from traceback import format_exception
from typing import Sequence


class ExceptionGroup(BaseException):
    """Raised when multiple exceptions have been raised in a task group."""

    SEPARATOR = '----------------------------\n'

    exceptions = ()  # type: Sequence[BaseException]
    del exceptions  # Needed for trio 0.12+ compatibility

    def __str__(self):
        tracebacks = ['\n'.join(format_exception(type(exc), exc, exc.__traceback__))
                      for exc in self.exceptions]
        return '{} exceptions were raised in the task group:\n{}{}'.\
            format(len(self.exceptions), self.SEPARATOR, self.SEPARATOR.join(tracebacks))

    def __repr__(self) -> str:
        return '<{} ({} exceptions)>'.format(self.__class__.__name__, len(self.exceptions))


class IncompleteRead(Exception):
    """"
    Raised during ``read_exactly()`` if the connection is closed before the requested amount of
    bytes has been read.

    :ivar bytes data: bytes read before the stream was closed
    """

    def __init__(self) -> None:
        super().__init__('The stream was closed before the read operation could be completed')


class DelimiterNotFound(Exception):
    """
    Raised during ``read_until()`` if the maximum number of bytes has been read without the
    delimiter being found.

    :ivar bytes data: bytes read before giving up
    """

    def __init__(self, max_bytes: int) -> None:
        super().__init__('The delimiter was not found among the first {} bytes'.format(max_bytes))


class ClosedResourceError(Exception):
    """Raised when a resource is closed by another task."""


class TLSRequired(Exception):
    """Raised when a TLS related stream method is called before the TLS handshake has been done."""


class ResourceBusyError(Exception):
    """Raised when two tasks are trying to read from or write to the same resource concurrently."""

    def __init__(self, action: str):
        super().__init__('Another task is already {} this resource'.format(action))


class WouldBlock(Exception):
    """Raised by ``X_nowait``functions if ``X()``would block."""