"""Helpers to help with integration platforms."""

import asyncio
from collections.abc import Awaitable, Callable
from dataclasses import dataclass
from functools import partial
import logging
from types import ModuleType
from typing import Any

from homeassistant.const import EVENT_COMPONENT_LOADED
from homeassistant.core import Event, HassJob, HomeAssistant, callback
from homeassistant.loader import (
    Integration,
    async_get_integration,
    async_get_integrations,
    async_get_loaded_integration,
    async_register_preload_platform,
)
from homeassistant.setup import ATTR_COMPONENT, EventComponentLoaded
from homeassistant.util.hass_dict import HassKey
from homeassistant.util.logging import catch_log_exception

_LOGGER = logging.getLogger(__name__)
DATA_INTEGRATION_PLATFORMS: HassKey[list[IntegrationPlatform]] = HassKey(
    "integration_platforms"
)


@dataclass(slots=True, frozen=True)
class IntegrationPlatform:
    """An integration platform."""

    platform_name: str
    process_job: HassJob[[HomeAssistant, str, Any], Awaitable[None] | None]
    seen_components: set[str]


@callback
def _async_integration_platform_component_loaded(
    hass: HomeAssistant,
    integration_platforms: list[IntegrationPlatform],
    event: Event[EventComponentLoaded],
) -> None:
    """Process integration platforms for a component."""
    if "." in (component_name := event.data[ATTR_COMPONENT]):
        return

    integration = async_get_loaded_integration(hass, component_name)
    # First filter out platforms that the integration already processed.
    integration_platforms_by_name: dict[str, IntegrationPlatform] = {}
    for integration_platform in integration_platforms:
        if component_name in integration_platform.seen_components:
            continue
        integration_platform.seen_components.add(component_name)
        integration_platforms_by_name[integration_platform.platform_name] = (
            integration_platform
        )

    if not integration_platforms_by_name:
        return

    # Next, check which platforms exist for this integration.
    platforms_that_exist = integration.platforms_exists(integration_platforms_by_name)
    if not platforms_that_exist:
        return

    # If everything is already loaded, we can avoid creating a task.
    can_use_cache = True
    platforms: dict[str, ModuleType] = {}
    for platform_name in platforms_that_exist:
        if platform := integration.get_platform_cached(platform_name):
            platforms[platform_name] = platform
        else:
            can_use_cache = False
            break

    if can_use_cache:
        _process_integration_platforms(
            hass,
            integration,
            platforms,
            integration_platforms_by_name,
        )
        return

    # At least one of the platforms is not loaded, we need to load them
    # so we have to fall back to creating a task.
    hass.async_create_task_internal(
        _async_process_integration_platforms_for_component(
            hass, integration, platforms_that_exist, integration_platforms_by_name
        ),
        eager_start=True,
    )


async def _async_process_integration_platforms_for_component(
    hass: HomeAssistant,
    integration: Integration,
    platforms_that_exist: list[str],
    integration_platforms_by_name: dict[str, IntegrationPlatform],
) -> None:
    """Process integration platforms for a component."""
    # Now we know which platforms to load, let's load them.
    try:
        platforms = await integration.async_get_platforms(platforms_that_exist)
    except ImportError:
        _LOGGER.debug(
            "Unexpected error importing integration platforms for %s",
            integration.domain,
        )
        return

    if futures := _process_integration_platforms(
        hass,
        integration,
        platforms,
        integration_platforms_by_name,
    ):
        await asyncio.gather(*futures)


@callback
def _process_integration_platforms(
    hass: HomeAssistant,
    integration: Integration,
    platforms: dict[str, ModuleType],
    integration_platforms_by_name: dict[str, IntegrationPlatform],
) -> list[asyncio.Future[Awaitable[None] | None]]:
    """Process integration platforms for a component.

    Only the platforms that are passed in will be processed.
    """
    return [
        future
        for platform_name, platform in platforms.items()
        if (integration_platform := integration_platforms_by_name[platform_name])
        and (
            future := hass.async_run_hass_job(
                integration_platform.process_job,
                hass,
                integration.domain,
                platform,
            )
        )
    ]


def _format_err(name: str, platform_name: str, *args: Any) -> str:
    """Format error message."""
    return f"Exception in {name} when processing platform '{platform_name}': {args}"


async def _async_import_platform(
    integration: Integration, platform_name: str
) -> ModuleType | None:
    """Import a single platform for an integration.

    Returns None if the integration does not provide the platform or it could
    not be imported.
    """
    if not integration.platforms_exists((platform_name,)):
        return None
    try:
        return await integration.async_get_platform(platform_name)
    except ImportError:
        _LOGGER.debug(
            "Error importing %s platform for %s", platform_name, integration.domain
        )
        return None


async def async_process_integration_platforms(
    hass: HomeAssistant,
    platform_name: str,
    # Any = platform.
    process_platform: Callable[[HomeAssistant, str, Any], Awaitable[None] | None],
    wait_for_platforms: bool = False,
) -> None:
    """Process a specific platform for all current and future loaded integrations."""
    if DATA_INTEGRATION_PLATFORMS not in hass.data:
        integration_platforms = hass.data[DATA_INTEGRATION_PLATFORMS] = []
        hass.bus.async_listen(
            EVENT_COMPONENT_LOADED,
            partial(
                _async_integration_platform_component_loaded,
                hass,
                integration_platforms,
            ),
        )
    else:
        integration_platforms = hass.data[DATA_INTEGRATION_PLATFORMS]

    # Tell the loader that it should try to pre-load the integration
    # for any future components that are loaded so we can reduce the
    # amount of import executor usage.
    async_register_preload_platform(hass, platform_name)
    top_level_components = hass.config.top_level_components.copy()
    process_job = HassJob(
        catch_log_exception(
            process_platform,
            partial(_format_err, str(process_platform), platform_name),
        ),
        f"process_platform {platform_name}",
    )
    integration_platform = IntegrationPlatform(
        platform_name, process_job, top_level_components
    )
    integration_platforms.append(integration_platform)
    if not top_level_components:
        return

    # We create a task here for two reasons:
    #
    # 1. We want the integration that provides the integration platform to
    #    not be delayed by waiting on each individual platform to be processed
    #    since the import or the integration platforms themselves may have to
    #    schedule I/O or executor jobs.
    #
    # 2. We want the behavior to be the same as if the integration that has
    #    the integration platform is loaded after the platform is processed.
    #
    # We use hass.async_create_task instead of asyncio.create_task because
    # we want to make sure that startup waits for the task to complete.
    #
    future = hass.async_create_task_internal(
        _async_process_integration_platforms(
            hass, platform_name, top_level_components.copy(), process_job
        ),
        eager_start=True,
    )
    if wait_for_platforms:
        await future


async def _async_process_integration_platforms(
    hass: HomeAssistant,
    platform_name: str,
    top_level_components: set[str],
    process_job: HassJob,
) -> None:
    """Process integration platforms for a component."""
    integrations = await async_get_integrations(hass, top_level_components)
    loaded_integrations: list[Integration] = [
        integration
        for integration in integrations.values()
        if not isinstance(integration, Exception)
    ]
    # Finally, fetch the platforms for each integration and process them.
    # This uses the import executor in a loop. If there are a lot
    # of integration with the integration platform to process,
    # this could be a bottleneck.
    futures: list[asyncio.Future[None]] = []
    for integration in loaded_integrations:
        if (
            platform := await _async_import_platform(integration, platform_name)
        ) is None:
            continue
        if future := hass.async_run_hass_job(
            process_job, hass, integration.domain, platform
        ):
            futures.append(future)

    if futures:
        await asyncio.gather(*futures)


# Any = platform.
type ProcessPlatform[_R] = Callable[[HomeAssistant, str, Any], _R | Awaitable[_R]]


class LazyIntegrationPlatforms[_R]:
    """Lazily load and process an integration platform on demand.

    Unlike async_process_integration_platforms, which imports and processes the
    platform for every loaded integration up front (and as integrations load),
    this only imports and processes the platform for an integration the first
    time it is requested, and only for integrations that are loaded.

    The process callback may be a coroutine function; its result is awaited.

    The platform is intentionally not registered for preloading, since for a
    rarely used platform that would import it for every integration during
    loading, defeating the point of loading it lazily.
    """

    def __init__(
        self,
        hass: HomeAssistant,
        platform_name: str,
        process_platform: ProcessPlatform[_R],
    ) -> None:
        """Initialize the lazy integration platforms."""
        self._hass = hass
        self._platform_name = platform_name
        self._process_platform = process_platform
        # A cached value of None means the integration does not provide the
        # platform (or it failed to import).
        self._processed: dict[str, _R | None] = {}
        # In-flight processing per domain, so concurrent callers share the work.
        self._processing: dict[str, asyncio.Future[_R | None]] = {}

    async def async_get_platform(self, domain: str) -> _R | None:
        """Return the processed platform for a loaded integration.

        Returns None if the integration is not loaded or does not provide the
        platform. The result for a loaded integration is cached.
        """
        if domain in self._processed:
            return self._processed[domain]
        # Only process integrations whose component is loaded, matching
        # async_process_integration_platforms.
        if domain not in self._hass.config.top_level_components:
            # Don't cache, the integration may be loaded later.
            return None
        integration = await async_get_integration(self._hass, domain)
        return await self._async_process(integration)

    async def async_get_platforms(self) -> dict[str, _R]:
        """Return the processed platform for all loaded integrations that have it."""
        integrations = await async_get_integrations(
            self._hass, self._hass.config.top_level_components
        )
        to_process = [
            integration
            for integration in integrations.values()
            if not isinstance(integration, Exception)
            and integration.platforms_exists((self._platform_name,))
        ]
        if missing := [
            integration
            for integration in to_process
            if integration.domain not in self._processed
        ]:
            await asyncio.gather(
                *(self._async_process(integration) for integration in missing)
            )
        return {
            integration.domain: result
            for integration in to_process
            if (result := self._processed[integration.domain]) is not None
        }

    async def _async_process(self, integration: Integration) -> _R | None:
        """Import, process and cache the platform for a loaded integration.

        Concurrent callers for the same domain wait on a shared future so the
        platform is imported and processed at most once.
        """
        domain = integration.domain
        if domain in self._processed:
            return self._processed[domain]
        if (processing := self._processing.get(domain)) is not None:
            return await processing

        future: asyncio.Future[_R | None] = self._hass.loop.create_future()
        self._processing[domain] = future
        try:
            platform = await _async_import_platform(integration, self._platform_name)
            result: _R | None = None
            if platform is not None:
                try:
                    processed = self._process_platform(self._hass, domain, platform)
                    if isinstance(processed, Awaitable):
                        processed = await processed
                    result = processed
                except Exception:
                    _LOGGER.exception(
                        "Error processing %s platform for %s",
                        self._platform_name,
                        domain,
                    )
            self._processed[domain] = result
        except BaseException as err:
            future.set_exception(err)
            # Retrieve so an unawaited future does not log the exception.
            future.exception()
            raise
        finally:
            del self._processing[domain]
        future.set_result(result)
        return result