"""FastAPI application factory and ASGI entry point."""

from __future__ import annotations

from typing import cast

from fastapi import FastAPI

from app.api.errors import ApiError, api_error_handler, unhandled_exception_handler
from app.api.middleware import RequestContextMiddleware
from app.api.registry import HandlerRegistry, register_contract_routes
from app.compatibility import build_report
from app.config import Settings, get_settings
from app.contracts.model import Snapshot
from app.db.pool import AsyncpgDatabase, Database
from app.handlers.core import build_core_handlers
from app.lifespan import DatabaseFactory, WorkerFactory, create_lifespan, default_database_factory
from app.logging import configure_logging
from app.observability.health import router as health_router
from app.simulation.clock import AcceleratedClock
from app.tasks.qemu import qemu_handler
from app.tasks.repository import TaskRepository
from app.tasks.worker import TaskWorker


def create_app(
    settings: Settings | None = None,
    database_factory: DatabaseFactory = default_database_factory,
    handlers: HandlerRegistry | None = None,
    worker_factories: tuple[WorkerFactory, ...] | None = None,
) -> FastAPI:
    """Create an isolated application instance with explicit resource factories."""

    resolved = settings or get_settings()
    configure_logging(resolved.log_level)
    resolved_workers = worker_factories
    if resolved_workers is None and resolved.contract_snapshot is not None and handlers is None:

        def task_worker(database: Database) -> TaskWorker:
            adapter = cast(AsyncpgDatabase, database)
            repository = TaskRepository(adapter.pool)
            handler = qemu_handler(repository, AcceleratedClock(resolved.simulation_time_scale))
            return TaskWorker(
                repository,
                "simulator-worker",
                {"qemu-start": handler, "qemu-stop": handler},
                concurrency=resolved.task_worker_concurrency,
                lease_seconds=resolved.task_lease_seconds,
            )

        resolved_workers = (task_worker,)
    app = FastAPI(
        title=resolved.app_name,
        version="0.1.0",
        lifespan=create_lifespan(resolved, database_factory, resolved_workers or ()),
    )
    app.state.settings = resolved
    app.add_middleware(RequestContextMiddleware, header_name=resolved.request_id_header)
    app.add_exception_handler(Exception, unhandled_exception_handler)
    app.add_exception_handler(ApiError, api_error_handler)
    app.include_router(health_router)
    if resolved.contract_snapshot is not None:
        snapshot = Snapshot.model_validate_json(resolved.contract_snapshot.read_bytes())
        resolved_handlers = handlers or build_core_handlers(resolved)
        register_contract_routes(
            app,
            snapshot,
            resolved_handlers,
            resolved.contract_fallback,
        )
        declared = frozenset(
            (path.path, method.verb) for path in snapshot.paths for method in path.methods
        )
        report = build_report(snapshot, implemented=resolved_handlers.keys() & declared)

        @app.get("/admin/compatibility", include_in_schema=False)
        async def compatibility_report() -> dict[str, object]:
            return report.as_json()

    return app


app = create_app()