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#
# This program 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 2
# of the License, or (at your option) any later version.
#
# This program 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.
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# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software Foundation,
# Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
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# ***** END GPL LICENCE BLOCK *****
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# (c) 2018, Blender Foundation - Sybren A. Stüvel
"""Callback class definition for BAT Pack progress reporting."""
import threading

import functools
import logging
import pathlib
import queue
import typing

import blender_asset_tracer.trace.progress

log = logging.getLogger(__name__)


class Callback(blender_asset_tracer.trace.progress.Callback):
    """BAT Pack progress reporting."""

    def pack_start(self) -> None:
        """Called when packing starts."""

    def pack_done(self,
                  output_blendfile: pathlib.PurePath,
                  missing_files: typing.Set[pathlib.Path]) -> None:
        """Called when packing is done."""

    def pack_aborted(self, reason: str):
        """Called when packing was aborted."""

    def trace_blendfile(self, filename: pathlib.Path) -> None:
        """Called for every blendfile opened when tracing dependencies."""

    def trace_asset(self, filename: pathlib.Path) -> None:
        """Called for every asset found when tracing dependencies.

        Note that this can also be a blend file.
        """

    def rewrite_blendfile(self, orig_filename: pathlib.Path) -> None:
        """Called for every rewritten blendfile."""

    def transfer_file(self, src: pathlib.Path, dst: pathlib.PurePath) -> None:
        """Called when a file transfer starts."""

    def transfer_file_skipped(self, src: pathlib.Path, dst: pathlib.PurePath) -> None:
        """Called when a file is skipped because it already exists."""

    def transfer_progress(self, total_bytes: int, transferred_bytes: int) -> None:
        """Called during file transfer, with per-pack info (not per file).

        :param total_bytes: The total amount of bytes to be transferred for
            the current packing operation. This can increase while transfer
            is happening, when more files are discovered (because transfer
            starts in a separate thread before all files are found).
        :param transferred_bytes: The total amount of bytes transfered for
            the current packing operation.
        """

    def missing_file(self, filename: pathlib.Path) -> None:
        """Called for every asset that does not exist on the filesystem."""


class ThreadSafeCallback(Callback):
    """Thread-safe wrapper for Callback instances.

    Progress calls are queued until flush() is called. The queued calls are
    called in the same thread as the one calling flush().
    """

    def __init__(self, wrapped: Callback) -> None:
        self.log = log.getChild('ThreadSafeCallback')
        self.wrapped = wrapped

        # Thread-safe queue for passing progress reports on the main thread.
        self._reporting_queue = queue.Queue()  # type: queue.Queue[typing.Callable]
        self._main_thread_id = threading.get_ident()

    def _queue(self, func: typing.Callable, *args, **kwargs):
        partial = functools.partial(func, *args, **kwargs)

        if self._main_thread_id == threading.get_ident():
            partial()
        else:
            self._reporting_queue.put(partial)

    def pack_start(self) -> None:
        self._queue(self.wrapped.pack_start)

    def pack_done(self,
                  output_blendfile: pathlib.PurePath,
                  missing_files: typing.Set[pathlib.Path]) -> None:
        self._queue(self.wrapped.pack_done, output_blendfile, missing_files)

    def pack_aborted(self, reason: str):
        self._queue(self.wrapped.pack_aborted, reason)

    def trace_blendfile(self, filename: pathlib.Path) -> None:
        self._queue(self.wrapped.trace_blendfile, filename)

    def trace_asset(self, filename: pathlib.Path) -> None:
        self._queue(self.wrapped.trace_asset, filename)

    def transfer_file(self, src: pathlib.Path, dst: pathlib.PurePath) -> None:
        self._queue(self.wrapped.transfer_file, src, dst)

    def transfer_file_skipped(self, src: pathlib.Path, dst: pathlib.PurePath) -> None:
        self._queue(self.wrapped.transfer_file_skipped, src, dst)

    def transfer_progress(self, total_bytes: int, transferred_bytes: int) -> None:
        self._queue(self.wrapped.transfer_progress, total_bytes, transferred_bytes)

    def missing_file(self, filename: pathlib.Path) -> None:
        self._queue(self.wrapped.missing_file, filename)

    def flush(self, timeout: float = None) -> None:
        """Call the queued calls, call this in the main thread."""

        while True:
            try:
                call = self._reporting_queue.get(block=timeout is not None,
                                                 timeout=timeout)
            except queue.Empty:
                return

            try:
                call()
            except Exception:
                # Don't let the handling of one callback call
                # block the entire flush process.
                self.log.exception('Error calling %s', call)