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# Source code for betty.app

    """Define Betty's core application functionality."""

    from __future__ import annotations

    from concurrent.futures import Executor, ProcessPoolExecutor
    from contextlib import asynccontextmanager
    from multiprocessing import get_context
    from os import environ
    from pathlib import Path
    from typing import TYPE_CHECKING, Self, Any, final

    import aiohttp
    from aiofiles.tempfile import TemporaryDirectory
    from betty import fs
    from betty.app import config
    from betty.app.config import AppConfiguration
    from betty.assets import AssetRepository
    from betty.asyncio import wait_to_thread
    from betty.cache.file import BinaryFileCache, PickledFileCache
    from betty.cache.no_op import NoOpCache
    from betty.config import Configurable, assert_configuration_file
    from betty.core import CoreComponent
    from betty.fetch import Fetcher, http
    from betty.fs import HOME_DIRECTORY_PATH
    from betty.locale import DEFAULT_LOCALE
    from betty.locale.localizer import Localizer, LocalizerRepository

    if TYPE_CHECKING:
        from betty.cache import Cache
        from collections.abc import AsyncIterator, Callable

    @final
    class App(Configurable[AppConfiguration], CoreComponent):
        """
        The Betty application.
        """

        def __init__(
            self,
            configuration: AppConfiguration,
            cache_directory_path: Path,
            *,
            cache_factory: Callable[[Self], Cache[Any]],
        ):
            super().__init__()
            self._configuration = configuration
            self._assets: AssetRepository | None = None
            self._localization_initialized = False
            self._localizer: Localizer | None = None
            self._localizers: LocalizerRepository | None = None
            self._http_client: aiohttp.ClientSession | None = None
            self._fetcher: Fetcher | None = None
            self._cache_directory_path = cache_directory_path
            self._cache: Cache[Any] | None = None
            self._cache_factory = cache_factory
            self._binary_file_cache: BinaryFileCache | None = None
            self._process_pool: Executor | None = None

        @classmethod
        @asynccontextmanager
        async def new_from_environment(cls) -> AsyncIterator[Self]:
            """
            Create a new application from the environment.
            """
            configuration = AppConfiguration()
            if config.CONFIGURATION_FILE_PATH.exists():
                assert_configuration_file(configuration)(config.CONFIGURATION_FILE_PATH)
            yield cls(
                configuration,
                Path(environ.get("BETTY_CACHE_DIRECTORY", HOME_DIRECTORY_PATH / "cache")),
                cache_factory=lambda app: PickledFileCache[Any](app._cache_directory_path),
            )

        @classmethod
        @asynccontextmanager
        async def new_temporary(cls) -> AsyncIterator[Self]:
            """
            Creat a new, temporary, isolated application.

            The application will not use any persistent caches, or leave
            any traces on the system.
            """
            async with (
                TemporaryDirectory() as cache_directory_path_str,
            ):
                yield cls(
                    AppConfiguration(),
                    Path(cache_directory_path_str),
                    cache_factory=lambda app: NoOpCache(),
                )

        @property
        def assets(self) -> AssetRepository:
            """
            The assets file system.
            """
            if self._assets is None:
                self._assert_bootstrapped()
                self._assets = AssetRepository(fs.ASSETS_DIRECTORY_PATH)
            return self._assets

        @property
        def localizer(self) -> Localizer:
            """
            Get the application's localizer.
            """
            if self._localizer is None:
                self._assert_bootstrapped()
                self._localizer = wait_to_thread(
                    self.localizers.get_negotiated(
                        self.configuration.locale or DEFAULT_LOCALE
                    )
                )
            return self._localizer

        @property
        def localizers(self) -> LocalizerRepository:
            """
            The available localizers.
            """
            if self._localizers is None:
                self._assert_bootstrapped()
                self._localizers = LocalizerRepository(self.assets)
            return self._localizers

        @property
        def http_client(self) -> aiohttp.ClientSession:
            """
            The HTTP client.
            """
            if self._http_client is None:
                self._assert_bootstrapped()
                self._http_client = aiohttp.ClientSession(
                    connector=aiohttp.TCPConnector(limit_per_host=5),
                    headers={
                        "User-Agent": "Betty (https://github.com/bartfeenstra/betty)",
                    },
                )
                wait_to_thread(
                    self._async_exit_stack.enter_async_context(self._http_client)
                )
            return self._http_client

        @property
        def fetcher(self) -> Fetcher:
            """
            The fetcher.
            """
            if self._fetcher is None:
                self._assert_bootstrapped()
                self._fetcher = http.HttpFetcher(
                    self.http_client,
                    self.cache.with_scope("fetch"),
                    self.binary_file_cache.with_scope("fetch"),
                )
            return self._fetcher

        @property
        def cache(self) -> Cache[Any]:
            """
            The cache.
            """
            if self._cache is None:
                self._assert_bootstrapped()
                self._cache = self._cache_factory(self)
            return self._cache

        @property
        def binary_file_cache(self) -> BinaryFileCache:
            """
            The binary file cache.
            """
            if self._binary_file_cache is None:
                self._assert_bootstrapped()
                self._binary_file_cache = BinaryFileCache(self._cache_directory_path)
            return self._binary_file_cache

        @property
        def process_pool(self) -> Executor:
            """
            The shared process pool.

            Use this to run CPU/computationally-heavy tasks in other processes.
            """
            if self._process_pool is None:
                self._assert_bootstrapped()
                # Avoid `fork` so as not to start worker processes with unneeded resources.
                # Settle for `spawn` so all environments use the same start method.
                self._process_pool = ProcessPoolExecutor(mp_context=get_context("spawn"))
            return self._process_pool