"""
backend/tools/trigger_webhook.py — P17-F4: Generic webhook trigger tool.

Permette all'agente di inviare notifiche / callback a URL esterni
(Zapier, Make, n8n, webhook Discord/Slack, CI/CD, ecc.) con payload arbitrario.

Registrato nel TOOL_REGISTRY come "trigger_webhook".

Sicurezza:
  - URL allowlist via WEBHOOK_ALLOWED_HOSTS env (CSV). Vuoto = tutti consentiti (dev).
  - Timeout massimo 10s — mai blocca il loop principale.
  - Payload massimo 32KB — protegge da exfiltration involontaria.
  - Metodi consentiti: POST, GET, PUT (default POST).
  - Rate limit per-host via sliding window: WEBHOOK_RATE_LIMIT_MAX (default 10) /
    WEBHOOK_RATE_LIMIT_WINDOW (default 60s).
"""
from __future__ import annotations

import json
import logging
import os
import asyncio
import time
from collections import defaultdict, deque
from typing import Any
from urllib.parse import urlparse

import httpx

_logger = logging.getLogger("agente_ai.tools.trigger_webhook")

_ALLOWED_HOSTS_ENV = os.getenv("WEBHOOK_ALLOWED_HOSTS", "")
_ALLOWED_HOSTS: set[str] = (
    {h.strip().lower() for h in _ALLOWED_HOSTS_ENV.split(",") if h.strip()}
    if _ALLOWED_HOSTS_ENV else set()
)
_MAX_PAYLOAD_BYTES = 32_768   # 32 KB
_TIMEOUT_S         = 10.0

# ── P17-F4 rate-limit guard (sliding window per-host) ─────────────────────────
_RATE_LIMIT_MAX: int   = int(os.getenv("WEBHOOK_RATE_LIMIT_MAX", "10"))      # max calls per window
_RATE_LIMIT_WIN: float = float(os.getenv("WEBHOOK_RATE_LIMIT_WINDOW", "60")) # window seconds
_rate_lock                              = asyncio.Lock()
_rate_windows: dict[str, deque[float]] = defaultdict(deque)                  # host → timestamps


async def _check_rate_limit(host: str) -> bool:
    """Sliding window rate limiter per host. Ritorna True se entro il limite."""
    async with _rate_lock:
        now = time.monotonic()
        win = _rate_windows[host]
        while win and win[0] < now - _RATE_LIMIT_WIN:
            win.popleft()
        if len(win) >= _RATE_LIMIT_MAX:
            return False
        win.append(now)
        return True


def _check_host(url: str) -> bool:
    """Verifica che l'host sia nell'allowlist (se configurata)."""
    if not _ALLOWED_HOSTS:
        return True  # dev mode — tutti consentiti
    try:
        host = urlparse(url).hostname or ""
        return host.lower() in _ALLOWED_HOSTS
    except Exception:
        return False


async def trigger_webhook(
    url: str,
    payload: dict[str, Any] | str | None = None,
    method: str = "POST",
    headers: dict[str, str] | None = None,
    timeout: float = _TIMEOUT_S,
) -> dict[str, Any]:
    """
    Trigger an HTTP webhook with an arbitrary payload.

    Args:
        url:     Target URL (https://...)
        payload: JSON-serializable dict, raw string, or None
        method:  HTTP method — POST (default), GET, PUT
        headers: Additional HTTP headers (optional)
        timeout: Request timeout in seconds (max 10)

    Returns:
        {"ok": bool, "status": int, "body": str, "error": str|None}
    """
    method = method.upper()
    if method not in ("POST", "GET", "PUT"):
        return {"ok": False, "status": 0, "body": "", "error": f"Metodo non consentito: {method}"}

    if not url.startswith(("https://", "http://")):
        return {"ok": False, "status": 0, "body": "", "error": "URL deve iniziare con http(s)://"}

    if not _check_host(url):
        return {"ok": False, "status": 0, "body": "", "error": "Host non nell'allowlist WEBHOOK_ALLOWED_HOSTS"}

    # P17-F4: rate-limit guard — sliding window per-host
    _rl_host = urlparse(url).hostname or url
    if not await _check_rate_limit(_rl_host):
        _logger.warning(
            "trigger_webhook rate limit superato: %s (%s req/%ss)",
            _rl_host, _RATE_LIMIT_MAX, int(_RATE_LIMIT_WIN),
        )
        return {
            "ok": False,
            "status": 429,
            "body": "",
            "error": f"Rate limit ({_RATE_LIMIT_MAX} chiamate/{_RATE_LIMIT_WIN:.0f}s) superato per {_rl_host}",
        }

    # Serializza payload
    body_bytes: bytes | None = None
    req_headers: dict[str, str] = {"User-Agent": "agente-ai/1.0"}
    if headers:
        req_headers.update(headers)

    if payload is not None:
        if isinstance(payload, dict):
            raw = json.dumps(payload, ensure_ascii=False)
            req_headers.setdefault("Content-Type", "application/json")
        else:
            raw = str(payload)
            req_headers.setdefault("Content-Type", "text/plain")
        body_bytes = raw.encode("utf-8")[:_MAX_PAYLOAD_BYTES]

    _effective_timeout = min(float(timeout), _TIMEOUT_S)
    try:
        async with httpx.AsyncClient(timeout=_effective_timeout, follow_redirects=True) as client:
            if method == "GET":
                resp = await client.get(url, headers=req_headers)
            elif method == "PUT":
                resp = await client.put(url, content=body_bytes, headers=req_headers)
            else:
                resp = await client.post(url, content=body_bytes, headers=req_headers)

        body_str = resp.text[:2000]
        ok = resp.is_success
        _logger.info(
            "trigger_webhook %s %s → %d (%s)",
            method, url[:80], resp.status_code, "OK" if ok else "FAIL",
        )
        return {"ok": ok, "status": resp.status_code, "body": body_str, "error": None}

    except httpx.TimeoutException:
        _logger.warning("trigger_webhook timeout (%.0fs): %s", _effective_timeout, url[:80])
        return {"ok": False, "status": 0, "body": "", "error": f"timeout dopo {_effective_timeout:.0f}s"}
    except Exception as exc:
        _logger.warning("trigger_webhook error: %s", exc)
        return {"ok": False, "status": 0, "body": "", "error": str(exc)[:200]}


# ── Tool registry descriptor ───────────────────────────────────────────────────
TOOL_DESCRIPTOR = {
    "name":        "trigger_webhook",
    "description": (
        "Invia una richiesta HTTP (POST/GET/PUT) a un URL esterno con payload JSON. "
        "Usa per notificare webhook Zapier/Make/n8n, CI/CD, Discord, Slack, ecc. "
        "Restituisce status HTTP + risposta body (max 2000 chars). "
        "Rate limit: max 10 call/60s per host (configurabile via WEBHOOK_RATE_LIMIT_MAX)."
    ),
    "parameters": {
        "type": "object",
        "properties": {
            "url":     {"type": "string", "description": "URL destinazione (https://...)"},
            "payload": {"type": "object", "description": "Payload JSON da inviare"},
            "method":  {"type": "string", "enum": ["POST", "GET", "PUT"], "default": "POST"},
            "headers": {"type": "object", "description": "Header HTTP aggiuntivi"},
            "timeout": {"type": "number", "description": "Timeout secondi (max 10)", "default": 10},
        },
        "required": ["url"],
    },
    "fn": trigger_webhook,
}