export interface TelegramUpdateUser {
  id: number;
  username?: string;
  first_name: string;
  last_name?: string;
}

export interface TelegramUpdateMessage {
  message_id: number;
  text?: string;
  from?: TelegramUpdateUser;
  chat: {
    id: number;
  };
}

export interface TelegramUpdate {
  update_id: number;
  message?: TelegramUpdateMessage;
}

export interface TelegramBotTransport {
  getUpdates(input: {
    offset?: number;
    timeoutSeconds: number;
  }): Promise<TelegramUpdate[]>;
  sendMessage(input: {
    chatId: number;
    text: string;
  }): Promise<void>;
}

export function createTelegramBotApiTransport(botToken: string): TelegramBotTransport {
  const baseUrl = `https://api.telegram.org/bot${botToken}`;

  return {
    async getUpdates({ offset, timeoutSeconds }) {
      const response = await fetch(`${baseUrl}/getUpdates`, {
        method: "POST",
        headers: {
          "content-type": "application/json",
        },
        body: JSON.stringify({
          timeout: timeoutSeconds,
          ...(offset !== undefined ? { offset } : {}),
        }),
      });

      const payload = (await response.json()) as {
        ok: boolean;
        result?: TelegramUpdate[];
        description?: string;
      };

      if (!response.ok || !payload.ok || !payload.result) {
        throw new Error(
          payload.description ?? `Telegram getUpdates failed with status ${response.status}.`,
        );
      }

      return payload.result;
    },

    async sendMessage({ chatId, text }) {
      const response = await fetch(`${baseUrl}/sendMessage`, {
        method: "POST",
        headers: {
          "content-type": "application/json",
        },
        body: JSON.stringify({
          chat_id: chatId,
          text,
        }),
      });

      const payload = (await response.json()) as {
        ok: boolean;
        description?: string;
      };

      if (!response.ok || !payload.ok) {
        throw new Error(
          payload.description ?? `Telegram sendMessage failed with status ${response.status}.`,
        );
      }
    },
  };
}