from datetime import datetime, timedelta
from operator import add
from os import statvfs
from typing import List, Optional

from selfprivacy_api.utils import ReadUserData, WriteUserData

from selfprivacy_api.services import get_service_by_id
from selfprivacy_api.services.service import Service

from selfprivacy_api.jobs import Jobs, JobStatus

from selfprivacy_api.graphql.queries.providers import (
    BackupProvider as BackupProviderEnum,
)

from selfprivacy_api.models.backup.snapshot import Snapshot

from selfprivacy_api.backup.providers.provider import AbstractBackupProvider
from selfprivacy_api.backup.providers import get_provider
from selfprivacy_api.backup.storage import Storage
from selfprivacy_api.backup.jobs import (
    get_backup_job,
    add_backup_job,
    get_restore_job,
    add_restore_job,
)

DEFAULT_JSON_PROVIDER = {
    "provider": "BACKBLAZE",
    "accountId": "",
    "accountKey": "",
    "bucket": "",
}


class Backups:
    """A stateless controller class for backups"""

### Providers

    @staticmethod
    def provider():
        return Backups._lookup_provider()

    @staticmethod
    def set_provider(
        kind: BackupProviderEnum,
        login: str,
        key: str,
        location: str,
        repo_id: str = "",
    ):
        provider = Backups._construct_provider(
            kind,
            login,
            key,
            location,
            repo_id,
        )
        Storage.store_provider(provider)

    @staticmethod
    def reset(reset_json=True):
        Storage.reset()
        if reset_json:
            try:
                Backups._reset_provider_json()
            except FileNotFoundError:
                # if there is no userdata file, we do not need to reset it
                pass


    @staticmethod
    def _lookup_provider() -> AbstractBackupProvider:
        redis_provider = Backups._load_provider_redis()
        if redis_provider is not None:
            return redis_provider

        try:
            json_provider = Backups._load_provider_json()
        except FileNotFoundError:
            json_provider = None

        if json_provider is not None:
            Storage.store_provider(json_provider)
            return json_provider

        none_provider = Backups._construct_provider(
            BackupProviderEnum.NONE, login="", key="", location=""
        )
        Storage.store_provider(none_provider)
        return none_provider

    @staticmethod
    def _construct_provider(
        kind: BackupProviderEnum,
        login: str,
        key: str,
        location: str,
        repo_id: str = "",
    ) -> AbstractBackupProvider:
        provider_class = get_provider(kind)

        return provider_class(
            login=login,
            key=key,
            location=location,
            repo_id=repo_id,
        )

    @staticmethod
    def _load_provider_redis() -> Optional[AbstractBackupProvider]:
        provider_model = Storage.load_provider()
        if provider_model is None:
            return None
        return Backups._construct_provider(
            BackupProviderEnum[provider_model.kind],
            provider_model.login,
            provider_model.key,
            provider_model.location,
            provider_model.repo_id,
        )

    @staticmethod
    def _load_provider_json() -> Optional[AbstractBackupProvider]:
        with ReadUserData() as user_data:
            provider_dict = {
                "provider": "",
                "accountId": "",
                "accountKey": "",
                "bucket": "",
            }

            if "backup" not in user_data.keys():
                if "backblaze" in user_data.keys():
                    provider_dict.update(user_data["backblaze"])
                    provider_dict["provider"] = "BACKBLAZE"
                return None
            else:
                provider_dict.update(user_data["backup"])

            if provider_dict == DEFAULT_JSON_PROVIDER:
                return None
            try:
                return Backups._construct_provider(
                    kind=BackupProviderEnum[provider_dict["provider"]],
                    login=provider_dict["accountId"],
                    key=provider_dict["accountKey"],
                    location=provider_dict["bucket"],
                )
            except KeyError:
                return None

    @staticmethod
    def _reset_provider_json() -> None:
        with WriteUserData() as user_data:
            if "backblaze" in user_data.keys():
                del user_data["backblaze"]

            user_data["backup"] = DEFAULT_JSON_PROVIDER

### Init 

    @staticmethod
    def init_repo():
        Backups.provider().backupper.init()
        Storage.mark_as_init()

    @staticmethod
    def is_initted() -> bool:
        if Storage.has_init_mark():
            return True

        initted = Backups.provider().backupper.is_initted()
        if initted:
            Storage.mark_as_init()
            return True

        return False

### Backup

    @staticmethod
    def back_up(service: Service):
        """The top-level function to back up a service"""
        folders = service.get_folders()
        tag = service.get_id()

        job = get_backup_job(service)
        if job is None:
            job = add_backup_job(service)
        Jobs.update(job, status=JobStatus.RUNNING)

        try:
            service.pre_backup()
            snapshot = Backups.provider().backupper.start_backup(
                folders,
                tag,
            )
            Backups._store_last_snapshot(tag, snapshot)
            service.post_restore()
        except Exception as e:
            Jobs.update(job, status=JobStatus.ERROR)
            raise e

        Jobs.update(job, status=JobStatus.FINISHED)
        return snapshot

### Restoring


    @staticmethod
    def restore_snapshot(snapshot: Snapshot):
        service = get_service_by_id(snapshot.service_name)

        if service is None:
            raise ValueError(
                f"snapshot has a nonexistent service: {snapshot.service_name}"
            )

        job = get_restore_job(service)
        if job is None:
            job = add_restore_job(snapshot)

        Jobs.update(
            job,
            status=JobStatus.RUNNING,
        )
        try:
            Backups._assert_restorable(snapshot)
            Backups._restore_service_from_snapshot(
                service,
                snapshot.id,
            )
            service.post_restore()
        except Exception as e:
            Jobs.update(
                job,
                status=JobStatus.ERROR,
            )
            raise e

        Jobs.update(
            job,
            status=JobStatus.FINISHED,
        )

    @staticmethod
    def _assert_restorable(snapshot: Snapshot):
        service = get_service_by_id(snapshot.service_name)
        if service is None:
            raise ValueError(
                f"snapshot has a nonexistent service: {snapshot.service_name}"
            )

        needed_space = Backups.service_snapshot_size(snapshot.id)
        available_space = Backups.space_usable_for_service(service)
        if needed_space > available_space:
            raise ValueError(
                f"we only have {available_space} bytes "
                f"but snapshot needs {needed_space}"
            )

    @staticmethod
    def _restore_service_from_snapshot(service: Service, snapshot_id: str):
        folders = service.get_folders()

        Backups.provider().backupper.restore_from_backup(
            snapshot_id,
            folders,
        )

### Snapshots

    @staticmethod
    def get_snapshots(service: Service) -> List[Snapshot]:
        snapshots = Backups.get_all_snapshots()
        service_id = service.get_id()
        return list(
            filter(
                lambda snap: snap.service_name == service_id,
                snapshots,
            )
        )

    @staticmethod
    def get_all_snapshots() -> List[Snapshot]:
        cached_snapshots = Storage.get_cached_snapshots()
        if cached_snapshots != []:
            return cached_snapshots
        # TODO: the oldest snapshots will get expired faster than the new ones.
        # How to detect that the end is missing?

        Backups.force_snapshot_cache_reload()
        return Storage.get_cached_snapshots()

    @staticmethod
    def get_snapshot_by_id(id: str) -> Optional[Snapshot]:
        snap = Storage.get_cached_snapshot_by_id(id)
        if snap is not None:
            return snap

        # Possibly our cache entry got invalidated, let's try one more time
        Backups.force_snapshot_cache_reload()
        snap = Storage.get_cached_snapshot_by_id(id)

        return snap

    @staticmethod
    def force_snapshot_cache_reload():
        upstream_snapshots = Backups.provider().backupper.get_snapshots()
        Storage.invalidate_snapshot_storage()
        for snapshot in upstream_snapshots:
            Storage.cache_snapshot(snapshot)

    @staticmethod
    def service_snapshot_size(snapshot_id: str) -> int:
        return Backups.provider().backupper.restored_size(
            snapshot_id,
        )

    @staticmethod
    def _store_last_snapshot(service_id: str, snapshot: Snapshot):
        """What do we do with a snapshot that is just made?"""
        # non-expiring timestamp of the last
        Storage.store_last_timestamp(service_id, snapshot)
        # expiring cache entry
        Storage.cache_snapshot(snapshot)


### Autobackup
    
    @staticmethod
    def is_autobackup_enabled(service: Service) -> bool:
        return Storage.is_autobackup_set(service.get_id())

    @staticmethod
    def enable_autobackup(service: Service):
        Storage.set_autobackup(service)

    @staticmethod
    def disable_autobackup(service: Service):
        """also see disable_all_autobackup()"""
        Storage.unset_autobackup(service)

    @staticmethod
    def disable_all_autobackup():
        """
        Disables all automatic backing up,
        but does not change per-service settings
        """
        Storage.delete_backup_period()

    @staticmethod
    def autobackup_period_minutes() -> Optional[int]:
        """None means autobackup is disabled"""
        return Storage.autobackup_period_minutes()

    @staticmethod
    def set_autobackup_period_minutes(minutes: int):
        """
        0 and negative numbers are equivalent to disable.
        Setting to a positive number may result in a backup very soon
        if some services are not backed up.
        """
        if minutes <= 0:
            Backups.disable_all_autobackup()
            return
        Storage.store_autobackup_period_minutes(minutes)

    @staticmethod
    def is_time_to_backup(time: datetime) -> bool:
        """
        Intended as a time validator for huey cron scheduler
        of automatic backups
        """

        return Backups._service_ids_to_back_up(time) != []

    @staticmethod
    def services_to_back_up(time: datetime) -> List[Service]:
        result = []
        for id in Backups._service_ids_to_back_up(time):
            service = get_service_by_id(id)
            if service is None:
                raise ValueError(
                    "Cannot look up a service scheduled for backup!",
                )
            result.append(service)
        return result

    @staticmethod
    def get_last_backed_up(service: Service) -> Optional[datetime]:
        """Get a timezone-aware time of the last backup of a service"""
        return Storage.get_last_backup_time(service.get_id())

    @staticmethod
    def is_time_to_backup_service(service_id: str, time: datetime):
        period = Backups.autobackup_period_minutes()
        if period is None:
            return False
        if not Storage.is_autobackup_set(service_id):
            return False

        last_backup = Storage.get_last_backup_time(service_id)
        if last_backup is None:
            # queue a backup immediately if there are no previous backups
            return True

        if time > last_backup + timedelta(minutes=period):
            return True
        return False

    @staticmethod
    def _service_ids_to_back_up(time: datetime) -> List[str]:
        services = Storage.services_with_autobackup()
        return [
            id
            for id in services
            if Backups.is_time_to_backup_service(
                id,
                time,
            )
        ]

### Helpers

    @staticmethod
    def space_usable_for_service(service: Service) -> int:
        folders = service.get_folders()
        if folders == []:
            raise ValueError("unallocated service", service.get_id())

        fs_info = statvfs(folders[0])
        usable_bytes = fs_info.f_frsize * fs_info.f_bavail
        return usable_bytes

    @staticmethod
    def set_localfile_repo(file_path: str):
        ProviderClass = get_provider(BackupProviderEnum.FILE)
        provider = ProviderClass(
            login="",
            key="",
            location=file_path,
            repo_id="",
        )
        Storage.store_provider(provider)