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

type LeaveGrantOrderByField = "expirationDate" | "grantedDate";

export interface ListLeaveGrantsByWorkerInput extends PaginationInput<LeaveGrantOrderByField> {
  workerId: string;
  leaveTypeKey?: string;
}

/**
 * Function: listLeaveGrantsByWorker
 * Lists a worker's LeaveGrant history (optionally scoped to a leave type),
 * including expired and fully-consumed grants, ordered by expirationDate
 * ascending (soonest-expiring first) — mirroring the FIFO order consumption
 * itself uses. The ledger is keyed to the Worker, not a specific employment
 * or assignment.
 */
export async function run(db: ReadonlyDB<DB>, input: ListLeaveGrantsByWorkerInput) {
  if (input.leaveTypeKey !== undefined) {
    const leaveType = await db
      .selectFrom("LeaveType")
      .select("id")
      .where("key", "=", input.leaveTypeKey)
      .executeTakeFirst();
    if (!leaveType) {
      return err(new LeaveTypeNotFoundError(input.leaveTypeKey));
    }
  }

  // NOTE: workerId references workforce's Worker (cross-module), and there is no query
  // injection wired into module.ts yet, so we cannot proactively verify the Worker exists
  // here (see WORKER_NOT_FOUND in the doc). Following the precedent in
  // modules/workforce/command/createWorker.ts, we skip that check; referential integrity
  // for workerId is left to the DB-level FK constraint.

  const limit = input.limit ?? DEFAULT_PAGE_SIZE;
  const offset = input.offset ?? 0;
  const orderBy = input.orderBy ?? "expirationDate";
  const orderDirection = input.orderDirection ?? "asc";

  let query = db.selectFrom("LeaveGrant").selectAll().where("workerId", "=", input.workerId);
  if (input.leaveTypeKey !== undefined) {
    query = query.where("leaveTypeKey", "=", input.leaveTypeKey);
  }

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

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