/**
 * V9 rectification Case state machine contracts.
 *
 * The server owns the authoritative Case status. The browser and the agent
 * never derive status from message counts, candidate existence or session
 * ordering.
 */

export const RECTIFICATION_CASE_STATUSES = [
  "draft",
  "collecting_evidence",
  "candidate_ready",
  "candidate_accepted",
  "needs_rebaseline",
  "paused",
  "confirmed",
  "closed",
  "abandoned",
  "superseded",
] as const;

export type RectificationCaseStatus =
  (typeof RECTIFICATION_CASE_STATUSES)[number];

/** Statuses that may be resumed by the user. */
export const RESUMABLE_CASE_STATUSES: readonly RectificationCaseStatus[] = [
  "draft",
  "collecting_evidence",
  "candidate_ready",
  "candidate_accepted",
  "needs_rebaseline",
  "paused",
];

/** Statuses that only allow read-only history access. */
export const TERMINAL_CASE_STATUSES: readonly RectificationCaseStatus[] = [
  "confirmed",
  "closed",
  "abandoned",
  "superseded",
];

const RESUMABLE_SET = new Set<string>(RESUMABLE_CASE_STATUSES);
const TERMINAL_SET = new Set<string>(TERMINAL_CASE_STATUSES);

export function isRectificationCaseStatus(
  value: unknown,
): value is RectificationCaseStatus {
  return (
    typeof value === "string" &&
    (RESUMABLE_SET.has(value) || TERMINAL_SET.has(value))
  );
}

export function isResumableStatus(
  status: RectificationCaseStatus,
): boolean {
  return RESUMABLE_SET.has(status);
}

export function isTerminalStatus(status: RectificationCaseStatus): boolean {
  return TERMINAL_SET.has(status);
}

/**
 * Legal terminal transitions. A resumable case may move to any terminal
 * status; terminal statuses are immutable.
 */
export function canTransitToTerminal(
  from: RectificationCaseStatus,
  to: RectificationCaseStatus,
): boolean {
  if (isTerminalStatus(from)) return false;
  return isTerminalStatus(to);
}

/** statuses that reject evidence/turn writes. Terminal cases are read-only. */
export function evidenceWritesAllowed(
  status: RectificationCaseStatus,
): boolean {
  return isResumableStatus(status);
}

/**
 * The one-resumable-case-per-user invariant, mirrored from the database
 * partial unique index. The database is the enforcement point; this is the
 * contract the service layer relies on.
 */
export const MAX_RESUMABLE_CASES_PER_USER = 1;

export const RECTIFICATION_SKILL_NAME = "jyotish-birth-time-rectification";
export const RECTIFICATION_SKILL_VERSION = "10.0.23";