import logging
import types
import attr
from typing import Any, Callable, Dict, List, Sequence, Iterator, TypeVar

from .._abc import Instrument

# Used to log exceptions in instruments
INSTRUMENT_LOGGER = logging.getLogger("trio.abc.Instrument")


F = TypeVar("F", bound=Callable[..., Any])

# Decorator to mark methods public. This does nothing by itself, but
# trio/_tools/gen_exports.py looks for it.
def _public(fn: F) -> F:
    return fn


class Instruments(Dict[str, Dict[Instrument, None]]):
    """A collection of `trio.abc.Instrument` organized by hook.

    Instrumentation calls are rather expensive, and we don't want a
    rarely-used instrument (like before_run()) to slow down hot
    operations (like before_task_step()). Thus, we cache the set of
    instruments to be called for each hook, and skip the instrumentation
    call if there's nothing currently installed for that hook.
    """

    __slots__ = ()

    def __init__(self, incoming: Sequence[Instrument]):
        self["_all"] = {}
        for instrument in incoming:
            self.add_instrument(instrument)

    @_public
    def add_instrument(self, instrument: Instrument) -> None:
        """Start instrumenting the current run loop with the given instrument.

        Args:
          instrument (trio.abc.Instrument): The instrument to activate.

        If ``instrument`` is already active, does nothing.

        """
        if instrument in self["_all"]:
            return
        self["_all"][instrument] = None
        try:
            for name in dir(instrument):
                if name.startswith("_"):
                    continue
                try:
                    prototype = getattr(Instrument, name)
                except AttributeError:
                    continue
                impl = getattr(instrument, name)
                if isinstance(impl, types.MethodType) and impl.__func__ is prototype:
                    # Inherited unchanged from _abc.Instrument
                    continue
                self.setdefault(name, {})[instrument] = None
        except:
            self.remove_instrument(instrument)
            raise

    @_public
    def remove_instrument(self, instrument: Instrument) -> None:
        """Stop instrumenting the current run loop with the given instrument.

        Args:
          instrument (trio.abc.Instrument): The instrument to de-activate.

        Raises:
          KeyError: if the instrument is not currently active. This could
              occur either because you never added it, or because you added it
              and then it raised an unhandled exception and was automatically
              deactivated.

        """
        # If instrument isn't present, the KeyError propagates out
        self["_all"].pop(instrument)
        for hookname, instruments in list(self.items()):
            if instrument in instruments:
                del instruments[instrument]
                if not instruments:
                    del self[hookname]

    def call(self, hookname: str, *args: Any) -> None:
        """Call hookname(*args) on each applicable instrument.

        You must first check whether there are any instruments installed for
        that hook, e.g.::

            if "before_task_step" in instruments:
                instruments.call("before_task_step", task)
        """
        for instrument in list(self[hookname]):
            try:
                getattr(instrument, hookname)(*args)
            except:
                self.remove_instrument(instrument)
                INSTRUMENT_LOGGER.exception(
                    "Exception raised when calling %r on instrument %r. "
                    "Instrument has been disabled.",
                    hookname,
                    instrument,
                )
