platypush/platypush/procedure/__init__.py

import enum
import logging
import re
from functools import wraps

from queue import LifoQueue

from ..common import exec_wrapper
from ..config import Config
from ..message.request import Request
from ..message.response import Response

logger = logging.getLogger('platypush')


class Statement(enum.Enum):
    BREAK = 'break'
    CONTINUE = 'continue'
    RETURN = 'return'


class Procedure(object):
    """ Procedure class. A procedure is a pre-configured list of requests """

    def __init__(self, name, _async, requests, args=None, backend=None):
        """
        Params:
            name     -- Procedure name
            _async    -- Whether the actions in the procedure are supposed to
                        be executed sequentially or in parallel (True or False)
            requests -- List of platypush.message.request.Request objects
        """

        self.name = name
        self._async = _async
        self.requests = requests
        self.backend = backend
        self.args = args or {}
        self._should_return = False

        for req in requests:
            req.backend = self.backend

    @classmethod
    def build(cls, name, _async, requests, args=None, backend=None, id=None, procedure_class=None, **kwargs):
        reqs = []
        for_count = 0
        while_count = 0
        if_count = 0
        if_config = LifoQueue()
        procedure_class = procedure_class or cls
        key = None

        for request_config in requests:
            # Check if it's a break/continue/return statement
            if isinstance(request_config, str):
                reqs.append(Statement(request_config))
                continue

            # Check if this request is an if-else
            if len(request_config.keys()) >= 1:
                key = list(request_config.keys())[0]
                m = re.match(r'\s*(if)\s+\${(.*)}\s*', key)

                if m:
                    if_count += 1
                    if_name = '{}__if_{}'.format(name, if_count)
                    condition = m.group(2)

                    if_config.put({
                        'name': if_name,
                        '_async': False,
                        'requests': request_config[key],
                        'condition': condition,
                        'else_branch': [],
                        'backend': backend,
                        'id': id,
                    })

                    continue

                if key == 'else':
                    if if_config.empty():
                        raise RuntimeError('else statement with no ' +
                                           'associated if in {}'.format(name))

                    conf = if_config.get()
                    conf['else_branch'] = request_config[key]
                    if_config.put(conf)

            if not if_config.empty():
                reqs.append(IfProcedure.build(**(if_config.get())))
                if key == 'else':
                    continue

            # Check if this request is a for loop
            if len(request_config.keys()) == 1:
                key = list(request_config.keys())[0]
                m = re.match(r'\s*(fork?)\s+([\w\d_]+)\s+in\s+(.*)\s*', key)

                if m:
                    for_count += 1
                    loop_name = '{}__for_{}'.format(name, for_count)

                    # A 'for' loop is synchronous. Declare a 'fork' loop if you
                    # want to process the elements in the iterable in parallel
                    _async = True if m.group(1) == 'fork' else False
                    iterator_name = m.group(2)
                    iterable = m.group(3)

                    loop = ForProcedure.build(name=loop_name, _async=_async,
                                              requests=request_config[key],
                                              backend=backend, id=id,
                                              iterator_name=iterator_name,
                                              iterable=iterable)

                    reqs.append(loop)
                    continue

            # Check if this request is a while loop
            if len(request_config.keys()) == 1:
                key = list(request_config.keys())[0]
                m = re.match(r'\s*while\s+\${(.*)}\s*', key)

                if m:
                    while_count += 1
                    loop_name = '{}__while_{}'.format(name, while_count)
                    condition = m.group(1).strip()

                    loop = WhileProcedure.build(name=loop_name, _async=False,
                                                requests=request_config[key],
                                                condition=condition,
                                                backend=backend, id=id)

                    reqs.append(loop)
                    continue

            request_config['origin'] = Config.get('device_id')
            request_config['id'] = id
            if 'target' not in request_config:
                request_config['target'] = request_config['origin']

            request = Request.build(request_config)
            reqs.append(request)

        while not if_config.empty():
            pending_if = if_config.get()
            reqs.append(IfProcedure.build(**pending_if))

        # noinspection PyArgumentList
        return procedure_class(name=name, _async=_async, requests=reqs, args=args, backend=backend, **kwargs)

    @staticmethod
    def _find_nearest_loop(stack):
        for proc in stack[::-1]:
            if isinstance(proc, LoopProcedure):
                return proc

        raise AssertionError('break/continue statement found outside of a loop')

    def execute(self, n_tries=1, __stack__=None, **context):
        """
        Execute the requests in the procedure
        Params:
            n_tries -- Number of tries in case of failure before raising a RuntimeError
        """
        if not __stack__:
            __stack__ = [self]
        else:
            __stack__.append(self)

        if self.args:
            args = self.args.copy()
            for k, v in args.items():
                v = Request.expand_value_from_context(v, **context)
                args[k] = v
                context[k] = v
            logger.info('Executing procedure {} with arguments {}'.format(self.name, args))
        else:
            logger.info('Executing procedure {}'.format(self.name))

        response = Response()
        token = Config.get('token')

        for request in self.requests:
            if callable(request):
                response = request(**context)
                continue

            if isinstance(request, Statement):
                if request == Statement.RETURN:
                    self._should_return = True
                    for proc in __stack__:
                        proc._should_return = True
                    break

                if request in [Statement.BREAK, Statement.CONTINUE]:
                    loop = self._find_nearest_loop(__stack__)
                    if request == Statement.BREAK:
                        loop._should_break = True
                    else:
                        loop._should_continue = True
                    break

            if isinstance(self, LoopProcedure):
                if self._should_continue or self._should_break:
                    if self._should_continue:
                        # noinspection PyAttributeOutsideInit
                        self._should_continue = False

                    break

            if token:
                request.token = token

            context['_async'] = self._async
            context['n_tries'] = n_tries
            response = request.execute(__stack__=__stack__, **context)

            if not self._async and response:
                if isinstance(response.output, dict):
                    for k, v in response.output.items():
                        context[k] = v

                context['output'] = response.output
                context['errors'] = response.errors

            if self._should_return:
                break

        return response or Response()


class LoopProcedure(Procedure):
    """
    Base class while and for/fork loops.
    """

    def __init__(self, name, requests, _async=False, args=None, backend=None):
        super(). __init__(name=name, _async=_async, requests=requests, args=args, backend=backend)
        self._should_break = False
        self._should_continue = False


class ForProcedure(LoopProcedure):
    """
    Models a loop procedure, which expresses a construct similar to a
    for loop in a programming language. The 'for' keyword implies a synchronous
    loop, i.e. the nested actions will be executed in sequence. Use 'fork'
    instead of 'for' if you want to run the actions in parallel.

    Example::

        procedure.sync.process_results:
            - action: http.get
              args:
                  url: https://some-service/some/json/endpoint
                  # Example response: { "results": [ {"id":1, "name":"foo"}, {"id":2,"name":"bar"} ]}
            - for result in ${results}:
                - action: some.custom.action
                  args:
                      id: ${result['id']}
                      name: ${result['name']}

    """

    def __init__(self, name, iterator_name, iterable, requests, _async=False, args=None, backend=None):
        super(). __init__(name=name, _async=_async, requests=requests, args=args, backend=backend)
        self.iterator_name = iterator_name
        self.iterable = iterable

    def execute(self, _async=None, **context):
        # noinspection PyBroadException
        try:
            iterable = eval(self.iterable)
            assert hasattr(iterable, '__iter__'), 'Object of type {} is not iterable: {}'.\
                format(type(iterable), iterable)
        except:
            iterable = Request.expand_value_from_context(self.iterable, **context)

        response = Response()

        # noinspection DuplicatedCode
        for item in iterable:
            if self._should_return:
                logger.info('Returning from {}'.format(self.name))
                break

            if self._should_continue:
                self._should_continue = False
                logger.info('Continuing loop {}'.format(self.name))
                continue

            if self._should_break:
                self._should_break = False
                logger.info('Breaking loop {}'.format(self.name))
                break

            context[self.iterator_name] = item
            response = super().execute(**context)

        return response


class WhileProcedure(LoopProcedure):
    """
    Models a while loop procedure.

    Example::

        procedure.process_results:
            - action: http.get
              args:
                  url: https://some-service/some/json/endpoint
                  # Example response: {"id":1, "name":"foo"}}

            - while ${output}:
                - action: some.custom.action
                  args:
                      id: ${id}
                      name: ${name}

                - action: http.get
                  args:
                      url: https://some-service/some/json/endpoint
                      # Example response: {"id":1, "name":"foo"}}

    """

    def __init__(self, name, condition, requests, _async=False, args=None, backend=None):
        super(). __init__(name=name, _async=_async, requests=requests, args=args, backend=backend)
        self.condition = condition

    @staticmethod
    def _get_context(**context):
        for (k, v) in context.items():
            # noinspection PyBroadException
            try:
                context[k] = eval(v)
            except:
                if isinstance(v, str):
                    # noinspection PyBroadException
                    try:
                        context[k] = eval('"{}"'.format(re.sub(r'(^|[^\\])"', '\1\\"', v)))
                    except Exception as e:
                        logger.warning('Could not parse value for context variable {}={}'.format(k, v))
                        logger.warning('Context: {}'.format(context))
                        logger.exception(e)

        return context

    # noinspection DuplicatedCode,PyBroadException
    def execute(self, _async=None, **context):
        response = Response()
        context = self._get_context(**context)
        for k, v in context.items():
            try:
                exec('{}={}'.format(k, v))
            except:
                pass

        while True:
            condition_true = eval(self.condition)
            if not condition_true:
                break

            if self._should_return:
                logger.info('Returning from {}'.format(self.name))
                break

            if self._should_continue:
                self._should_continue = False
                logger.info('Continuing loop {}'.format(self.name))
                continue

            if self._should_break:
                self._should_break = False
                logger.info('Breaking loop {}'.format(self.name))
                break

            response = super().execute(**context)

            if response.output:
                if isinstance(response.output, dict):
                    new_context = self._get_context(**response.output)
                    for k, v in new_context.items():
                        try:
                            exec('{}={}'.format(k, v))
                        except:
                            pass

        return response


# noinspection PyBroadException
class IfProcedure(Procedure):
    """
    Models an if-else construct.

    Example:

        procedure.sync.process_results:
            -
                action: http.get
                args:
                    url: https://some-service/some/json/endpoint
                    # Example response: { "sensors": [ {"temperature": 18 } ] }
            -
                if ${sensors['temperature'] < 20}:
                    -
                        action: shell.exec
                        args:
                            cmd: '/path/turn_on_heating.sh'
                else:
                    -
                        action: shell.exec
                        args:
                            cmd: '/path/turn_off_heating.sh'
    """

    def __init__(self, name, condition, requests, else_branch=None, args=None, backend=None, id=None, **kwargs):
        kwargs['_async'] = False
        self.condition = condition
        self.else_branch = else_branch
        reqs = []

        for req in requests:
            if isinstance(req, dict):
                req['origin'] = Config.get('device_id')
                req['id'] = id
                if 'target' not in req:
                    req['target'] = req['origin']

                req = Request.build(req)

            reqs.append(req)

        super(). __init__(name=name, requests=reqs, args=args, backend=backend, **kwargs)

    @classmethod
    def build(cls, name, condition, requests, else_branch=None, args=None, backend=None, id=None, **kwargs):
        kwargs['_async'] = False
        if else_branch:
            else_branch = super().build(name=name+'__else', requests=else_branch,
                                        args=args, backend=backend, id=id,
                                        procedure_class=Procedure, **kwargs)

        return super().build(name=name, condition=condition, requests=requests,
                             else_branch=else_branch, args=args, backend=backend, id=id,
                             **kwargs)

    def execute(self, **context):
        for (k, v) in context.items():
            try:
                exec('{}={}'.format(k, v))
            except:
                if isinstance(v, str):
                    try:
                        exec('{}="{}"'.format(k, re.sub(r'(^|[^\\])"', '\1\\"', v)))
                    except Exception as e:
                        logger.debug('Could not set context variable {}={}: {}'.format(k, v, str(e)))
                        logger.debug('Context: {}'.format(context))

        condition_true = eval(self.condition)
        response = Response()

        if condition_true:
            response = super().execute(**context)
        elif self.else_branch:
            response = self.else_branch.execute(**context)

        return response


def procedure(f):
    f.procedure = True

    @wraps(f)
    def _execute_procedure(*args, **kwargs):
        return exec_wrapper(f, *args, **kwargs)

    return _execute_procedure


# vim:sw=4:ts=4:et: