#updateCheck.py
#A part of NonVisual Desktop Access (NVDA)
#This file is covered by the GNU General Public License.
#See the file COPYING for more details.
#Copyright (C) 2012-2015 NV Access Limited

"""Update checking functionality.
@note: This module may raise C{RuntimeError} on import if update checking for this build is not supported.
"""

import globalVars
if globalVars.appArgs.secure:
	raise RuntimeError("updates disabled in secure mode")
import versionInfo
if not versionInfo.updateVersionType:
	raise RuntimeError("No update version type, update checking not supported")

import winVersion
import os
import threading
import time
import cPickle
import urllib
import tempfile
import hashlib
import ctypes.wintypes
import ssl
import wx
import languageHandler
import gui
from logHandler import log
import config
import shellapi
import winUser

#: The URL to use for update checks.
CHECK_URL = "https://www.nvaccess.org/nvdaUpdateCheck"
#: The time to wait between checks.
CHECK_INTERVAL = 86400 # 1 day
#: The time to wait before retrying a failed check.
RETRY_INTERVAL = 600 # 10 min
#: The download block size in bytes.
DOWNLOAD_BLOCK_SIZE = 8192 # 8 kb

#: Persistent state information.
#: @type: dict
state = None
_stateFileName = None
#: The single instance of L{AutoUpdateChecker} if automatic update checking is enabled,
#: C{None} if it is disabled.
autoChecker = None

def checkForUpdate(auto=False):
	"""Check for an updated version of NVDA.
	This will block, so it generally shouldn't be called from the main thread.
	@param auto: Whether this is an automatic check for updates.
	@type auto: bool
	@return: Information about the update or C{None} if there is no update.
	@rtype: dict
	@raise RuntimeError: If there is an error checking for an update.
	"""
	params = {
		"autoCheck": auto,
		"version": versionInfo.version,
		"versionType": versionInfo.updateVersionType,
		"osVersion": winVersion.winVersionText,
		"x64": os.environ.get("PROCESSOR_ARCHITEW6432") == "AMD64",
		"language": languageHandler.getLanguage(),
		"installed": config.isInstalledCopy(),
	}
	url = "%s?%s" % (CHECK_URL, urllib.urlencode(params))
	try:
		res = urllib.urlopen(url)
	except IOError as e:
		if isinstance(e.strerror, ssl.SSLError) and e.strerror.reason == "CERTIFICATE_VERIFY_FAILED":
			# #4803: Windows fetches trusted root certificates on demand.
			# Python doesn't trigger this fetch (PythonIssue:20916), so try it ourselves
			_updateWindowsRootCertificates()
			# and then retry the update check.
			res = urllib.urlopen(url)
		else:
			raise
	if res.code != 200:
		raise RuntimeError("Checking for update failed with code %d" % res.code)
	info = {}
	for line in res:
		line = line.rstrip()
		try:
			key, val = line.split(": ", 1)
		except ValueError:
			raise RuntimeError("Error in update check output")
		info[key] = val
	if not info:
		return None
	return info

class UpdateChecker(object):
	"""Check for an updated version of NVDA, presenting appropriate user interface.
	The check is performed in the background.
	This class is for manual update checks.
	To use, call L{check} on an instance.
	"""
	AUTO = False

	def check(self):
		"""Check for an update.
		"""
		t = threading.Thread(target=self._bg)
		t.daemon = True
		self._started()
		t.start()

	def _bg(self):
		try:
			info = checkForUpdate(self.AUTO)
		except:
			log.debugWarning("Error checking for update", exc_info=True)
			self._error()
			return
		self._result(info)
		if info:
			state["dontRemindVersion"] = info["version"]
		state["lastCheck"] = time.time()
		saveState()
		if autoChecker:
			autoChecker.setNextCheck()

	def _started(self):
		self._progressDialog = gui.IndeterminateProgressDialog(gui.mainFrame,
			# Translators: The title of the dialog displayed while manually checking for an NVDA update.
			_("Checking for Update"),
			# Translators: The progress message displayed while manually checking for an NVDA update.
			_("Checking for update"))

	def _error(self):
		wx.CallAfter(self._progressDialog.done)
		self._progressDialog = None
		wx.CallAfter(gui.messageBox,
			# Translators: A message indicating that an error occurred while checking for an update to NVDA.
			_("Error checking for update."),
			# Translators: The title of an error message dialog.
			_("Error"),
			wx.OK | wx.ICON_ERROR)

	def _result(self, info):
		wx.CallAfter(self._progressDialog.done)
		self._progressDialog = None
		wx.CallAfter(UpdateResultDialog, gui.mainFrame, info, False)

class AutoUpdateChecker(UpdateChecker):
	"""Automatically check for an updated version of NVDA.
	To use, create a single instance and maintain a reference to it.
	Checks will then be performed automatically.
	"""
	AUTO = True

	def __init__(self):
		self._checkTimer = wx.PyTimer(self.check)
		# Set the initial check based on the last check time.
		# #3260: If the system time is earlier than the last check,
		# treat the last check as being right now (so the next will be tomorrow).
		secsSinceLast = max(time.time() - state["lastCheck"], 0)
		# The maximum time till the next check is CHECK_INTERVAL.
		secsTillNext = CHECK_INTERVAL - int(min(secsSinceLast, CHECK_INTERVAL))
		self._checkTimer.Start(secsTillNext * 1000, True)

	def terminate(self):
		self._checkTimer.Stop()
		self._checkTimer = None

	def setNextCheck(self, isRetry=False):
		self._checkTimer.Stop()
		self._checkTimer.Start((RETRY_INTERVAL if isRetry else CHECK_INTERVAL) * 1000, True)

	def _started(self):
		log.info("Performing automatic update check")

	def _error(self):
		self.setNextCheck(isRetry=True)

	def _result(self, info):
		if not info:
			return
		if info["version"] == state["dontRemindVersion"]:
			return
		wx.CallAfter(UpdateResultDialog, gui.mainFrame, info, True)

class UpdateResultDialog(wx.Dialog):

	def __init__(self, parent, updateInfo, auto):
		# Translators: The title of the dialog informing the user about an NVDA update.
		super(UpdateResultDialog, self).__init__(parent, title=_("NVDA Update"))
		self.updateInfo = updateInfo
		mainSizer = wx.BoxSizer(wx.VERTICAL)

		if updateInfo:
			self.isInstalled = config.isInstalledCopy()
			self.urls = updateInfo["launcherUrl"].split(" ")
			self.fileHash = updateInfo.get("launcherHash")
			# Translators: A message indicating that an updated version of NVDA is available.
			# {version} will be replaced with the version; e.g. 2011.3.
			message = _("NVDA version {version} is available.").format(**updateInfo)
		else:
			# Translators: A message indicating that no update to NVDA is available.
			message = _("No update available.")
		mainSizer.Add(wx.StaticText(self, label=message))

		if updateInfo:
			if self.isInstalled:
				# Translators: The label of a button to download and install an NVDA update.
				label = _("Download and &install update")
			else:
				# Translators: The label of a button to download an NVDA update.
				label = _("&Download update")
			item = wx.Button(self, label=label)
			item.Bind(wx.EVT_BUTTON, self.onDownloadButton)

			mainSizer.Add(item)

			if auto:
				# Translators: The label of a button to remind the user later about performing some action.
				item = wx.Button(self, label=_("Remind me &later"))
				item.Bind(wx.EVT_BUTTON, self.onLaterButton)
				mainSizer.Add(item)
				item.SetFocus()

		# Translators: The label of a button to close a dialog.
		item = wx.Button(self, wx.ID_CLOSE, label=_("&Close"))
		item.Bind(wx.EVT_BUTTON, lambda evt: self.Close())
		mainSizer.Add(item)
		self.Bind(wx.EVT_CLOSE, lambda evt: self.Destroy())
		self.EscapeId = wx.ID_CLOSE

		self.Sizer = mainSizer
		mainSizer.Fit(self)
		self.Center(wx.BOTH | wx.CENTER_ON_SCREEN)
		self.Show()

	def onDownloadButton(self, evt):
		self.Hide()
		DonateRequestDialog(gui.mainFrame, self._download)

	def _download(self):
		if self.isInstalled:
			UpdateDownloader(self.urls, fileHash=self.fileHash).start()
		else:
			os.startfile(self.urls[0])
		self.Destroy()

	def onLaterButton(self, evt):
		state["dontRemindVersion"] = None
		saveState()
		self.Close()

class UpdateDownloader(object):
	"""Download and start installation of an updated version of NVDA, presenting appropriate user interface.
	To use, call L{start} on an instance.
	"""

	def __init__(self, urls, fileHash=None):
		"""Constructor.
		@param urls: URLs to try for the update file.
		@type urls: list of str
		@param fileHash: The SHA-1 hash of the file as a hex string.
		@type fileHash: basestring
		"""
		self.urls = urls
		self.destPath = tempfile.mktemp(prefix="nvda_update_", suffix=".exe")
		self.fileHash = fileHash

	def start(self):
		"""Start the download.
		"""
		self._shouldCancel = False
		# Use a timer because timers aren't re-entrant.
		self._guiExecTimer = wx.PyTimer(self._guiExecNotify)
		gui.mainFrame.prePopup()
		# Translators: The title of the dialog displayed while downloading an NVDA update.
		self._progressDialog = wx.ProgressDialog(_("Downloading Update"),
			# Translators: The progress message indicating that a connection is being established.
			_("Connecting"),
			# PD_AUTO_HIDE is required because ProgressDialog.Update blocks at 100%
			# and waits for the user to press the Close button.
			style=wx.PD_CAN_ABORT | wx.PD_ELAPSED_TIME | wx.PD_REMAINING_TIME | wx.PD_AUTO_HIDE,
			parent=gui.mainFrame)
		self._progressDialog.Raise()
		t = threading.Thread(target=self._bg)
		t.daemon = True
		t.start()

	def _guiExec(self, func, *args):
		self._guiExecFunc = func
		self._guiExecArgs = args
		if not self._guiExecTimer.IsRunning():
			self._guiExecTimer.Start(50, True)

	def _guiExecNotify(self):
		self._guiExecFunc(*self._guiExecArgs)

	def _bg(self):
		success=False
		for url in self.urls:
			try:
				self._download(url)
			except:
				log.debugWarning("Error downloading %s" % url, exc_info=True)
			else: #Successfully downloaded or canceled
				if not self._shouldCancel:
					success=True
				break
		else:
			# None of the URLs succeeded.
			self._guiExec(self._error)
			return
		if not success:
			try:
				os.remove(self.destPath)
			except OSError:
				pass
			return
		self._guiExec(self._downloadSuccess)

	def _download(self, url):
		remote = urllib.urlopen(url)
		if remote.code != 200:
			raise RuntimeError("Download failed with code %d" % remote.code)
		# #2352: Some security scanners such as Eset NOD32 HTTP Scanner
		# cause huge read delays while downloading.
		# Therefore, set a higher timeout.
		remote.fp._sock.settimeout(120)
		size = int(remote.headers["content-length"])
		local = file(self.destPath, "wb")
		if self.fileHash:
			hasher = hashlib.sha1()
		self._guiExec(self._downloadReport, 0, size)
		read = 0
		chunk=DOWNLOAD_BLOCK_SIZE
		while True:
			if self._shouldCancel:
				return
			if size -read <chunk:
				chunk =size -read
			block = remote.read(chunk)
			if not block:
				break
			read += len(block)
			if self._shouldCancel:
				return
			local.write(block)
			if self.fileHash:
				hasher.update(block)
			self._guiExec(self._downloadReport, read, size)
		if read < size:
			raise RuntimeError("Content too short")
		if self.fileHash and hasher.hexdigest() != self.fileHash:
			raise RuntimeError("Content has incorrect file hash")
		self._guiExec(self._downloadReport, read, size)

	def _downloadReport(self, read, size):
		if self._shouldCancel:
			return
		percent = int(float(read) / size * 100)
		# Translators: The progress message indicating that a download is in progress.
		cont, skip = self._progressDialog.Update(percent, _("Downloading"))
		if not cont:
			self._shouldCancel = True
			self._stopped()

	def _stopped(self):
		self._guiExecTimer = None
		self._guiExecFunc = None
		self._guiExecArgs = None
		self._progressDialog.Hide()
		self._progressDialog.Destroy()
		self._progressDialog = None
		# Not sure why, but this doesn't work if we call it directly here.
		wx.CallLater(50, gui.mainFrame.postPopup)

	def _error(self):
		self._stopped()
		gui.messageBox(
			# Translators: A message indicating that an error occurred while downloading an update to NVDA.
			_("Error downloading update."),
			_("Error"),
			wx.OK | wx.ICON_ERROR)

	def _downloadSuccess(self):
		self._stopped()
		# Translators: The message presented when the update has been successfully downloaded
		# and is about to be installed.
		gui.messageBox(_("Update downloaded. It will now be installed."),
			# Translators: The title of the dialog displayed when the update is about to be installed.
			_("Install Update"))
		state["removeFile"] = self.destPath
		saveState()
		# #4475: ensure that the new process shows its first window, by providing SW_SHOWNORMAL
		shellapi.ShellExecute(None, None,
			self.destPath.decode("mbcs"),
			u"--install -m",
			None, winUser.SW_SHOWNORMAL)

class DonateRequestDialog(wx.Dialog):
	# Translators: The message requesting donations from users.
	MESSAGE = _(
		"We need your help in order to continue to improve NVDA.\n"
		"This project relies primarily on donations and grants. By donating, you are helping to fund full time development.\n"
		"If even $10 is donated for every download, we will be able to cover all of the ongoing costs of the project.\n"
		"All donations are received by NV Access, the non-profit organisation which develops NVDA.\n"
		"Thank you for your support."
	)

	def __init__(self, parent, continueFunc):
		# Translators: The title of the dialog requesting donations from users.
		super(DonateRequestDialog, self).__init__(parent, title=_("Please Donate"))
		self._continue = continueFunc

		mainSizer=wx.BoxSizer(wx.VERTICAL)
		item = wx.StaticText(self, label=self.MESSAGE)
		mainSizer.Add(item, border=20, flag=wx.LEFT | wx.RIGHT | wx.TOP)
		sizer = wx.BoxSizer(wx.HORIZONTAL)
		# Translators: The label of the button to donate
		# in the "Please Donate" dialog.
		item = self.donateButton = wx.Button(self, label=_("&Donate"))
		item.Bind(wx.EVT_BUTTON, self.onDonate)
		sizer.Add(item)
		# Translators: The label of the button to decline donation
		# in the "Please Donate" dialog.
		item = wx.Button(self, wx.ID_CLOSE, label=_("&Not now"))
		item.Bind(wx.EVT_BUTTON, lambda evt: self.Close())
		sizer.Add(item)
		self.Bind(wx.EVT_CLOSE, self.onClose)
		self.EscapeId = wx.ID_CLOSE
		mainSizer.Add(sizer, flag=wx.TOP | wx.BOTTOM | wx.ALIGN_CENTER_HORIZONTAL, border=20)

		self.Sizer = mainSizer
		mainSizer.Fit(self)
		self.Center(wx.BOTH | wx.CENTER_ON_SCREEN)
		self.Show()

	def onDonate(self, evt):
		os.startfile(gui.DONATE_URL)
		# Translators: The label of a button to indicate that the user is finished donating
		# in the "Please Donate" dialog.
		self.donateButton.Label = _("&Done")
		self.donateButton.Bind(wx.EVT_BUTTON, lambda evt: self.Close())

	def onClose(self, evt):
		self.Hide()
		self._continue()
		self.Destroy()

def saveState():
	try:
		cPickle.dump(state, file(_stateFilename, "wb"))
	except:
		log.debugWarning("Error saving state", exc_info=True)

def initialize():
	global state, _stateFilename, autoChecker
	_stateFilename = os.path.join(globalVars.appArgs.configPath, "updateCheckState.pickle")
	try:
		state = cPickle.load(file(_stateFilename, "r"))
	except:
		# Defaults.
		state = {
			"lastCheck": 0,
			"dontRemindVersion": None,
		}

	# If we just updated, remove the updater file.
	try:
		os.remove(state.pop("removeFile"))
		saveState()
	except (KeyError, OSError):
		pass

	if config.conf["update"]["autoCheck"] and not globalVars.appArgs.launcher:
		autoChecker = AutoUpdateChecker()

def terminate():
	global state, autoChecker
	state = None
	if autoChecker:
		autoChecker.terminate()
		autoChecker = None

# These structs are only complete enough to achieve what we need.
class CERT_USAGE_MATCH(ctypes.Structure):
	_fields_ = (
		("dwType", ctypes.wintypes.DWORD),
		# CERT_ENHKEY_USAGE struct
		("cUsageIdentifier", ctypes.wintypes.DWORD),
		("rgpszUsageIdentifier", ctypes.c_void_p), # LPSTR *
	)

class CERT_CHAIN_PARA(ctypes.Structure):
	_fields_ = (
		("cbSize", ctypes.wintypes.DWORD),
		("RequestedUsage", CERT_USAGE_MATCH),
		("RequestedIssuancePolicy", CERT_USAGE_MATCH),
		("dwUrlRetrievalTimeout", ctypes.wintypes.DWORD),
		("fCheckRevocationFreshnessTime", ctypes.wintypes.BOOL),
		("dwRevocationFreshnessTime", ctypes.wintypes.DWORD),
		("pftCacheResync", ctypes.c_void_p), # LPFILETIME
		("pStrongSignPara", ctypes.c_void_p), # PCCERT_STRONG_SIGN_PARA
		("dwStrongSignFlags", ctypes.wintypes.DWORD),
	)

def _updateWindowsRootCertificates():
	crypt = ctypes.windll.crypt32
	# Get the server certificate.
	sslCont = ssl._create_unverified_context()
	u = urllib.urlopen("https://www.nvaccess.org/nvdaUpdateCheck", context=sslCont)
	cert = u.fp._sock.getpeercert(True)
	u.close()
	# Convert to a form usable by Windows.
	certCont = crypt.CertCreateCertificateContext(
		0x00000001, # X509_ASN_ENCODING
		cert,
		len(cert))
	# Ask Windows to build a certificate chain, thus triggering a root certificate update.
	chainCont = ctypes.c_void_p()
	crypt.CertGetCertificateChain(None, certCont, None, None,
		ctypes.byref(CERT_CHAIN_PARA(cbSize=ctypes.sizeof(CERT_CHAIN_PARA),
			RequestedUsage=CERT_USAGE_MATCH())),
		0, None,
		ctypes.byref(chainCont))
	crypt.CertFreeCertificateChain(chainCont)
	crypt.CertFreeCertificateContext(certCont)