet/ormsupport'

# This supports source code extraction from a full
# backtrace from any exception and also exposes class
# methods incase you wish to harness them from elsewhere.
#--
# TODO: Cache source code? Memory vs Speed - Is it worth
# it?
# FIXME: Don't change the Exception class, use NitroException
# or something.
#++

class Exception # :nodoc: all

  # Radius of the source code to display arround the error line.
  
  SOURCE_RADIUS = 5
  
  class << self

    # Extracts the filename and line from the given line (step)
    # of the backtrace.
      
    def file_and_line_no(step)
      file = no = nil
      if res = step.match(/^(.+):(\d+)$/)
        file = res[1]
        no = res[2]
      elsif res = step.match(/^(.+):(\d+):in `.+'$/)
        file = res[1]
        no = res[2]
      end
      if file and no
        [file,no.to_i]
      else
        nil
      end
    end

    # Extract the source arround the error line.
        
    def source_extract(step, indent = 0)
      begin
        file, no = file_and_line_no(step)        
        source = File.read(file)

        if file =~ /\.xhtml$/
          source = Compiler.new(Nitro::Controller).transform_template(:action, source)
          no -= 2
        end

        source = source.split("\n")
        start = (no-1) - SOURCE_RADIUS
        finish = (no-1) + SOURCE_RADIUS
        start = 0 if start < 0
        finish = source.size if finish > source.size
  
        number = start
        extract = source[start..finish].collect do |line| 
          number += 1
          line = line.gsub(/; @out #{Nitro::TemplateMixin::START_DELIM}/, ' ?>').gsub(/#{Nitro::TemplateMixin::END_DELIM}/, '<?r ')
          "#{' ' * indent}#{number}: #{line}"
        end  

        return extract.join("\n")
      rescue Object => ex
        ''
      end
    end
    
  end

  # Identifies the 'hot' index in the backtrace, where the error
  # actually happened.
  
  def hot_trace_index
    index = 0
    while backtrace[index] =~ /controller\.rb(.*)method_missing/ 
      index += 1
    end
    return index
  end

  # Returns the 'hot' backtrace line.
    
  def hot_trace_step
    backtrace[hot_trace_index]
  end

  # Returns the 'hot' backtrace file.
    
  def hot_file
    file_and_line_no(hot_trace_step).first
  end
  
  def file_and_line_no(step)
    self.class.file_and_line_no(step)
  end
  
  def source_extract(step = hot_trace_step, indent = 0)
    self.class.source_extract(step,indent)
  end
  
  # Extract source for backtrace.
  
  def source_for_backtrace(indent = 0)
    backtrace.inject([]) do |sources, step| 
      sources << source_extract(step, indent)
    end
  end
  
end