"""Application factory, lifespan and error handling."""

from __future__ import annotations

import logging
from collections.abc import AsyncIterator
from contextlib import asynccontextmanager

from fastapi import FastAPI, Request, status
from fastapi.responses import JSONResponse, Response
from fastapi.staticfiles import StaticFiles
from starlette.exceptions import HTTPException as StarletteHTTPException

from lembas import __version__
from lembas.api import (
    admin,
    admin_agents,
    admin_audio,
    admin_branding,
    admin_extraction,
    admin_images,
    admin_models,
    admin_prompts,
    admin_schedules,
    admin_search,
    admin_suggestions,
    admin_tools,
    admin_updates,
    admin_users,
    agents,
    audio,
    auth,
    branding,
    canvas,
    chats,
    files,
    folders,
    library,
    messages,
    pages,
    preferences,
    push,
    reports,
    schedules,
    sharing,
    terminal,
)
from lembas.api.deps import RedirectToLogin, is_htmx, login_redirect
from lembas.config import settings
from lembas.db.session import init_db
from lembas.services.library import indexing
from lembas.web.templating import STATIC_DIR, render

log = logging.getLogger("lembas")


def configure_logging() -> None:
    logging.basicConfig(
        level=settings.log_level.upper(),
        format="%(asctime)s  %(levelname)-7s %(name)s: %(message)s",
        datefmt="%H:%M:%S",
    )


@asynccontextmanager
async def lifespan(app: FastAPI) -> AsyncIterator[None]:
    configure_logging()
    settings.ensure_dirs()
    init_db()

    if settings.secret_key_is_ephemeral:
        log.warning(
            "No LEMBAS_SECRET_KEY set, so a temporary one was generated. Every "
            "restart will sign all users out and make stored API keys "
            "unreadable. Generate a permanent key with:\n"
            '    python -c "import secrets; print(secrets.token_urlsafe(48))"'
        )

    # Files chosen in a composer that was never sent would otherwise sit on
    # disk forever. Cheap, and startup is the natural moment for it.
    try:
        from lembas.db.session import session_scope
        from lembas.services.chat import sweep_temporary
        from lembas.services.files import sweep_orphans
        from lembas.services.library.documents import sweep_unfiled
        from lembas.services.library.indexing import sweep_orphans as sweep_chunks
        from lembas.services.suggestions import seed_defaults as seed_suggestions

        with session_scope() as db:
            sweep_orphans(db)
            # Documents that predate knowledge bases have nowhere to live until
            # this runs; see services/library/documents.py.
            sweep_unfiled(db)
            # Temporary chats older than a day. Startup only, like the sweeps
            # above it -- see services/chat.py:sweep_temporary.
            sweep_temporary(db)
            # Chunks whose record has gone. A backstop for a delete that
            # happened with no event loop to schedule the tidy-up -- a CLI
            # command, or a cascade from removing an account.
            sweep_chunks(db)
            # Three starting points on the empty screen, written once ever.
            seed_suggestions(db)
    except Exception:  # noqa: BLE001 - housekeeping must never block startup
        log.exception("orphaned upload sweep failed")

    # Background jobs that were still running when we last stopped keep running
    # on their own hosts; pick their watchers back up so the model is still
    # woken when they finish. Best-effort, and inside the loop so its tasks land
    # in this event loop.
    try:
        from lembas.services.agent.jobs import rehydrate as rehydrate_jobs

        rehydrate_jobs()
    except Exception:  # noqa: BLE001 - a job that cannot be rehydrated is not fatal
        log.exception("could not rehydrate background jobs")

    # Schedules. `release_claims` first, because a firing interrupted by the
    # last shutdown left a claim stamp that would otherwise read as permanently
    # running. Then the ticker, started here rather than lazily like the
    # terminal reaper: a schedule can be due at startup with nobody logged in,
    # which is most of the point of having one. Inside the loop, so its tasks
    # land in this event loop.
    #
    # Catching up on what was missed is deliberately NOT done here. It lives in
    # the sweep, because a suspended laptop, a paused container and a long stall
    # all reproduce "its time passed while nothing was running" with no restart
    # for a startup hook to hang on.
    try:
        from lembas.services.schedule.ticker import release_claims
        from lembas.services.schedule.ticker import start as start_ticker

        released = release_claims()
        if released:
            log.info("released %s interrupted schedule claim(s)", released)
        start_ticker()
    except Exception:  # noqa: BLE001 - scheduling failing must not block startup
        log.exception("could not start the schedule ticker")

    log.info("LLeMbas %s starting on http://%s:%s", __version__, settings.host, settings.port)
    log.info("data directory: %s", settings.data_dir.resolve())
    yield

    # Replies still being written are cancelled and persisted with whatever
    # they have, rather than left as permanently unfinished rows.
    from lembas.services.agent.jobs import shutdown as stop_jobs
    from lembas.services.agent.terminal import shutdown as stop_terminals
    from lembas.services.generation import shutdown as stop_generations
    from lembas.services.schedule.ticker import shutdown as stop_ticker

    # Before the generations, so nothing new is fired into a chat whose reply is
    # about to be cancelled and persisted.
    await stop_ticker()
    await stop_generations()
    # Open shells have nothing to persist: whatever was running on the far side
    # is cut off mid-command. Every deploy does this, and the panel is told why
    # rather than left to guess -- see deploy/README.md.
    await stop_terminals()
    # Background jobs are the exception: cancelling a watcher does NOT stop the
    # detached remote job, which keeps running and is rehydrated on the next
    # start. Only the watching stops here.
    await stop_jobs()
    # A chunk set is written whole or not at all, so cancelling loses nothing
    # a rebuild does not pick up again.
    await indexing.shutdown()
    log.info("LLeMbas stopped")


def create_app() -> FastAPI:
    app = FastAPI(
        title="LLeMbas",
        version=__version__,
        lifespan=lifespan,
        # The API is an implementation detail of the UI, not a product surface.
        docs_url="/api/docs" if settings.log_level == "debug" else None,
        redoc_url=None,
    )

    app.mount("/static", StaticFiles(directory=str(STATIC_DIR)), name="static")

    # One place that notices a library record changing, rather than a call in
    # each of the ten writers that touch those tables. Idempotent, because the
    # factory is called per test. See services/library/indexing.py:install.
    indexing.install()

    app.include_router(pages.router)
    app.include_router(auth.router)
    app.include_router(preferences.router)
    app.include_router(chats.router)
    app.include_router(canvas.router)
    app.include_router(terminal.router)
    app.include_router(audio.router)
    app.include_router(files.router)
    app.include_router(folders.router)
    app.include_router(library.router)
    app.include_router(messages.router)
    app.include_router(reports.router)
    app.include_router(schedules.router)
    app.include_router(agents.router)
    app.include_router(sharing.router)
    app.include_router(admin.router)
    app.include_router(admin_users.router)
    app.include_router(admin_updates.router)
    app.include_router(admin_models.router)
    app.include_router(admin_audio.router)
    app.include_router(admin_branding.router)
    app.include_router(admin_extraction.router)
    app.include_router(admin_search.router)
    app.include_router(admin_schedules.router)
    app.include_router(admin_images.router)
    app.include_router(admin_prompts.router)
    app.include_router(admin_suggestions.router)
    app.include_router(admin_tools.router)
    app.include_router(admin_agents.router)
    app.include_router(push.router)
    app.include_router(branding.router)

    register_error_handlers(app)
    return app


def register_error_handlers(app: FastAPI) -> None:
    @app.exception_handler(RedirectToLogin)
    async def _not_signed_in(request: Request, exc: RedirectToLogin) -> Response:
        # An htmx request must not swap a login page into a fragment of the
        # chat UI, so tell the browser to navigate instead.
        if is_htmx(request):
            response = Response(status_code=status.HTTP_204_NO_CONTENT)
            response.headers["HX-Redirect"] = "/auth/login"
            return response
        return login_redirect(exc.next_url)

    @app.exception_handler(StarletteHTTPException)
    async def _http_error(request: Request, exc: StarletteHTTPException) -> Response:
        # JSON callers and htmx fragments want the bare status; humans loading a
        # page want a themed page they can navigate away from.
        wants_page = "text/html" in request.headers.get("accept", "") and not is_htmx(request)
        if not wants_page:
            return JSONResponse({"detail": exc.detail}, status_code=exc.status_code)

        return render(
            request,
            "error.html",
            {
                "status_code": exc.status_code,
                "detail": exc.detail,
                "flavour": error_flavour(exc.status_code),
            },
            status_code=exc.status_code,
        )

    @app.exception_handler(Exception)
    async def _unhandled(request: Request, exc: Exception) -> Response:
        log.exception("unhandled error at %s", request.url.path)
        if is_htmx(request) or "text/html" not in request.headers.get("accept", ""):
            return JSONResponse({"detail": "Internal server error"}, status_code=500)
        return render(
            request,
            "error.html",
            {"status_code": 500, "detail": "Something went wrong.",
             "flavour": error_flavour(500)},
            status_code=500,
        )


# Flavour lives in error pages, empty states and theme names -- never in the
# functional UI. See the working notes.
#
# The three lines themselves moved into `services/branding.py` with the rest of
# what an administrator can replace. What is left here is the mapping from a
# status code to which of them, which is not something anybody would want to
# edit. `snapshot()` never raises, so an error page can still render its error
# on an instance whose database is the thing that broke.
def error_flavour(status_code: int) -> str:
    from lembas.services import branding

    text = branding.snapshot().text
    return text.get(f"error_{status_code}") or text["error_500"]


app = create_app()
