# -*- coding: utf-8 -*-
# Copyright 2018 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.

"""The build API entry point."""

from __future__ import print_function

import importlib
import os

from google.protobuf import json_format
from google.protobuf import symbol_database

from chromite.api import controller
from chromite.api.gen.chromite.api import artifacts_pb2
from chromite.api.gen.chromite.api import binhost_pb2
from chromite.api.gen.chromite.api import build_api_pb2
from chromite.api.gen.chromite.api import depgraph_pb2
from chromite.api.gen.chromite.api import image_pb2
from chromite.api.gen.chromite.api import sdk_pb2
from chromite.api.gen.chromite.api import test_pb2
from chromite.lib import commandline
from chromite.lib import cros_build_lib
from chromite.lib import osutils
from chromite.utils import matching


class Error(Exception):
  """Base error class for the module."""


class InvalidInputFileError(Error):
  """Raised when the input file cannot be read."""


class InvalidInputFormatError(Error):
  """Raised when the passed input protobuf can't be parsed."""


class InvalidOutputFileError(Error):
  """Raised when the output file cannot be written."""


# API Service Errors.
class UnknownServiceError(Error):
  """Error raised when the requested service has not been registered."""


class ControllerModuleNotDefinedError(Error):
  """Error class for when no controller is defined for a service."""


class ServiceControllerNotFoundError(Error):
  """Error raised when the service's controller cannot be imported."""


# API Method Errors.
class UnknownMethodError(Error):
  """The service is defined in the proto but the method is not."""


class MethodNotFoundError(Error):
  """The method's implementation cannot be found in the service's controller."""


def GetParser():
  """Build the argument parser."""
  parser = commandline.ArgumentParser(description=__doc__)

  parser.add_argument('service_method',
                      help='The "chromite.api.Service/Method" that is being '
                           'called.')

  parser.add_argument(
      '--input-json', type='path', required=True,
      help='Path to the JSON serialized input argument protobuf message.')
  parser.add_argument(
      '--output-json', type='path', required=True,
      help='The path to which the result protobuf message should be written.')

  return parser


def _ParseArgs(argv, router):
  """Parse and validate arguments."""
  parser = GetParser()
  opts = parser.parse_args(argv)

  methods = router.ListMethods()
  if opts.service_method not in methods:
    matched = matching.GetMostLikelyMatchedObject(methods, opts.service_method,
                                                  matched_score_threshold=0.6)
    error = 'Unrecognized service name.'
    if matched:
      error += '\nDid you mean: \n%s' % '\n'.join(matched)
    parser.error(error)

  parts = opts.service_method.split('/')

  if len(parts) != 2:
    parser.error('Must pass "Service/Method".')

  opts.service = parts[0]
  opts.method = parts[1]

  if not os.path.exists(opts.input_json):
    parser.error('Input file does not exist.')

  opts.Freeze()
  return opts


class Router(object):
  """Encapsulates the request dispatching logic."""

  def __init__(self):
    self._services = {}
    self._aliases = {}
    # All imported generated messages get added to this symbol db.
    self._sym_db = symbol_database.Default()

    extensions = build_api_pb2.DESCRIPTOR.extensions_by_name
    self._service_options = extensions['service_options']
    self._method_options = extensions['method_options']

  def Register(self, proto_module):
    """Register the services from a generated proto module.

    Args:
      proto_module (module): The generated proto module whose service is being
        registered.

    Raises:
      ServiceModuleNotDefinedError when the service cannot be found in the
        provided module.
    """
    services = proto_module.DESCRIPTOR.services_by_name
    for service_name, svc in services.items():
      module_name = svc.GetOptions().Extensions[self._service_options].module

      if not module_name:
        raise ControllerModuleNotDefinedError(
            'The module must be defined in the service definition: %s.%s' %
            (proto_module, service_name))

      self._services[svc.full_name] = (svc, module_name)

  def ListMethods(self):
    """List all methods registered with the router."""
    services = []
    for service_name, (svc, _module) in self._services.items():
      for method_name in svc.methods_by_name.keys():
        services.append('%s/%s' % (service_name, method_name))

    return sorted(services)

  def Route(self, service_name, method_name, input_path, output_path):
    """Dispatch the request.

    Args:
      service_name (str): The fully qualified service name.
      method_name (str): The name of the method being called.
      input_path (str): The path to the input message file.
      output_path (str): The path where the output message should be written.

    Returns:
      int: The return code.

    Raises:
      InvalidInputFileError when the input file cannot be read.
      InvalidOutputFileError when the output file cannot be written.
      ServiceModuleNotFoundError when the service module cannot be imported.
      MethodNotFoundError when the method cannot be retrieved from the module.
    """
    try:
      input_json = osutils.ReadFile(input_path)
    except IOError as e:
      raise InvalidInputFileError('Unable to read input file: %s' % e.message)

    try:
      svc, module_name = self._services[service_name]
    except KeyError:
      raise UnknownServiceError('The %s service has not been registered.'
                                % service_name)

    try:
      method_desc = svc.methods_by_name[method_name]
    except KeyError:
      raise UnknownMethodError('The %s method has not been defined in the %s '
                               'service.' % (method_name, service_name))

    # Parse the input file to build an instance of the input message.
    input_msg = self._sym_db.GetPrototype(method_desc.input_type)()
    try:
      json_format.Parse(input_json, input_msg, ignore_unknown_fields=True)
    except json_format.ParseError as e:
      raise InvalidInputFormatError(
          'Unable to parse the input json: %s' % e.message)

    # Get an empty output message instance.
    output_msg = self._sym_db.GetPrototype(method_desc.output_type)()

    # Allow proto-based method name override.
    method_options = method_desc.GetOptions().Extensions[self._method_options]
    if method_options.HasField('implementation_name'):
      method_name = method_options.implementation_name

    # Check the chroot assertion settings before running.
    service_options = svc.GetOptions().Extensions[self._service_options]
    self._HandleChrootAssert(service_options, method_options)

    # Import the module and get the method.
    method_impl = self._GetMethod(module_name, method_name)

    # Successfully located; call and return.
    return_code = method_impl(input_msg, output_msg)
    if return_code is None:
      return_code = 0

    try:
      osutils.WriteFile(output_path, json_format.MessageToJson(output_msg))
    except IOError as e:
      raise InvalidOutputFileError('Cannot write output file: %s' % e.message)

    return return_code

  def _HandleChrootAssert(self, service_options, method_options):
    """Check the chroot assert options and execute assertion as needed.

    Args:
      service_options (google.protobuf.Message): The service options.
      method_options (google.protobuf.Message): The method options.
    """
    chroot_assert = build_api_pb2.NO_ASSERTION
    if method_options.HasField('method_chroot_assert'):
      # Prefer the method option when set.
      chroot_assert = method_options.method_chroot_assert
    elif service_options.HasField('service_chroot_assert'):
      # Fall back to the service option.
      chroot_assert = service_options.service_chroot_assert

    # Execute appropriate assertion if set.
    if chroot_assert == build_api_pb2.INSIDE:
      cros_build_lib.AssertInsideChroot()
    elif chroot_assert == build_api_pb2.OUTSIDE:
      cros_build_lib.AssertOutsideChroot()

  def _GetMethod(self, module_name, method_name):
    """Get the implementation of the method for the service module.

    Args:
      module_name (str): The name of the service module.
      method_name (str): The name of the method.

    Returns:
      callable - The method.

    Raises:
      MethodNotFoundError when the method cannot be found in the module.
      ServiceModuleNotFoundError when the service module cannot be imported.
    """
    try:
      module = importlib.import_module(controller.IMPORT_PATTERN % module_name)
    except ImportError as e:
      raise ServiceControllerNotFoundError(e.message)
    try:
      return getattr(module, method_name)
    except AttributeError as e:
      raise MethodNotFoundError(e.message)


def RegisterServices(router):
  """Register all the services.

  Args:
    router (Router): The router.
  """
  router.Register(artifacts_pb2)
  router.Register(binhost_pb2)
  router.Register(depgraph_pb2)
  router.Register(image_pb2)
  router.Register(sdk_pb2)
  router.Register(test_pb2)


def main(argv):
  router = Router()
  RegisterServices(router)

  opts = _ParseArgs(argv, router)

  try:
    return router.Route(opts.service, opts.method, opts.input_json,
                        opts.output_json)
  except Error as e:
    # Error derivatives are handled nicely, but let anything else bubble up.
    cros_build_lib.Die(e.message)