/**
 * Turns the rows of `chat_messages` into the {@link ChatMessage} the API sends.
 * Only `services/chat-service.ts` uses it, on the rows of its one query.
 *
 * @module
 */

import type { SQLOutputValue } from "node:sqlite";
import type { ChatMessage } from "../../shared/chat.ts";

/**
 * Returned by chat-service's query, which joins each message to its author and
 * to the message it replies to. `reply_to_id` is kept when the message it
 * points to is deleted, while `reply_to_author` and `reply_to_body` then read
 * null.
 */
export interface ChatMessageRow {
  id: string;
  user_id: string;
  body: string;
  created_at: string;
  updated_at: string | null;
  author_username: string;
  author_avatar_mime: string | null;
  reply_to_id: string | null;
  reply_to_author: string | null;
  /** Cut to chat-service's `REPLY_SNIPPET_LEN` characters. */
  reply_to_body: string | null;
  [key: string]: SQLOutputValue;
}

/**
 * Checks whether `obj`, a row read by chat-service, is a
 * {@link ChatMessageRow}.
 */
export function isChatMessageRow(obj: unknown): obj is ChatMessageRow {
  return !!obj && typeof obj === "object" &&
    "id" in obj && typeof obj.id === "string" &&
    "user_id" in obj && typeof obj.user_id === "string" &&
    "body" in obj && typeof obj.body === "string" &&
    "created_at" in obj && typeof obj.created_at === "string" &&
    "updated_at" in obj &&
    (typeof obj.updated_at === "string" || obj.updated_at === null) &&
    "author_username" in obj && typeof obj.author_username === "string" &&
    "author_avatar_mime" in obj &&
    (typeof obj.author_avatar_mime === "string" ||
      obj.author_avatar_mime === null) &&
    "reply_to_id" in obj &&
    (typeof obj.reply_to_id === "string" || obj.reply_to_id === null) &&
    "reply_to_author" in obj &&
    (typeof obj.reply_to_author === "string" || obj.reply_to_author === null) &&
    "reply_to_body" in obj &&
    (typeof obj.reply_to_body === "string" || obj.reply_to_body === null);
}

/**
 * Converts a row to the {@link ChatMessage} that chat-service returns, turning
 * its timestamps into Dates and its nulls into absent fields.
 */
export function chatMessageRowToApi(row: ChatMessageRow): ChatMessage {
  return {
    id: row.id,
    userId: row.user_id,
    body: row.body,
    createdAt: new Date(row.created_at),
    updatedAt: row.updated_at ? new Date(row.updated_at) : undefined,
    authorUsername: row.author_username,
    authorAvatarMime: row.author_avatar_mime ?? undefined,
    replyToId: row.reply_to_id ?? undefined,
    replyToAuthor: row.reply_to_author ?? undefined,
    replyToBody: row.reply_to_body ?? undefined,
  };
}