# vim: ft=python fileencoding=utf-8 sts=4 sw=4 et:

# Copyright 2014-2016 Florian Bruhin (The Compiler) <mail@qutebrowser.org>
#
# This file is part of qutebrowser.
#
# qutebrowser 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.
#
# qutebrowser 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 qutebrowser.  If not, see <http://www.gnu.org/licenses/>.

"""Misc. utilities related to Qt.

Module attributes:
    MAXVALS: A dictionary of C/Qt types (as string) mapped to their maximum
             value.
    MINVALS: A dictionary of C/Qt types (as string) mapped to their minimum
             value.
"""


import io
import os
import sys
import operator
import contextlib

from PyQt5.QtCore import (qVersion, QEventLoop, QDataStream, QByteArray,
                          QIODevice, QSaveFile)
from PyQt5.QtWidgets import QApplication

from qutebrowser.utils import log

with log.ignore_py_warnings(category=PendingDeprecationWarning, module='imp'):
    with log.ignore_py_warnings(category=ImportWarning):
        # This imports 'imp' and gives us a PendingDeprecationWarning on
        # Debian Jessie.
        #
        # On Archlinux, we get ImportWarning from
        # importlib/_bootstrap_external.py for modules with missing __init__.
        import pkg_resources


MAXVALS = {
    'int': 2 ** 31 - 1,
    'int64': 2 ** 63 - 1,
}

MINVALS = {
    'int': -(2 ** 31),
    'int64': -(2 ** 63),
}


class QtOSError(OSError):

    """An OSError triggered by a QFileDevice.

    Attributes:
        qt_errno: The error attribute of the given QFileDevice, if applicable.
    """

    def __init__(self, dev, msg=None):
        if msg is None:
            msg = dev.errorString()

        super().__init__(msg)

        try:
            self.qt_errno = dev.error()
        except AttributeError:
            self.qt_errno = None


def version_check(version, op=operator.ge):
    """Check if the Qt runtime version is the version supplied or newer.

    Args:
        version: The version to check against.
        op: The operator to use for the check.
    """
    return op(pkg_resources.parse_version(qVersion()),
              pkg_resources.parse_version(version))


def check_overflow(arg, ctype, fatal=True):
    """Check if the given argument is in bounds for the given type.

    Args:
        arg: The argument to check
        ctype: The C/Qt type to check as a string.
        fatal: Whether to raise exceptions (True) or truncate values (False)

    Return
        The truncated argument if fatal=False
        The original argument if it's in bounds.
    """
    maxval = MAXVALS[ctype]
    minval = MINVALS[ctype]
    if arg > maxval:
        if fatal:
            raise OverflowError(arg)
        else:
            return maxval
    elif arg < minval:
        if fatal:
            raise OverflowError(arg)
        else:
            return minval
    else:
        return arg


def get_args(namespace):
    """Get the Qt QApplication arguments based on an argparse namespace.

    Args:
        namespace: The argparse namespace.

    Return:
        The argv list to be passed to Qt.
    """
    argv = [sys.argv[0]]
    if namespace.qt_flag is not None:
        argv.append('-' + namespace.qt_flag[0])
    if namespace.qt_arg is not None:
        argv.append('-' + namespace.qt_arg[0])
        argv.append(namespace.qt_arg[1])
    return argv


def check_print_compat():
    """Check if printing should work in the given Qt version."""
    # WORKAROUND (remove this when we bump the requirements to 5.3.0)
    return not (os.name == 'nt' and version_check('5.3.0', operator.lt))


def ensure_valid(obj):
    """Ensure a Qt object with an .isValid() method is valid."""
    if not obj.isValid():
        raise QtValueError(obj)


def ensure_not_null(obj):
    """Ensure a Qt object with an .isNull() method is not null."""
    if obj.isNull():
        raise QtValueError(obj, null=True)


def check_qdatastream(stream):
    """Check the status of a QDataStream and raise OSError if it's not ok."""
    status_to_str = {
        QDataStream.Ok: "The data stream is operating normally.",
        QDataStream.ReadPastEnd: ("The data stream has read past the end of "
                                  "the data in the underlying device."),
        QDataStream.ReadCorruptData: "The data stream has read corrupt data.",
        QDataStream.WriteFailed: ("The data stream cannot write to the "
                                  "underlying device."),
    }
    if stream.status() != QDataStream.Ok:
        raise OSError(status_to_str[stream.status()])


def serialize(obj):
    """Serialize an object into a QByteArray."""
    data = QByteArray()
    stream = QDataStream(data, QIODevice.WriteOnly)
    serialize_stream(stream, obj)
    return data


def deserialize(data, obj):
    """Deserialize an object from a QByteArray."""
    stream = QDataStream(data, QIODevice.ReadOnly)
    deserialize_stream(stream, obj)


def serialize_stream(stream, obj):
    """Serialize an object into a QDataStream."""
    check_qdatastream(stream)
    stream << obj  # pylint: disable=pointless-statement
    check_qdatastream(stream)


def deserialize_stream(stream, obj):
    """Deserialize a QDataStream into an object."""
    check_qdatastream(stream)
    stream >> obj  # pylint: disable=pointless-statement
    check_qdatastream(stream)


@contextlib.contextmanager
def savefile_open(filename, binary=False, encoding='utf-8'):
    """Context manager to easily use a QSaveFile."""
    f = QSaveFile(filename)
    cancelled = False
    try:
        open_ok = f.open(QIODevice.WriteOnly)
        if not open_ok:
            raise QtOSError(f)
        if binary:
            new_f = PyQIODevice(f)
        else:
            new_f = io.TextIOWrapper(PyQIODevice(f), encoding=encoding)
        yield new_f
        new_f.flush()
    except:
        f.cancelWriting()
        cancelled = True
        raise
    finally:
        commit_ok = f.commit()
        if not commit_ok and not cancelled:
            raise QtOSError(f, msg="Commit failed!")


@contextlib.contextmanager
def unset_organization():
    """Temporarily unset QApplication.organizationName().

    This is primarily needed in config.py.
    """
    qapp = QApplication.instance()
    orgname = qapp.organizationName()
    qapp.setOrganizationName(None)
    try:
        yield
    finally:
        qapp.setOrganizationName(orgname)


class PyQIODevice(io.BufferedIOBase):

    """Wrapper for a QIODevice which provides a python interface.

    Attributes:
        dev: The underlying QIODevice.
    """

    def __init__(self, dev):
        super().__init__()
        self.dev = dev

    def __len__(self):
        return self.dev.size()

    def _check_open(self):
        """Check if the device is open, raise ValueError if not."""
        if not self.dev.isOpen():
            raise ValueError("IO operation on closed device!")

    def _check_random(self):
        """Check if the device supports random access, raise OSError if not."""
        if not self.seekable():
            raise OSError("Random access not allowed!")

    def _check_readable(self):
        """Check if the device is readable, raise OSError if not."""
        if not self.dev.isReadable():
            raise OSError("Trying to read unreadable file!")

    def _check_writable(self):
        """Check if the device is writable, raise OSError if not."""
        if not self.writable():
            raise OSError("Trying to write to unwritable file!")

    def open(self, mode):
        """Open the underlying device and ensure opening succeeded.

        Raises OSError if opening failed.

        Args:
            mode: QIODevice::OpenMode flags.

        Return:
            A contextlib.closing() object so this can be used as
            contextmanager.
        """
        ok = self.dev.open(mode)
        if not ok:
            raise QtOSError(self.dev)
        return contextlib.closing(self)

    def close(self):
        """Close the underlying device."""
        self.dev.close()

    def fileno(self):
        raise io.UnsupportedOperation

    def seek(self, offset, whence=io.SEEK_SET):
        self._check_open()
        self._check_random()
        if whence == io.SEEK_SET:
            ok = self.dev.seek(offset)
        elif whence == io.SEEK_CUR:
            ok = self.dev.seek(self.tell() + offset)
        elif whence == io.SEEK_END:
            ok = self.dev.seek(len(self) + offset)
        else:
            raise io.UnsupportedOperation("whence = {} is not "
                                          "supported!".format(whence))
        if not ok:
            raise QtOSError(self.dev, msg="seek failed!")

    def truncate(self, size=None):  # pylint: disable=unused-argument
        raise io.UnsupportedOperation

    @property
    def closed(self):
        return not self.dev.isOpen()

    def flush(self):
        self._check_open()
        self.dev.waitForBytesWritten(-1)

    def isatty(self):
        self._check_open()
        return False

    def readable(self):
        return self.dev.isReadable()

    def readline(self, size=-1):
        self._check_open()
        self._check_readable()

        if size < 0:
            qt_size = 0  # no maximum size
        elif size == 0:
            return QByteArray()
        else:
            qt_size = size + 1  # Qt also counts the NUL byte

        if self.dev.canReadLine():
            buf = self.dev.readLine(qt_size)
        else:
            if size < 0:
                buf = self.dev.readAll()
            else:
                buf = self.dev.read(size)

        if buf is None:
            raise QtOSError(self.dev)
        return buf

    def seekable(self):
        return not self.dev.isSequential()

    def tell(self):
        self._check_open()
        self._check_random()
        return self.dev.pos()

    def writable(self):
        return self.dev.isWritable()

    def write(self, b):
        self._check_open()
        self._check_writable()
        num = self.dev.write(b)
        if num == -1 or num < len(b):
            raise QtOSError(self.dev)
        return num

    def read(self, size=-1):
        self._check_open()
        self._check_readable()
        if size < 0:
            buf = self.dev.readAll()
        else:
            buf = self.dev.read(size)
        if buf is None:
            raise QtOSError(self.dev)
        return buf


class QtValueError(ValueError):

    """Exception which gets raised by ensure_valid."""

    def __init__(self, obj, null=False):
        try:
            self.reason = obj.errorString()
        except AttributeError:
            self.reason = None
        if null:
            err = "{} is null".format(obj)
        else:
            err = "{} is not valid".format(obj)
        if self.reason:
            err += ": {}".format(self.reason)
        super().__init__(err)


class EventLoop(QEventLoop):

    """A thin wrapper around QEventLoop.

    Raises an exception when doing exec_() multiple times.
    """

    def __init__(self, parent=None):
        super().__init__(parent)
        self._executing = False

    def exec_(self, flags=QEventLoop.AllEvents):
        """Override exec_ to raise an exception when re-running."""
        if self._executing:
            raise AssertionError("Eventloop is already running!")
        self._executing = True
        super().exec_(flags)
        self._executing = False
