class Erubis::Engine

#
# subclass must include evaluator and converter module.
# (abstract) abstract engine class.
#

def self.load_file(filename, properties={})

#
# or filname + 'cache' is used as default.
# cachefile name can be specified with properties[:cachename],
# this method create code cache file automatically.
# load file, write cache file, and return engine object.
# 
def self.load_file(filename, properties={})
  cachename = properties[:cachename] || (filename + '.cache')
  properties[:filename] = filename
  timestamp = File.mtime(filename)
  if test(?f, cachename) && timestamp == File.mtime(cachename)
    engine = self.new(nil, properties)
    engine.src = File.read(cachename)
  else
    input = File.open(filename, 'rb') {|f| f.read }
    engine = self.new(input, properties)
    tmpname = cachename + rand().to_s[1,8]
    File.open(tmpname, 'wb') {|f| f.write(engine.src) }
    File.rename(tmpname, cachename)
    File.utime(timestamp, timestamp, cachename)
  end
  engine.src.untaint   # ok?
  return engine
end

def convert!(input)

#
# convert input string and set it to @src
# 
def convert!(input)
  @src = convert(input)
end

def initialize(input=nil, properties={}) 

def initialize(input=nil, properties={})
  #@input = input
  init_generator(properties)
  init_converter(properties)
  init_evaluator(properties)
  @src    = convert(input) if input
end

def process(input, context=nil, filename=nil)

#
# context may be Binding, Hash, or Object.
# helper method to convert and evaluate input text with context object.
# 
def process(input, context=nil, filename=nil)
  code = convert(input)
  filename ||= '(erubis)'
  if context.is_a?(Binding)
    return eval(code, context, filename)
  else
    context = Context.new(context) if context.is_a?(Hash)
    return context.instance_eval(code, filename)
  end
end

def process_proc(proc_obj, context=nil, filename=nil)

#
# context may be Binding, Hash, or Object.
# helper method evaluate Proc object with contect object.
# 
def process_proc(proc_obj, context=nil, filename=nil)
  if context.is_a?(Binding)
    filename ||= '(erubis)'
    return eval(proc_obj, context, filename)
  else
    context = Context.new(context) if context.is_a?(Hash)
    return context.instance_eval(&proc_obj)
  end
end