# Copyright (c) 2012 The Chromium OS Authors. All rights reserved.
# Use of this source code is governed by a BSD-style license that can be
# found in the LICENSE file.

"""
Purpose of this module is to hold common script/commandline functionality.

This ranges from optparse, to a basic script wrapper setup (much like
what is used for chromite.bin.* ).
"""

import argparse
import collections
import functools
import logging
import os
import optparse
import signal
import sys
import tempfile

# TODO(build): sort the buildbot.constants/lib.constants issue;
# lib shouldn't have to import from buildbot like this.
from chromite.buildbot import constants
from chromite.lib import git
from chromite.lib import gclient
from chromite.lib import gs
from chromite.lib import osutils


def AbsolutePath(_option, _opt, value):
  """Expand paths and make them absolute."""
  return osutils.ExpandPath(value)


def NormalizeGSPath(value):
  """Expand paths and make them absolute."""
  return gs.CanonicalizeURL(value, strict=True).rstrip('/')


def OptparseWrapCheck(desc, check_f, _option, opt, value):
  """Optparse adapter for type checking functionality."""
  try:
    return check_f(value)
  except ValueError:
    raise optparse.OptionValueError(
        'Invalid %s given: --%s=%s' % (desc, opt, value))


VALID_TYPES = {
    'path': osutils.ExpandPath,
    'gs_path': NormalizeGSPath,
}


class Option(optparse.Option):
  """
  Subclass Option class to implement path evaluation, and other useful types.
  """
  _EXTRA_TYPES = ("path", "gs_path")
  TYPES = optparse.Option.TYPES + _EXTRA_TYPES
  TYPE_CHECKER = optparse.Option.TYPE_CHECKER.copy()
  for t in _EXTRA_TYPES:
    TYPE_CHECKER[t] = functools.partial(OptparseWrapCheck, t, VALID_TYPES[t])


class FilteringOption(Option):
  """Subclass that supports Option filtering for FilteringOptionParser"""
  def take_action(self, action, dest, opt, value, values, parser):
    if action in FilteringOption.ACTIONS:
      Option.take_action(self, action, dest, opt, value, values, parser)

    if value is None:
      value = []
    elif not self.nargs or self.nargs <= 1:
      value = [value]

    parser.AddParsedArg(self, opt, [str(v) for v in value])


class BaseParser(object):
  """Base parser class that includes the logic to add logging controls."""
  DEFAULT_LOG_LEVELS = ("critical", "debug", "error", "fatal", "info",
                        "warning")
  DEFAULT_LOG_LEVEL = "info"
  ALLOW_LOGGING = True
  SUPPORTS_CACHING = False

  def __init__(self, **kwargs):
    """Initialize this parser instance.

    kwargs:
      logging: Defaults to ALLOW_LOGGING from the class; if given,
        add --log-level.
      default_log_level: If logging is enabled, override the default logging
        level.  Defaults to the class's DEFAULT_LOG_LEVEL value.
      log_levels: If logging is enabled, this overrides the enumeration of
        allowed logging levels.  If not given, defaults to the classes
        DEFAULT_LOG_LEVELS value.
      manual_debug: If logging is enabled and this is True, suppress addition
        of a --debug alias.  This option defaults to True unless 'debug' has
        been exempted from the allowed logging level targets.
      caching: If given, must be either a callable that discerns the cache
        location if it wasn't specified (the prototype must be akin to
        lambda parser, values:calculated_cache_dir_path; it may return None to
        indicate that it handles setting the value on its own later in the
        parsing including setting the env), or True; if True, the
        machinery defaults to invoking the class's FindCacheDir method
        (which can be overridden).  FindCacheDir $CROS_CACHEDIR, falling
        back to $REPO/.cache, finally falling back to $TMP.
        Note that the cache_dir is not created, just discerned where it
        should live.
        If False, or caching is not given and the class attr SUPPORTS_CACHING
        is False, then no --cache-dir option will be added.
    """
    self.debug_enabled = False
    self.caching_group = None
    self.debug_group = None
    self.default_log_level = None
    self.log_levels = None
    self.logging_enabled = kwargs.get('logging', self.ALLOW_LOGGING)
    self.default_log_level = kwargs.get('default_log_level',
                                        self.DEFAULT_LOG_LEVEL)
    self.log_levels = tuple(x.lower() for x in
                            kwargs.get('log_levels', self.DEFAULT_LOG_LEVELS))
    self.debug_enabled = (not kwargs.get('manual_debug', False)
                          and 'debug' in self.log_levels)
    self.caching = kwargs.get('caching', self.SUPPORTS_CACHING)

  @staticmethod
  def PopUsedArgs(kwarg_dict):
    """Removes keys used by the base parser from the kwarg namespace."""
    parser_keys = ['logging', 'default_log_level', 'log_levels', 'manual_debug',
                   'caching']
    for key in parser_keys:
      kwarg_dict.pop(key, None)

  def SetupOptions(self):
    """Sets up special chromite options for an OptionParser."""
    if self.logging_enabled:
      self.debug_group = self.add_option_group("Debug options")
      self.add_option_to_group(
          self.debug_group, "--log-level", choices=self.log_levels,
          default=self.default_log_level,
          help="Set logging level to report at.")
      if self.debug_enabled:
        self.add_option_to_group(
          self.debug_group, "--debug", action="store_const", const="debug",
          dest="log_level", help="Alias for `--log-level=debug`. "
          "Useful for debugging bugs/failures.")

    if self.caching:
      self.caching_group = self.add_option_group("Caching Options")
      self.add_option_to_group(
          self.caching_group, "--cache-dir", default=None, type='path',
          help="Override the calculated chromeos cache directory; "
          "typically defaults to '$REPO/.cache' .")

  def SetupLogging(self, opts):
    value = opts.log_level.upper()
    logging.getLogger().setLevel(getattr(logging, value))
    return value

  def DoPostParseSetup(self, opts, args):
    """Method called to handle post opts/args setup.

    This can be anything from logging setup to positional arg count validation.
    Args:
      opts: optparse.Values instance
      args: position arguments unconsumed from parsing.
    Returns:
      (opts, args), w/ whatever modification done.
    """
    if self.logging_enabled:
      value = self.SetupLogging(opts)
      if self.debug_enabled:
        opts.debug = (value == "DEBUG")

    if self.caching:
      if opts.cache_dir is None:
        func = self.FindCacheDir if not callable(self.caching) else self.caching
        opts.cache_dir = func(self, opts)
      if opts.cache_dir is not None:
        self.ConfigureCacheDir(opts.cache_dir)

    return opts, args

  @staticmethod
  def ConfigureCacheDir(cache_dir):
    os.environ[constants.SHARED_CACHE_ENVVAR] = cache_dir
    logging.debug("Configured cache_dir to %r", cache_dir)

  @staticmethod
  def FindCacheDir(_parser, _opts):
    path = os.environ.get(constants.SHARED_CACHE_ENVVAR)
    if path is not None:
      return os.path.abspath(path)

    debug_msg = 'Cache dir lookup: looking for %s checkout root.'
    logging.debug(debug_msg, 'repo')
    path = git.FindRepoCheckoutRoot(os.getcwd())
    path = os.path.join(path, '.cache') if path else path
    if path is None:
      logging.debug(debug_msg, 'gclient')
      path = gclient.FindGclientCheckoutRoot(os.getcwd())
      path = os.path.join(path, '.cros_cache') if path else path
    if path is None:
      path = os.path.join(tempfile.gettempdir(), 'chromeos-cache')

    return path

  def add_option_group(self, *args, **kwargs):
    """Returns a new option group see optparse.OptionParser.add_option_group."""
    raise NotImplementedError('Subclass must override this method')

  @staticmethod
  def add_option_to_group(group, *args, **kwargs):
    """Adds the given option defined by args and kwargs to group."""
    group.add_option(*args, **kwargs)


class OptionParser(optparse.OptionParser, BaseParser):
  """Custom parser adding our custom option class in.

  Aside from adding a couple of types (path for absolute paths,
  gs_path for google storage urls, and log_level for logging level control),
  this additionally exposes logging control by default; if undesired,
  either derive from this class setting ALLOW_LOGGING to False, or
  pass in logging=False to the constructor.
  """

  DEFAULT_OPTION_CLASS = Option

  def __init__(self, usage=None, **kwargs):
    BaseParser.__init__(self, **kwargs)
    self.PopUsedArgs(kwargs)
    kwargs.setdefault("option_class", self.DEFAULT_OPTION_CLASS)
    optparse.OptionParser.__init__(self, usage=usage, **kwargs)
    self.SetupOptions()

  def parse_args(self, args=None, values=None):
    opts, remaining = optparse.OptionParser.parse_args(
        self, args=args, values=values)
    return self.DoPostParseSetup(opts, remaining)


PassedOption = collections.namedtuple(
        'PassedOption', ['opt_inst', 'opt_str', 'value_str'])


class FilteringParser(OptionParser):

  DEFAULT_OPTION_CLASS = FilteringOption

  def parse_args(self, args=None, values=None):
    if values is None:
      values = self.get_default_values()
    values.parsed_args = []

    return OptionParser.parse_args(self, args=args, values=values)

  def AddParsedArg(self, opt_inst, opt_str, value_str):
    """Add a parsed argument with attributes.

    Arguments:
      opt_inst: An instance of a raw optparse.Option object that represents the
                option.
      opt_str: The option string.
      value_str: A list of string-ified values dentified by OptParse.
    """
    self.values.parsed_args.append(PassedOption(opt_inst, opt_str, value_str))

  @staticmethod
  def FilterArgs(parsed_args, filter_fn):
    """Filter the argument by passing it through a function.

    Arguments:
      parsed_args:  The list of parsed argument namedtuples to filter.  Tuples
        are of the form (opt_inst, opt_str, value_str).
      filter_fn: A function with signature f(PassedOption), and returns True if
        the argument is to be passed through.  False if not.

     Returns:
       A tuple containing two lists - one of accepted arguments and one of
       removed arguments.
    """
    removed = []
    accepted = []
    for arg in parsed_args:
      target = accepted if filter_fn(arg) else removed
      target.append(arg.opt_str)
      target.extend(arg.value_str)

    return accepted, removed


# pylint: disable=R0901
class ArgumentParser(BaseParser, argparse.ArgumentParser):
  """Custom argument parser for use by chromite.

  This class additionally exposes logging control by default; if undesired,
  either derive from this class setting ALLOW_LOGGING to False, or
  pass in logging=False to the constructor.
  """
  # pylint: disable=W0231
  def __init__(self, usage=None, **kwargs):
    BaseParser.__init__(self, **kwargs)
    self.PopUsedArgs(kwargs)
    argparse.ArgumentParser.__init__(self, usage=usage, **kwargs)
    self._SetupTypes()
    self.SetupOptions()

  def _SetupTypes(self):
    """Register types with ArgumentParser."""
    for t, check_f in VALID_TYPES.iteritems():
      self.register('type', t, check_f)

  def add_option_group(self, *args, **kwargs):
    """Return an argument group rather than an option group."""
    return self.add_argument_group(*args, **kwargs)

  @staticmethod
  def add_option_to_group(group, *args, **kwargs):
    """Adds an argument rather than an option to the given group."""
    return group.add_argument(*args, **kwargs)

  def parse_args(self, args=None, namespace=None):
    """Translates OptionParser call to equivalent ArgumentParser call."""
    # Unlike OptionParser, ArgParser works only with a single namespace and no
    # args. Re-use BaseParser DoPostParseSetup but only take the namespace.
    namespace = argparse.ArgumentParser.parse_args(
        self, args=args, namespace=namespace)
    return self.DoPostParseSetup(namespace, None)[0]


class _ShutDownException(SystemExit):

  def __init__(self, sig_num, message):
    self.signal = sig_num
    # Setup a usage message primarily for any code that may intercept it
    # while this exception is crashing back up the stack to us.
    SystemExit.__init__(self, message)
    self.args = (sig_num, message)


def _DefaultHandler(signum, _frame):
  # Don't double process sigterms; just trigger shutdown from the first
  # exception.
  signal.signal(signum, signal.SIG_IGN)
  raise _ShutDownException(
      signum, "Received signal %i; shutting down" % (signum,))


def ScriptWrapperMain(find_target_func, argv=None,
                      log_level=logging.DEBUG,
                      log_format=constants.LOGGER_FMT):
  """Function usable for chromite.script.* style wrapping.

  Note that this function invokes sys.exit on the way out by default.

  Args:
    find_target_func: a function, which, when given the absolute
      pathway the script was invoked via (for example,
      /home/ferringb/cros/trunk/chromite/bin/cros_sdk; note that any
      trailing .py from the path name will be removed),
      will return the main function to invoke (that functor will take
      a single arg- a list of arguments, and shall return either None
      or an integer, to indicate the exit code).
    argv: sys.argv, or an equivalent tuple for testing.  If nothing is
      given, sys.argv is defaulted to.
    log_level: Default logging level to start at.
    log_format: Default logging format to use.
  """
  if argv is None:
    argv = sys.argv[:]
  target = os.path.abspath(argv[0])
  name = os.path.basename(target)
  if target.endswith('.py'):
    target = os.path.splitext(target)[0]
  target = find_target_func(target)
  if target is None:
    print >> sys.stderr, ("Internal error detected- no main "
                          "functor found in module %r." % (name,))
    sys.exit(100)

  # Set up basic logging information for all modules that use logging.
  # Note a script target may setup default logging in its module namespace
  # which will take precedence over this.
  logging.basicConfig(
      level=log_level,
      format=log_format,
      datefmt=constants.LOGGER_DATE_FMT)

  signal.signal(signal.SIGTERM, _DefaultHandler)

  ret = 1
  try:
    ret = target(argv[1:])
  except _ShutDownException, e:
    sys.stdout.flush()
    print >> sys.stderr, ("%s: Signaled to shutdown: caught %i signal." %
                          (name, e.signal,))
    sys.stderr.flush()
  except SystemExit, e:
    # Right now, let this crash through- longer term, we'll update the scripts
    # in question to not use sys.exit, and make this into a flagged error.
    raise
  except Exception, e:
    sys.stdout.flush()
    print >> sys.stderr, ("%s: Unhandled exception:" % (name,))
    sys.stderr.flush()
    raise
  finally:
    logging.shutdown()

  if ret is None:
    ret = 0
  sys.exit(ret)