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

// The polymorphic target of an EligibilityRule / WorkRuleAssignment. Each variant is a workforce
// entity referenced by id.
export type EligibilityTargetType =
  | "WORKER"
  | "POSITION"
  | "JOB_PROFILE"
  | "EMPLOYMENT_TYPE"
  | "WORK_REGIME";

// The erp-kit Result union, narrowed to what the target guard reads.
type Result<T> = { ok: true; value: T } | { ok: false; error: { code: string } };

// One workforce lookup per targetType, resolving an id to an entity (ok) or reporting it missing.
// Declared as minimal structural signatures (the `_approvalDeps` precedent) rather than derived from
// WorkforceModule["queries"], so time-tracking stays free of the workforce module types — the app
// composition adapts the real queries onto these seams.
type TargetLookupFn = (
  db: Transaction,
  input: { id: string },
  ctx: CommandContext,
) => Promise<Result<unknown>>;

export interface EligibilityTargetQueries {
  getWorker: TargetLookupFn;
  getPosition: TargetLookupFn;
  getJobProfile: TargetLookupFn;
  getEmploymentType: TargetLookupFn;
  getWorkRegime: TargetLookupFn;
}

/**
 * Function: eligibilityTargetExists
 * Description: Resolves a polymorphic target against workforce — dispatches on `targetType` to the
 * matching workforce lookup and reports whether `targetId` resolves to an existing entity. Shared by
 * createEligibilityRule / updateEligibilityRule / assignWorkRule so all three reject a dangling
 * cross-module target the same way (M17).
 */
export async function eligibilityTargetExists(
  db: Transaction,
  queries: EligibilityTargetQueries,
  targetType: EligibilityTargetType,
  targetId: string,
  ctx: CommandContext,
): Promise<boolean> {
  switch (targetType) {
    case "WORKER":
      return (await queries.getWorker(db, { id: targetId }, ctx)).ok;
    case "POSITION":
      return (await queries.getPosition(db, { id: targetId }, ctx)).ok;
    case "JOB_PROFILE":
      return (await queries.getJobProfile(db, { id: targetId }, ctx)).ok;
    case "EMPLOYMENT_TYPE":
      return (await queries.getEmploymentType(db, { id: targetId }, ctx)).ok;
    case "WORK_REGIME":
      return (await queries.getWorkRegime(db, { id: targetId }, ctx)).ok;
  }
}