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# Parallel processing
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import cPickle
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import itertools
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import Queue
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import rand
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import types
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import warnings
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import collection
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import dicts
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import exc
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from Runnable import Runnable
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def try_pickle(value):
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    try: cPickle.dumps(value)
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    except Exception, e:
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        exc.add_msg(e, 'Tried to pickle: '+repr(value))
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        raise
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def prepickle(value, vars_id_dict_):
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    def filter_(value, is_leaf):
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        id_ = id(value)
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        if id_ in vars_id_dict_: value = id_
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        # Try pickling the value. If it fails, we'll get a full traceback here,
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        # which is not provided with pickling errors in multiprocessing's Pool.
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        elif is_leaf: try_pickle(value)
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        return value
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    return collection.rmap(filter_, value)
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def post_unpickle(value, vars_id_dict_):
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    def filter_(value, is_leaf):
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        if type(value) == int: value = vars_id_dict_.get(value, value)
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            # get() returns the value itself if it isn't a known id()
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        return value
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    return collection.rmap(filter_, value)
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class SyncPool:
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    '''A dummy synchronous Pool to use if multiprocessing is not available'''
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    def __init__(self, processes=None): pass
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    class Result:
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        def __init__(self, value): self.value = value
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        def get(timeout=None): return self.value
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        def wait(timeout=None): pass
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        def ready(): return True
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        def successful(): return True # TODO: False if raised exception
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    def apply_async(self, func, args=(), kw_args={}, callback=None):
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        if callback == None: callback = lambda v: None
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        value = func(*args, **kw_args)
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        callback(value)
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        return self.Result(value)
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class MultiProducerPool:
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    '''A multi-producer pool. You must call pool.main_loop() in the thread that
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    created this to process new tasks.'''
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    def __init__(self, processes=None, locals_={}, *shared):
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        '''
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        @param processes If 0, uses SyncPool
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        @post The # processes actually used is made available in self.process_ct
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        '''
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        try:
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            if processes == 0: raise ImportError('turned off')
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            import multiprocessing
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            import multiprocessing.pool
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        except ImportError, e:
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            warnings.warn(UserWarning('Not using parallel processing: '+str(e)))
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            processes = 1
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            Pool_ = SyncPool
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            Queue_ = Queue.Queue
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        else:
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            if processes == None: processes = multiprocessing.cpu_count()
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            Pool_ = multiprocessing.pool.Pool
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            Queue_ = multiprocessing.Queue
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        self.process_ct = processes
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        self.pool = Pool_(processes)
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        self.queue = Queue_()
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        self.active_tasks = 0
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        # Store a reference to the manager in self, because it will otherwise be
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        # shutdown right away when it goes out of scope
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        #self.manager = processing.Manager()
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        #self.shared_rw = self.manager.Namespace()
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        # Values that may be pickled by id()
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        self.vars_id_dict = dicts.IdDict()
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        self.share(self, *shared).share_vars(locals_).share_vars(globals())
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    def share(self, *values):
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        '''Call this on all values that should be shared writably between all
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        processes (and be pickled by id())'''
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        self.vars_id_dict.add(*values)
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        return self
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    def share_vars(self, vars_):
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        '''Call this on all vars that should be pickled by id().
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        Usage: self.share_vars(locals())
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        @param vars_ {var_name: value}
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        '''
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        self.vars_id_dict.add_vars(vars_)
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        return self
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    def main_loop(self):
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        '''Prime the task queue with at least one task before calling this''' 
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        while True:
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            try: call = self.queue.get(timeout=0.1) # sec
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            except Queue.Empty:
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                if self.active_tasks == 0: break # program done
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                else: continue
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            def handle_result(*args, **kw_args):
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                self.active_tasks -= 1
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                if call.callback != None: call.callback(*args, **kw_args)
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            self.active_tasks += 1
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            self.pool.apply_async(call.func, self.post_unpickle(call.args),
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                self.post_unpickle(call.kw_args), handle_result)
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    class Result:
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        def get(timeout=None): raise NotImplementedError()
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        def wait(timeout=None): raise NotImplementedError()
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        def ready(): raise NotImplementedError()
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        def successful(): raise NotImplementedError()
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    def apply_async(self, func, args=(), kw_args={}, callback=None):
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        assert callback == None, 'Callbacks not supported'
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        call = Runnable(func, *self.prepickle(args), **self.prepickle(kw_args))
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        call.callback = callback # store this inside the Runnable
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        self.queue.put_nowait(call)
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        return self.Result()
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    def prepickle(self, value): return prepickle(value, self.vars_id_dict)
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    def post_unpickle(self, value):
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        return post_unpickle(value, self.vars_id_dict)
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