#!/usr/bin/env python
#
# Copyright (C) 2008 The Android Open Source Project
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#      http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

"""
Given a target-files zipfile, produces an OTA package that installs
that build.  An incremental OTA is produced if -i is given, otherwise
a full OTA is produced.

Usage:  ota_from_target_files [flags] input_target_files output_ota_package

  -b  (--board_config)  <file>
      Deprecated.

  -k  (--package_key)  <key>
      Key to use to sign the package (default is
      "build/target/product/security/testkey").

  -i  (--incremental_from)  <file>
      Generate an incremental OTA using the given target-files zip as
      the starting build.

  -w  (--wipe_user_data)
      Generate an OTA package that will wipe the user data partition
      when installed.

  -n  (--no_prereq)
      Omit the timestamp prereq check normally included at the top of
      the build scripts (used for developer OTA packages which
      legitimately need to go back and forth).

  -e  (--extra_script)  <file>
      Insert the contents of file at the end of the update script.

"""

import sys

if sys.hexversion < 0x02040000:
  print >> sys.stderr, "Python 2.4 or newer is required."
  sys.exit(1)

import copy
import errno
import os
import re
import sha
import subprocess
import tempfile
import threading
import time
import zipfile

import common
import edify_generator

OPTIONS = common.OPTIONS
OPTIONS.package_key = "build/target/product/security/testkey"
OPTIONS.incremental_source = None
OPTIONS.require_verbatim = set()
OPTIONS.prohibit_verbatim = set(("system/build.prop",))
OPTIONS.patch_threshold = 0.95
OPTIONS.wipe_user_data = False
OPTIONS.omit_prereq = False
OPTIONS.extra_script = None
OPTIONS.worker_threads = 3

def MostPopularKey(d, default):
  """Given a dict, return the key corresponding to the largest
  value.  Returns 'default' if the dict is empty."""
  x = [(v, k) for (k, v) in d.iteritems()]
  if not x: return default
  x.sort()
  return x[-1][1]


def IsSymlink(info):
  """Return true if the zipfile.ZipInfo object passed in represents a
  symlink."""
  return (info.external_attr >> 16) == 0120777


class Item:
  """Items represent the metadata (user, group, mode) of files and
  directories in the system image."""
  ITEMS = {}
  def __init__(self, name, dir=False):
    self.name = name
    self.uid = None
    self.gid = None
    self.mode = None
    self.dir = dir

    if name:
      self.parent = Item.Get(os.path.dirname(name), dir=True)
      self.parent.children.append(self)
    else:
      self.parent = None
    if dir:
      self.children = []

  def Dump(self, indent=0):
    if self.uid is not None:
      print "%s%s %d %d %o" % ("  "*indent, self.name, self.uid, self.gid, self.mode)
    else:
      print "%s%s %s %s %s" % ("  "*indent, self.name, self.uid, self.gid, self.mode)
    if self.dir:
      print "%s%s" % ("  "*indent, self.descendants)
      print "%s%s" % ("  "*indent, self.best_subtree)
      for i in self.children:
        i.Dump(indent=indent+1)

  @classmethod
  def Get(cls, name, dir=False):
    if name not in cls.ITEMS:
      cls.ITEMS[name] = Item(name, dir=dir)
    return cls.ITEMS[name]

  @classmethod
  def GetMetadata(cls, input_zip):

    try:
      # See if the target_files contains a record of what the uid,
      # gid, and mode is supposed to be.
      output = input_zip.read("META/filesystem_config.txt")
    except KeyError:
      # Run the external 'fs_config' program to determine the desired
      # uid, gid, and mode for every Item object.  Note this uses the
      # one in the client now, which might not be the same as the one
      # used when this target_files was built.
      p = common.Run(["fs_config"], stdin=subprocess.PIPE,
                     stdout=subprocess.PIPE, stderr=subprocess.PIPE)
      suffix = { False: "", True: "/" }
      input = "".join(["%s%s\n" % (i.name, suffix[i.dir])
                       for i in cls.ITEMS.itervalues() if i.name])
      output, error = p.communicate(input)
      assert not error

    for line in output.split("\n"):
      if not line: continue
      name, uid, gid, mode = line.split()
      i = cls.ITEMS.get(name, None)
      if i is not None:
        i.uid = int(uid)
        i.gid = int(gid)
        i.mode = int(mode, 8)
        if i.dir:
          i.children.sort(key=lambda i: i.name)

    # set metadata for the files generated by this script.
    i = cls.ITEMS.get("system/recovery-from-boot.p", None)
    if i: i.uid, i.gid, i.mode = 0, 0, 0644
    i = cls.ITEMS.get("system/etc/install-recovery.sh", None)
    if i: i.uid, i.gid, i.mode = 0, 0, 0544

  def CountChildMetadata(self):
    """Count up the (uid, gid, mode) tuples for all children and
    determine the best strategy for using set_perm_recursive and
    set_perm to correctly chown/chmod all the files to their desired
    values.  Recursively calls itself for all descendants.

    Returns a dict of {(uid, gid, dmode, fmode): count} counting up
    all descendants of this node.  (dmode or fmode may be None.)  Also
    sets the best_subtree of each directory Item to the (uid, gid,
    dmode, fmode) tuple that will match the most descendants of that
    Item.
    """

    assert self.dir
    d = self.descendants = {(self.uid, self.gid, self.mode, None): 1}
    for i in self.children:
      if i.dir:
        for k, v in i.CountChildMetadata().iteritems():
          d[k] = d.get(k, 0) + v
      else:
        k = (i.uid, i.gid, None, i.mode)
        d[k] = d.get(k, 0) + 1

    # Find the (uid, gid, dmode, fmode) tuple that matches the most
    # descendants.

    # First, find the (uid, gid) pair that matches the most
    # descendants.
    ug = {}
    for (uid, gid, _, _), count in d.iteritems():
      ug[(uid, gid)] = ug.get((uid, gid), 0) + count
    ug = MostPopularKey(ug, (0, 0))

    # Now find the dmode and fmode that match the most descendants
    # with that (uid, gid), and choose those.
    best_dmode = (0, 0755)
    best_fmode = (0, 0644)
    for k, count in d.iteritems():
      if k[:2] != ug: continue
      if k[2] is not None and count >= best_dmode[0]: best_dmode = (count, k[2])
      if k[3] is not None and count >= best_fmode[0]: best_fmode = (count, k[3])
    self.best_subtree = ug + (best_dmode[1], best_fmode[1])

    return d

  def SetPermissions(self, script):
    """Append set_perm/set_perm_recursive commands to 'script' to
    set all permissions, users, and groups for the tree of files
    rooted at 'self'."""

    self.CountChildMetadata()

    def recurse(item, current):
      # current is the (uid, gid, dmode, fmode) tuple that the current
      # item (and all its children) have already been set to.  We only
      # need to issue set_perm/set_perm_recursive commands if we're
      # supposed to be something different.
      if item.dir:
        if current != item.best_subtree:
          script.SetPermissionsRecursive("/"+item.name, *item.best_subtree)
          current = item.best_subtree

        if item.uid != current[0] or item.gid != current[1] or \
           item.mode != current[2]:
          script.SetPermissions("/"+item.name, item.uid, item.gid, item.mode)

        for i in item.children:
          recurse(i, current)
      else:
        if item.uid != current[0] or item.gid != current[1] or \
               item.mode != current[3]:
          script.SetPermissions("/"+item.name, item.uid, item.gid, item.mode)

    recurse(self, (-1, -1, -1, -1))


def CopySystemFiles(input_zip, output_zip=None,
                    substitute=None):
  """Copies files underneath system/ in the input zip to the output
  zip.  Populates the Item class with their metadata, and returns a
  list of symlinks.  output_zip may be None, in which case the copy is
  skipped (but the other side effects still happen).  substitute is an
  optional dict of {output filename: contents} to be output instead of
  certain input files.
  """

  symlinks = []

  for info in input_zip.infolist():
    if info.filename.startswith("SYSTEM/"):
      basefilename = info.filename[7:]
      if IsSymlink(info):
        symlinks.append((input_zip.read(info.filename),
                         "/system/" + basefilename))
      else:
        info2 = copy.copy(info)
        fn = info2.filename = "system/" + basefilename
        if substitute and fn in substitute and substitute[fn] is None:
          continue
        if output_zip is not None:
          if substitute and fn in substitute:
            data = substitute[fn]
          else:
            data = input_zip.read(info.filename)
          output_zip.writestr(info2, data)
        if fn.endswith("/"):
          Item.Get(fn[:-1], dir=True)
        else:
          Item.Get(fn, dir=False)

  symlinks.sort()
  return symlinks


def SignOutput(temp_zip_name, output_zip_name):
  key_passwords = common.GetKeyPasswords([OPTIONS.package_key])
  pw = key_passwords[OPTIONS.package_key]

  common.SignFile(temp_zip_name, output_zip_name, OPTIONS.package_key, pw,
                  whole_file=True)


def AppendAssertions(script, input_zip):
  device = GetBuildProp("ro.product.device", input_zip)
  script.AssertDevice(device)


def MakeRecoveryPatch(output_zip, recovery_img, boot_img):
  """Generate a binary patch that creates the recovery image starting
  with the boot image.  (Most of the space in these images is just the
  kernel, which is identical for the two, so the resulting patch
  should be efficient.)  Add it to the output zip, along with a shell
  script that is run from init.rc on first boot to actually do the
  patching and install the new recovery image.

  recovery_img and boot_img should be File objects for the
  corresponding images.

  Returns an Item for the shell script, which must be made
  executable.
  """

  d = Difference(recovery_img, boot_img)
  _, _, patch = d.ComputePatch()
  common.ZipWriteStr(output_zip, "recovery/recovery-from-boot.p", patch)
  Item.Get("system/recovery-from-boot.p", dir=False)

  # Images with different content will have a different first page, so
  # we check to see if this recovery has already been installed by
  # testing just the first 2k.
  HEADER_SIZE = 2048
  header_sha1 = sha.sha(recovery_img.data[:HEADER_SIZE]).hexdigest()
  sh = """#!/system/bin/sh
if ! applypatch -c MTD:recovery:%(header_size)d:%(header_sha1)s; then
  log -t recovery "Installing new recovery image"
  applypatch MTD:boot:%(boot_size)d:%(boot_sha1)s MTD:recovery %(recovery_sha1)s %(recovery_size)d %(boot_sha1)s:/system/recovery-from-boot.p
else
  log -t recovery "Recovery image already installed"
fi
""" % { 'boot_size': boot_img.size,
        'boot_sha1': boot_img.sha1,
        'header_size': HEADER_SIZE,
        'header_sha1': header_sha1,
        'recovery_size': recovery_img.size,
        'recovery_sha1': recovery_img.sha1 }
  common.ZipWriteStr(output_zip, "recovery/etc/install-recovery.sh", sh)
  return Item.Get("system/etc/install-recovery.sh", dir=False)


def WriteFullOTAPackage(input_zip, output_zip, info):
  # TODO: how to determine this?  We don't know what version it will
  # be installed on top of.  For now, we expect the API just won't
  # change very often.
  script = edify_generator.EdifyGenerator(3, info)

  metadata = {"post-build": GetBuildProp("ro.build.fingerprint", input_zip),
              "pre-device": GetBuildProp("ro.product.device", input_zip),
              "post-timestamp": GetBuildProp("ro.build.date.utc", input_zip),
              }

  device_specific = common.DeviceSpecificParams(
      input_zip=input_zip,
      input_version=GetRecoveryAPIVersion(input_zip),
      output_zip=output_zip,
      script=script,
      input_tmp=OPTIONS.input_tmp,
      metadata=metadata)

  if not OPTIONS.omit_prereq:
    ts = GetBuildProp("ro.build.date.utc", input_zip)
    script.AssertOlderBuild(ts)

  AppendAssertions(script, input_zip)
  device_specific.FullOTA_Assertions()

  script.ShowProgress(0.5, 0)

  if OPTIONS.wipe_user_data:
    script.FormatPartition("userdata")

  script.FormatPartition("system")
  script.Mount("system", "/system")
  script.UnpackPackageDir("recovery", "/system")
  script.UnpackPackageDir("system", "/system")

  symlinks = CopySystemFiles(input_zip, output_zip)
  script.MakeSymlinks(symlinks)

  boot_img = File("boot.img", common.BuildBootableImage(
      os.path.join(OPTIONS.input_tmp, "BOOT")))
  recovery_img = File("recovery.img", common.BuildBootableImage(
      os.path.join(OPTIONS.input_tmp, "RECOVERY")))
  MakeRecoveryPatch(output_zip, recovery_img, boot_img)

  Item.GetMetadata(input_zip)
  Item.Get("system").SetPermissions(script)

  common.CheckSize(boot_img.data, "boot.img")
  common.ZipWriteStr(output_zip, "boot.img", boot_img.data)
  script.ShowProgress(0.2, 0)

  script.ShowProgress(0.2, 10)
  script.WriteRawImage("boot", "boot.img")

  script.ShowProgress(0.1, 0)
  device_specific.FullOTA_InstallEnd()

  if OPTIONS.extra_script is not None:
    script.AppendExtra(OPTIONS.extra_script)

  script.UnmountAll()
  script.AddToZip(input_zip, output_zip)
  WriteMetadata(metadata, output_zip)


def WriteMetadata(metadata, output_zip):
  common.ZipWriteStr(output_zip, "META-INF/com/android/metadata",
                     "".join(["%s=%s\n" % kv
                              for kv in sorted(metadata.iteritems())]))


class File(object):
  def __init__(self, name, data):
    self.name = name
    self.data = data
    self.size = len(data)
    self.sha1 = sha.sha(data).hexdigest()

  def WriteToTemp(self):
    t = tempfile.NamedTemporaryFile()
    t.write(self.data)
    t.flush()
    return t

  def AddToZip(self, z):
    common.ZipWriteStr(z, self.name, self.data)


def LoadSystemFiles(z):
  """Load all the files from SYSTEM/... in a given target-files
  ZipFile, and return a dict of {filename: File object}."""
  out = {}
  for info in z.infolist():
    if info.filename.startswith("SYSTEM/") and not IsSymlink(info):
      fn = "system/" + info.filename[7:]
      data = z.read(info.filename)
      out[fn] = File(fn, data)
  return out


DIFF_PROGRAM_BY_EXT = {
    ".gz" : "imgdiff",
    ".zip" : ["imgdiff", "-z"],
    ".jar" : ["imgdiff", "-z"],
    ".apk" : ["imgdiff", "-z"],
    ".img" : "imgdiff",
    }


class Difference(object):
  def __init__(self, tf, sf):
    self.tf = tf
    self.sf = sf
    self.patch = None

  def ComputePatch(self):
    """Compute the patch (as a string of data) needed to turn sf into
    tf.  Returns the same tuple as GetPatch()."""

    tf = self.tf
    sf = self.sf

    ext = os.path.splitext(tf.name)[1]
    diff_program = DIFF_PROGRAM_BY_EXT.get(ext, "bsdiff")

    ttemp = tf.WriteToTemp()
    stemp = sf.WriteToTemp()

    ext = os.path.splitext(tf.name)[1]

    try:
      ptemp = tempfile.NamedTemporaryFile()
      if isinstance(diff_program, list):
        cmd = copy.copy(diff_program)
      else:
        cmd = [diff_program]
      cmd.append(stemp.name)
      cmd.append(ttemp.name)
      cmd.append(ptemp.name)
      p = common.Run(cmd, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
      _, err = p.communicate()
      if err or p.returncode != 0:
        print "WARNING: failure running %s:\n%s\n" % (diff_program, err)
        return None
      diff = ptemp.read()
    finally:
      ptemp.close()
      stemp.close()
      ttemp.close()

    self.patch = diff
    return self.tf, self.sf, self.patch


  def GetPatch(self):
    """Return a tuple (target_file, source_file, patch_data).
    patch_data may be None if ComputePatch hasn't been called, or if
    computing the patch failed."""
    return self.tf, self.sf, self.patch


def ComputeDifferences(diffs):
  """Call ComputePatch on all the Difference objects in 'diffs'."""
  print len(diffs), "diffs to compute"

  # Do the largest files first, to try and reduce the long-pole effect.
  by_size = [(i.tf.size, i) for i in diffs]
  by_size.sort(reverse=True)
  by_size = [i[1] for i in by_size]

  lock = threading.Lock()
  diff_iter = iter(by_size)   # accessed under lock

  def worker():
    try:
      lock.acquire()
      for d in diff_iter:
        lock.release()
        start = time.time()
        d.ComputePatch()
        dur = time.time() - start
        lock.acquire()

        tf, sf, patch = d.GetPatch()
        if sf.name == tf.name:
          name = tf.name
        else:
          name = "%s (%s)" % (tf.name, sf.name)
        if patch is None:
          print "patching failed!                                  %s" % (name,)
        else:
          print "%8.2f sec %8d / %8d bytes (%6.2f%%) %s" % (
              dur, len(patch), tf.size, 100.0 * len(patch) / tf.size, name)
      lock.release()
    except Exception, e:
      print e
      raise

  # start worker threads; wait for them all to finish.
  threads = [threading.Thread(target=worker)
             for i in range(OPTIONS.worker_threads)]
  for th in threads:
    th.start()
  while threads:
    threads.pop().join()


def GetBuildProp(property, z):
  """Return the fingerprint of the build of a given target-files
  ZipFile object."""
  bp = z.read("SYSTEM/build.prop")
  if not property:
    return bp
  m = re.search(re.escape(property) + r"=(.*)\n", bp)
  if not m:
    raise common.ExternalError("couldn't find %s in build.prop" % (property,))
  return m.group(1).strip()


def GetRecoveryAPIVersion(zip):
  """Returns the version of the recovery API.  Version 0 is the older
  amend code (no separate binary)."""
  try:
    version = zip.read("META/recovery-api-version.txt")
    return int(version)
  except KeyError:
    try:
      # version one didn't have the recovery-api-version.txt file, but
      # it did include an updater binary.
      zip.getinfo("OTA/bin/updater")
      return 1
    except KeyError:
      return 0


def WriteIncrementalOTAPackage(target_zip, source_zip, output_zip, info):
  source_version = GetRecoveryAPIVersion(source_zip)
  target_version = GetRecoveryAPIVersion(target_zip)

  if source_version == 0:
    print ("WARNING: generating edify script for a source that "
           "can't install it.")
  script = edify_generator.EdifyGenerator(source_version, info)

  metadata = {"pre-device": GetBuildProp("ro.product.device", source_zip),
              "post-timestamp": GetBuildProp("ro.build.date.utc", target_zip),
              }

  device_specific = common.DeviceSpecificParams(
      source_zip=source_zip,
      source_version=source_version,
      target_zip=target_zip,
      target_version=target_version,
      output_zip=output_zip,
      script=script,
      metadata=metadata)

  print "Loading target..."
  target_data = LoadSystemFiles(target_zip)
  print "Loading source..."
  source_data = LoadSystemFiles(source_zip)

  verbatim_targets = []
  patch_list = []
  diffs = []
  largest_source_size = 0
  for fn in sorted(target_data.keys()):
    tf = target_data[fn]
    assert fn == tf.name
    sf = source_data.get(fn, None)

    if sf is None or fn in OPTIONS.require_verbatim:
      # This file should be included verbatim
      if fn in OPTIONS.prohibit_verbatim:
        raise common.ExternalError("\"%s\" must be sent verbatim" % (fn,))
      print "send", fn, "verbatim"
      tf.AddToZip(output_zip)
      verbatim_targets.append((fn, tf.size))
    elif tf.sha1 != sf.sha1:
      # File is different; consider sending as a patch
      diffs.append(Difference(tf, sf))
    else:
      # Target file identical to source.
      pass

  ComputeDifferences(diffs)

  for diff in diffs:
    tf, sf, d = diff.GetPatch()
    if d is None or len(d) > tf.size * OPTIONS.patch_threshold:
      # patch is almost as big as the file; don't bother patching
      tf.AddToZip(output_zip)
      verbatim_targets.append((tf.name, tf.size))
    else:
      common.ZipWriteStr(output_zip, "patch/" + tf.name + ".p", d)
      patch_list.append((tf.name, tf, sf, tf.size, sha.sha(d).hexdigest()))
      largest_source_size = max(largest_source_size, sf.size)

  source_fp = GetBuildProp("ro.build.fingerprint", source_zip)
  target_fp = GetBuildProp("ro.build.fingerprint", target_zip)
  metadata["pre-build"] = source_fp
  metadata["post-build"] = target_fp

  script.Mount("system", "/system")
  script.AssertSomeFingerprint(source_fp, target_fp)

  source_boot = File("/tmp/boot.img",
                     common.BuildBootableImage(
      os.path.join(OPTIONS.source_tmp, "BOOT")))
  target_boot = File("/tmp/boot.img",
                     common.BuildBootableImage(
      os.path.join(OPTIONS.target_tmp, "BOOT")))
  updating_boot = (source_boot.data != target_boot.data)

  source_recovery = File("system/recovery.img",
                         common.BuildBootableImage(
      os.path.join(OPTIONS.source_tmp, "RECOVERY")))
  target_recovery = File("system/recovery.img",
                         common.BuildBootableImage(
      os.path.join(OPTIONS.target_tmp, "RECOVERY")))
  updating_recovery = (source_recovery.data != target_recovery.data)

  # Here's how we divide up the progress bar:
  #  0.1 for verifying the start state (PatchCheck calls)
  #  0.8 for applying patches (ApplyPatch calls)
  #  0.1 for unpacking verbatim files, symlinking, and doing the
  #      device-specific commands.

  AppendAssertions(script, target_zip)
  device_specific.IncrementalOTA_Assertions()

  script.Print("Verifying current system...")

  script.ShowProgress(0.1, 0)
  total_verify_size = float(sum([i[2].size for i in patch_list]) + 1)
  if updating_boot:
    total_verify_size += source_boot.size
  so_far = 0

  for fn, tf, sf, size, patch_sha in patch_list:
    script.PatchCheck("/"+fn, tf.sha1, sf.sha1)
    so_far += sf.size
    script.SetProgress(so_far / total_verify_size)

  if updating_boot:
    d = Difference(target_boot, source_boot)
    _, _, d = d.ComputePatch()
    print "boot      target: %d  source: %d  diff: %d" % (
        target_boot.size, source_boot.size, len(d))

    common.ZipWriteStr(output_zip, "patch/boot.img.p", d)

    script.PatchCheck("MTD:boot:%d:%s:%d:%s" %
                      (source_boot.size, source_boot.sha1,
                       target_boot.size, target_boot.sha1))
    so_far += source_boot.size
    script.SetProgress(so_far / total_verify_size)

  if patch_list or updating_recovery or updating_boot:
    script.CacheFreeSpaceCheck(largest_source_size)

  device_specific.IncrementalOTA_VerifyEnd()

  script.Comment("---- start making changes here ----")

  if OPTIONS.wipe_user_data:
    script.Print("Erasing user data...")
    script.FormatPartition("userdata")

  script.Print("Removing unneeded files...")
  script.DeleteFiles(["/"+i[0] for i in verbatim_targets] +
                     ["/"+i for i in sorted(source_data)
                            if i not in target_data] +
                     ["/system/recovery.img"])

  script.ShowProgress(0.8, 0)
  total_patch_size = float(sum([i[1].size for i in patch_list]) + 1)
  if updating_boot:
    total_patch_size += target_boot.size
  so_far = 0

  script.Print("Patching system files...")
  for fn, tf, sf, size, _ in patch_list:
    script.ApplyPatch("/"+fn, "-", tf.size, tf.sha1, sf.sha1, "patch/"+fn+".p")
    so_far += tf.size
    script.SetProgress(so_far / total_patch_size)

  if updating_boot:
    # Produce the boot image by applying a patch to the current
    # contents of the boot partition, and write it back to the
    # partition.
    script.Print("Patching boot image...")
    script.ApplyPatch("MTD:boot:%d:%s:%d:%s"
                      % (source_boot.size, source_boot.sha1,
                         target_boot.size, target_boot.sha1),
                      "-",
                      target_boot.size, target_boot.sha1,
                      source_boot.sha1, "patch/boot.img.p")
    so_far += target_boot.size
    script.SetProgress(so_far / total_patch_size)
    print "boot image changed; including."
  else:
    print "boot image unchanged; skipping."

  if updating_recovery:
    # Is it better to generate recovery as a patch from the current
    # boot image, or from the previous recovery image?  For large
    # updates with significant kernel changes, probably the former.
    # For small updates where the kernel hasn't changed, almost
    # certainly the latter.  We pick the first option.  Future
    # complicated schemes may let us effectively use both.
    #
    # A wacky possibility: as long as there is room in the boot
    # partition, include the binaries and image files from recovery in
    # the boot image (though not in the ramdisk) so they can be used
    # as fodder for constructing the recovery image.
    MakeRecoveryPatch(output_zip, target_recovery, target_boot)
    script.DeleteFiles(["/system/recovery-from-boot.p",
                        "/system/etc/install-recovery.sh"])
    print "recovery image changed; including as patch from boot."
  else:
    print "recovery image unchanged; skipping."

  script.ShowProgress(0.1, 10)

  target_symlinks = CopySystemFiles(target_zip, None)

  target_symlinks_d = dict([(i[1], i[0]) for i in target_symlinks])
  temp_script = script.MakeTemporary()
  Item.GetMetadata(target_zip)
  Item.Get("system").SetPermissions(temp_script)

  # Note that this call will mess up the tree of Items, so make sure
  # we're done with it.
  source_symlinks = CopySystemFiles(source_zip, None)
  source_symlinks_d = dict([(i[1], i[0]) for i in source_symlinks])

  # Delete all the symlinks in source that aren't in target.  This
  # needs to happen before verbatim files are unpacked, in case a
  # symlink in the source is replaced by a real file in the target.
  to_delete = []
  for dest, link in source_symlinks:
    if link not in target_symlinks_d:
      to_delete.append(link)
  script.DeleteFiles(to_delete)

  if verbatim_targets:
    script.Print("Unpacking new files...")
    script.UnpackPackageDir("system", "/system")

  if updating_recovery:
    script.Print("Unpacking new recovery...")
    script.UnpackPackageDir("recovery", "/system")

  script.Print("Symlinks and permissions...")

  # Create all the symlinks that don't already exist, or point to
  # somewhere different than what we want.  Delete each symlink before
  # creating it, since the 'symlink' command won't overwrite.
  to_create = []
  for dest, link in target_symlinks:
    if link in source_symlinks_d:
      if dest != source_symlinks_d[link]:
        to_create.append((dest, link))
    else:
      to_create.append((dest, link))
  script.DeleteFiles([i[1] for i in to_create])
  script.MakeSymlinks(to_create)

  # Now that the symlinks are created, we can set all the
  # permissions.
  script.AppendScript(temp_script)

  # Do device-specific installation (eg, write radio image).
  device_specific.IncrementalOTA_InstallEnd()

  if OPTIONS.extra_script is not None:
    scirpt.AppendExtra(OPTIONS.extra_script)

  script.AddToZip(target_zip, output_zip)
  WriteMetadata(metadata, output_zip)


def main(argv):

  def option_handler(o, a):
    if o in ("-b", "--board_config"):
      pass   # deprecated
    elif o in ("-k", "--package_key"):
      OPTIONS.package_key = a
    elif o in ("-i", "--incremental_from"):
      OPTIONS.incremental_source = a
    elif o in ("-w", "--wipe_user_data"):
      OPTIONS.wipe_user_data = True
    elif o in ("-n", "--no_prereq"):
      OPTIONS.omit_prereq = True
    elif o in ("-e", "--extra_script"):
      OPTIONS.extra_script = a
    elif o in ("--worker_threads"):
      OPTIONS.worker_threads = int(a)
    else:
      return False
    return True

  args = common.ParseOptions(argv, __doc__,
                             extra_opts="b:k:i:d:wne:",
                             extra_long_opts=["board_config=",
                                              "package_key=",
                                              "incremental_from=",
                                              "wipe_user_data",
                                              "no_prereq",
                                              "extra_script=",
                                              "worker_threads="],
                             extra_option_handler=option_handler)

  if len(args) != 2:
    common.Usage(__doc__)
    sys.exit(1)

  if OPTIONS.extra_script is not None:
    OPTIONS.extra_script = open(OPTIONS.extra_script).read()

  print "unzipping target target-files..."
  OPTIONS.input_tmp = common.UnzipTemp(args[0])

  if OPTIONS.device_specific is None:
    # look for the device-specific tools extension location in the input
    try:
      f = open(os.path.join(OPTIONS.input_tmp, "META", "tool-extensions.txt"))
      ds = f.read().strip()
      f.close()
      if ds:
        ds = os.path.normpath(ds)
        print "using device-specific extensions in", ds
        OPTIONS.device_specific = ds
    except IOError, e:
      if e.errno == errno.ENOENT:
        # nothing specified in the file
        pass
      else:
        raise

  info = common.LoadInfoDict()
  common.LoadMaxSizes(info)
  if not OPTIONS.max_image_size:
    print
    print "  WARNING:  Failed to load max image sizes; will not enforce"
    print "  image size limits."
    print

  OPTIONS.target_tmp = OPTIONS.input_tmp
  input_zip = zipfile.ZipFile(args[0], "r")
  if OPTIONS.package_key:
    temp_zip_file = tempfile.NamedTemporaryFile()
    output_zip = zipfile.ZipFile(temp_zip_file, "w",
                                 compression=zipfile.ZIP_DEFLATED)
  else:
    output_zip = zipfile.ZipFile(args[1], "w",
                                 compression=zipfile.ZIP_DEFLATED)

  if OPTIONS.incremental_source is None:
    WriteFullOTAPackage(input_zip, output_zip, info)
  else:
    print "unzipping source target-files..."
    OPTIONS.source_tmp = common.UnzipTemp(OPTIONS.incremental_source)
    source_zip = zipfile.ZipFile(OPTIONS.incremental_source, "r")
    WriteIncrementalOTAPackage(input_zip, source_zip, output_zip, info)

  output_zip.close()
  if OPTIONS.package_key:
    SignOutput(temp_zip_file.name, args[1])
    temp_zip_file.close()

  common.Cleanup()

  print "done."


if __name__ == '__main__':
  try:
    main(sys.argv[1:])
  except common.ExternalError, e:
    print
    print "   ERROR: %s" % (e,)
    print
    sys.exit(1)