"""
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 3 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.


You should have received a copy of the GNU General Public License
 along with this program.  If not, see <https://www.gnu.org/licenses/>.

Copyright © 2019 Cloud Linux Software Inc.

This software is also available under ImunifyAV commercial license,
see <https://www.imunify360.com/legal/eula>
"""
import asyncio
import os
import time
from contextlib import suppress
from datetime import datetime, timedelta
from logging import getLogger
from pathlib import Path

from imav.malwarelib.config import (
    MalwareHitStatus,
    MalwareScanResourceType,
    MalwareScanType,
)
from imav.malwarelib.cleanup.cleaner import MalwareCleanupProxy
from imav.malwarelib.model import MalwareHistory, MalwareHit, MalwareScan
from imav.subsys import realtime_av
from defence360agent.api import inactivity
from defence360agent.contracts.messages import MessageType
from defence360agent.internals.global_scope import g
from defence360agent.mr_proper import BaseCleaner
from defence360agent.subsys import persistent_state
from defence360agent.utils import nice_iterator, split_for_chunk

logger = getLogger(__name__)


class OutdatedScansCleaner(BaseCleaner):
    PERIOD = timedelta(days=1).total_seconds()
    CLEANUP_LIMIT_DELTA = timedelta(days=30)

    @classmethod
    async def cleanup(cls) -> None:
        cleanup_time_limit = int(
            (datetime.now() - cls.CLEANUP_LIMIT_DELTA).timestamp()
        )
        deleted = (
            MalwareScan.delete()
            .where(MalwareScan.started < cleanup_time_limit)
            .execute()
        )
        logger.info("Cleaned %s outdated scans", deleted)


class OutdatedHistoryCleaner(BaseCleaner):
    PERIOD = timedelta(days=1).total_seconds()
    CLEANUP_LIMIT_DELTA = timedelta(days=30)

    @classmethod
    async def cleanup(cls) -> None:
        keep_time_threshold = int(
            (datetime.now() - cls.CLEANUP_LIMIT_DELTA).timestamp()
        )
        deleted = (
            MalwareHistory.delete()
            .where(MalwareHistory.ctime < keep_time_threshold)
            .execute()
        )
        logger.info("Cleaned %s outdated malware history", deleted)


class OutdatedHitsCleaner(BaseCleaner):
    PERIOD = int(
        os.environ.get(
            "IMUNIFY360_OUTDATED_HITS_CHECK_INTERVAL",
            timedelta(days=1).total_seconds(),
        )
    )
    REALTIME_SCAN_THRESHOLD = timedelta(minutes=10).total_seconds()
    CHUNK_SIZE = 1000

    @classmethod
    async def _cleanup(cls) -> None:
        """Rescan irrelevant malware hits"""
        to_rescan = []
        not_exist_hits = []
        hits = (
            MalwareHit.select()
            .where(
                MalwareHit.status == MalwareHitStatus.FOUND,
                MalwareHit.resource_type == MalwareScanResourceType.FILE.value,
            )
            .order_by(MalwareHit.timestamp.asc())
        )
        async for hit in nice_iterator(hits, chunk_size=cls.CHUNK_SIZE):
            orig_file_path = Path(hit.orig_file)
            try:
                file_ctime = orig_file_path.stat().st_ctime
                if hit.timestamp < file_ctime:
                    # rescan the modified files after scanning,
                    # they may not be infected anymore
                    realtime_threshold = (
                        time.time() - cls.REALTIME_SCAN_THRESHOLD
                    )  # don't scan file twice
                    if (
                        not realtime_av.should_be_running()
                        or file_ctime < realtime_threshold
                    ):
                        to_rescan.append(hit.orig_file)
            except FileNotFoundError:
                not_exist_hits.append(hit.id)
            except OSError as exc:
                logger.warning("Can't check file due to %s", exc)
        if to_rescan:
            for files in split_for_chunk(to_rescan, chunk_size=cls.CHUNK_SIZE):
                logger.info("Rescan %s outdated malware files", len(files))
                await g.sink.process_message(
                    MessageType.MalwareRescanFiles(
                        files=files, type=MalwareScanType.RESCAN_OUTDATED
                    )
                )
        # delete db entries for non-existent files
        for hits_to_delete in split_for_chunk(
            not_exist_hits, chunk_size=cls.CHUNK_SIZE
        ):
            deleted = (
                MalwareHit.delete()
                .where(MalwareHit.id.in_(hits_to_delete))
                .where(MalwareHit.status == MalwareHitStatus.FOUND)
                .execute()
            )
            logger.info("Deleted %s not exist malware hits", deleted)
            # don't block the whole loop for too long,
            # return control to the loop every iteration
            await asyncio.sleep(0)

    @classmethod
    async def cleanup(cls):
        last_clean_timestamp = persistent_state.load_state(
            "OutdatedHitsCleaner"
        ).get("last_clean_timestamp", 0)
        if (
            not last_clean_timestamp
            or (time.time() - last_clean_timestamp) >= cls.PERIOD
        ):  # don't run it too often
            with inactivity.track.task("malware hits relevance check"):
                try:
                    await cls._cleanup()
                finally:
                    persistent_state.save_state(
                        "OutdatedHitsCleaner",
                        {"last_clean_timestamp": time.time()},
                    )