# cython: infer_types=True, cdivision=True, boundscheck=False
from __future__ import print_function
from cymem.cymem cimport Pool
cimport numpy as np
from itertools import islice
from libcpp.vector cimport vector
from libc.string cimport memset
from libc.stdlib cimport calloc, free

import srsly

from ._parser_internals.stateclass cimport StateClass
from ..ml.parser_model cimport alloc_activations, free_activations
from ..ml.parser_model cimport predict_states, arg_max_if_valid
from ..ml.parser_model cimport WeightsC, ActivationsC, SizesC, cpu_log_loss
from ..ml.parser_model cimport get_c_weights, get_c_sizes

from ..tokens.doc cimport Doc
from ..errors import Errors, Warnings
from .. import util
from ..util import create_default_optimizer

from thinc.api import set_dropout_rate
import numpy.random
import numpy
import warnings


cdef class Parser(Pipe):
    """
    Base class of the DependencyParser and EntityRecognizer.
    """

    def __init__(
        self,
        Vocab vocab,
        model,
        name="base_parser",
        moves=None,
        *,
        update_with_oracle_cut_size,
        multitasks=tuple(),
        min_action_freq,
        learn_tokens,
    ):
        """Create a Parser.

        vocab (Vocab): The vocabulary object. Must be shared with documents
            to be processed. The value is set to the `.vocab` attribute.
        **cfg: Configuration parameters. Set to the `.cfg` attribute.
             If it doesn't include a value for 'moves',  a new instance is
             created with `self.TransitionSystem()`. This defines how the
             parse-state is created, updated and evaluated.
        """
        self.vocab = vocab
        self.name = name
        cfg = {
            "moves": moves,
            "update_with_oracle_cut_size": update_with_oracle_cut_size,
            "multitasks": list(multitasks),
            "min_action_freq": min_action_freq,
            "learn_tokens": learn_tokens
        }
        if moves is None:
            # defined by EntityRecognizer as a BiluoPushDown
            moves = self.TransitionSystem(self.vocab.strings)
        self.moves = moves
        self.model = model
        if self.moves.n_moves != 0:
            self.set_output(self.moves.n_moves)
        self.cfg = cfg
        self._multitasks = []
        for multitask in cfg["multitasks"]:
            self.add_multitask_objective(multitask)

        self._rehearsal_model = None

    def __getnewargs_ex__(self):
        """This allows pickling the Parser and its keyword-only init arguments"""
        args = (self.vocab, self.model, self.name, self.moves)
        return args, self.cfg

    @property
    def move_names(self):
        names = []
        for i in range(self.moves.n_moves):
            name = self.moves.move_name(self.moves.c[i].move, self.moves.c[i].label)
            # Explicitly removing the internal "U-" token used for blocking entities
            if name != "U-":
                names.append(name)
        return names

    @property
    def labels(self):
        class_names = [self.moves.get_class_name(i) for i in range(self.moves.n_moves)]
        return class_names

    @property
    def tok2vec(self):
        """Return the embedding and convolutional layer of the model."""
        return self.model.get_ref("tok2vec")

    @property
    def postprocesses(self):
        # Available for subclasses, e.g. to deprojectivize
        return []

    def add_label(self, label):
        resized = False
        for action in self.moves.action_types:
            added = self.moves.add_action(action, label)
            if added:
                resized = True
        if resized:
            self._resize()
            return 1
        return 0

    def _resize(self):
        self.model.attrs["resize_output"](self.model, self.moves.n_moves)
        if self._rehearsal_model not in (True, False, None):
            self._rehearsal_model.attrs["resize_output"](
                self._rehearsal_model, self.moves.n_moves
            )

    def add_multitask_objective(self, target):
        # Defined in subclasses, to avoid circular import
        raise NotImplementedError

    def init_multitask_objectives(self, get_examples, pipeline, **cfg):
        """Setup models for secondary objectives, to benefit from multi-task
        learning. This method is intended to be overridden by subclasses.

        For instance, the dependency parser can benefit from sharing
        an input representation with a label prediction model. These auxiliary
        models are discarded after training.
        """
        pass

    def use_params(self, params):
        # Can't decorate cdef class :(. Workaround.
        with self.model.use_params(params):
            yield

    def __call__(self, Doc doc):
        """Apply the parser or entity recognizer, setting the annotations onto
        the `Doc` object.

        doc (Doc): The document to be processed.
        """
        states = self.predict([doc])
        self.set_annotations([doc], states)
        return doc

    def pipe(self, docs, *, int batch_size=256):
        """Process a stream of documents.

        stream: The sequence of documents to process.
        batch_size (int): Number of documents to accumulate into a working set.
        YIELDS (Doc): Documents, in order.
        """
        cdef Doc doc
        for batch in util.minibatch(docs, size=batch_size):
            batch_in_order = list(batch)
            by_length = sorted(batch, key=lambda doc: len(doc))
            for subbatch in util.minibatch(by_length, size=max(batch_size//4, 2)):
                subbatch = list(subbatch)
                parse_states = self.predict(subbatch)
                self.set_annotations(subbatch, parse_states)
            yield from batch_in_order

    def predict(self, docs):
        if isinstance(docs, Doc):
            docs = [docs]
        if not any(len(doc) for doc in docs):
            result = self.moves.init_batch(docs)
            self._resize()
            return result
        return self.greedy_parse(docs, drop=0.0)

    def greedy_parse(self, docs, drop=0.):
        cdef vector[StateC*] states
        cdef StateClass state
        set_dropout_rate(self.model, drop)
        batch = self.moves.init_batch(docs)
        # This is pretty dirty, but the NER can resize itself in init_batch,
        # if labels are missing. We therefore have to check whether we need to
        # expand our model output.
        self._resize()
        model = self.model.predict(docs)
        weights = get_c_weights(model)
        for state in batch:
            if not state.is_final():
                states.push_back(state.c)
        sizes = get_c_sizes(model, states.size())
        with nogil:
            self._parseC(&states[0],
                weights, sizes)
        model.clear_memory()
        del model
        return batch

    cdef void _parseC(self, StateC** states,
            WeightsC weights, SizesC sizes) nogil:
        cdef int i, j
        cdef vector[StateC*] unfinished
        cdef ActivationsC activations = alloc_activations(sizes)
        while sizes.states >= 1:
            predict_states(&activations,
                states, &weights, sizes)
            # Validate actions, argmax, take action.
            self.c_transition_batch(states,
                activations.scores, sizes.classes, sizes.states)
            for i in range(sizes.states):
                if not states[i].is_final():
                    unfinished.push_back(states[i])
            for i in range(unfinished.size()):
                states[i] = unfinished[i]
            sizes.states = unfinished.size()
            unfinished.clear()
        free_activations(&activations)

    def set_annotations(self, docs, states):
        cdef StateClass state
        cdef Doc doc
        for i, (state, doc) in enumerate(zip(states, docs)):
            self.moves.finalize_state(state.c)
            for j in range(doc.length):
                doc.c[j] = state.c._sent[j]
            self.moves.finalize_doc(doc)
            for hook in self.postprocesses:
                hook(doc)

    def transition_states(self, states, float[:, ::1] scores):
        cdef StateClass state
        cdef float* c_scores = &scores[0, 0]
        cdef vector[StateC*] c_states
        for state in states:
            c_states.push_back(state.c)
        self.c_transition_batch(&c_states[0], c_scores, scores.shape[1], scores.shape[0])
        return [state for state in states if not state.c.is_final()]

    cdef void c_transition_batch(self, StateC** states, const float* scores,
            int nr_class, int batch_size) nogil:
        # n_moves should not be zero at this point, but make sure to avoid zero-length mem alloc
        with gil:
            assert self.moves.n_moves > 0
        is_valid = <int*>calloc(self.moves.n_moves, sizeof(int))
        cdef int i, guess
        cdef Transition action
        for i in range(batch_size):
            self.moves.set_valid(is_valid, states[i])
            guess = arg_max_if_valid(&scores[i*nr_class], is_valid, nr_class)
            if guess == -1:
                # This shouldn't happen, but it's hard to raise an error here,
                # and we don't want to infinite loop. So, force to end state.
                states[i].force_final()
            else:
                action = self.moves.c[guess]
                action.do(states[i], action.label)
                states[i].push_hist(guess)
        free(is_valid)

    def update(self, examples, *, drop=0., set_annotations=False, sgd=None, losses=None):
        cdef StateClass state
        if losses is None:
            losses = {}
        losses.setdefault(self.name, 0.)
        for multitask in self._multitasks:
            multitask.update(examples, drop=drop, sgd=sgd)
        n_examples = len([eg for eg in examples if self.moves.has_gold(eg)])
        if n_examples == 0:
            return losses
        set_dropout_rate(self.model, drop)
        # Prepare the stepwise model, and get the callback for finishing the batch
        model, backprop_tok2vec = self.model.begin_update(
            [eg.predicted for eg in examples])
        if self.cfg["update_with_oracle_cut_size"] >= 1:
            # Chop sequences into lengths of this many transitions, to make the
            # batch uniform length.
            # We used to randomize this, but it's not clear that actually helps?
            cut_size = self.cfg["update_with_oracle_cut_size"]
            states, golds, max_steps = self._init_gold_batch(
                examples,
                max_length=cut_size
            )
        else:
            states, golds, _ = self.moves.init_gold_batch(examples)
            max_steps = max([len(eg.x) for eg in examples])
        if not states:
            return losses
        all_states = list(states)
        states_golds = list(zip(states, golds))
        while states_golds:
            states, golds = zip(*states_golds)
            scores, backprop = model.begin_update(states)
            d_scores = self.get_batch_loss(states, golds, scores, losses)
            # Note that the gradient isn't normalized by the batch size
            # here, because our "samples" are really the states...But we
            # can't normalize by the number of states either, as then we'd
            # be getting smaller gradients for states in long sequences.
            backprop(d_scores)
            # Follow the predicted action
            self.transition_states(states, scores)
            states_golds = [(s, g) for (s, g) in zip(states, golds) if not s.is_final()]

        backprop_tok2vec(golds)
        if sgd not in (None, False):
            self.model.finish_update(sgd)
        if set_annotations:
            docs = [eg.predicted for eg in examples]
            self.set_annotations(docs, all_states)
        # Ugh, this is annoying. If we're working on GPU, we want to free the
        # memory ASAP. It seems that Python doesn't necessarily get around to
        # removing these in time if we don't explicitly delete? It's confusing.
        del backprop
        del backprop_tok2vec
        model.clear_memory()
        del model
        return losses

    def rehearse(self, examples, sgd=None, losses=None, **cfg):
        """Perform a "rehearsal" update, to prevent catastrophic forgetting."""
        if losses is None:
            losses = {}
        for multitask in self._multitasks:
            if hasattr(multitask, 'rehearse'):
                multitask.rehearse(examples, losses=losses, sgd=sgd)
        if self._rehearsal_model is None:
            return None
        losses.setdefault(self.name, 0.)

        docs = [eg.predicted for eg in examples]
        states = self.moves.init_batch(docs)
        # This is pretty dirty, but the NER can resize itself in init_batch,
        # if labels are missing. We therefore have to check whether we need to
        # expand our model output.
        self._resize()
        # Prepare the stepwise model, and get the callback for finishing the batch
        set_dropout_rate(self._rehearsal_model, 0.0)
        set_dropout_rate(self.model, 0.0)
        tutor, _ = self._rehearsal_model.begin_update(docs)
        model, backprop_tok2vec = self.model.begin_update(docs)
        n_scores = 0.
        loss = 0.
        while states:
            targets, _ = tutor.begin_update(states)
            guesses, backprop = model.begin_update(states)
            d_scores = (guesses - targets) / targets.shape[0]
            # If all weights for an output are 0 in the original model, don't
            # supervise that output. This allows us to add classes.
            loss += (d_scores**2).sum()
            backprop(d_scores, sgd=sgd)
            # Follow the predicted action
            self.transition_states(states, guesses)
            states = [state for state in states if not state.is_final()]
            n_scores += d_scores.size
        # Do the backprop
        backprop_tok2vec(docs)
        if sgd is not None:
            self.model.finish_update(sgd)
        losses[self.name] += loss / n_scores
        del backprop
        del backprop_tok2vec
        model.clear_memory()
        tutor.clear_memory()
        del model
        del tutor
        return losses

    def get_batch_loss(self, states, golds, float[:, ::1] scores, losses):
        cdef StateClass state
        cdef Pool mem = Pool()
        cdef int i

        # n_moves should not be zero at this point, but make sure to avoid zero-length mem alloc
        assert self.moves.n_moves > 0

        is_valid = <int*>mem.alloc(self.moves.n_moves, sizeof(int))
        costs = <float*>mem.alloc(self.moves.n_moves, sizeof(float))
        cdef np.ndarray d_scores = numpy.zeros((len(states), self.moves.n_moves),
                                        dtype='f', order='C')
        c_d_scores = <float*>d_scores.data
        unseen_classes = self.model.attrs["unseen_classes"]
        for i, (state, gold) in enumerate(zip(states, golds)):
            memset(is_valid, 0, self.moves.n_moves * sizeof(int))
            memset(costs, 0, self.moves.n_moves * sizeof(float))
            self.moves.set_costs(is_valid, costs, state, gold)
            for j in range(self.moves.n_moves):
                if costs[j] <= 0.0 and j in unseen_classes:
                    unseen_classes.remove(j)
            cpu_log_loss(c_d_scores,
                costs, is_valid, &scores[i, 0], d_scores.shape[1])
            c_d_scores += d_scores.shape[1]
        # Note that we don't normalize this. See comment in update() for why.
        if losses is not None:
            losses.setdefault(self.name, 0.)
            losses[self.name] += (d_scores**2).sum()
        return d_scores

    def create_optimizer(self):
        return create_default_optimizer()

    def set_output(self, nO):
        self.model.attrs["resize_output"](self.model, nO)

    def begin_training(self, get_examples, pipeline=None, sgd=None, **kwargs):
        self.cfg.update(kwargs)
        lexeme_norms = self.vocab.lookups.get_table("lexeme_norm", {})
        if len(lexeme_norms) == 0 and self.vocab.lang in util.LEXEME_NORM_LANGS:
            langs = ", ".join(util.LEXEME_NORM_LANGS)
            warnings.warn(Warnings.W033.format(model="parser or NER", langs=langs))
        if not hasattr(get_examples, '__call__'):
            gold_tuples = get_examples
            get_examples = lambda: gold_tuples
        actions = self.moves.get_actions(
            examples=get_examples(),
            min_freq=self.cfg['min_action_freq'],
            learn_tokens=self.cfg["learn_tokens"]
        )
        for action, labels in self.moves.labels.items():
            actions.setdefault(action, {})
            for label, freq in labels.items():
                if label not in actions[action]:
                    actions[action][label] = freq
        self.moves.initialize_actions(actions)
        # make sure we resize so we have an appropriate upper layer
        self._resize()
        if sgd is None:
            sgd = self.create_optimizer()
        doc_sample = []
        for example in islice(get_examples(), 10):
            doc_sample.append(example.predicted)

        if pipeline is not None:
            for name, component in pipeline:
                if component is self:
                    break
                if hasattr(component, "pipe"):
                    doc_sample = list(component.pipe(doc_sample, batch_size=8))
                else:
                    doc_sample = [component(doc) for doc in doc_sample]
        if doc_sample:
            self.model.initialize(doc_sample)
        else:
            self.model.initialize()
        if pipeline is not None:
            self.init_multitask_objectives(get_examples, pipeline, sgd=sgd, **self.cfg)
        return sgd

    def to_disk(self, path, exclude=tuple()):
        serializers = {
            'model': lambda p: (self.model.to_disk(p) if self.model is not True else True),
            'vocab': lambda p: self.vocab.to_disk(p),
            'moves': lambda p: self.moves.to_disk(p, exclude=["strings"]),
            'cfg': lambda p: srsly.write_json(p, self.cfg)
        }
        util.to_disk(path, serializers, exclude)

    def from_disk(self, path, exclude=tuple()):
        deserializers = {
            'vocab': lambda p: self.vocab.from_disk(p),
            'moves': lambda p: self.moves.from_disk(p, exclude=["strings"]),
            'cfg': lambda p: self.cfg.update(srsly.read_json(p)),
            'model': lambda p: None,
        }
        util.from_disk(path, deserializers, exclude)
        if 'model' not in exclude:
            path = util.ensure_path(path)
            with (path / 'model').open('rb') as file_:
                bytes_data = file_.read()
            try:
                self._resize()
                self.model.from_bytes(bytes_data)
            except AttributeError:
                raise ValueError(Errors.E149) from None
        return self

    def to_bytes(self, exclude=tuple()):
        serializers = {
            "model": lambda: (self.model.to_bytes()),
            "vocab": lambda: self.vocab.to_bytes(),
            "moves": lambda: self.moves.to_bytes(exclude=["strings"]),
            "cfg": lambda: srsly.json_dumps(self.cfg, indent=2, sort_keys=True)
        }
        return util.to_bytes(serializers, exclude)

    def from_bytes(self, bytes_data, exclude=tuple()):
        deserializers = {
            "vocab": lambda b: self.vocab.from_bytes(b),
            "moves": lambda b: self.moves.from_bytes(b, exclude=["strings"]),
            "cfg": lambda b: self.cfg.update(srsly.json_loads(b)),
            "model": lambda b: None,
        }
        msg = util.from_bytes(bytes_data, deserializers, exclude)
        if 'model' not in exclude:
            if 'model' in msg:
                try:
                    self.model.from_bytes(msg['model'])
                except AttributeError:
                    raise ValueError(Errors.E149) from None
        return self

    def _init_gold_batch(self, examples, min_length=5, max_length=500):
        """Make a square batch, of length equal to the shortest transition
        sequence or a cap. A long
        doc will get multiple states. Let's say we have a doc of length 2*N,
        where N is the shortest doc. We'll make two states, one representing
        long_doc[:N], and another representing long_doc[N:]."""
        cdef:
            StateClass start_state
            StateClass state
            Transition action
        all_states = self.moves.init_batch([eg.predicted for eg in examples])
        states = []
        golds = []
        kept = []
        max_length_seen = 0
        for state, eg in zip(all_states, examples):
            if self.moves.has_gold(eg) and not state.is_final():
                gold = self.moves.init_gold(state, eg)
                if len(eg.x) < max_length:
                    states.append(state)
                    golds.append(gold)
                else:
                    oracle_actions = self.moves.get_oracle_sequence_from_state(
                        state.copy(), gold)
                    kept.append((eg, state, gold, oracle_actions))
                    min_length = min(min_length, len(oracle_actions))
                    max_length_seen = max(max_length, len(oracle_actions))
        if not kept:
            return states, golds, 0
        max_length = max(min_length, min(max_length, max_length_seen))
        cdef int clas
        max_moves = 0
        for eg, state, gold, oracle_actions in kept:
            for i in range(0, len(oracle_actions), max_length):
                start_state = state.copy()
                n_moves = 0
                for clas in oracle_actions[i:i+max_length]:
                    action = self.moves.c[clas]
                    action.do(state.c, action.label)
                    state.c.push_hist(action.clas)
                    n_moves += 1
                    if state.is_final():
                        break
                max_moves = max(max_moves, n_moves)
                if self.moves.has_gold(eg, start_state.B(0), state.B(0)):
                    states.append(start_state)
                    golds.append(gold)
                    max_moves = max(max_moves, n_moves)
                if state.is_final():
                    break
        return states, golds, max_moves