export type ReviewStatus = "draft" | "accepted" | "rejected" | "cancelled";
export type ReviewAction = "revise" | "accept" | "reject" | "cancel";
export interface ReviewState {
  revision: number;
  status: ReviewStatus;
  text: string;
}

export const ENTRY_TYPE = "workbook-review-desk-state";
export const MESSAGE_TYPE = "workbook-review-desk";
export const MAX_TEXT_LENGTH = 12_000;

export function isReviewState(value: unknown): value is ReviewState {
  if (typeof value !== "object" || value === null) return false;
  return "revision" in value && Number.isSafeInteger(value.revision) && Number(value.revision) >= 0
    && "text" in value && typeof value.text === "string" && value.text.length <= MAX_TEXT_LENGTH
    && "status" in value && ["draft", "accepted", "rejected", "cancelled"].includes(String(value.status));
}

export function transition(state: ReviewState, action: ReviewAction, text?: string): ReviewState {
  if (text !== undefined && (text.trim().length === 0 || text.length > MAX_TEXT_LENGTH)) {
    throw new Error(`Draft must contain 1–${MAX_TEXT_LENGTH} characters, including non-whitespace text.`);
  }
  if (action === "revise" && text === undefined) throw new Error("revise requires text.");
  if (action !== "revise" && action !== "accept" && text !== undefined) {
    throw new Error("Rejection and cancellation preserve the original draft.");
  }
  return {
    revision: state.revision + 1,
    status: action === "revise" ? "draft" : action === "accept" ? "accepted" : action === "reject" ? "rejected" : "cancelled",
    text: text ?? state.text,
  };
}