"""Data-only scoring policy. No executable expressions or arbitrary regex rules."""
import copy
import hashlib
import json
from pathlib import Path

DEFAULT_POLICY = Path(__file__).resolve().parents[1] / 'assets' / 'scoring_policy.json'
RULES = {'installed_workload_role', 'running_application_service', 'attributed_application_listener',
         'observed_application_clients', 'configured_business_share', 'observed_smb_transport',
         'observed_business_share_clients', 'configured_custom_schedule', 'verified_domain_controller'}


def load_policy(source=None):
    if source is not None and not isinstance(source,(dict,str,Path)):
        raise ValueError('A scoring policy must be a JSON object or file path.')
    if isinstance(source, dict):
        policy = copy.deepcopy(source)
    else:
        path = Path(source) if source is not None else DEFAULT_POLICY
        try:
            if path.stat().st_size > 65536:
                raise ValueError('Scoring policy exceeds 64 KiB.')
            policy = json.loads(path.read_text(encoding='utf-8'))
        except (OSError, UnicodeError, json.JSONDecodeError, RecursionError):
            raise ValueError('Unable to read a valid UTF-8 scoring policy JSON file.') from None
    try:
        limits, weights = policy['thresholds'], policy['coverage_weights']
        valid = (
            set(policy) == {'model_version','name','scores','thresholds','coverage_weights','partial_check_credit'}
            and policy['model_version'] == '2.0' and isinstance(policy['name'],str) and 0<len(policy['name'])<=120
            and set(policy['scores']) == RULES
            and all(type(value) is int and 0<=value<=100 for value in policy['scores'].values())
            and set(limits) == {'low','medium','high','critical'}
            and all(type(value) is int for value in limits.values())
            and 1 == limits['low'] < limits['medium'] < limits['high'] < limits['critical'] <= 100
            and set(weights) == {'system','roles','services','network','tasks','software','storage','shares','certificates'}
            and all(type(weight) is int and 1<=weight<=10 for weight in weights.values())
            and type(policy['partial_check_credit']) in (int,float) and 0<=policy['partial_check_credit']<1
        )
    except (KeyError,TypeError,AttributeError):
        valid = False
    if not valid:
        raise ValueError('Invalid scoring policy. Use the bundled v2 policy structure, integer scores 0–100, ordered thresholds and positive coverage weights.')
    policy['name']='Deployment scoring policy'
    return policy


def policy_id(policy):
    return hashlib.sha256(json.dumps(policy, sort_keys=True).encode('utf-8')).hexdigest()


def risk_level(score, policy):
    for name in ('critical','high','medium','low'):
        if score >= policy['thresholds'][name]:
            return name
    return 'informational'