"""Additional handlers that are used as the base classes of the buildlogger handler."""

from collections import deque
from enum import Enum
import json
import logging
import re
import threading
import warnings

import requests
import requests.adapters
import requests.auth

try:
    import requests.packages.urllib3.exceptions as urllib3_exceptions
except ImportError:
    # Versions of the requests package prior to 1.2.0 did not vendor the urllib3 package.
    urllib3_exceptions = None

import urllib3.util.retry as urllib3_retry

from buildscripts.resmokelib.logging import flush
from buildscripts.resmokelib import utils

_TIMEOUT_SECS = 55
MAX_EXCEPTION_LENGTH = 10


class Truncate(Enum):
    """Enum to specify to truncate first/last part of exceptions upon overflow."""

    FIRST = "FIRST"
    LAST = "LAST"


class ExceptionExtractor:
    """A class which extracts an exception based on regex."""

    def __init__(self, start_regex, end_regex, truncate):
        """Initialize the exception extractor."""
        self.start_re = re.compile(start_regex)
        self.end_re = re.compile(end_regex)

        self.current_exception = deque([])
        self.active = False

        self.truncate = truncate
        self.current_exception_is_truncated = False

        self.exception_detected = False

    def process_log_line(self, log_line):
        """Process the log line."""
        if self.exception_detected:
            return
        if not self.active and self.start_re.search(log_line):
            self.active = True
            self.current_exception.append(log_line)
        elif self.active:
            self.current_exception.append(log_line)
            if len(self.current_exception) > MAX_EXCEPTION_LENGTH:
                self.current_exception_is_truncated = True
                if self.truncate == Truncate.FIRST:
                    self.current_exception.popleft()
                else:
                    self.current_exception.pop()

            # Finalize Exception
            if self.end_re.search(log_line):
                self.exception_detected = True
                if self.current_exception_is_truncated:
                    self.current_exception.appendleft(
                        "[LAST Part of Exception]" if self.truncate ==
                        Truncate.FIRST else "[FIRST Part of Exception]")

    def get_exception(self):
        """Get the exception as a list of strings if it exists."""
        if not self.exception_detected:
            return []
        return list(self.current_exception)


class ExceptionExtractionHandler(logging.Handler):
    """A handler class that extracts exceptions using the logger."""

    def __init__(self, exception_extractor):
        """Initialize the handler with the specified regex."""

        logging.Handler.__init__(self)
        self.exception_extractor = exception_extractor

    def emit(self, record):
        """Pass the log line to the exception extractor."""
        self.exception_extractor.process_log_line(record.getMessage())


class BufferedHandler(logging.Handler):
    """A handler class that buffers logging records in memory.

    Whenever each record is added to the buffer, a check is made to see if the buffer
    should be flushed. If it should, then flush() is expected to do what's needed.
    """

    def __init__(self, capacity, interval_secs):
        """Initialize the handler with the buffer size and timeout.

        These values determine when the buffer is flushed regardless.
        """

        logging.Handler.__init__(self)

        if not isinstance(capacity, int):
            raise TypeError("capacity must be an integer")
        elif capacity <= 0:
            raise ValueError("capacity must be a positive integer")

        if not isinstance(interval_secs, (int, float)):
            raise TypeError("interval_secs must be a number")
        elif interval_secs <= 0.0:
            raise ValueError("interval_secs must be a positive number")

        self.capacity = capacity
        self.interval_secs = interval_secs

        # self.__emit_lock prohibits concurrent access to 'self.__emit_buffer',
        # 'self.__flush_event', and self.__flush_scheduled_by_emit.
        self.__emit_lock = threading.Lock()
        self.__emit_buffer = []
        self.__flush_event = None  # A handle to the event that calls self.flush().
        self.__flush_scheduled_by_emit = False
        self.__close_called = False

        self.__flush_lock = threading.Lock()  # Serializes callers of self.flush().

    # We override createLock(), acquire(), and release() to be no-ops since emit(), flush(), and
    # close() serialize accesses to 'self.__emit_buffer' in a more granular way via
    # 'self.__emit_lock'.
    def createLock(self):
        """Create lock."""
        pass

    def acquire(self):
        """Acquire."""
        pass

    def release(self):
        """Release."""
        pass

    def process_record(self, record):
        """Apply a transformation to the record before it gets added to the buffer.

        The default implementation returns 'record' unmodified.
        """

        return record

    def emit(self, record):
        """Emit a record.

        Append the record to the buffer after it has been transformed by
        process_record(). If the length of the buffer is greater than or
        equal to its capacity, then the flush() event is rescheduled to
        immediately process the buffer.
        """

        processed_record = self.process_record(record)

        with self.__emit_lock:
            self.__emit_buffer.append(processed_record)

            if self.__flush_event is None:
                # Now that we've added our first record to the buffer, we schedule a call to flush()
                # to occur 'self.interval_secs' seconds from now. 'self.__flush_event' should never
                # be None after this point.
                self.__flush_event = flush.flush_after(self, delay=self.interval_secs)

            if not self.__flush_scheduled_by_emit and len(self.__emit_buffer) >= self.capacity:
                # Attempt to flush the buffer early if we haven't already done so. We don't bother
                # calling flush.cancel() and flush.flush_after() when 'self.__flush_event' is
                # already scheduled to happen as soon as possible to avoid introducing unnecessary
                # delays in emit().
                if flush.cancel(self.__flush_event):
                    self.__flush_event = flush.flush_after(self, delay=0.0)
                    self.__flush_scheduled_by_emit = True

    def flush(self):
        """Ensure all logging output has been flushed."""

        self.__flush(close_called=False)

        with self.__emit_lock:
            if self.__flush_event is not None and not self.__close_called:
                # We cancel 'self.__flush_event' in case flush() was called by someone other than
                # the flush thread to avoid having multiple flush() events scheduled.
                flush.cancel(self.__flush_event)
                self.__flush_event = flush.flush_after(self, delay=self.interval_secs)
                self.__flush_scheduled_by_emit = False

    def __flush(self, close_called):
        """Ensure all logging output has been flushed."""

        with self.__emit_lock:
            buf = self.__emit_buffer
            self.__emit_buffer = []

        # The buffer 'buf' is flushed without holding 'self.__emit_lock' to avoid causing callers of
        # self.emit() to block behind the completion of a potentially long-running flush operation.
        if buf:
            with self.__flush_lock:
                self._flush_buffer_with_lock(buf, close_called)

    def _flush_buffer_with_lock(self, buf, close_called):
        """Ensure all logging output has been flushed."""

        raise NotImplementedError("_flush_buffer_with_lock must be implemented by BufferedHandler"
                                  " subclasses")

    def close(self):
        """Flush the buffer and tidies up any resources used by this handler."""

        with self.__emit_lock:
            self.__close_called = True

            if self.__flush_event is not None:
                flush.cancel(self.__flush_event)

        self.__flush(close_called=True)

        logging.Handler.close(self)


class HTTPHandler(object):
    """A class which sends data to a web server using POST requests."""

    def __init__(self, url_root, username, password, should_retry=False):
        """Initialize the handler with the necessary authentication credentials."""

        self.auth_handler = requests.auth.HTTPBasicAuth(username, password)

        self.session = requests.Session()

        if should_retry:
            retry_status = [500, 502, 503, 504]  # Retry for these statuses.
            retry = urllib3_retry.Retry(
                backoff_factor=0.1,  # Enable backoff starting at 0.1s.
                allowed_methods=False,  # Support all HTTP verbs.
                status_forcelist=retry_status)

            adapter = requests.adapters.HTTPAdapter(max_retries=retry)
            self.session.mount('http://', adapter)
            self.session.mount('https://', adapter)

        self.url_root = url_root

    def _make_url(self, endpoint):
        return "%s/%s/" % (self.url_root.rstrip("/"), endpoint.strip("/"))

    def post(self, endpoint, data=None, headers=None, timeout_secs=_TIMEOUT_SECS):
        """Send a POST request to the specified endpoint with the supplied data.

        Return the response, either as a string or a JSON object based
        on the content type.
        """

        data = utils.default_if_none(data, [])
        data = json.dumps(data)

        headers = utils.default_if_none(headers, {})
        headers["Content-Type"] = "application/json; charset=utf-8"

        url = self._make_url(endpoint)

        with warnings.catch_warnings():
            if urllib3_exceptions is not None:
                try:
                    warnings.simplefilter("ignore", urllib3_exceptions.InsecurePlatformWarning)
                except AttributeError:
                    # Versions of urllib3 prior to 1.10.3 didn't define InsecurePlatformWarning.
                    # Versions of requests prior to 2.6.0 didn't have a vendored copy of urllib3
                    # that defined InsecurePlatformWarning.
                    pass

                try:
                    warnings.simplefilter("ignore", urllib3_exceptions.InsecureRequestWarning)
                except AttributeError:
                    # Versions of urllib3 prior to 1.9 didn't define InsecureRequestWarning.
                    # Versions of requests prior to 2.4.0 didn't have a vendored copy of urllib3
                    # that defined InsecureRequestWarning.
                    pass

            response = self.session.post(url, data=data, headers=headers, timeout=timeout_secs,
                                         auth=self.auth_handler, verify=True)

        response.raise_for_status()

        if not response.encoding:
            response.encoding = "utf-8"

        headers = response.headers

        if headers["Content-Type"].startswith("application/json"):
            return response.json()

        return response.text