"""Fail-closed quarantine decisions for validated data assets.

Persistence is intentionally delegated to the caller's transaction.  This
module derives stable decisions from immutable validation reports and blocks a
quarantined or failed asset from training, production inference and derived
processing until an explicit, separately persisted release action exists.
"""

from __future__ import annotations

from dataclasses import dataclass
from enum import StrEnum
from hashlib import sha256
from typing import Any
import json

from app.core.errors import AppError
from app.services.data_contract_validation import QuarantineStatus, ValidationReport, ValidationStatus


class AssetUse(StrEnum):
    TRAINING = "training"
    PRODUCTION_INFERENCE = "production_inference"
    DERIVED_PROCESSING = "derived_processing"
    EXPORT = "export"


@dataclass(frozen=True)
class QuarantineDecision:
    """A deterministic, auditable quarantine decision for one report."""

    asset_id: str
    data_contract_key: str
    data_contract_version: str
    validation_report_sha256: str
    validation_status: ValidationStatus
    quarantine_status: QuarantineStatus
    reason_codes: tuple[str, ...]
    idempotency_key: str
    requires_explicit_release: bool = False

    @property
    def eligible_for_use(self) -> bool:
        return self.validation_status == ValidationStatus.PASSED and self.quarantine_status == QuarantineStatus.NOT_QUARANTINED

    def to_dict(self) -> dict[str, Any]:
        return {
            "asset_id": self.asset_id,
            "data_contract_key": self.data_contract_key,
            "data_contract_version": self.data_contract_version,
            "validation_report_sha256": self.validation_report_sha256,
            "validation_status": self.validation_status.value,
            "quarantine_status": self.quarantine_status.value,
            "reason_codes": list(self.reason_codes),
            "idempotency_key": self.idempotency_key,
            "requires_explicit_release": self.requires_explicit_release,
            "eligible_for_use": self.eligible_for_use,
        }


class DataQuarantineService:
    """Derive and enforce safe use decisions from validation results."""

    @staticmethod
    def decide(
        report: ValidationReport,
        *,
        previous: QuarantineDecision | None = None,
    ) -> QuarantineDecision:
        """Create a stable decision without silently releasing old quarantines.

        A fresh passing validation report can be persisted as a new validated
        version by the import transaction.  It cannot automatically release an
        existing quarantined record: the caller must explicitly record that
        reviewed state transition against the new report/version.
        """

        is_quarantined = report.validation_status == ValidationStatus.FAILED or report.quarantine_status == QuarantineStatus.QUARANTINED
        failure_codes = tuple(
            sorted(
                {
                    issue.code
                    for issue in report.issues
                    if issue.severity.value == "error" or is_quarantined
                }
            )
        )
        requires_explicit_release = False
        reason_codes = failure_codes
        status = QuarantineStatus.QUARANTINED if is_quarantined else QuarantineStatus.NOT_QUARANTINED

        if previous is not None and previous.quarantine_status == QuarantineStatus.QUARANTINED and not is_quarantined:
            status = QuarantineStatus.QUARANTINED
            requires_explicit_release = True
            reason_codes = ("QUARANTINE_RELEASE_REQUIRES_EXPLICIT_PERSISTENCE",)

        idempotency_key = _decision_key(
            asset_id=report.asset_id,
            contract_key=report.data_contract_key,
            contract_version=report.data_contract_version,
            report_sha256=report.report_sha256,
            quarantine_status=status,
            reason_codes=reason_codes,
            requires_explicit_release=requires_explicit_release,
        )
        return QuarantineDecision(
            asset_id=report.asset_id,
            data_contract_key=report.data_contract_key,
            data_contract_version=report.data_contract_version,
            validation_report_sha256=report.report_sha256,
            validation_status=report.validation_status,
            quarantine_status=status,
            reason_codes=reason_codes,
            idempotency_key=idempotency_key,
            requires_explicit_release=requires_explicit_release,
        )

    @staticmethod
    def require_eligible(decision: QuarantineDecision, *, use: AssetUse) -> None:
        """Raise a typed error before a non-eligible artifact reaches a pipeline."""

        if decision.eligible_for_use:
            return
        raise AppError(
            code="DATASET_QUARANTINED",
            message="Dataset is quarantined or failed validation and cannot enter this pipeline.",
            status_code=409,
            details={
                "asset_id": decision.asset_id,
                "use": use.value,
                "quarantine_status": decision.quarantine_status.value,
                "validation_status": decision.validation_status.value,
                "reason_codes": list(decision.reason_codes),
                "validation_report_sha256": decision.validation_report_sha256,
                "idempotency_key": decision.idempotency_key,
                "requires_explicit_release": decision.requires_explicit_release,
            },
        )


def _decision_key(
    *,
    asset_id: str,
    contract_key: str,
    contract_version: str,
    report_sha256: str,
    quarantine_status: QuarantineStatus,
    reason_codes: tuple[str, ...],
    requires_explicit_release: bool,
) -> str:
    payload = {
        "asset_id": asset_id,
        "contract_key": contract_key,
        "contract_version": contract_version,
        "report_sha256": report_sha256,
        "quarantine_status": quarantine_status.value,
        "reason_codes": list(reason_codes),
        "requires_explicit_release": requires_explicit_release,
    }
    return sha256(json.dumps(payload, sort_keys=True, separators=(",", ":"), ensure_ascii=True).encode("utf-8")).hexdigest()