/**

 * This function throws an error, if you're not a room member.

 *

 * Expected return values:

 *

 * {

 *   "is_joined": false,

 *   "user_info": null

 * }

 *

 * or

 *

 * {

 *   "is_member": true,

 *   "user_info": {

 *     "avatar_url": "mxc://matrix.org/abc123",

 *     "display_name": "Jane Doe"

 *   }

 * }

 */

type Matrix = {

  baseUrl: string;

  token: string;

};

export async function main(

  matrix_res: Matrix,

  room_id: string,

  user_id: string,

) {

  const url = `${

    matrix_res.baseUrl

  }/_matrix/client/v3/rooms/${encodeURIComponent(room_id)}/joined_members`;

  const resp = await fetch(url, {

    headers: {

      Authorization: `Bearer ${matrix_res.token}`,

    },

  });

  if (!resp.ok) {

    throw Error(`Failed to fetch joined member list: Error HTTP${resp.status}`);

  }

  const data = await resp.json();

  return {

    is_joined: user_id in data?.joined,

    user_info: data?.joined?.[user_id],

  };

}