from __future__ import absolute_import
from __future__ import division
from __future__ import print_function

import inspect
import logging
import numpy as np
# use cloudpickle instead of pickle to make lambda funcs
# in dragonfly pickleable
from ray import cloudpickle
from typing import Dict, List, Optional, Union

from ray.tune.result import DEFAULT_METRIC
from ray.tune.sample import Domain, Float, Quantized
from ray.tune.suggest.suggestion import UNRESOLVED_SEARCH_SPACE, \
    UNDEFINED_METRIC_MODE, UNDEFINED_SEARCH_SPACE
from ray.tune.suggest.variant_generator import parse_spec_vars
from ray.tune.utils.util import flatten_dict, is_nan_or_inf, unflatten_dict

try:  # Python 3 only -- needed for lint test.
    import dragonfly
    from dragonfly.opt.blackbox_optimiser import BlackboxOptimiser
except ImportError:
    dragonfly = None
    BlackboxOptimiser = None

from ray.tune.suggest.suggestion import Searcher

logger = logging.getLogger(__name__)


class DragonflySearch(Searcher):
    """Uses Dragonfly to optimize hyperparameters.

    Dragonfly provides an array of tools to scale up Bayesian optimisation to
    expensive large scale problems, including high dimensional optimisation.
    parallel evaluations in synchronous or asynchronous settings,
    multi-fidelity optimisation (using cheap approximations to speed up the
    optimisation process), and multi-objective optimisation. For more info:

    * Dragonfly Website: https://github.com/dragonfly/dragonfly
    * Dragonfly Documentation: https://dragonfly-opt.readthedocs.io/

    To use this search algorithm, install Dragonfly:

    .. code-block:: bash

        $ pip install dragonfly-opt


    This interface requires using FunctionCallers and optimizers provided by
    Dragonfly.

    This searcher will automatically filter out any NaN, inf or -inf
    results.

    Parameters:
        optimizer (dragonfly.opt.BlackboxOptimiser|str): Optimizer provided
            from dragonfly. Choose an optimiser that extends BlackboxOptimiser.
            If this is a string, `domain` must be set and `optimizer` must be
            one of [random, bandit, genetic].
        domain (str): Optional domain. Should only be set if you don't pass
            an optimizer as the `optimizer` argument.
            Has to be one of [cartesian, euclidean].
        space (list|dict): Search space. Should only be set if you don't pass
            an optimizer as the `optimizer` argument. Defines the search space
            and requires a `domain` to be set. Can be automatically converted
            from the `config` dict passed to `tune.run()`.
        metric (str): The training result objective value attribute. If None
            but a mode was passed, the anonymous metric `_metric` will be used
            per default.
        mode (str): One of {min, max}. Determines whether objective is
            minimizing or maximizing the metric attribute.
        points_to_evaluate (list): Initial parameter suggestions to be run
            first. This is for when you already have some good parameters
            you want to run first to help the algorithm make better suggestions
            for future parameters. Needs to be a list of dicts containing the
            configurations.
        evaluated_rewards (list): If you have previously evaluated the
            parameters passed in as points_to_evaluate you can avoid
            re-running those trials by passing in the reward attributes
            as a list so the optimiser can be told the results without
            needing to re-compute the trial. Must be the same length as
            points_to_evaluate.
        random_state_seed (int, None): Seed for reproducible
            results. Defaults to None. Please note that setting this to a value
            will change global random state for `numpy`
            on initalization and loading from checkpoint.

    Tune automatically converts search spaces to Dragonfly's format:


    .. code-block:: python

        from ray import tune

        config = {
            "LiNO3_vol": tune.uniform(0, 7),
            "Li2SO4_vol": tune.uniform(0, 7),
            "NaClO4_vol": tune.uniform(0, 7)
        }

        df_search = DragonflySearch(
            optimizer="bandit",
            domain="euclidean",
            metric="objective",
            mode="max")

        tune.run(my_func, config=config, search_alg=df_search)

    If you would like to pass the search space/optimizer manually,
    the code would look like this:

    .. code-block:: python

        from ray import tune

        space = [{
            "name": "LiNO3_vol",
            "type": "float",
            "min": 0,
            "max": 7
        }, {
            "name": "Li2SO4_vol",
            "type": "float",
            "min": 0,
            "max": 7
        }, {
            "name": "NaClO4_vol",
            "type": "float",
            "min": 0,
            "max": 7
        }]

        df_search = DragonflySearch(
            optimizer="bandit",
            domain="euclidean",
            space=space,
            metric="objective",
            mode="max")

        tune.run(my_func, search_alg=df_search)

    """

    def __init__(self,
                 optimizer: Optional[Union[str, BlackboxOptimiser]] = None,
                 domain: Optional[str] = None,
                 space: Optional[Union[Dict, List[Dict]]] = None,
                 metric: Optional[str] = None,
                 mode: Optional[str] = None,
                 points_to_evaluate: Optional[List[Dict]] = None,
                 evaluated_rewards: Optional[List] = None,
                 random_state_seed: Optional[int] = None,
                 **kwargs):
        assert dragonfly is not None, """dragonfly must be installed!
            You can install Dragonfly with the command:
            `pip install dragonfly-opt`."""
        if mode:
            assert mode in ["min", "max"], "`mode` must be 'min' or 'max'."
        if random_state_seed is not None:
            assert isinstance(
                random_state_seed, int
            ), "random_state_seed must be None or int, got '{}'.".format(
                type(random_state_seed))

        super(DragonflySearch, self).__init__(
            metric=metric, mode=mode, **kwargs)

        self._opt_arg = optimizer
        self._domain = domain

        if isinstance(space, dict) and space:
            resolved_vars, domain_vars, grid_vars = parse_spec_vars(space)
            if domain_vars or grid_vars:
                logger.warning(
                    UNRESOLVED_SEARCH_SPACE.format(
                        par="space", cls=type(self)))
                space = self.convert_search_space(space)

        self._space = space
        self._points_to_evaluate = points_to_evaluate
        self._evaluated_rewards = evaluated_rewards
        self._initial_points = []
        self._live_trial_mapping = {}
        self._point_parameter_names = []
        self._random_state_seed = random_state_seed

        self._opt = None
        if isinstance(optimizer, BlackboxOptimiser):
            if domain or space:
                raise ValueError(
                    "If you pass an optimizer instance to dragonfly, do not "
                    "pass a `domain` or `space`.")
            self._opt = optimizer
            self.init_dragonfly()
        elif self._space:
            self._setup_dragonfly()

    def _setup_dragonfly(self):
        """Setup dragonfly when no optimizer has been passed."""
        assert not self._opt, "Optimizer already set."

        from dragonfly import load_config
        from dragonfly.exd.experiment_caller import CPFunctionCaller, \
            EuclideanFunctionCaller
        from dragonfly.opt.blackbox_optimiser import BlackboxOptimiser
        from dragonfly.opt.random_optimiser import CPRandomOptimiser, \
            EuclideanRandomOptimiser
        from dragonfly.opt.cp_ga_optimiser import CPGAOptimiser
        from dragonfly.opt.gp_bandit import CPGPBandit, EuclideanGPBandit

        if not self._space:
            raise ValueError(
                "You have to pass a `space` when initializing dragonfly, or "
                "pass a search space definition to the `config` parameter "
                "of `tune.run()`.")

        if not self._domain:
            raise ValueError(
                "You have to set a `domain` when initializing dragonfly. "
                "Choose one of [Cartesian, Euclidean].")

        self._point_parameter_names = [param["name"] for param in self._space]

        if self._random_state_seed is not None:
            np.random.seed(self._random_state_seed)

        if self._domain.lower().startswith("cartesian"):
            function_caller_cls = CPFunctionCaller
        elif self._domain.lower().startswith("euclidean"):
            function_caller_cls = EuclideanFunctionCaller
        else:
            raise ValueError("Dragonfly's `domain` argument must be one of "
                             "[Cartesian, Euclidean].")

        optimizer_cls = None
        if inspect.isclass(self._opt_arg) and issubclass(
                self._opt_arg, BlackboxOptimiser):
            optimizer_cls = self._opt_arg
        elif isinstance(self._opt_arg, str):
            if self._opt_arg.lower().startswith("random"):
                if function_caller_cls == CPFunctionCaller:
                    optimizer_cls = CPRandomOptimiser
                else:
                    optimizer_cls = EuclideanRandomOptimiser
            elif self._opt_arg.lower().startswith("bandit"):
                if function_caller_cls == CPFunctionCaller:
                    optimizer_cls = CPGPBandit
                else:
                    optimizer_cls = EuclideanGPBandit
            elif self._opt_arg.lower().startswith("genetic"):
                if function_caller_cls == CPFunctionCaller:
                    optimizer_cls = CPGAOptimiser
                else:
                    raise ValueError(
                        "Currently only the `cartesian` domain works with "
                        "the `genetic` optimizer.")
            else:
                raise ValueError(
                    "Invalid optimizer specification. Either pass a full "
                    "dragonfly optimizer, or a string "
                    "in [random, bandit, genetic].")

        assert optimizer_cls, "No optimizer could be determined."
        domain_config = load_config({"domain": self._space})
        function_caller = function_caller_cls(
            None, domain_config.domain.list_of_domains[0])
        self._opt = optimizer_cls(function_caller, ask_tell_mode=True)
        self.init_dragonfly()

    def init_dragonfly(self):
        if self._points_to_evaluate:
            points_to_evaluate = [[
                config[par] for par in self._point_parameter_names
            ] for config in self._points_to_evaluate]
        else:
            points_to_evaluate = None

        self._opt.initialise()
        if points_to_evaluate and self._evaluated_rewards:
            self._opt.tell([(points_to_evaluate, self._evaluated_rewards)])
        elif points_to_evaluate:
            self._initial_points = points_to_evaluate
        # Dragonfly internally maximizes, so "min" => -1
        if self._mode == "min":
            self._metric_op = -1.
        elif self._mode == "max":
            self._metric_op = 1.

        if self._metric is None and self._mode:
            # If only a mode was passed, use anonymous metric
            self._metric = DEFAULT_METRIC

    def set_search_properties(self, metric: Optional[str], mode: Optional[str],
                              config: Dict, **spec) -> bool:
        if self._opt:
            return False
        space = self.convert_search_space(config)
        self._space = space
        if metric:
            self._metric = metric
        if mode:
            self._mode = mode

        self._setup_dragonfly()
        return True

    def suggest(self, trial_id: str) -> Optional[Dict]:
        if not self._opt:
            raise RuntimeError(
                UNDEFINED_SEARCH_SPACE.format(
                    cls=self.__class__.__name__, space="space"))

        if not self._metric or not self._mode:
            raise RuntimeError(
                UNDEFINED_METRIC_MODE.format(
                    cls=self.__class__.__name__,
                    metric=self._metric,
                    mode=self._mode))

        if self._initial_points:
            suggested_config = self._initial_points[0]
            del self._initial_points[0]
        else:
            try:
                suggested_config = self._opt.ask()
            except Exception as exc:
                logger.warning(
                    "Dragonfly errored when querying. This may be due to a "
                    "higher level of parallelism than supported. Try reducing "
                    "parallelism in the experiment: %s", str(exc))
                return None
        self._live_trial_mapping[trial_id] = suggested_config

        config = dict(zip(self._point_parameter_names, suggested_config))
        # Keep backwards compatibility
        config.update(point=suggested_config)
        return unflatten_dict(config)

    def on_trial_complete(self,
                          trial_id: str,
                          result: Optional[Dict] = None,
                          error: bool = False):
        """Passes result to Dragonfly unless early terminated or errored."""
        trial_info = self._live_trial_mapping.pop(trial_id)
        if result and not is_nan_or_inf(result[self._metric]):
            self._opt.tell([(trial_info,
                             self._metric_op * result[self._metric])])

    @staticmethod
    def convert_search_space(spec: Dict) -> List[Dict]:
        resolved_vars, domain_vars, grid_vars = parse_spec_vars(spec)

        if grid_vars:
            raise ValueError(
                "Grid search parameters cannot be automatically converted "
                "to a Dragonfly search space.")

        # Flatten and resolve again after checking for grid search.
        spec = flatten_dict(spec, prevent_delimiter=True)
        resolved_vars, domain_vars, grid_vars = parse_spec_vars(spec)

        def resolve_value(par: str, domain: Domain) -> Dict:
            sampler = domain.get_sampler()
            if isinstance(sampler, Quantized):
                logger.warning(
                    "Dragonfly search does not support quantization. "
                    "Dropped quantization.")
                sampler = sampler.get_sampler()

            if isinstance(domain, Float):
                if domain.sampler is not None:
                    logger.warning(
                        "Dragonfly does not support specific sampling methods."
                        " The {} sampler will be dropped.".format(sampler))
                return {
                    "name": par,
                    "type": "float",
                    "min": domain.lower,
                    "max": domain.upper
                }

            raise ValueError("Dragonfly does not support parameters of type "
                             "`{}`".format(type(domain).__name__))

        # Parameter name is e.g. "a/b/c" for nested dicts
        space = [
            resolve_value("/".join(path), domain)
            for path, domain in domain_vars
        ]
        return space

    def save(self, checkpoint_path: str):
        if self._random_state_seed is not None:
            numpy_random_state = np.random.get_state()
        else:
            numpy_random_state = None
        save_object = self.__dict__
        save_object["_random_state_seed_to_set"] = numpy_random_state
        with open(checkpoint_path, "wb") as outputFile:
            cloudpickle.dump(save_object, outputFile)

    def restore(self, checkpoint_path: str):
        with open(checkpoint_path, "rb") as inputFile:
            save_object = cloudpickle.load(inputFile)
        numpy_random_state = save_object.pop("_random_state_seed_to_set", None)
        self.__dict__.update(save_object)
        if numpy_random_state is not None:
            np.random.set_state(numpy_random_state)
