# This file is part of Radicale - CalDAV and CardDAV server
# Copyright © 2011-2017 Guillaume Ayoub
# Copyright © 2017-2019 Unrud <unrud@outlook.com>
#
# This library is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This library is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with Radicale.  If not, see <http://www.gnu.org/licenses/>.

"""
Functions to set up Python's logging facility for Radicale's WSGI application.

Log messages are sent to the first available target of:

  - Error stream specified by the WSGI server in "wsgi.errors"
  - ``sys.stderr``

"""

import contextlib
import logging
import os
import socket
import struct
import sys
import threading
import time
from typing import (Any, Callable, ClassVar, Dict, Iterator, Optional, Tuple,
                    Union)

from radicale import types

LOGGER_NAME: str = "radicale"
LOGGER_FORMAT: str = "[%(asctime)s] [%(ident)s] [%(levelname)s] %(message)s"
DATE_FORMAT: str = "%Y-%m-%d %H:%M:%S %z"

logger: logging.Logger = logging.getLogger(LOGGER_NAME)


class RemoveTracebackFilter(logging.Filter):

    def filter(self, record: logging.LogRecord) -> bool:
        record.exc_info = None
        return True


REMOVE_TRACEBACK_FILTER: logging.Filter = RemoveTracebackFilter()


class IdentLogRecordFactory:
    """LogRecordFactory that adds ``ident`` attribute."""

    def __init__(self, upstream_factory: Callable[..., logging.LogRecord]
                 ) -> None:
        self._upstream_factory = upstream_factory

    def __call__(self, *args: Any, **kwargs: Any) -> logging.LogRecord:
        record = self._upstream_factory(*args, **kwargs)
        ident = "%d" % os.getpid()
        main_thread = threading.main_thread()
        current_thread = threading.current_thread()
        if current_thread.name and main_thread != current_thread:
            ident += "/%s" % current_thread.name
        record.ident = ident  # type:ignore[attr-defined]
        record.tid = None  # type:ignore[attr-defined]
        if sys.version_info >= (3, 8):
            record.tid = current_thread.native_id
        return record


class ThreadedStreamHandler(logging.Handler):
    """Sends logging output to the stream registered for the current thread or
       ``sys.stderr`` when no stream was registered."""

    terminator: ClassVar[str] = "\n"

    _streams: Dict[int, types.ErrorStream]
    _journal_stream_id: Optional[Tuple[int, int]]
    _journal_socket: Optional[socket.socket]

    def __init__(self) -> None:
        super().__init__()
        self._streams = {}
        self._journal_stream_id = None
        with contextlib.suppress(TypeError, ValueError):
            dev, inode = os.environ.get("JOURNAL_STREAM", "").split(":", 1)
            self._journal_stream_id = int(dev), int(inode)
        self._journal_socket = None
        if self._journal_stream_id and hasattr(socket, "AF_UNIX"):
            journal_socket = socket.socket(socket.AF_UNIX, socket.SOCK_DGRAM)
            try:
                journal_socket.connect("/run/systemd/journal/socket")
            except OSError:
                journal_socket.close()
            else:
                self._journal_socket = journal_socket

    def _detect_journal(self, stream):
        if not self._journal_stream_id:
            return False
        try:
            stat = os.fstat(stream.fileno())
        except Exception:
            return False
        return self._journal_stream_id == (stat.st_dev, stat.st_ino)

    @staticmethod
    def _encode_journal(data):
        msg = b""
        for key, value in data.items():
            if value is None:
                continue
            key = key.encode()
            value = str(value).encode()
            if b"\n" in value:
                msg += (key + b"\n" +
                        struct.pack("<Q", len(value)) + value + b"\n")
            else:
                msg += key + b"=" + value + b"\n"
        return msg

    def _emit_journal(self, record):
        priority = {"DEBUG": 7,
                    "INFO": 6,
                    "WARNING": 4,
                    "ERROR": 3,
                    "CRITICAL": 2}.get(record.levelname, 4)
        timestamp = time.strftime("%Y-%m-%dT%H:%M:%S.%%03dZ",
                                  time.gmtime(record.created)) % record.msecs
        data = {"PRIORITY": priority,
                "TID": record.tid,
                "SYSLOG_IDENTIFIER": record.name,
                "SYSLOG_FACILITY": 1,
                "SYSLOG_PID": record.process,
                "SYSLOG_TIMESTAMP": timestamp,
                "CODE_FILE": record.pathname,
                "CODE_LINE": record.lineno,
                "CODE_FUNC": record.funcName,
                "MESSAGE": self.format(record)}
        self._journal_socket.sendall(self._encode_journal(data))

    def emit(self, record: logging.LogRecord) -> None:
        try:
            stream = self._streams.get(threading.get_ident(), sys.stderr)
            if self._journal_socket and self._detect_journal(stream):
                self._emit_journal(record)
                return
            msg = self.format(record)
            stream.write(msg)
            stream.write(self.terminator)
            if hasattr(stream, "flush"):
                stream.flush()
        except Exception:
            self.handleError(record)

    @types.contextmanager
    def register_stream(self, stream: types.ErrorStream) -> Iterator[None]:
        """Register stream for logging output of the current thread."""
        key = threading.get_ident()
        self._streams[key] = stream
        try:
            yield
        finally:
            del self._streams[key]


@types.contextmanager
def register_stream(stream: types.ErrorStream) -> Iterator[None]:
    """Register stream for logging output of the current thread."""
    yield


def setup() -> None:
    """Set global logging up."""
    global register_stream
    handler = ThreadedStreamHandler()
    logging.basicConfig(format=LOGGER_FORMAT, datefmt=DATE_FORMAT,
                        handlers=[handler])
    register_stream = handler.register_stream
    log_record_factory = IdentLogRecordFactory(logging.getLogRecordFactory())
    logging.setLogRecordFactory(log_record_factory)
    set_level(logging.WARNING)


def set_level(level: Union[int, str]) -> None:
    """Set logging level for global logger."""
    if isinstance(level, str):
        level = getattr(logging, level.upper())
        assert isinstance(level, int)
    logger.setLevel(level)
    logger.removeFilter(REMOVE_TRACEBACK_FILTER)
    if level > logging.DEBUG:
        logger.addFilter(REMOVE_TRACEBACK_FILTER)