"""
Backup notification policy snapshot.

Loads the latest committed, read-only backup notification policy. The policy
defines success-noise suppression, failure/action-required escalation, and
daily summary expectations; it never sends notifications, runs backups,
starts restore drills, syncs offsite backups, writes credential markers,
changes schedules, or writes workflows.
"""

from __future__ import annotations

import json
from pathlib import Path
from typing import Any

from src.services.snapshot_paths import default_evaluations_dir

_DEFAULT_EVALUATIONS_DIR = default_evaluations_dir(Path(__file__))
_SNAPSHOT_PATTERN = "backup_notification_policy_*.json"
_SCHEMA_VERSION = "backup_notification_policy_v1"


def load_latest_backup_notification_policy(
    evaluations_dir: Path | None = None,
) -> dict[str, Any]:
    """Load the newest committed backup notification policy snapshot."""
    directory = evaluations_dir or _DEFAULT_EVALUATIONS_DIR
    candidates = sorted(directory.glob(_SNAPSHOT_PATTERN))
    if not candidates:
        raise FileNotFoundError(f"no backup notification policy snapshots found in {directory}")

    latest = candidates[-1]
    with latest.open(encoding="utf-8") as handle:
        payload = json.load(handle)

    if not isinstance(payload, dict):
        raise ValueError(f"{latest}: expected JSON object")
    _require_schema(payload, _SCHEMA_VERSION, str(latest))
    _require_read_only_boundaries(payload, str(latest))
    _require_operation_boundaries(payload, str(latest))
    _require_rollup_consistency(payload, str(latest))
    _require_success_noise_suppression(payload, str(latest))
    return payload


def _require_schema(payload: dict[str, Any], expected: str, label: str) -> None:
    actual = payload.get("schema_version")
    if actual != expected:
        raise ValueError(f"{label}: expected schema_version={expected}, got {actual!r}")


def _require_read_only_boundaries(payload: dict[str, Any], label: str) -> None:
    program_status = payload.get("program_status") or {}
    if program_status.get("read_only_mode") is not True:
        raise ValueError(f"{label}: program_status.read_only_mode must be true")

    boundaries = payload.get("approval_boundaries") or {}
    blocked_flags = {
        "sdk_installation_allowed",
        "paid_api_call_allowed",
        "shadow_or_canary_allowed",
        "production_routing_allowed",
        "destructive_operation_allowed",
    }
    allowed = sorted(flag for flag in blocked_flags if boundaries.get(flag) is not False)
    if allowed:
        raise ValueError(f"{label}: approval boundaries must remain false: {allowed}")


def _require_operation_boundaries(payload: dict[str, Any], label: str) -> None:
    boundaries = payload.get("operation_boundaries") or {}
    if boundaries.get("read_only_policy_allowed") is not True:
        raise ValueError(f"{label}: read_only_policy_allowed must be true")

    blocked_flags = {
        "notification_send_allowed",
        "backup_execution_allowed",
        "restore_execution_allowed",
        "offsite_sync_execution_allowed",
        "credential_marker_write_allowed",
        "schedule_change_allowed",
        "workflow_write_allowed",
        "telegram_test_message_allowed",
    }
    allowed = sorted(flag for flag in blocked_flags if boundaries.get(flag) is not False)
    if allowed:
        raise ValueError(f"{label}: operation boundaries must remain false: {allowed}")


def _require_rollup_consistency(payload: dict[str, Any], label: str) -> None:
    rules = payload.get("policy_rules") or []
    rollups = payload.get("rollups") or {}
    if rollups.get("total_rules") != len(rules):
        raise ValueError(f"{label}: rollups.total_rules must match policy_rules")

    by_decision: dict[str, int] = {}
    for rule in rules:
        decision = str(rule.get("decision"))
        by_decision[decision] = by_decision.get(decision, 0) + 1
    if rollups.get("by_decision") != by_decision:
        raise ValueError(f"{label}: rollups.by_decision must match policy rule decisions")

    immediate_ids = {
        rule.get("rule_id")
        for rule in rules
        if rule.get("decision") == "escalate_immediate"
    }
    if set(rollups.get("immediate_escalation_rule_ids") or []) != immediate_ids:
        raise ValueError(f"{label}: rollups.immediate_escalation_rule_ids must match immediate rules")

    suppressed_success_ids = {
        rule.get("rule_id")
        for rule in rules
        if rule.get("backup_state") == "success"
        and rule.get("decision") == "suppress_immediate_success"
    }
    if set(rollups.get("suppressed_success_rule_ids") or []) != suppressed_success_ids:
        raise ValueError(f"{label}: rollups.suppressed_success_rule_ids must match suppressed success rules")


def _require_success_noise_suppression(payload: dict[str, Any], label: str) -> None:
    summary = payload.get("daily_summary_contract") or {}
    if summary.get("success_immediate_notifications_allowed") is not False:
        raise ValueError(f"{label}: daily summary must suppress immediate success notifications")

    channels = payload.get("notification_channels") or []
    noisy_channels = [
        channel.get("channel_id")
        for channel in channels
        if channel.get("success_immediate_allowed") is not False
    ]
    if noisy_channels:
        raise ValueError(f"{label}: channels must not allow success immediate notifications: {noisy_channels}")

    success_escalations = [
        rule.get("rule_id")
        for rule in payload.get("policy_rules") or []
        if rule.get("backup_state") == "success"
        and rule.get("decision") != "suppress_immediate_success"
    ]
    if success_escalations:
        raise ValueError(f"{label}: success rules must suppress immediate notification: {success_escalations}")