import {
  ok,
  err,
  type ReadonlyDB,
  UnauthenticatedError,
  type CallerContext,
} from "@tailor-platform/erp-kit/core";
import type { DB } from "../generated/kysely-tailordb";
import { ForbiddenError } from "../lib/errors.generated";

export interface GetNotificationPreferenceInput {
  userId: string;
  categoryId: string;
  channelId: string;
}

/**
 * Returns the caller's NotificationPreference row for a (categoryId, channelId), or null (default opt-in). Self-service only.
 */
export async function run(
  db: ReadonlyDB<DB>,
  input: GetNotificationPreferenceInput,
  ctx: CallerContext,
) {
  // Every result here is scoped to the caller, so there is nothing to return when
  // there is no caller. Queries carry no permission gate of their own.
  const { actorId } = ctx;
  if (actorId === null) return err(new UnauthenticatedError());
  const { userId, categoryId, channelId } = input;

  if (actorId !== userId) {
    return err(new ForbiddenError(userId));
  }

  const preference = await db
    .selectFrom("NotificationPreference")
    .selectAll()
    .where("userId", "=", userId)
    .where("categoryId", "=", categoryId)
    .where("channelId", "=", channelId)
    .executeTakeFirst();

  return ok({ preference: preference ?? null });
}