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

type SubscriptionOrderByField = "subscribedAt" | "createdAt";

export interface ListNotificationSubscriptionsInput extends PaginationInput<SubscriptionOrderByField> {
  // Optional source narrowing, applied on top of the caller's own rows.
  sourceType?: string;
  sourceId?: string;
  // Optional explicit user filter; must match the caller.
  userId?: string;
}

/**
 * Returns the caller's own NotificationSubscriptions, optionally narrowed by source, as a paginated result.
 */
export async function run(
  db: ReadonlyDB<DB>,
  input: ListNotificationSubscriptionsInput,
  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 limit = input.limit ?? DEFAULT_PAGE_SIZE;
  const offset = input.offset ?? 0;
  const orderBy = input.orderBy ?? "subscribedAt";
  const orderDirection = input.orderDirection ?? "desc";

  // Self-scope: an explicit userId filter must match the caller; results are
  // always restricted to the caller's own subscriptions.
  if (input.userId !== undefined && input.userId !== actorId) {
    return err(new ForbiddenError(input.userId));
  }

  let query = db.selectFrom("NotificationSubscription").selectAll().where("userId", "=", actorId);

  if (input.sourceType !== undefined) {
    query = query.where("sourceType", "=", input.sourceType);
  }
  if (input.sourceId !== undefined) {
    query = query.where("sourceId", "=", input.sourceId);
  }

  const rows = await query
    .orderBy(orderBy, orderDirection)
    .limit(limit + 1)
    .offset(offset)
    .execute();

  return ok(buildPaginatedResult(rows, limit));
}