import type { CommandContext } from "@tailor-platform/erp-kit/core";
import type { Transaction } from "../generated/kysely-tailordb";

// The erp-kit Result discriminated union, narrowed to what this module reads — the same
// `_approvalDeps.ts` trick leave-management uses, so the injected query's own error type does
// not have to be nameable here.
type Result<T> = { ok: true; value: T } | { ok: false; error: { code: string } };

/**
 * Cross-module reads shiftSchedule needs, declared structurally rather than imported.
 *
 * shiftSchedule cannot see workforce's tables — its generated Kysely types cover its own schema
 * only — so "is this Assignment effective on the shift's date?" cannot be answered by a join.
 * Following the `_approvalDeps.ts` precedent in leave-management, the command takes the reader
 * as an injected function typed by the shape it uses, which keeps the module free of a compile
 * -time dependency on workforce while still enforcing the invariant server-side.
 */
export interface GetAssignmentDep {
  getAssignment: (
    db: Transaction,
    input: { id: string },
    ctx: CommandContext,
  ) => Promise<Result<{ assignment: { effectiveStart: Date; effectiveEnd: Date | null } }>>;
}

/**
 * An Assignment may staff a slot only on a date its generation actually covers. Effective dates
 * are whole days, so the comparison is on the date part: a generation starting on the 15th does
 * not cover the 1st, however the timestamps happen to be stored.
 */
export function isEffectiveOn(
  assignment: { effectiveStart: Date; effectiveEnd: Date | null },
  date: Date,
): boolean {
  const day = (d: Date) => Date.UTC(d.getUTCFullYear(), d.getUTCMonth(), d.getUTCDate());
  const on = day(date);
  return (
    day(assignment.effectiveStart) <= on &&
    (assignment.effectiveEnd == null || day(assignment.effectiveEnd) >= on)
  );
}