"""Brain of Reese — application entrypoint.

Boots logging + conditional debugpy, then creates the FastAPI app:
API routes first (so they win over the catch-all), and the static frontend
mounted last. No CDN: everything the browser needs is served by this
process from local files (see PLAN §UI/UX — No External Dependencies).

Phase 16 (A10 revised): before anything is served, admin auth must be
configured (fail-loud), and the app wraps every route in Starlette's
SessionMiddleware — a signed ``bor_session`` cookie is the only session
state in the system.
"""
from __future__ import annotations

import logging
from pathlib import Path

from fastapi import FastAPI
from fastapi.staticfiles import StaticFiles
from starlette.middleware.sessions import SessionMiddleware
from starlette.responses import FileResponse, Response

from app.api.admin_settings import router as admin_settings_router
from app.api.auth import router as auth_router
from app.api.chat import reset_runtime_caches
from app.api.chat import router as chat_router
from app.api.chat_images import router as chat_images_router
from app.api.chats import (
    public_router as chats_public_router,
)
from app.api.chats import (
    router as chats_router,
)
from app.api.chats import (
    shared_page_router as chats_shared_page_router,
)
from app.api.config import router as config_router
from app.api.doc_drafts import router as doc_drafts_router
from app.api.docs import router as docs_router
from app.api.git_sources import router as git_sources_router
from app.api.health import router as health_router
from app.api.steering import router as steering_router
from app.api.suggestions import router as suggestions_router
from app.api.sync import router as sync_router
from app.api.tokens import router as tokens_router
from app.api.ui_settings import router as ui_settings_router
from app.config import get_settings, invalidate_settings
from app.core import theming
from app.core.auth import ensure_admin_configured
from app.core.caching import configure_caching
from app.core.compression import SelectiveGZipMiddleware
from app.core.debugging import configure_debugging
from app.core.logging import configure_logging
from app.core.response_budget import ResponseBudgetMiddleware
from app.core.security_headers import SecurityHeadersMiddleware
from app.core.settings_migrate import migrate_legacy_docs_creds
from app.core.settings_overlay import enabled as settings_db_enabled
from app.core.settings_overlay import load_overrides, register_invalidator
from app.db import SessionLocal

configure_logging()
configure_debugging()

settings = get_settings()
logger = logging.getLogger("app")


def _shell_routes(app: FastAPI, static_dir: Path, paths: tuple[str, ...]) -> None:
    """Phase 76: the navbar views are views of ONE shell document.

    Every registered path serves ``frontend/index.html`` (the shell)
    instead of its own page file: the client-side router
    (``frontend/assets/router.js``) reads ``location.pathname`` at boot
    and shows the matching view, so a direct load of e.g.
    ``/tuning.html`` deep-links to the Tuning view. Registered AFTER the
    API routers and BEFORE the static catch-all mount (routes-first),
    so the phase-33 caching middleware — which wraps the whole app and
    already lists every one of these paths in ``HTML_PAGES`` — applies
    the no-cache + ``?v=<token>`` contract to the response untouched.
    The list is driven by the caller: tasks 02/03 fold the remaining
    views in by extending the tuple (task 03 lands History — all four
    non-chat navbar views are in; the old per-view ``.html`` files are
    deleted in the same change as their shell route lands — one source
    of truth).
    """
    shell_file = static_dir / "index.html"

    async def _shell_view() -> FileResponse:
        return FileResponse(shell_file, media_type="text/html")

    for path in paths:
        # GET (document loads, the browser path) + HEAD — the pre-fold
        # static file answered both, so the shell route keeps that
        # method parity (the body is the same FileResponse; HEAD ships
        # headers only).
        app.api_route(
            path, methods=["GET", "HEAD"], include_in_schema=False
        )(_shell_view)


def _favicon() -> Response:
    """Phase 177 (task 02, D2 — A2/A3 owner-confirmed): the themed
    favicon over the wire.

    Renders :func:`app.core.theming.favicon_svg` from the EFFECTIVE
    palette on EVERY request — one short-lived ``SessionLocal()``
    session, the ``caching.py`` middleware's house pattern: NO process
    cache, so a runtime theme change (the admin Theme tab's Save) is
    visible on the next request without a restart (a single-row SELECT
    is negligible at homelab traffic). ANY exception (a DB blip, a
    pre-migration boot) falls back to the BUILT-IN palette with 200 —
    never 500 (the theme-tag's never-break contract, ``caching.py``'s
    DB-blip fallback): the tab icon degrades to the built-in art, the
    app never errors on it.

    Deliberately OUTSIDE ``/api/*``: no per-response byte-budget line
    (AGENTS rule 10 is ``/api/*``-only) and NO auth dependency — the
    favicon is chrome, public like the login page.
    ``CachingMiddleware`` passes the response through untouched
    (``/favicon.svg`` is neither in ``HTML_PAGES`` nor under
    ``/assets/``) → the route's own ``Cache-Control: no-cache`` is the
    freshness contract (the palette changes at runtime; the pages are
    no-cache too, so the browser revalidates the favicon together with
    them — freshness is revalidation, not a ``?v=`` bust). The route is
    not under ``/assets/``, so its ``<link>`` ref can never be touched
    by the ``?v=`` rewrite. ``SecurityHeadersMiddleware`` still adds the
    CSP — no change needed (the phase-123 ``img-src 'self' data:``
    carve-out covers task 04's ``data:`` preview; CSP3 governs
    ``link[rel=icon]`` by ``img-src``).
    """
    try:
        db = SessionLocal()
        try:
            effective = theming.effective_settings(db)
        finally:
            db.close()
        svg = theming.favicon_svg(effective)
    except Exception:
        logger.exception(
            "favicon: theme read failed — serving the built-in favicon"
        )
        svg = theming.favicon_svg(theming.BUILTIN_COLORS)
    return Response(
        svg,
        media_type="image/svg+xml",
        headers={"Cache-Control": "no-cache"},
    )


def create_app() -> FastAPI:
    # Fail loud BEFORE serving anything (phase 16): missing
    # BOR_ADMIN_PASSWORD / BOR_SESSION_SECRET raises at boot, naming the
    # variable(s) — the app never starts in a half-authenticated state.
    ensure_admin_configured(settings)

    # Phase 168 (task 02, D2/D3): prime the DB-over-env resolver now
    # that auth is verified. The module-level ``settings`` above stays
    # the pre-boot value the middleware wiring below uses (LOCKED A4:
    # those boot-wired settings apply on the NEXT boot); every consumer
    # that calls get_settings() from here on resolves DB-over-env — no
    # restart. invalidate_settings() runs the runtime reset hooks
    # (task 03) and clears the cache; a boot-time DB miss is fail-soft
    # (one WARNING, env values in effect) and the next resolution
    # retries, so the prime can never cache an env-only view forever.
    invalidate_settings()
    if settings_db_enabled():
        get_settings()
        logger.info("settings overrides loaded count=%d", len(load_overrides()))
    else:
        get_settings()
        logger.info("settings overrides loaded source=env-only disabled")

    # Phase 173 (task 04, C3): the one-time startup migration — a
    # legacy credentials-bearing ``docs_repo`` (env or DB) is split
    # into ``app_settings`` rows (clean repo + ``docs_user`` +
    # ``docs_token``); the DB rows shadow the env, ``.env`` is never
    # rewritten, a second run is a no-op. Called ONCE, after the DB is
    # available; a migration hiccup logs a WARNING and never blocks
    # startup — the app boots with the pre-phase behavior (the
    # migration is a convenience, not a dependency).
    try:
        migrate_legacy_docs_creds()
    except Exception as exc:  # noqa: BLE001 — boot must never block
        logger.warning("settings migration failed (%s)", type(exc).__name__)

    # Phase 168 (task 03): the settings panel's Save must retune the
    # running process, and app/core must never import app/api (PLAN §3's
    # direction) — so create_app(), the composition root, wires the
    # reset hook. It runs on every invalidate_settings() after the cache
    # clear: the next chat turn rebuilds the shared LLMClient and the
    # concurrency semaphore from the CURRENT settings (no restart), while
    # in-flight turns keep the client they started with (A12 semantics).
    register_invalidator(reset_runtime_caches)
    logger.info("settings invalidator registered name=chat_runtime_caches")

    app = FastAPI(title=settings.app_name, version=settings.app_version)

    # Signed single-admin session cookie (Starlette middleware, itsdangerous
    # signer — no server-side store, no new services). Homelab HTTP: same_site
    # is "lax" and https_only stays off (documented in the README).
    app.add_middleware(
        SessionMiddleware,
        secret_key=settings.session_secret,
        session_cookie=settings.session_cookie,
        max_age=settings.session_max_age,
        same_site="lax",
        https_only=False,
    )

    # API routes first so they take precedence over the catch-all static mount.
    app.include_router(health_router, prefix="/api")
    app.include_router(config_router, prefix="/api")
    app.include_router(auth_router, prefix="/api")
    app.include_router(suggestions_router, prefix="/api")
    app.include_router(docs_router, prefix="/api")
    app.include_router(git_sources_router, prefix="/api")
    app.include_router(chat_router, prefix="/api")
    # Phase 123: the question-image upload/serve pair (POST is
    # user-gated like the chat turn; GET is public like saved-chat
    # content — the uuid filename is the credential).
    app.include_router(chat_images_router, prefix="/api")
    app.include_router(steering_router, prefix="/api")
    app.include_router(sync_router, prefix="/api")
    app.include_router(chats_router, prefix="/api")
    app.include_router(doc_drafts_router, prefix="/api")
    # Phase 79: the admin token surface (create/list/revoke) — admin-only
    # (router-wide require_admin; a token USER stays 403 here, task 03).
    app.include_router(tokens_router, prefix="/api")
    # Phase 91 (task 01): the admin UI-settings surface (GET/PUT the
    # single ui_settings row — the Theme tab's persistence) — admin-only
    # (router-wide require_admin; anonymous AND token users stay 403).
    app.include_router(ui_settings_router, prefix="/api")
    # Phase 168 (task 04): the admin settings panel surface (read/write
    # the app_settings overrides — DB-over-env, live on Save) — admin-only
    # (router-wide require_admin; a token user stays 403).
    app.include_router(admin_settings_router, prefix="/api")
    # Phase 51: the anonymous shared-chat read — NO admin dependency.
    # /api/shared/<token> is the JSON snapshot; /shared/<token> (the
    # page route below, registered without a prefix) is the page.
    app.include_router(chats_public_router, prefix="/api")
    app.include_router(chats_shared_page_router)  # no prefix — /shared/<token>

    # Phase 177 (task 02, D2 — A2/A3 owner-confirmed): the themed
    # favicon route — registered AFTER the router includes and BEFORE
    # the static catch-all mount (routes-first, the phase-51/76
    # pattern): a file named favicon.svg in the static dir could never
    # shadow it. HEAD joins GET for static-file parity (the
    # phase-76 ``_shell_routes`` parity idiom — the pre-phase static
    # file answered both methods, the dynamic route keeps that).
    # See the handler docstring for the never-break DB-blip fallback
    # and the /api/*-out rationale.
    app.api_route(
        "/favicon.svg", methods=["GET", "HEAD"], include_in_schema=False
    )(_favicon)

    # Cache busting (phase 33): the five HTML pages revalidate (no-cache)
    # with ?v=<token> asset refs; /assets/* becomes immutable for a year.
    # Added after the session middleware, so it wraps the whole app
    # (including the static catch-all below); /api/* — the SSE chat
    # stream in particular — passes through untouched.
    configure_caching(app)

    # Phase 167 (task 05, TODO L5): the byte budget — ONE
    # ``api method=… path=… status=… bytes=… enc=… duration_ms=…`` line per
    # /api/* response (INFO at/over BOR_LOG_LARGE_RESPONSE_BYTES, DEBUG
    # below), so "which endpoint is heavy, right now" is a
    # ``grep ' :: api '`` away. Position: added BEFORE the gzip call below,
    # i.e. INSIDE it (SecurityHeaders → gzip → response-budget → caching →
    # session → routes), so ``bytes=`` is the bytes the ROUTE produced
    # (uncompressed) while ``enc=`` reports what went on the wire — the two
    # together answer "how fat is it, and how fat did the client see it".
    # Pure ASGI (never BaseHTTPMiddleware): the SSE stream is counted as it
    # passes and logged once, when the stream ends.
    app.add_middleware(ResponseBudgetMiddleware)

    # Phase 167 (TODO L5): selective gzip — every response except the
    # POST /api/chat SSE stream (skipped by EXACT path, A15) compresses
    # when it is >= compress_min_bytes (the 2 MB /api/docs/tree defect).
    # 0 = the feature is OFF: no middleware is added at all (the
    # kill-switch convention). Position: added AFTER configure_caching but
    # BEFORE the SecurityHeaders line below, so SecurityHeaders stays
    # OUTERMOST (A20, the last add_middleware is outermost) and gzip sits
    # outside the caching layer — an already-rewritten HTML page compresses
    # too, and /api/* still passes the caching layer byte-identically
    # before compression.
    if settings.compress_min_bytes > 0:
        app.add_middleware(
            SelectiveGZipMiddleware, minimum_size=settings.compress_min_bytes
        )

    # Phase 82: security headers (CSP + no-framing + nosniff) — outermost on
    # purpose (last add_middleware): every response carries them, including
    # the static catch-all's 404s below (audit SEC-04).
    app.add_middleware(SecurityHeadersMiddleware)

    static_dir = Path(settings.static_dir).resolve()
    if static_dir.is_dir():
        # Phase 76: the folded navbar views serve the shell — the
        # router picks the view from the pathname. Task 01 landed
        # Tuning; task 02 folds RAG + Sources; task 03 lands History
        # (list-driven — all four non-chat navbar views are in);
        # phase 79 task 06 folds the sixth view (Tokens).
        _shell_routes(
            app,
            static_dir,
            (
                "/tuning.html",
                "/sources.html",
                "/git-sources.html",
                "/history.html",
                "/tokens.html",  # phase 79 task 06: the Tokens view
                "/theme.html",  # phase 91 task 04: the Theme view (shell route)
                "/settings.html",  # phase 168 task 05: the Settings view (shell route)
            ),
        )
        app.mount("/", StaticFiles(directory=static_dir, html=True), name="static")
    else:
        logger.warning("static dir %s not found — serving API only", static_dir)

    return app


app = create_app()