import os
import time
from threading import Thread, Lock
from contextlib import contextmanager

import sentry_sdk
from sentry_sdk.envelope import Envelope
from sentry_sdk.session import Session
from sentry_sdk._types import MYPY
from sentry_sdk.utils import format_timestamp

if MYPY:
    from typing import Callable
    from typing import Optional
    from typing import Any
    from typing import Dict
    from typing import List
    from typing import Generator


def is_auto_session_tracking_enabled(hub=None):
    # type: (Optional[sentry_sdk.Hub]) -> bool
    """Utility function to find out if session tracking is enabled."""
    if hub is None:
        hub = sentry_sdk.Hub.current
    should_track = hub.scope._force_auto_session_tracking
    if should_track is None:
        client_options = hub.client.options if hub.client else {}
        should_track = client_options["auto_session_tracking"]
    return should_track


@contextmanager
def auto_session_tracking(hub=None, session_mode="application"):
    # type: (Optional[sentry_sdk.Hub], str) -> Generator[None, None, None]
    """Starts and stops a session automatically around a block."""
    if hub is None:
        hub = sentry_sdk.Hub.current
    should_track = is_auto_session_tracking_enabled(hub)
    if should_track:
        hub.start_session(session_mode=session_mode)
    try:
        yield
    finally:
        if should_track:
            hub.end_session()


TERMINAL_SESSION_STATES = ("exited", "abnormal", "crashed")
MAX_ENVELOPE_ITEMS = 100


def make_aggregate_envelope(aggregate_states, attrs):
    # type: (Any, Any) -> Any
    return {"attrs": dict(attrs), "aggregates": list(aggregate_states.values())}


class SessionFlusher(object):
    def __init__(
        self,
        capture_func,  # type: Callable[[Envelope], None]
        flush_interval=60,  # type: int
    ):
        # type: (...) -> None
        self.capture_func = capture_func
        self.flush_interval = flush_interval
        self.pending_sessions = []  # type: List[Any]
        self.pending_aggregates = {}  # type: Dict[Any, Any]
        self._thread = None  # type: Optional[Thread]
        self._thread_lock = Lock()
        self._aggregate_lock = Lock()
        self._thread_for_pid = None  # type: Optional[int]
        self._running = True

    def flush(self):
        # type: (...) -> None
        pending_sessions = self.pending_sessions
        self.pending_sessions = []

        with self._aggregate_lock:
            pending_aggregates = self.pending_aggregates
            self.pending_aggregates = {}

        envelope = Envelope()
        for session in pending_sessions:
            if len(envelope.items) == MAX_ENVELOPE_ITEMS:
                self.capture_func(envelope)
                envelope = Envelope()

            envelope.add_session(session)

        for (attrs, states) in pending_aggregates.items():
            if len(envelope.items) == MAX_ENVELOPE_ITEMS:
                self.capture_func(envelope)
                envelope = Envelope()

            envelope.add_sessions(make_aggregate_envelope(states, attrs))

        if len(envelope.items) > 0:
            self.capture_func(envelope)

    def _ensure_running(self):
        # type: (...) -> None
        if self._thread_for_pid == os.getpid() and self._thread is not None:
            return None
        with self._thread_lock:
            if self._thread_for_pid == os.getpid() and self._thread is not None:
                return None

            def _thread():
                # type: (...) -> None
                while self._running:
                    time.sleep(self.flush_interval)
                    if self._running:
                        self.flush()

            thread = Thread(target=_thread)
            thread.daemon = True
            thread.start()
            self._thread = thread
            self._thread_for_pid = os.getpid()
        return None

    def add_aggregate_session(
        self, session  # type: Session
    ):
        # type: (...) -> None
        # NOTE on `session.did`:
        # the protocol can deal with buckets that have a distinct-id, however
        # in practice we expect the python SDK to have an extremely high cardinality
        # here, effectively making aggregation useless, therefore we do not
        # aggregate per-did.

        # For this part we can get away with using the global interpreter lock
        with self._aggregate_lock:
            attrs = session.get_json_attrs(with_user_info=False)
            primary_key = tuple(sorted(attrs.items()))
            secondary_key = session.truncated_started  # (, session.did)
            states = self.pending_aggregates.setdefault(primary_key, {})
            state = states.setdefault(secondary_key, {})

            if "started" not in state:
                state["started"] = format_timestamp(session.truncated_started)
            # if session.did is not None:
            #     state["did"] = session.did
            if session.status == "crashed":
                state["crashed"] = state.get("crashed", 0) + 1
            elif session.status == "abnormal":
                state["abnormal"] = state.get("abnormal", 0) + 1
            elif session.errors > 0:
                state["errored"] = state.get("errored", 0) + 1
            else:
                state["exited"] = state.get("exited", 0) + 1

    def add_session(
        self, session  # type: Session
    ):
        # type: (...) -> None
        if session.session_mode == "request":
            self.add_aggregate_session(session)
        else:
            self.pending_sessions.append(session.to_json())
        self._ensure_running()

    def kill(self):
        # type: (...) -> None
        self._running = False

    def __del__(self):
        # type: (...) -> None
        self.kill()
