"""FastAPI application factory for SneakySwole.

Creates and configures the FastAPI app with routes, templates,
static files, and structured logging.
"""

from pathlib import Path

import structlog
from alembic import command as alembic_command
from alembic.config import Config as AlembicConfig
from fastapi import FastAPI
from fastapi.staticfiles import StaticFiles
from fastapi.templating import Jinja2Templates
from sqlmodel import Session

from starlette.middleware.base import BaseHTTPMiddleware, RequestResponseEndpoint
from starlette.requests import Request as StarletteRequest
from starlette.responses import Response
from fastapi.responses import RedirectResponse

from app.models.user import User
from app.config import get_settings
from app.database import get_engine, get_db_session
from app.logging_config import setup_logging
from app.routes.exercises import router as exercises_router
from app.routes.history import router as history_router
from app.routes.health import router as health_router
from app.routes.pages import router as pages_router
from app.routes.profiles import router as profiles_router
from app.routes.logging import router as logging_router
from app.routes.workouts import router as workouts_router
from app.routes.dashboard import router as dashboard_router
from app.services.seed_service import SeedService
from app.services.user_service import UserService
from app.utils.auth import NoProfileSelectedError

logger = structlog.get_logger(__name__)

# Template and static file directories
_BASE_DIR = Path(__file__).resolve().parent
TEMPLATES_DIR = _BASE_DIR / "templates"
STATIC_DIR = _BASE_DIR / "static"


class NavContextMiddleware(BaseHTTPMiddleware):
    """Injects profiles and active_profile into request.state for templates."""

    async def dispatch(self, request: StarletteRequest, call_next: RequestResponseEndpoint) -> Response:
        request.state.profiles = []
        request.state.active_profile = None

        if hasattr(request.app.state, "engine"):
            try:
                with Session(request.app.state.engine) as session:
                    user_service = UserService(session)
                    request.state.profiles = user_service.list_users()

                    profile_id = request.cookies.get("active_profile_id")
                    if profile_id and profile_id.isdigit():
                        request.state.active_profile = user_service.get_user_by_id(int(profile_id))
            except Exception:
                pass

        return await call_next(request)


def _run_migrations(database_url: str) -> None:
    """Run Alembic migrations to bring the DB schema up to date.

    On a fresh DB this creates all tables via the initial migration.
    On an existing DB created by create_all (no alembic_version table),
    stamps the last known pre-migration revision, then upgrades.
    """
    from sqlalchemy import create_engine as sa_create_engine, inspect

    project_root = Path(__file__).resolve().parent.parent
    alembic_cfg = AlembicConfig(str(project_root / "alembic.ini"))
    alembic_cfg.set_main_option("script_location", str(project_root / "alembic"))
    alembic_cfg.set_main_option("sqlalchemy.url", database_url)

    engine = sa_create_engine(database_url)
    inspector = inspect(engine)
    existing_tables = inspector.get_table_names()

    if existing_tables and "alembic_version" not in existing_tables:
        # DB was created by create_all — stamp it at the last revision
        # that matches the current schema so migrations run from there.
        # Check which schema state we're in by looking at columns.
        columns = {c["name"] for c in inspector.get_columns("user_exercise_programs")}
        if "wk1_reps" in columns:
            # Old schema: stamp at remove-auth migration (before rep ladder)
            alembic_command.stamp(alembic_cfg, "a1b2c3d4e5f6")
            logger.info("alembic_stamped", revision="a1b2c3d4e5f6", reason="legacy_db_old_schema")
        elif "starting_weight" in columns:
            # New schema already: stamp at head
            alembic_command.stamp(alembic_cfg, "head")
            logger.info("alembic_stamped", revision="head", reason="legacy_db_new_schema")
        else:
            # Unknown state — stamp at initial and let migrations sort it out
            alembic_command.stamp(alembic_cfg, "1855836abf6c")
            logger.info("alembic_stamped", revision="1855836abf6c", reason="legacy_db_unknown")
    elif not existing_tables:
        # Fresh DB — create alembic_version table so upgrade starts from scratch
        logger.info("fresh_database_detected")

    engine.dispose()
    alembic_command.upgrade(alembic_cfg, "head")
    logger.info("migrations_applied")


def create_app() -> FastAPI:
    """Create and configure the FastAPI application.

    Returns:
        A fully configured FastAPI application instance.
    """
    settings = get_settings()
    setup_logging(log_level=settings.app_log_level)

    app = FastAPI(
        title="SneakySwole",
        description="Open-source workout tracking and programming",
        version="0.1.0",
    )

    # Redirect to home when no profile is selected
    @app.exception_handler(NoProfileSelectedError)
    async def _no_profile_handler(request, exc):
        return RedirectResponse(url="/", status_code=302)

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

    # Jinja2 templates (available to routes via request.state or dependency)
    templates = Jinja2Templates(directory=str(TEMPLATES_DIR))
    app.state.templates = templates

    # Nav context middleware — injects profiles/active_profile into request.state
    app.add_middleware(NavContextMiddleware)

    # Register route modules
    app.include_router(exercises_router)
    app.include_router(health_router)
    app.include_router(history_router)
    app.include_router(logging_router)
    app.include_router(pages_router)
    app.include_router(profiles_router)
    app.include_router(workouts_router)
    app.include_router(dashboard_router)

    # Database setup — run Alembic migrations instead of create_all
    engine = get_engine(settings.database_url)
    _run_migrations(settings.database_url)
    app.state.engine = engine

    # DB session dependency for routes
    def _get_session():
        yield from get_db_session(engine)

    app.dependency_overrides[get_db_session] = _get_session

    # Seed database on startup
    @app.on_event("startup")
    async def on_startup():
        with Session(engine) as session:
            seed_service = SeedService(session)
            seed_service.seed_all()

    logger.info("app_started", environment=settings.app_env)

    return app


# Uvicorn entry point
app = create_app()