"""Backup platform for the cloud integration."""

from __future__ import annotations

import asyncio
from collections.abc import AsyncIterator, Callable, Coroutine, Mapping
import logging
import random
from typing import Any

from aiohttp import ClientError
from hass_nabucasa import Cloud, CloudError
from hass_nabucasa.api import CloudApiNonRetryableError
from hass_nabucasa.cloud_api import (
    FilesHandlerListEntry,
    async_files_delete_file,
    async_files_list,
)
from hass_nabucasa.files import FilesError, StorageType, calculate_b64md5

from homeassistant.components.backup import AgentBackup, BackupAgent, BackupAgentError
from homeassistant.core import HomeAssistant, callback
from homeassistant.helpers.aiohttp_client import ChunkAsyncStreamIterator
from homeassistant.helpers.dispatcher import async_dispatcher_connect

from .client import CloudClient
from .const import DATA_CLOUD, DOMAIN, EVENT_CLOUD_EVENT

_LOGGER = logging.getLogger(__name__)
_RETRY_LIMIT = 5
_RETRY_SECONDS_MIN = 60
_RETRY_SECONDS_MAX = 600


async def async_get_backup_agents(
    hass: HomeAssistant,
    **kwargs: Any,
) -> list[BackupAgent]:
    """Return the cloud backup agent."""
    cloud = hass.data[DATA_CLOUD]
    if not cloud.is_logged_in:
        return []

    return [CloudBackupAgent(hass=hass, cloud=cloud)]


@callback
def async_register_backup_agents_listener(
    hass: HomeAssistant,
    *,
    listener: Callable[[], None],
    **kwargs: Any,
) -> Callable[[], None]:
    """Register a listener to be called when agents are added or removed."""

    @callback
    def unsub() -> None:
        """Unsubscribe from events."""
        unsub_signal()

    @callback
    def handle_event(data: Mapping[str, Any]) -> None:
        """Handle event."""
        if data["type"] not in ("login", "logout"):
            return
        listener()

    unsub_signal = async_dispatcher_connect(hass, EVENT_CLOUD_EVENT, handle_event)
    return unsub


class CloudBackupAgent(BackupAgent):
    """Cloud backup agent."""

    domain = name = unique_id = DOMAIN

    def __init__(self, hass: HomeAssistant, cloud: Cloud[CloudClient]) -> None:
        """Initialize the cloud backup sync agent."""
        super().__init__()
        self._cloud = cloud
        self._hass = hass

    async def async_download_backup(
        self,
        backup_id: str,
        **kwargs: Any,
    ) -> AsyncIterator[bytes]:
        """Download a backup file.

        :param backup_id: The ID of the backup that was returned in async_list_backups.
        :return: An async iterator that yields bytes.
        """
        if not (backup := await self._async_get_backup(backup_id)):
            raise BackupAgentError("Backup not found")

        try:
            content = await self._cloud.files.download(
                storage_type=StorageType.BACKUP,
                filename=backup["Key"],
            )
        except CloudError as err:
            raise BackupAgentError(f"Failed to download backup: {err}") from err

        return ChunkAsyncStreamIterator(content)

    async def async_upload_backup(
        self,
        *,
        open_stream: Callable[[], Coroutine[Any, Any, AsyncIterator[bytes]]],
        backup: AgentBackup,
        **kwargs: Any,
    ) -> None:
        """Upload a backup.

        :param open_stream: A function returning an async iterator that yields bytes.
        :param backup: Metadata about the backup that should be uploaded.
        """
        if not backup.protected:
            raise BackupAgentError("Cloud backups must be protected")

        size = backup.size
        try:
            base64md5hash = await calculate_b64md5(open_stream, size)
        except FilesError as err:
            raise BackupAgentError(err) from err
        filename = f"{self._cloud.client.prefs.instance_id}.tar"
        metadata = backup.as_dict()

        tries = 1
        while tries <= _RETRY_LIMIT:
            try:
                await self._cloud.files.upload(
                    storage_type=StorageType.BACKUP,
                    open_stream=open_stream,
                    filename=filename,
                    base64md5hash=base64md5hash,
                    metadata=metadata,
                    size=size,
                )
                break
            except CloudApiNonRetryableError as err:
                if err.code == "NC-SH-FH-03":
                    raise BackupAgentError(
                        translation_domain=DOMAIN,
                        translation_key="backup_size_too_large",
                        translation_placeholders={
                            "size": str(round(size / (1024**3), 2))
                        },
                    ) from err
                raise BackupAgentError(f"Failed to upload backup {err}") from err
            except CloudError as err:
                if tries == _RETRY_LIMIT:
                    raise BackupAgentError(f"Failed to upload backup {err}") from err
                tries += 1
                retry_timer = random.randint(_RETRY_SECONDS_MIN, _RETRY_SECONDS_MAX)
                _LOGGER.info(
                    "Failed to upload backup, retrying (%s/%s) in %ss: %s",
                    tries,
                    _RETRY_LIMIT,
                    retry_timer,
                    err,
                )
                await asyncio.sleep(retry_timer)

    async def async_delete_backup(
        self,
        backup_id: str,
        **kwargs: Any,
    ) -> None:
        """Delete a backup file.

        :param backup_id: The ID of the backup that was returned in async_list_backups.
        """
        if not (backup := await self._async_get_backup(backup_id)):
            return

        try:
            await async_files_delete_file(
                self._cloud,
                storage_type=StorageType.BACKUP,
                filename=backup["Key"],
            )
        except (ClientError, CloudError) as err:
            raise BackupAgentError("Failed to delete backup") from err

    async def async_list_backups(self, **kwargs: Any) -> list[AgentBackup]:
        """List backups."""
        backups = await self._async_list_backups()
        return [AgentBackup.from_dict(backup["Metadata"]) for backup in backups]

    async def _async_list_backups(self) -> list[FilesHandlerListEntry]:
        """List backups."""
        try:
            backups = await async_files_list(
                self._cloud, storage_type=StorageType.BACKUP
            )
        except (ClientError, CloudError) as err:
            raise BackupAgentError("Failed to list backups") from err

        _LOGGER.debug("Cloud backups: %s", backups)
        return backups

    async def async_get_backup(
        self,
        backup_id: str,
        **kwargs: Any,
    ) -> AgentBackup | None:
        """Return a backup."""
        if not (backup := await self._async_get_backup(backup_id)):
            return None
        return AgentBackup.from_dict(backup["Metadata"])

    async def _async_get_backup(
        self,
        backup_id: str,
    ) -> FilesHandlerListEntry | None:
        """Return a backup."""
        backups = await self._async_list_backups()

        for backup in backups:
            if backup["Metadata"]["backup_id"] == backup_id:
                return backup

        return None