"""Audit logging with request context and integrity hashing."""

from __future__ import annotations

import hashlib
from datetime import datetime, timezone

from sqlalchemy.orm import Session

from app.middleware.request_context import request_ip, request_user_agent
from app.models.audit import AuditLog


def _integrity_payload(entry: AuditLog) -> str:
    ts = entry.timestamp
    if ts is None:
        ts = datetime.now(timezone.utc)
    user_part = str(entry.user_id) if entry.user_id else ""
    entity_type = entry.entity_type or ""
    entity_id = entry.entity_id or ""
    return f"{user_part}:{entry.action}:{entity_type}:{entity_id}:{ts.isoformat()}"


def compute_integrity_hash(entry: AuditLog) -> str:
    """Return the SHA-256 hex digest for an audit log entry."""
    return hashlib.sha256(_integrity_payload(entry).encode()).hexdigest()


def verify_audit_integrity(entry: AuditLog) -> bool:
    """Return whether the stored hash matches the entry's current fields."""
    if not entry.integrity_hash:
        return False
    return entry.integrity_hash == compute_integrity_hash(entry)


def log_action(
    db: Session,
    user_id,
    action: str,
    entity_type: str | None = None,
    entity_id: str | None = None,
    details: dict | None = None,
    *,
    ip_address: str | None = None,
    user_agent: str | None = None,
    session_id: str | None = None,
) -> AuditLog:
    """Record an audit event. Does not commit — the caller owns the transaction."""
    ip = ip_address if ip_address is not None else request_ip.get("")
    ua = user_agent if user_agent is not None else request_user_agent.get("")

    entry = AuditLog(
        user_id=user_id,
        action=action,
        entity_type=entity_type,
        entity_id=str(entity_id) if entity_id else None,
        details=details,
        ip_address=ip or None,
        user_agent=ua or None,
        session_id=session_id,
        timestamp=datetime.now(timezone.utc),
    )
    db.add(entry)
    db.flush()
    entry.integrity_hash = compute_integrity_hash(entry)
    return entry
