"""ImportManager

Manages imported modules and protects against concurrent imports.

Keeps lists of all imported Python modules and templates as well as other
config files used by Webware for Python. For modules which are not directly
imported, ImportManager can use ImportSpy to keep track of them. This can
be used to detect changes in source files, templates or config files in order
to reload them automatically by the AutoReloadingAppServer. The use of
ImportSpy can be suppressed with the``UseImportSpy`` setting.

"""

import imp

from Common import *


class ImportLock:
	"""Lock for multi-threaded imports.

	Provides a lock for protecting against concurrent imports. This is
	necessary because WebKit is multithreaded and uses its own import hook.

	This class abstracts the difference between using the Python interpreter's
	global import lock, and using our own RLock. The global lock is the correct
	solution, but is only available in Python since version 2.2.3. If it's not
	available, we fall back to using an RLock (which is not as good, but better
	than nothing).

	"""

	def __init__(self):
		"""Create the lock.

		Aliases the `acquire` and `release` methods to
		`imp.acquire_lock` and `imp.release_lock` (if available),
		or to acquire and release our own RLock.

		"""
		if hasattr(imp, 'acquire_lock'):
			self.acquire = imp.acquire_lock
			self.release = imp.release_lock
		else: # fallback for Python < 2.3
			from threading import RLock
			self._lock = RLock()
			self.acquire = self._lock.acquire
			self.release = self._lock.release


class ImportManager(Object):
	"""The import manager.

	Keeps track of the Python modules and other system files that have been
	imported and are used by Webware.

	"""

	_imp = _spy = None

	def __init__(self):
		"""Create import hook."""
		assert not self._imp, "Only one instance of ImportManager is possible."
		self._imp = True
		Object.__init__(self)
		self._lock = ImportLock()
		self._fileList = {}
		self._moduleFiles = {}
		self._notifyHook = None

	def load_module(self, name, file, filename, info):
		"""Replaces imp.load_module."""
		try:
			try:
				self._lock.acquire()
				mod = imp.load_module(name, file, filename, info)
			finally:
				self._lock.release()
				if file:
					file.close()
			self.recordModule(mod)
		except:
			# Also record filepaths which weren't successfully loaded, which
			# may happen due to a syntax error in a servlet, because we also
			# want to know when such a file is modified:
			self.recordFile(filename)
			raise
		return mod

	def find_module(self, name, path=None):
		"""Replaces imp.find_module."""
		return imp.find_module(name, path)

	def activateImportSpy(self):
		"""Activate ImportSpy to keep track of modules loaded elsewhere."""
		if not self._spy:
			from ImportSpy import activate
			self._spy = activate(self)
		return self._spy

	def fileList(self, update=True):
		"""Return the list of tracked files."""
		if not self._spy and update:
			# Update list of files of imported modules
			moduleNames = []
			for modname in sys.modules:
				if not self._moduleFiles.has_key(modname):
					moduleNames.append(modname)
			if moduleNames:
				self.recordModules(moduleNames)
		return self._fileList

	def notifyOfNewFiles(self, hook):
		"""Register notification hook.

		Called by someone else to register that they'd like to be know
		when a new file is imported.

		"""
		self._notifyHook = hook

	def watchFile(self, path, modname=None, getmtime=os.path.getmtime):
		"""Add more files to watch without importing them."""
		modtime = getmtime(path)
		self._fileList[path] = modtime
		if modname:
			self._moduleFiles[modname] = path
		# send notification that this file was imported
		if self._notifyHook:
			self._notifyHook(path, modtime)

	def recordModule(self, mod, isfile=os.path.isfile):
		"""Record a module."""
		modname = getattr(mod, '__name__', None)
		if not modname or not sys.modules.has_key(modname):
			return
		fileList = self._fileList
		# __orig_file__ is used for PSP, Kid and Cheetah templates; we want
		# to record the source filenames, not the auto-generated modules:
		f = getattr(mod, '__orig_file__', None)
		if f and not fileList.has_key(f):
			try:
				if isfile(f):
					self.watchFile(f, modname)
			except OSError:
				pass
		else:
			f = getattr(mod, '__file__', None)
			if f and not fileList.has_key(f):
				# record the .py file corresponding to each .pyc or .pyo
				if f[-4:].lower() in ['.pyc', '.pyo']:
					f = f[:-1]
				try:
					if isfile(f):
						self.watchFile(f, modname)
					else:
						self.watchFile(os.path.join(f, '__init__.py'))
				except OSError:
					pass

	def recordModules(self, moduleNames=None):
		"""Record a list of modules (or all modules)."""
		if moduleNames is None:
			moduleNames = sys.modules.keys()
		for modname in moduleNames:
			mod = sys.modules[modname]
			self.recordModule(mod)

	def recordFile(self, filename, isfile=os.path.isfile):
		"""Record a file."""
		if isfile(filename):
			self.watchFile(filename)

	def fileUpdated(self, filename, update=True, getmtime=os.path.getmtime):
		"""Check whether file has been updated."""
		fileList = self.fileList(update)
		try:
			mtime = fileList[filename]
		except KeyError:
			return True
		try:
			newmtime = getmtime(filename)
		except OSError:
			return True
		if mtime < newmtime:
			fileList[filename] = newmtime
			for modname, modfile in self._moduleFiles.items():
				if modfile == filename:
					break
			else:
				return True # it's not a module, we must reload
			mod = sys.modules.get(modname, None)
			if not mod or not getattr(mod, '__donotreload__', None):
				return True # it's a module that needs to be reloaded
		return False

	def updatedFile(self, update=True, getmtime=os.path.getmtime):
		"""Check whether one of the files has been updated."""
		fileList = self.fileList(update)
		for filename, mtime in fileList.items():
			try:
				newmtime = getmtime(filename)
			except OSError:
				return filename
			if mtime < newmtime:
				fileList[filename] = newmtime
				for modname, modfile in self._moduleFiles.items():
					if modfile == filename:
						break
				else:
					return filename # it's not a module, we must reload
				mod = sys.modules.get(modname, None)
				if not mod or not getattr(mod, '__donotreload__', None):
					return filename # it's a module that needs to be reloaded
		return False

	def delModules(self, includePythonModules=False, excludePrefixes=None):
		"""Delete imported modules.

		Deletes all the modules that the ImportSpy has ever imported unless
		they are part of WebKit. This in support of DebugAppServer's useful
		(yet imperfect) support for AutoReload.

		"""
		moduleFiles = self._moduleFiles
		moduleNames = moduleFiles.keys()
		fileList = self._fileList
		for modname in moduleNames:
			if modname == __name__:
				continue
			filename = self._moduleFiles[modname]
			if not includePythonModules:
				if not filename or filename.startswith(sys.prefix):
					continue
			for prefix in excludePrefixes or []:
				if modname.startswith(prefix):
					break
			else:
				try:
					del sys.modules[modname]
				except KeyError:
					pass
				try:
					del moduleFiles[modname]
				except KeyError:
					pass
				try:
					del fileList[filename]
				except KeyError:
					pass