platypush/platypush/procedure/__init__.py

import logging
import re

from queue import LifoQueue
from ..config import Config
from ..message.request import Request
from ..message.response import Response

logger = logging.getLogger(__name__)


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 platylist.message.request.Request objects
        """

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

        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 = []
        loop_count = 0
        if_count = 0
        if_config = LifoQueue()
        procedure_class = procedure_class or cls

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

                if m:
                    loop_count += 1
                    loop_name = '{}__loop_{}'.format(name, loop_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 = LoopProcedure.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 an if-else
            if len(request_config.keys()) >= 1:
                key = list(request_config.keys())[0]
                m = re.match('\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

            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)

        for pending_if in if_config.queue:
            reqs.append(IfProcedure.build(**pending_if))

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


    def execute(self, n_tries=1, **context):
        """
        Execute the requests in the procedure
        Params:
            n_tries -- Number of tries in case of failure before raising a RuntimeError
        """
        if self.args:
            logger.info('Executing procedure {} with arguments {}'.format(self.name, self.args))
            for (k,v) in self.args.items():
                context[k] = v
        else:
            logger.info('Executing procedure {}'.format(self.name))

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

        for request in self.requests:
            if token:
                request.token = token

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

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

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

        return response


class LoopProcedure(Procedure):
    """
    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']}
    """

    context = {}

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

        self.iterator_name = iterator_name
        self.iterable = iterable
        self.requests = requests


    def execute(self, _async=None, **context):
        iterable = Request.expand_value_from_context(self.iterable, **context)
        response = Response()

        for item in iterable:
            context[self.iterator_name] = item
            response = super().execute(**context)

        return response


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'
    """

    context = {}

    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('(^|[^\\\])"', '\1\\"', v)))
                    except:
                        pass

        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


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