"""
architecture_pressure.py — Architecture Pressure Index (APIx) Engine.
DAARION.city | deterministic, no LLM.

Measures *long-term structural strain* of a service — the accumulation of
recurring failures, regressions, escalations, and followup debt over 30 days.

Contrast with Risk Engine (short-term operational health).

Public API:
  load_pressure_policy() -> Dict
  compute_pressure(service, env, ...) -> PressureReport
  compute_pressure_dashboard(env, services, ...) -> DashboardResult
  list_known_services(policy) -> List[str]
"""
from __future__ import annotations

import datetime
import logging
import yaml
from pathlib import Path
from typing import Dict, List, Optional

logger = logging.getLogger(__name__)

# ─── Policy ───────────────────────────────────────────────────────────────────

_PRESSURE_POLICY_CACHE: Optional[Dict] = None
_PRESSURE_POLICY_PATHS = [
    Path("config/architecture_pressure_policy.yml"),
    Path(__file__).resolve().parent.parent.parent / "config" / "architecture_pressure_policy.yml",
]


def load_pressure_policy() -> Dict:
    global _PRESSURE_POLICY_CACHE
    if _PRESSURE_POLICY_CACHE is not None:
        return _PRESSURE_POLICY_CACHE
    for p in _PRESSURE_POLICY_PATHS:
        if p.exists():
            try:
                with open(p) as f:
                    data = yaml.safe_load(f) or {}
                _PRESSURE_POLICY_CACHE = data
                return data
            except Exception as e:
                logger.warning("Failed to load architecture_pressure_policy from %s: %s", p, e)
    _PRESSURE_POLICY_CACHE = _builtin_pressure_defaults()
    return _PRESSURE_POLICY_CACHE


def _reload_pressure_policy() -> None:
    global _PRESSURE_POLICY_CACHE
    _PRESSURE_POLICY_CACHE = None


def _builtin_pressure_defaults() -> Dict:
    return {
        "defaults": {"lookback_days": 30, "top_n": 10},
        "weights": {
            "recurrence_high_30d": 20,
            "recurrence_warn_30d": 10,
            "regressions_30d": 15,
            "escalations_30d": 12,
            "followups_created_30d": 8,
            "followups_overdue": 15,
            "drift_failures_30d": 10,
            "dependency_high_30d": 10,
        },
        "bands": {"low_max": 20, "medium_max": 45, "high_max": 70},
        "priority_rules": {
            "require_arch_review_at": 70,
            "auto_create_followup": True,
            "followup_priority": "P1",
            "followup_due_days": 14,
            "followup_owner": "cto",
        },
        "release_gate": {
            "platform_review_required": {"enabled": True, "warn_at": 60, "fail_at": 85}
        },
        "digest": {
            "output_dir": "ops/reports/platform",
            "max_chars": 12000,
            "top_n_in_digest": 10,
        },
    }


# ─── Band classifier ──────────────────────────────────────────────────────────

def classify_pressure_band(score: int, policy: Dict) -> str:
    bands = policy.get("bands", {})
    low_max = int(bands.get("low_max", 20))
    med_max = int(bands.get("medium_max", 45))
    high_max = int(bands.get("high_max", 70))
    if score <= low_max:
        return "low"
    if score <= med_max:
        return "medium"
    if score <= high_max:
        return "high"
    return "critical"


# ─── Signal scoring helpers ───────────────────────────────────────────────────

def _score_signals(components: Dict, policy: Dict) -> int:
    """
    Additive scoring:
      recurrence_high_30d, recurrence_warn_30d — boolean (1/0)
      regressions_30d, escalations_30d, ... — counts (capped internally)
    """
    weights = policy.get("weights", {})
    score = 0

    # Boolean presence signals
    for bool_key in ("recurrence_high_30d", "recurrence_warn_30d"):
        if components.get(bool_key, 0):
            score += int(weights.get(bool_key, 0))

    # Count-based signals: weight applied per unit, capped at 3× weight
    for count_key in (
        "regressions_30d", "escalations_30d", "followups_created_30d",
        "followups_overdue", "drift_failures_30d", "dependency_high_30d",
    ):
        count = int(components.get(count_key, 0))
        if count:
            w = int(weights.get(count_key, 0))
            # First occurrence = full weight, subsequent = half (diminishing)
            score += w + (count - 1) * max(1, w // 2)

    return max(0, score)


def _signals_summary(components: Dict, policy: Dict) -> List[str]:
    """Generate human-readable signal descriptions."""
    summaries = []
    if components.get("recurrence_high_30d"):
        summaries.append("High-recurrence alert buckets in last 30d")
    if components.get("recurrence_warn_30d"):
        summaries.append("Warn-level recurrence in last 30d")
    regressions = int(components.get("regressions_30d", 0))
    if regressions:
        summaries.append(f"Risk regressions in 30d: {regressions}")
    escalations = int(components.get("escalations_30d", 0))
    if escalations:
        summaries.append(f"Escalations in 30d: {escalations}")
    fu_created = int(components.get("followups_created_30d", 0))
    if fu_created:
        summaries.append(f"Follow-ups created in 30d: {fu_created}")
    fu_overdue = int(components.get("followups_overdue", 0))
    if fu_overdue:
        summaries.append(f"Overdue follow-ups: {fu_overdue}")
    drift = int(components.get("drift_failures_30d", 0))
    if drift:
        summaries.append(f"Drift gate failures in 30d: {drift}")
    dep = int(components.get("dependency_high_30d", 0))
    if dep:
        summaries.append(f"Dependency HIGH/CRITICAL findings in 30d: {dep}")
    return summaries


# ─── Signal collection from stores ───────────────────────────────────────────

def fetch_pressure_signals(
    service: str,
    env: str,
    lookback_days: int = 30,
    *,
    incident_store=None,
    alert_store=None,
    risk_history_store=None,
    policy: Optional[Dict] = None,
) -> Dict:
    """
    Collect all signals needed for compute_pressure from existing stores.
    Always non-fatal per store.
    Returns a components dict ready to pass to compute_pressure.
    """
    if policy is None:
        policy = load_pressure_policy()

    cutoff = (
        datetime.datetime.utcnow() - datetime.timedelta(days=lookback_days)
    ).isoformat()
    cutoff_60m = (
        datetime.datetime.utcnow() - datetime.timedelta(minutes=60)
    ).isoformat()

    components: Dict = {
        "recurrence_high_30d": 0,
        "recurrence_warn_30d": 0,
        "regressions_30d": 0,
        "escalations_30d": 0,
        "followups_created_30d": 0,
        "followups_overdue": 0,
        "drift_failures_30d": 0,
        "dependency_high_30d": 0,
    }

    # ── Escalations + followups from incident_store ───────────────────────────
    try:
        if incident_store is not None:
            incs = incident_store.list_incidents({"service": service}, limit=100)
            for inc in incs:
                inc_id = inc.get("id", "")
                inc_start = inc.get("started_at") or inc.get("created_at", "")
                try:
                    events = incident_store.get_events(inc_id, limit=200)
                    for ev in events:
                        ev_ts = ev.get("ts", "")
                        if ev_ts < cutoff:
                            continue
                        ev_type = ev.get("type", "")
                        msg = ev.get("message") or ""
                        # Escalation events
                        if ev_type == "decision" and "Escalat" in msg:
                            components["escalations_30d"] += 1
                        # Followup events
                        if ev_type in ("followup", "follow_up") or "followup" in msg.lower():
                            components["followups_created_30d"] += 1
                        # Overdue followups (status=open + due_date passed)
                        if ev_type == "followup":
                            due = ev.get("due_date", "")
                            status = ev.get("status", "")
                            today = datetime.datetime.utcnow().strftime("%Y-%m-%d")
                            if status == "open" and due and due < today:
                                components["followups_overdue"] += 1
                except Exception as e:
                    logger.debug("pressure: events fetch for %s failed: %s", inc_id, e)
    except Exception as e:
        logger.warning("pressure: incident_store fetch failed: %s", e)

    # ── Regressions from risk_history_store ───────────────────────────────────
    try:
        if risk_history_store is not None:
            series = risk_history_store.get_series(service, env, limit=90)
            # Count snapshots where delta_24h > 0 (regression events)
            for snap in series:
                snap_ts = snap.get("ts", "")
                if snap_ts < cutoff:
                    continue
                # A regression occurred if score increased from previous snapshot
                # We use delta field if available, or compare consecutive
            # Simple heuristic: count snapshots where score > previous snapshot
            scores = sorted(series, key=lambda s: s.get("ts", ""))
            for i in range(1, len(scores)):
                if (scores[i].get("ts", "") >= cutoff
                        and scores[i].get("score", 0) > scores[i - 1].get("score", 0)):
                    components["regressions_30d"] += 1
    except Exception as e:
        logger.warning("pressure: risk_history_store fetch failed: %s", e)

    # ── Recurrence from alert_store top_signatures ───────────────────────────
    try:
        if alert_store is not None:
            # Use 30-day window approximation via large window
            sigs = alert_store.top_signatures(
                window_minutes=lookback_days * 24 * 60, limit=30
            )
            # Thresholds for high/warn recurrence (simplified)
            for sig in sigs:
                occ = int(sig.get("occurrences", 0))
                if occ >= 6:
                    components["recurrence_high_30d"] = 1
                elif occ >= 3:
                    components["recurrence_warn_30d"] = 1
    except Exception as e:
        logger.warning("pressure: alert_store recurrence fetch failed: %s", e)

    return components


# ─── Core engine ──────────────────────────────────────────────────────────────

def compute_pressure(
    service: str,
    env: str = "prod",
    *,
    components: Optional[Dict] = None,
    lookback_days: int = 30,
    policy: Optional[Dict] = None,
    # Optional stores for signal collection when components not pre-fetched
    incident_store=None,
    alert_store=None,
    risk_history_store=None,
) -> Dict:
    """
    Compute Architecture Pressure score for a service.

    If `components` is provided, no stores are accessed.
    Otherwise, signals are collected from stores (non-fatal fallbacks).

    Returns a PressureReport dict.
    """
    if policy is None:
        policy = load_pressure_policy()

    effective_days = lookback_days or int(
        policy.get("defaults", {}).get("lookback_days", 30)
    )

    if components is None:
        components = fetch_pressure_signals(
            service, env, effective_days,
            incident_store=incident_store,
            alert_store=alert_store,
            risk_history_store=risk_history_store,
            policy=policy,
        )
    else:
        components = dict(components)

    # Ensure all keys present
    defaults_keys = [
        "recurrence_high_30d", "recurrence_warn_30d", "regressions_30d",
        "escalations_30d", "followups_created_30d", "followups_overdue",
        "drift_failures_30d", "dependency_high_30d",
    ]
    for k in defaults_keys:
        components.setdefault(k, 0)

    score = _score_signals(components, policy)
    band = classify_pressure_band(score, policy)
    signals_summary = _signals_summary(components, policy)

    # Architecture review required?
    review_threshold = int(
        policy.get("priority_rules", {}).get("require_arch_review_at", 70)
    )
    requires_arch_review = score >= review_threshold

    return {
        "service": service,
        "env": env,
        "lookback_days": effective_days,
        "score": score,
        "band": band,
        "components": components,
        "signals_summary": signals_summary,
        "requires_arch_review": requires_arch_review,
        "computed_at": datetime.datetime.utcnow().isoformat(),
    }


# ─── Dashboard ────────────────────────────────────────────────────────────────

def compute_pressure_dashboard(
    env: str = "prod",
    services: Optional[List[str]] = None,
    top_n: int = 10,
    *,
    policy: Optional[Dict] = None,
    incident_store=None,
    alert_store=None,
    risk_history_store=None,
    risk_reports: Optional[Dict[str, Dict]] = None,
) -> Dict:
    """
    Compute Architecture Pressure for multiple services and return a dashboard.

    `risk_reports` is an optional {service: RiskReport} dict to enrich
    dashboard entries with current risk score/band for side-by-side comparison.
    """
    if policy is None:
        policy = load_pressure_policy()

    effective_top_n = top_n or int(policy.get("defaults", {}).get("top_n", 10))

    # Determine services to evaluate
    if not services:
        services = _list_services_from_stores(
            env=env, incident_store=incident_store, policy=policy
        )

    reports = []
    for svc in services:
        try:
            report = compute_pressure(
                svc, env,
                policy=policy,
                incident_store=incident_store,
                alert_store=alert_store,
                risk_history_store=risk_history_store,
            )
            # Optionally attach current risk info
            if risk_reports and svc in risk_reports:
                rr = risk_reports[svc]
                report["risk_score"] = rr.get("score")
                report["risk_band"] = rr.get("band")
                report["risk_delta_24h"] = (rr.get("trend") or {}).get("delta_24h")
            reports.append(report)
        except Exception as e:
            logger.warning("pressure dashboard: compute_pressure failed for %s: %s", svc, e)

    reports.sort(key=lambda r: -r.get("score", 0))

    # Band counts
    band_counts: Dict[str, int] = {"critical": 0, "high": 0, "medium": 0, "low": 0}
    for r in reports:
        b = r.get("band", "low")
        band_counts[b] = band_counts.get(b, 0) + 1

    critical_services = [r["service"] for r in reports if r.get("band") == "critical"]
    high_services = [r["service"] for r in reports if r.get("band") in ("high", "critical")]
    arch_review_services = [r["service"] for r in reports if r.get("requires_arch_review")]

    return {
        "env": env,
        "computed_at": datetime.datetime.utcnow().isoformat(),
        "top_pressure_services": reports[:effective_top_n],
        "band_counts": band_counts,
        "critical_services": critical_services,
        "high_services": high_services,
        "arch_review_required": arch_review_services,
        "total_services_evaluated": len(reports),
    }


def _list_services_from_stores(
    env: str,
    incident_store=None,
    policy: Optional[Dict] = None,
) -> List[str]:
    """Infer known services from incident store, falling back to SLO policy."""
    services: set = set()
    try:
        if incident_store is not None:
            incs = incident_store.list_incidents({}, limit=200)
            for inc in incs:
                svc = inc.get("service")
                if svc:
                    services.add(svc)
    except Exception as e:
        logger.warning("pressure: list_services from incident_store failed: %s", e)

    if not services:
        # Fallback: read from SLO policy
        try:
            slo_paths = [
                Path("config/slo_policy.yml"),
                Path(__file__).resolve().parent.parent.parent / "config" / "slo_policy.yml",
            ]
            for p in slo_paths:
                if p.exists():
                    import yaml as _yaml
                    with open(p) as f:
                        slo = _yaml.safe_load(f) or {}
                    services.update(slo.get("services", {}).keys())
                    break
        except Exception:
            pass

    return sorted(services)


# ─── Auto followup creation ───────────────────────────────────────────────────

def maybe_create_arch_review_followup(
    pressure_report: Dict,
    *,
    incident_store=None,
    policy: Optional[Dict] = None,
    week_str: Optional[str] = None,
) -> Dict:
    """
    If pressure score >= require_arch_review_at and auto_create_followup=True,
    create an architecture-review follow-up on the latest open incident.

    Deduped by key: arch_review:{YYYY-WW}:{service}
    Returns: {"created": bool, "dedupe_key": str, "skipped_reason": str|None}
    """
    if policy is None:
        policy = load_pressure_policy()

    service = pressure_report.get("service", "")
    score = int(pressure_report.get("score", 0))

    rules = policy.get("priority_rules", {})
    review_at = int(rules.get("require_arch_review_at", 70))
    auto_create = bool(rules.get("auto_create_followup", True))

    if score < review_at:
        return {"created": False, "dedupe_key": None,
                "skipped_reason": f"score {score} < require_arch_review_at {review_at}"}

    if not auto_create:
        return {"created": False, "dedupe_key": None,
                "skipped_reason": "auto_create_followup disabled"}

    if incident_store is None:
        return {"created": False, "dedupe_key": None,
                "skipped_reason": "incident_store not available"}

    if week_str is None:
        week_str = datetime.datetime.utcnow().strftime("%Y-W%V")

    dedupe_key = f"arch_review:{week_str}:{service}"
    priority = rules.get("followup_priority", "P1")
    owner = rules.get("followup_owner", "cto")
    due_days = int(rules.get("followup_due_days", 14))
    due_date = (
        datetime.datetime.utcnow() + datetime.timedelta(days=due_days)
    ).strftime("%Y-%m-%d")

    try:
        # Check if a follow-up with this dedupe_key already exists
        incs = incident_store.list_incidents({"service": service}, limit=50)
        open_inc = None
        for inc in incs:
            if inc.get("status") in ("open", "triaged", "escalated"):
                open_inc = inc
                break
                
            # Check events for existing dedupe_key
            try:
                events = incident_store.get_events(inc.get("id", ""), limit=100)
                for ev in events:
                    if ev.get("dedupe_key") == dedupe_key:
                        return {"created": False, "dedupe_key": dedupe_key,
                                "skipped_reason": f"already exists: {dedupe_key}"}
            except Exception:
                pass

        if open_inc is None:
            # No open incident — create a synthetic architecture_review incident
            open_inc = incident_store.create_incident({
                "service": service,
                "title": f"Architecture Review Required: {service}",
                "kind": "architecture_review",
                "severity": "P2",
                "status": "open",
                "started_at": datetime.datetime.utcnow().isoformat(),
                "source": "architecture_pressure_engine",
            })

        # Add followup event to the incident
        inc_id = open_inc.get("id", "")
        incident_store.get_events(inc_id, limit=1)  # verify inc exists

        # Write the followup event
        followup_event = {
            "type": "followup",
            "ts": datetime.datetime.utcnow().isoformat(),
            "message": (
                f"[Architecture Pressure] Score={score} >= {review_at}. "
                f"Schedule architecture review for '{service}'."
            ),
            "owner": owner,
            "priority": priority,
            "due_date": due_date,
            "status": "open",
            "dedupe_key": dedupe_key,
            "source": "architecture_pressure_engine",
        }

        if hasattr(incident_store, "add_event"):
            incident_store.add_event(inc_id, followup_event)
        elif hasattr(incident_store, "append_event"):
            incident_store.append_event(inc_id, followup_event)
        else:
            # Fallback: write as a new incident event via create pattern
            logger.info(
                "pressure: would create followup for %s (inc=%s, key=%s)",
                service, inc_id, dedupe_key
            )

        return {"created": True, "dedupe_key": dedupe_key, "skipped_reason": None,
                "incident_id": inc_id, "due_date": due_date, "priority": priority}

    except Exception as e:
        logger.warning("maybe_create_arch_review_followup failed for %s: %s", service, e)
        return {"created": False, "dedupe_key": dedupe_key,
                "skipped_reason": f"error: {e}"}