modelverse/kernel/modelverse_kernel/request_handler.py

import sys
import modelverse_kernel.primitives as primitive_functions
import modelverse_kernel.jit as jit
from collections import defaultdict

class KnownRequestHandled(Exception):
    """An exception that signifies that a known request was handled."""
    pass

class UnhandledRequestHandlerException(Exception):
    """The type of exception that is thrown when the request handler encounters an
       unhandled exception."""
    def __init__(self, inner_exception, stack_trace):
        import traceback
        Exception.__init__(
            self,
            """The request handler encountered an unknown exception.\n
               Inner exception: %s\n
            """ % (traceback.format_exc()))
        self.inner_exception = inner_exception
        self.stack_trace = stack_trace

class RequestHandler(object):
    """A type of object that intercepts logic-related Modelverse requests, and
       forwards Modelverse state requests."""
    def __init__(self):
        # generator_stack is a stack of GeneratorStackEntry values.
        self.generator_stack = []
        # exception_handlers is a stack of
        # (generator_stack index, [(exception type, handler function)])
        # tuples.
        self.produce_stack_trace = True
        self.handlers = {
            'CALL' : self.execute_call,
            'CALL_ARGS' : self.execute_call_args,
            'CALL_KWARGS' : self.execute_call_kwargs,
            'SLEEP' : self.execute_sleep,
        }

    def is_active(self):
        """Tests if this request handler has a top-of-stack generator."""
        return len(self.generator_stack) > 0

    def handle_request(self, reply):
        """Replies to a request from the top-of-stack generator, and returns a new request."""
        if not self.generator_stack:
            raise ValueError('handle_request cannot be called with an empty generator stack.')

        # Append the server's replies to the list of replies.
        if reply is not None:
            gen = self.generator_stack[-1]

            if gen["replies"]:
                gen["replies"].extend(reply)
            else:
                gen["replies"] = reply

        while 1:
            # Silence pylint's warning about catching Exception.
            # pylint: disable=I0011,W0703
            try:
                gen = self.generator_stack[-1]
                if gen["finished_requests"]:
                    gen["pending_requests"] = gen["generator"].send(gen["replies"])
                    gen["finished_requests"] = False
                    gen["replies"] = None
                return self.pop_requests()

            except KnownRequestHandled:
                pass
            except StopIteration:
                # Done, so remove the generator
                del self.generator_stack[-1]
                if self.generator_stack:
                    # This generator was called from another generator.
                    # Append 'None' to the caller's list of replies.
                    self.append_reply(None)
                else:
                    # Looks like we're done here.
                    return None
            except primitive_functions.PrimitiveFinished as ex:
                # Done, so remove the generator
                del self.generator_stack[-1]
                if self.generator_stack:
                    # This generator was called from another generator.
                    # Append the callee's result to the caller's list of replies.
                    self.append_reply(ex.result)
                else:
                    # Looks like we're done here.
                    return None

    def push_generator(self, gen):
        """Pushes a new generator onto the stack."""
        dd = defaultdict(lambda : None)
        dd["generator"] = gen
        dd["finished_requests"] = True
        self.generator_stack.append(dd)
        # print('Pushed generator %s. Generator count: %d' % (gen, len(self.generator_stack)))

    def append_reply(self, new_reply):
        """Appends a reply to the top-of-stack generator's list of pending replies."""
        if self.generator_stack[-1]["replies"] is None:
            self.generator_stack[-1]["replies"] = [new_reply]
        else:
            self.generator_stack[-1]["replies"].append(new_reply)

    def pop_requests(self):
        """Tries to pop a batch of Modelverse _state_ requests from the
           current list of requests. Known requests are executed immediately.

           A list of requests and a Boolean are returned. The latter is True
           if there are no more requests to process, and false otherwise."""
        requests = self.generator_stack[-1]["pending_requests"]
        if requests:
            if requests[0][0] in self.handlers:
                # First element is a known request
                elem = requests.pop(0)

                # The list of requests might be empty now. If so, then flag this
                # batch of requests as finished.
                if not requests:
                    self.generator_stack[-1]["finished_requests"] = True

                # Handle the request.
                self.handlers[elem[0]](elem[1])
                raise KnownRequestHandled()
            else:
                for i, elem in enumerate(requests):
                    if elem[0] in self.handlers:
                        # Handle any requests that precede the known request first.
                        pre_requests = requests[:i]
                        del requests[:i]
                        return pre_requests

        # We couldn't find a known request in the batch of requests, so we might as well
        # handle them all at once then.
        self.generator_stack[-1]["finished_requests"] = True
        return requests

    def execute_call(self, request_args):
        """Executes a CALL-request with the given argument list."""
        # Format: ("CALL", [gen])
        gen, = request_args
        self.push_generator(gen)

    def execute_call_kwargs(self, request_args):
        """Executes a CALL_KWARGS-request with the given argument list."""
        # Format: ("CALL_KWARGS", [func, kwargs])
        # This format is useful because it also works for functions that
        # throw an exception but never yield.
        func, kwargs = request_args
        # We need to be extra careful here, because func(**kwargs) might
        # not be a generator at all: it might simply be a method that
        # raises an exception. To cope with this we need to push a dummy
        # entry onto the stack if a StopIteration or PrimtiveFinished
        # exception is thrown. The logic in execute_yields will then pop
        # that dummy entry.
        try:
            self.push_generator(func(**kwargs))
        except StopIteration:
            self.push_generator(None)
            raise
        except primitive_functions.PrimitiveFinished:
            self.push_generator(None)
            raise
        except:
            print("EXCEPTION for " + str(locals()))
            raise

    def execute_call_args(self, request_args):
        """Executes a CALL_ARGS-request with the given argument list."""
        # Format: ("CALL_ARGS", [gen, args])
        func, args = request_args
        # We need to be extra careful here, because func(*args) might
        # not be a generator at all: it might simply be a method that
        # raises an exception. To cope with this we need to push a dummy
        # entry onto the stack if a StopIteration or PrimtiveFinished
        # exception is thrown. The logic in execute_yields will then pop
        # that dummy entry.
        try:
            self.push_generator(func(*args))
        except StopIteration:
            self.push_generator(None)
            raise
        except primitive_functions.PrimitiveFinished:
            self.push_generator(None)
            raise

    def execute_sleep(self, request_args):
        """Executes a SLEEP-request with the given argument list."""
        self.append_reply(None)
        raise primitive_functions.SleepKernel(request_args[0], request_args[1])