from __future__ import annotations

import os
import sys
import time
import uuid
from pathlib import Path

if __package__ in {None, ""}:
    sys.path.insert(0, str(Path(__file__).resolve().parents[1]))

from fastapi import FastAPI, Request
from fastapi.middleware.cors import CORSMiddleware
from fastapi.staticfiles import StaticFiles
from starlette.middleware.base import BaseHTTPMiddleware

from api.routes import admin, analyses, auth, exercises, health, templates
from core.config import get_settings
from core.logging import (
    bind_request_context,
    clear_request_context,
    get_logger,
    setup_logging,
)
from services.bootstrap import initialize_runtime


setup_logging()
_log = get_logger("app.api")

DIAGNOSTIC_RESPONSE_HEADERS = [
    "x-request-id",
    "x-ai-coach-request-body-wait-ms",
    "x-ai-coach-handler-ms",
    "x-ai-coach-ingest-mbps-est",
    "x-ai-coach-upload-mode",
]


def _request_metrics(request: Request, request_started_at: float, duration_ms: float) -> dict[str, object]:
    route_entered_at = getattr(request.state, "route_entered_at", None)
    file_saved_at = getattr(request.state, "analysis_file_saved_at", None)
    enqueued_at = getattr(request.state, "analysis_enqueued_at", None)
    metrics: dict[str, object] = {}

    if route_entered_at is not None:
        body_wait_ms = round((route_entered_at - request_started_at) * 1000, 1)
        metrics["request_body_wait_ms"] = body_wait_ms
        metrics["request_handler_ms"] = round(max(duration_ms - body_wait_ms, 0), 1)

        if file_saved_at is not None:
            metrics["request_file_save_ms"] = round((file_saved_at - route_entered_at) * 1000, 1)

        if enqueued_at is not None:
            metrics["request_enqueue_ms"] = round((enqueued_at - route_entered_at) * 1000, 1)

        content_length_raw = request.headers.get("content-length")
        if content_length_raw and content_length_raw.isdigit():
            content_length = int(content_length_raw)
            metrics["content_length"] = content_length
            if body_wait_ms > 0:
                metrics["ingest_mbps_est"] = round((content_length * 8) / (body_wait_ms / 1000) / 1_000_000, 3)

    return metrics


class RequestContextMiddleware(BaseHTTPMiddleware):
    """Tag every request with a request_id, log start/end with latency."""

    async def dispatch(self, request: Request, call_next):
        request_id = request.headers.get("x-request-id") or uuid.uuid4().hex[:12]
        bind_request_context(
            request_id=request_id,
            method=request.method,
            path=request.url.path,
        )
        start = time.perf_counter()
        request.state.request_started_at = start
        status_code = 500
        try:
            response = await call_next(request)
            status_code = response.status_code
            response.headers["x-request-id"] = request_id
            # Cache-Control for static uploads — browser cache avoids re-fetch
            path = request.url.path
            if path.startswith("/uploads/templates"):
                response.headers["Cache-Control"] = "public, max-age=2592000"  # 30 days
            elif path.startswith("/uploads/"):
                response.headers["Cache-Control"] = "public, max-age=604800"  # 7 days
            return response
        except Exception:
            _log.exception("request_unhandled_exception")
            raise
        finally:
            duration_ms = round((time.perf_counter() - start) * 1000, 1)
            # Skip noisy access logs for static + health.
            path = request.url.path
            if not (path.startswith("/uploads") or path == "/health"):
                extra_metrics = _request_metrics(request, start, duration_ms)
                _log.info(
                    "request_finished",
                    status=status_code,
                    duration_ms=duration_ms,
                    **extra_metrics,
                )
            clear_request_context()


def _start_temp_template_cleanup_thread() -> None:
    """Background thread that removes expired temporary templates every 30 minutes."""
    from threading import Thread

    CLEANUP_INTERVAL = 30 * 60  # 30 minutes

    def _loop() -> None:
        while True:
            time.sleep(CLEANUP_INTERVAL)
            try:
                from exercises.push_up.template_registry import cleanup_expired_temporary_templates
                deleted = cleanup_expired_temporary_templates()
                if deleted:
                    _log.info("temp_template_cleanup", deleted_count=len(deleted), deleted_ids=deleted)
            except Exception:
                _log.exception("temp_template_cleanup_error")

    Thread(target=_loop, daemon=True, name="temp-template-cleanup").start()


def create_app() -> FastAPI:
    settings = get_settings()
    initialize_runtime(settings)

    is_prod = os.getenv("ENV", "dev").lower() == "production"
    api = FastAPI(
        title=settings.app_name,
        version=settings.api_version,
        description="FastAPI backend for AI Coach Gym video analysis.",
        docs_url=None if is_prod else "/docs",
        redoc_url=None if is_prod else "/redoc",
        openapi_url=None if is_prod else "/openapi.json",
    )
    api.add_middleware(RequestContextMiddleware)
    api.add_middleware(
        CORSMiddleware,
        allow_origins=settings.cors_origins,
        allow_credentials=True,
        allow_methods=["*"],
        allow_headers=["*"],
        expose_headers=DIAGNOSTIC_RESPONSE_HEADERS,
    )
    api.include_router(health.router)
    api.include_router(auth.router, prefix="/auth", tags=["auth"])
    api.include_router(exercises.router, prefix="/exercises", tags=["exercises"])
    api.include_router(templates.router, prefix="/templates", tags=["templates"])
    api.include_router(analyses.router, prefix="/analyses", tags=["analyses"])
    api.include_router(admin.router, prefix="/admin", tags=["admin"])

    api.mount(
        settings.upload_url_prefix,
        StaticFiles(directory=str(settings.upload_dir)),
        name="uploads",
    )
    _start_temp_template_cleanup_thread()
    return api


app = create_app()


if __name__ == "__main__":
    import uvicorn

    uvicorn.run("api.main:app", host="127.0.0.1", port=8000)