import type { Db } from "../libs/db.js";
import type { ChatMessage } from "../types.js";

interface MessageRow {
  chat_id: number;
  message_id: number;
  user_id: number | null;
  date: number;
  author: string;
  text: string;
  reply_to_message_id: number | null;
}

const toMessage = (row: MessageRow): ChatMessage => ({
  chatId: row.chat_id,
  messageId: row.message_id,
  userId: row.user_id,
  date: row.date,
  author: row.author,
  text: row.text,
  replyToMessageId: row.reply_to_message_id,
});

export const createMessageRepository = (db: Db) => {
  const statements = {
    upsert: db.prepare(`
      INSERT INTO messages (chat_id, message_id, user_id, date, author, text, reply_to_message_id)
      VALUES (@chatId, @messageId, @userId, @date, @author, @text, @replyToMessageId)
      ON CONFLICT(chat_id, message_id) DO UPDATE SET text = excluded.text
    `),
    insertIfMissing: db.prepare(`
      INSERT OR IGNORE INTO messages (chat_id, message_id, user_id, date, author, text, reply_to_message_id)
      VALUES (@chatId, @messageId, @userId, @date, @author, @text, @replyToMessageId)
    `),
    pruneChat: db.prepare(`
      DELETE FROM messages WHERE chat_id = ? AND message_id <= (
        SELECT message_id FROM messages WHERE chat_id = ?
        ORDER BY message_id DESC LIMIT 1 OFFSET ?
      )
    `),
    latest: db.prepare("SELECT * FROM messages WHERE chat_id = ? ORDER BY message_id DESC LIMIT ?"),
    latestByUser: db.prepare(
      "SELECT * FROM messages WHERE chat_id = ? AND user_id = ? ORDER BY message_id DESC LIMIT ?",
    ),
    findById: db.prepare("SELECT * FROM messages WHERE chat_id = ? AND message_id = ?"),
    statsByChat: db.prepare("SELECT COUNT(*) AS count, MIN(date) AS oldest FROM messages WHERE chat_id = ?"),
  };

  const toChronological = (rows: unknown[]): ChatMessage[] => (rows as MessageRow[]).reverse().map(toMessage);

  /** Сохраняет сообщение (при повторе — обновляет текст) и оставляет в чате не больше `keep` последних. */
  const upsertAndPrune = db.transaction((message: ChatMessage, keep: number) => {
    statements.upsert.run(message);
    statements.pruneChat.run(message.chatId, message.chatId, keep);
  });

  /**
   * Массовая загрузка (импорт): уже сохранённые сообщения не трогаем — живые данные точнее экспорта.
   * Возвращает, сколько сообщений добавлено; затем историю чата обрезаем до `keep` последних.
   */
  const insertManyAndPrune = db.transaction((chatId: number, messages: ChatMessage[], keep: number): number => {
    const inserted = messages.reduce((sum, message) => sum + statements.insertIfMissing.run(message).changes, 0);

    statements.pruneChat.run(chatId, chatId, keep);

    return inserted;
  });

  /** Последние `limit` сообщений чата в хронологическом порядке. */
  const latest = (chatId: number, limit: number): ChatMessage[] =>
    toChronological(statements.latest.all(chatId, limit));

  /** Последние `limit` сообщений конкретного участника в хронологическом порядке. */
  const latestByUser = (chatId: number, userId: number, limit: number): ChatMessage[] =>
    toChronological(statements.latestByUser.all(chatId, userId, limit));

  const findById = (chatId: number, messageId: number): ChatMessage | undefined => {
    const row = statements.findById.get(chatId, messageId) as MessageRow | undefined;

    return row && toMessage(row);
  };

  /** Сколько сообщений чата сохранено и дата самого старого (null — если пусто). */
  const statsByChat = (chatId: number): { count: number; oldest: number | null } =>
    statements.statsByChat.get(chatId) as { count: number; oldest: number | null };

  return { upsertAndPrune, insertManyAndPrune, latest, latestByUser, findById, statsByChat };
};

export type MessageRepository = ReturnType<typeof createMessageRepository>;