/**
 * vscode-free mutations on the Artifact (spec §6.5). Keeping thread logic here
 * (not in the vscode controller) keeps it unit-testable; ThreadController is a
 * thin adapter that calls these and persists via CoauthorStore.
 */
import {
  newId,
  type Artifact,
  type Fingerprint,
  type Provenance,
  type ThreadStatus,
} from "./model";

export interface NewMessage {
  author: Provenance;
  body: string;
}

function message(m: NewMessage) {
  return { id: newId("m"), author: m.author, body: m.body, createdAt: new Date().toISOString() };
}

/** Lazily-created anchor + thread for a new region discussion (PUC-1). */
export function addThread(
  artifact: Artifact,
  fingerprint: Fingerprint,
  first: NewMessage,
): { threadId: string; anchorId: string } {
  const anchorId = newId("a");
  const threadId = newId("t");
  artifact.anchors[anchorId] = { fingerprint };
  artifact.threads.push({ id: threadId, anchorId, status: "open", messages: [message(first)] });
  return { threadId, anchorId };
}

/** Append a reply (PUC-2). Throws if the thread is unknown. */
export function appendMessage(artifact: Artifact, threadId: string, m: NewMessage): void {
  const t = artifact.threads.find((x) => x.id === threadId);
  if (!t) throw new Error(`unknown thread id: ${threadId}`);
  t.messages.push(message(m));
}

/** Resolve/reopen a thread (PUC-2). Throws if the thread is unknown. */
export function setStatus(artifact: Artifact, threadId: string, status: ThreadStatus): void {
  const t = artifact.threads.find((x) => x.id === threadId);
  if (!t) throw new Error(`unknown thread id: ${threadId}`);
  t.status = status;
}