"""Pure cache and dataset-freshness policies for offline and real evaluations."""

import hashlib
import json


VALID, NEEDS_REVALIDATION, CONFLICT = "VALID", "NEEDS_REVALIDATION", "CONFLICT"


def cache_key(input_fingerprint, candidate_set_hash, model, prompt_version, dataset_versions):
    """Return a stable key covering every input that can change an answer."""
    payload = {
        "input_fingerprint": str(input_fingerprint),
        "candidate_set_hash": str(candidate_set_hash),
        "model": str(model),
        "prompt_version": str(prompt_version),
        "dataset_versions": dict(sorted((dataset_versions or {}).items())),
    }
    return hashlib.sha256(json.dumps(payload, sort_keys=True, separators=(",", ":")).encode()).hexdigest()


def classify_knowledge_freshness(record_versions, active_versions):
    """Classify versioned knowledge without deleting or rewriting history."""
    recorded = dict(record_versions or {})
    active = dict(active_versions or {})
    if any(key in recorded and key in active and recorded[key] != active[key] for key in recorded):
        return CONFLICT
    if recorded != active:
        return NEEDS_REVALIDATION
    return VALID