/**
 * @factory/realtime — comment-event → `comment.event` frame builder
 * (TASK-0094 R1).
 *
 * Pure (no sockets, no Redis — unit-testable): maps a `comment.*` domain
 * event from the `factory:events` stream to the shared
 * {@link CommentEventFrame} the server fans out over the page room.
 *
 * The API's CommentModule is the ONLY emitter (one service call → one
 * stream event; the frame is derived from it). Payload shape (the emitters
 * in `apps/api/src/modules/comments` include these fields — kept in
 * lockstep with the zod validation below):
 *
 *   comment.created   { workspaceId, commentId, pageId?, blockId?, recordId?,
 *                       replyId?, actorId, body }
 *   comment.resolved  { workspaceId, commentId, pageId?, actorId }
 *   comment.reopened  { workspaceId, commentId, pageId?, actorId }
 *   comment.reaction  { workspaceId, commentId, pageId?, actorId, emoji, active }
 *   comment.deleted   { workspaceId, commentId, pageId?, actorId }
 *
 * A frame is ONLY built when a `pageId` is present (the fan-out room is
 * `comment:{pageId}` — a comment with no resolvable page has no room; the
 * API's target resolver always resolves one for blocks/pages/records, so
 * this is defensive).
 */

import { z } from "zod";
import type { DomainEvent } from "@factory/shared";
import { CommentEventFrameSchema, type CommentEventFrame } from "@factory/shared/realtime/frames";
import { commentEventKindForEvent } from "@factory/shared/realtime/comment-events";

/** The preview length (the full comment is fetched on demand — R2). */
export const COMMENT_PREVIEW_MAX = 200;

/** The comment stream-event payload (the fields the frame needs). */
const CommentEventPayloadSchema = z.object({
  commentId: z.string().min(1),
  /** The fan-out room's page (the API resolves it from the target). */
  pageId: z.string().min(1).optional(),
  /** The acting user (server-side — the client never supplies identity). */
  actorId: z.string().min(1),
  /** New-thread / reply body (the preview source). */
  body: z.string().optional(),
  /** A reply (a `comment.created` with a `replyId` → kind `replied`). */
  replyId: z.string().optional(),
});
type CommentEventPayload = z.infer<typeof CommentEventPayloadSchema>;

/**
 * Build the `comment.event` frame for a domain event. `null` when the event
 * does not map to a comment frame (another event name), the payload is
 * malformed, or no `pageId` is present (no room to fan out to).
 */
export function commentEventFrameFor(event: DomainEvent): CommentEventFrame | null {
  const kind = commentEventKindForEvent(event);
  if (kind === null) return null;

  const parsed = CommentEventPayloadSchema.safeParse(event.payload);
  if (!parsed.success) return null;
  const p = parsed.data as CommentEventPayload;
  if (p.pageId === undefined) return null;

  const preview =
    kind === "created" || kind === "replied" ? (p.body ?? "").slice(0, COMMENT_PREVIEW_MAX) : "";

  const frame = CommentEventFrameSchema.safeParse({
    type: "comment.event",
    kind,
    commentId: p.commentId,
    pageId: p.pageId,
    actorId: p.actorId,
    preview,
  });
  return frame.success ? frame.data : null;
}