"""
alert_routing.py — Alert routing policy loader and matcher.

Loads config/alert_routing_policy.yml and provides:
  - match_alert(alert) → matched rule actions dict
  - default_actions()  → fallback actions when no rule matches
  - Policy dataclass for easy access to defaults/limits
"""
from __future__ import annotations

import hashlib
import logging
import re
from pathlib import Path
from typing import Any, Dict, List, Optional

import yaml

logger = logging.getLogger(__name__)

def _find_policy_path() -> Path:
    """Walk up from this file to find config/alert_routing_policy.yml."""
    here = Path(__file__).resolve()
    for parent in here.parents:
        candidate = parent / "config" / "alert_routing_policy.yml"
        if candidate.exists():
            return candidate
    # Safe fallback path for container/local runs; file may be absent and
    # load_policy() will fall back to built-in defaults.
    return Path("/app/config/alert_routing_policy.yml")

_POLICY_PATH = _find_policy_path()


def load_policy(path: Optional[Path] = None) -> Dict:
    """Load and return raw YAML policy dict. Caches nothing (caller may cache)."""
    p = path or _POLICY_PATH
    try:
        with open(p) as f:
            return yaml.safe_load(f) or {}
    except FileNotFoundError:
        logger.warning("alert_routing_policy.yml not found at %s — using built-in defaults", p)
        return _builtin_defaults()
    except Exception as e:
        logger.error("Failed to load alert routing policy: %s", e)
        return _builtin_defaults()


def _builtin_defaults() -> Dict:
    return {
        "defaults": {
            "poll_interval_seconds": 300,
            "max_alerts_per_run": 20,
            "only_unacked": True,
            "max_incidents_per_run": 5,
            "max_triages_per_run": 5,
            "dedupe_window_minutes_default": 120,
            "ack_note_prefix": "alert_triage_loop",
            "llm_mode": "off",
            "llm_on": {"triage": False, "postmortem": False},
        },
        "routing": [
            {
                "match": {"env_in": ["prod"], "severity_in": ["P0", "P1"]},
                "actions": {
                    "auto_incident": True,
                    "auto_triage": True,
                    "triage_mode": "deterministic",
                    "incident_severity_cap": "P1",
                    "dedupe_window_minutes": 120,
                    "attach_alert_artifact": True,
                    "ack": True,
                },
            },
            {
                "match": {"severity_in": ["P2", "P3", "INFO"]},
                "actions": {"auto_incident": False, "digest_only": True, "ack": True},
            },
        ],
    }


def _normalize_kind(kind: str, kind_map: Dict[str, List[str]]) -> str:
    """Resolve kind aliases to canonical name."""
    if not kind_map:
        return kind
    for canonical, aliases in kind_map.items():
        if kind in aliases or kind == canonical:
            return canonical
    return kind


def match_alert(alert: Dict, policy: Optional[Dict] = None) -> Dict:
    """
    Find the first matching routing rule for an alert and return its actions.
    Falls back to digest_only if no rule matches.
    """
    if policy is None:
        policy = load_policy()

    kind_map = policy.get("kind_map", {})
    routing = policy.get("routing", [])
    defaults_cfg = policy.get("defaults", {})

    normalized_kind = _normalize_kind(alert.get("kind", "custom"), kind_map)
    env = alert.get("env", "prod")
    severity = alert.get("severity", "P2")

    for rule in routing:
        m = rule.get("match", {})
        if not _rule_matches(m, env=env, severity=severity, kind=normalized_kind):
            continue
        actions = dict(rule.get("actions", {}))
        # Inject defaults for missing action fields
        actions.setdefault("auto_incident", False)
        actions.setdefault("auto_triage", False)
        actions.setdefault("digest_only", False)
        actions.setdefault("ack", True)
        actions.setdefault("triage_mode", "deterministic")
        actions.setdefault(
            "incident_severity_cap",
            policy.get("severity_caps", {}).get(normalized_kind, "P1"),
        )
        actions.setdefault(
            "dedupe_window_minutes",
            defaults_cfg.get("dedupe_window_minutes_default", 120),
        )
        actions["_normalized_kind"] = normalized_kind
        return actions

    # No match → safe fallback
    return {
        "auto_incident": False,
        "digest_only": True,
        "ack": True,
        "triage_mode": "deterministic",
        "incident_severity_cap": "P2",
        "dedupe_window_minutes": defaults_cfg.get("dedupe_window_minutes_default", 120),
        "_normalized_kind": normalized_kind,
    }


def _rule_matches(match: Dict, env: str, severity: str, kind: str) -> bool:
    """Return True if all match conditions are satisfied."""
    if "env_in" in match and env not in match["env_in"]:
        return False
    if "severity_in" in match and severity not in match["severity_in"]:
        return False
    if "kind_in" in match and kind not in match["kind_in"]:
        return False
    return True


# ─── Incident Signature ────────────────────────────────────────────────────────

def compute_incident_signature(
    alert: Dict,
    policy: Optional[Dict] = None,
) -> str:
    """
    Compute an incident signature for deduplication.
    Components controlled by `policy.signature`.
    """
    if policy is None:
        policy = load_policy()

    sig_cfg = policy.get("signature", {})
    kind_map = policy.get("kind_map", {})

    service = alert.get("service", "unknown")
    env = alert.get("env", "prod")
    kind = _normalize_kind(alert.get("kind", "custom"), kind_map)

    parts = [service, env]

    if sig_cfg.get("use_kind", True):
        parts.append(kind)

    if sig_cfg.get("use_fingerprint", True):
        fp = (alert.get("labels") or {}).get("fingerprint", "")
        parts.append(fp)

    if sig_cfg.get("use_node_label", False):
        node = (alert.get("labels") or {}).get("node", "")
        parts.append(node)

    raw = "|".join(parts)
    return hashlib.sha256(raw.encode()).hexdigest()[:32]


def is_llm_allowed(action: str, policy: Optional[Dict] = None) -> bool:
    """
    Return True only if global llm_mode != off AND the specific action is enabled.
    Used to guard any LLM call.
    """
    if policy is None:
        policy = load_policy()
    defaults = policy.get("defaults", {})
    llm_mode = defaults.get("llm_mode", "off")
    if llm_mode == "off":
        return False
    llm_on = defaults.get("llm_on", {})
    return bool(llm_on.get(action, False))