"""
Simple Python API service.
Exposes:
  GET /            -> basic info
  GET /health       -> liveness/readiness probe
  GET /metrics      -> runtime metrics consumed by the monitoring dashboard
"""

import os
import time
import threading
from datetime import datetime, timezone

from flask import Flask, jsonify

app = Flask(__name__)

START_TIME = time.time()

# --- In-memory metrics (thread-safe) --------------------------------------
_lock = threading.Lock()
_metrics = {
    "requests_total": 0,
    "total_response_time_ms": 0.0,
}


@app.before_request
def _start_timer():
    from flask import g
    g.start_time = time.perf_counter()


@app.after_request
def _record_metrics(response):
    from flask import g
    elapsed_ms = (time.perf_counter() - getattr(g, "start_time", time.perf_counter())) * 1000
    with _lock:
        _metrics["requests_total"] += 1
        _metrics["total_response_time_ms"] += elapsed_ms
    # Allow the standalone dashboard.html to call this API from any origin
    response.headers["Access-Control-Allow-Origin"] = "*"
    return response


@app.route("/")
def index():
    return jsonify({
        "service": "sample-api",
        "message": "API is running. See /health and /metrics."
    })


@app.route("/health")
def health():
    """Used by the container platform's health checks and the monitor.py script."""
    return jsonify({
        "status": "healthy",
        "timestamp": datetime.now(timezone.utc).isoformat(),
        "uptime_seconds": round(time.time() - START_TIME, 2),
    }), 200


@app.route("/metrics")
def metrics():
    """Used by dashboard.html to render live stats."""
    with _lock:
        total = _metrics["requests_total"]
        total_time = _metrics["total_response_time_ms"]
    avg_ms = round(total_time / total, 2) if total else 0.0

    return jsonify({
        "status": "healthy",
        "uptime_seconds": round(time.time() - START_TIME, 2),
        "requests_total": total,
        "avg_response_time_ms": avg_ms,
        "timestamp": datetime.now(timezone.utc).isoformat(),
    })


if __name__ == "__main__":
    port = int(os.environ.get("PORT", 8080))
    app.run(host="0.0.0.0", port=port)