import hashlib
import secrets
from datetime import datetime, timedelta, timezone
from uuid import uuid4

from app.services.db import db_connection

CALLBACK_STATE_TTL_SECONDS = 15 * 60


def _now_utc() -> datetime:
    return datetime.now(timezone.utc)


def _state_hash(state: str) -> str:
    return hashlib.sha256(state.encode("utf-8")).hexdigest()


def create_broker_callback_state(
    *,
    user_id: str,
    session_id: str,
    broker: str,
    flow: str,
    ttl_seconds: int = CALLBACK_STATE_TTL_SECONDS,
) -> str:
    state = secrets.token_urlsafe(32)
    now = _now_utc()
    expires_at = now + timedelta(seconds=ttl_seconds)
    state_hash = _state_hash(state)
    with db_connection() as conn:
        with conn:
            with conn.cursor() as cur:
                cur.execute(
                    """
                    DELETE FROM broker_callback_state
                    WHERE expires_at <= %s OR consumed_at IS NOT NULL
                    """,
                    (now,),
                )
                cur.execute(
                    """
                    INSERT INTO broker_callback_state (
                        id,
                        state_hash,
                        user_id,
                        session_id,
                        broker,
                        flow,
                        created_at,
                        expires_at,
                        consumed_at
                    )
                    VALUES (%s, %s, %s, %s, %s, %s, %s, %s, NULL)
                    """,
                    (
                        str(uuid4()),
                        state_hash,
                        user_id,
                        session_id,
                        broker.strip().upper(),
                        flow.strip().lower(),
                        now,
                        expires_at,
                    ),
                )
    return state


def consume_broker_callback_state(
    *,
    state: str,
    user_id: str,
    session_id: str,
    broker: str,
    flow: str,
):
    if not state:
        return None
    now = _now_utc()
    state_hash = _state_hash(state)
    with db_connection() as conn:
        with conn:
            with conn.cursor() as cur:
                cur.execute(
                    """
                    UPDATE broker_callback_state
                    SET consumed_at = %s
                    WHERE state_hash = %s
                      AND user_id = %s
                      AND session_id = %s
                      AND broker = %s
                      AND flow = %s
                      AND consumed_at IS NULL
                      AND expires_at > %s
                    RETURNING id, expires_at
                    """,
                    (
                        now,
                        state_hash,
                        user_id,
                        session_id,
                        broker.strip().upper(),
                        flow.strip().lower(),
                        now,
                    ),
                )
                row = cur.fetchone()
                if not row:
                    return None
                return {"id": row[0], "expires_at": row[1].isoformat() if row[1] else None}