"""Stable repeat identity for Config Drift reports.

The drift scanner emits a fresh ``report_id`` for every run. Operators need a
stable identity that answers whether two reports describe the same drift, not
just whether they have the same HIGH/MEDIUM/INFO counts.
"""

from __future__ import annotations

import hashlib
import json
from datetime import datetime, timedelta, timezone
from typing import Any

SCHEMA_VERSION = "drift_repeat_state_v1"
FINGERPRINT_VERSION = "drift_fingerprint_v1"
SEMANTIC_FINGERPRINT_VERSION = "drift_fingerprint_v2"
VALUE_AWARE_MATCHING_STRATEGY = "namespace_and_stable_items_v1"
SEMANTIC_MATCHING_STRATEGY = "namespace_resource_field_level_v2"


def _get(obj: Any, key: str, default: Any = None) -> Any:
    if isinstance(obj, dict):
        return obj.get(key, default)
    return getattr(obj, key, default)


def _enum_value(value: Any) -> Any:
    return getattr(value, "value", value)


def _jsonable(value: Any) -> Any:
    value = _enum_value(value)
    if isinstance(value, dict):
        return {str(k): _jsonable(v) for k, v in value.items()}
    if isinstance(value, list):
        return [_jsonable(v) for v in value]
    if isinstance(value, tuple):
        return [_jsonable(v) for v in value]
    if isinstance(value, datetime):
        return value.isoformat()
    return value


def _canonical_json(value: Any) -> str:
    return json.dumps(
        _jsonable(value),
        ensure_ascii=False,
        sort_keys=True,
        separators=(",", ":"),
        default=str,
    )


def _parse_datetime(value: Any) -> datetime | None:
    if value is None:
        return None
    if isinstance(value, datetime):
        parsed = value
        if parsed.tzinfo is not None:
            return parsed.astimezone(timezone.utc).replace(tzinfo=None)
        return parsed
    if isinstance(value, str):
        try:
            parsed = datetime.fromisoformat(value.replace("Z", "+00:00"))
            if parsed.tzinfo is not None:
                return parsed.astimezone(timezone.utc).replace(tzinfo=None)
            return parsed
        except ValueError:
            return None
    return None


def _iso(value: Any) -> str | None:
    parsed = _parse_datetime(value)
    return parsed.isoformat() if parsed else None


def drift_item_identity(item: Any, *, include_values: bool = True) -> dict[str, Any]:
    """Return the stable fields that define one drift item."""
    identity = {
        "resource_kind": str(_get(item, "resource_kind", "")),
        "resource_name": str(_get(item, "resource_name", "")),
        "namespace": str(_get(item, "namespace", "")),
        "field_path": str(_get(item, "field_path", "")),
        "drift_level": str(_enum_value(_get(item, "drift_level", ""))),
        "is_allowlisted": bool(_get(item, "is_allowlisted", False)),
    }
    if include_values:
        identity["git_value"] = _jsonable(_get(item, "git_value"))
        identity["actual_value"] = _jsonable(_get(item, "actual_value"))
    return identity


def build_drift_fingerprint(
    namespace: str,
    items: list[Any],
    *,
    include_values: bool = True,
) -> str:
    """Build a deterministic fingerprint from namespace + sorted drift items."""
    identities = [
        drift_item_identity(item, include_values=include_values)
        for item in items
    ]
    identities.sort(key=_canonical_json)
    payload = {
        "version": FINGERPRINT_VERSION
        if include_values
        else SEMANTIC_FINGERPRINT_VERSION,
        "namespace": namespace,
        "items": identities,
    }
    digest = hashlib.sha256(_canonical_json(payload).encode("utf-8")).hexdigest()
    return f"dfp_{digest[:16]}"


def _report_identity(report: Any, *, include_values: bool = True) -> dict[str, Any]:
    items = _get(report, "items", []) or []
    namespace = str(_get(report, "namespace", ""))
    strict_fingerprint = build_drift_fingerprint(
        namespace,
        list(items),
        include_values=True,
    )
    return {
        "report_id": _get(report, "report_id"),
        "namespace": namespace,
        "status": str(_enum_value(_get(report, "status", ""))),
        "scanned_at": _get(report, "scanned_at"),
        "created_at": _get(report, "created_at"),
        "fingerprint": build_drift_fingerprint(
            namespace,
            list(items),
            include_values=include_values,
        ),
        "strict_fingerprint": strict_fingerprint,
    }


def build_drift_repeat_state(
    report: Any,
    recent_reports: list[Any],
    *,
    include_values: bool = True,
    window_hours: int = 12,
    max_reports: int = 20,
) -> dict[str, Any]:
    """Summarize repeat state for one drift report using stable fingerprints."""
    current = _report_identity(report, include_values=include_values)
    current_time = (
        _parse_datetime(current.get("scanned_at"))
        or _parse_datetime(current.get("created_at"))
        or datetime.now()
    )
    cutoff = current_time - timedelta(hours=window_hours)

    by_id: dict[str, dict[str, Any]] = {}
    for candidate in [report, *recent_reports]:
        identity = _report_identity(candidate, include_values=include_values)
        report_id = str(identity.get("report_id") or "")
        if not report_id:
            continue
        candidate_time = (
            _parse_datetime(identity.get("scanned_at"))
            or _parse_datetime(identity.get("created_at"))
        )
        if candidate_time is not None and candidate_time < cutoff:
            continue
        if identity["fingerprint"] != current["fingerprint"]:
            continue
        by_id[report_id] = identity

    matches = sorted(
        by_id.values(),
        key=lambda row: (
            _parse_datetime(row.get("scanned_at"))
            or _parse_datetime(row.get("created_at"))
            or datetime.min
        ),
    )
    first = matches[0] if matches else current
    last = matches[-1] if matches else current
    status = current.get("status") or "unknown"
    operator_stage = "pending_human" if status == "pending" else str(status)

    return {
        "schema_version": SCHEMA_VERSION,
        "fingerprint": current["fingerprint"],
        "strict_fingerprint": current["strict_fingerprint"],
        "matching_strategy": (
            VALUE_AWARE_MATCHING_STRATEGY
            if include_values
            else SEMANTIC_MATCHING_STRATEGY
        ),
        "window_hours": window_hours,
        "occurrences_12h": len(matches),
        "first_scanned_at": _iso(first.get("scanned_at") or first.get("created_at")),
        "last_scanned_at": _iso(last.get("scanned_at") or last.get("created_at")),
        "operator_stage": operator_stage,
        "reports": [
            {
                "report_id": row.get("report_id"),
                "scanned_at": _iso(row.get("scanned_at")),
                "created_at": _iso(row.get("created_at")),
                "status": row.get("status"),
                "strict_fingerprint": row.get("strict_fingerprint"),
            }
            for row in reversed(matches[-max_reports:])
        ],
    }