import { ok, err, type CommandContext } from "@tailor-platform/erp-kit/core";
import type { Transaction } from "../generated/kysely-tailordb";
import {
  WorkerEmploymentNotFoundError,
  AlreadyTerminatedError,
  TerminationDateBeforeEffectiveStartError,
} from "../lib/errors.generated";

export interface TerminateWorkerEmploymentInput {
  id: string;
  terminationDate: Date;
}

/** Function: run
 Description: Sets the termination date on a WorkerEmployment and closes its currently open generation, ending the employment relationship while preserving the Worker for possible re-hire. */
export async function run(
  db: Transaction,
  input: TerminateWorkerEmploymentInput,
  _ctx: CommandContext,
) {
  const workerEmployment = await db
    .selectFrom("WorkerEmployment")
    .selectAll()
    .where("id", "=", input.id)
    .forUpdate()
    .executeTakeFirst();

  if (!workerEmployment) return err(new WorkerEmploymentNotFoundError(input.id));
  if (workerEmployment.effectiveEnd !== null) return err(new AlreadyTerminatedError(input.id));
  if (input.terminationDate.getTime() < workerEmployment.effectiveStart.getTime()) {
    return err(new TerminationDateBeforeEffectiveStartError(input.id));
  }

  const updated = await db
    .updateTable("WorkerEmployment")
    .set({ terminationDate: input.terminationDate, effectiveEnd: input.terminationDate })
    .where("id", "=", input.id)
    .returningAll()
    .executeTakeFirstOrThrow();

  // Close the employment's open Assignments at the termination date in the same transaction (M03).
  // Otherwise the worker keeps resolving as currently assigned and the Position occupancy is never
  // released (blocking new hires as over-headcount). Only assignments already in force by the
  // termination date are closed; a new assignment can no longer be opened on a terminated employment
  // (createAssignment's EMPLOYMENT_TERMINATED guard).
  await db
    .updateTable("Assignment")
    .set({ effectiveEnd: input.terminationDate })
    .where("workerEmploymentId", "=", input.id)
    .where("effectiveEnd", "is", null)
    .where("effectiveStart", "<=", input.terminationDate)
    .execute();

  return ok({ workerEmployment: updated });
}