bun-activitypub/src/admin.ts

import { createFollowing, deleteFollowing, doActivity, getFollowing, listFollowers } from "./db"
import { ACTOR, ADMIN_PASSWORD, ADMIN_USERNAME, BASE_URL } from "./env"
import { send } from "./request"

export default (req: Request): Response | Promise<Response> | undefined => {
  const url = new URL(req.url)

  if(!url.pathname.startsWith('/admin')) return undefined
  url.pathname = url.pathname.substring(6)
  
  if(ADMIN_USERNAME && ADMIN_PASSWORD && !checkAuth(req.headers)) return new Response("", { status: 401 })

  let match
  if(req.method === "GET" && (match = url.pathname.match(/^\/test\/?$/i))) return new Response("", { status: 204 })
  else if(req.method == "POST" && (match = url.pathname.match(/^\/create\/?$/i))) return create(req)
  else if(req.method == "POST" && (match = url.pathname.match(/^\/follow\/([^\/]+)\/?$/i))) return follow(req, match[1])
  else if(req.method == "DELETE" && (match = url.pathname.match(/^\/follow\/([^\/]+)\/?$/i))) return unfollow(req, match[1])
  
  return undefined
}

const checkAuth = (headers: Headers): Boolean => {
  // check the basic auth header
  const auth = headers.get("Authorization")
  const split = auth?.split("")
  if(!split || split.length != 2 || split[0] !== "Basic") return false
  const decoded = atob(split[1])
  const [username, password] = decoded.split(":")
  return username === ADMIN_USERNAME && password === ADMIN_PASSWORD
}

// create an activity
const create = async (req:Request):Promise<Response> => {
  const body = await req.json()

  // create the object, merging in supplied data
  const date = new Date()
  const id = date.getTime().toString(16)
  const object = {
    attributedTo: ACTOR,
    published: date.toISOString(),
    to: ["https://www.w3.org/ns/activitystreams#Public"],
    cc: [`${ACTOR}/followers`],
    url: `${ACTOR}/post/${id}`,
    id: `${ACTOR}/post/${id}`,
    ...body.object
  }

  const activity = {
    "@context": "https://www.w3.org/ns/activitystreams", 
    id: `${ACTOR}/post/${id}/activity`,
    type: "Create",
    published: date.toISOString(),
    actor: ACTOR,
    to: ["https://www.w3.org/ns/activitystreams#Public"],
    cc: [`${ACTOR}/followers`],
    ...body,
    object: { ...object }
  }

  // TODO: actually create the object (and the activity??)
  await doActivity(activity, id)

  // loop through the list of followers
  for (const follower of await listFollowers()) {
    // send the activity to each follower
    send(ACTOR, follower.actor, {
      ...activity,
      cc: [follower.actor],
    });
  }
  
  // return HTTP 204: no content (success)
  return new Response("", { status: 204 })
}

const follow = async (req:Request, handle:string):Promise<Response> => {
  const id = BASE_URL + '@' + handle
  // send the follow request to the supplied actor
  await send(ACTOR, handle, {
    "@context": "https://www.w3.org/ns/activitystreams",
    id,
    type: "Follow",
    actor: ACTOR,
    object: handle,
  });
  await createFollowing(handle, id)

  return new Response("", { status: 204 })
}

const unfollow = async (req:Request, handle:string):Promise<Response> => {
  // check to see if we are already following. If not, just return success
  const existing = await getFollowing(handle)
  if (!existing) return new Response("", { status: 204 })

  // TODO: send the unfollow request (technically an undo follow activity)
  await send(ACTOR, handle, {
    "@context": "https://www.w3.org/ns/activitystreams",
    id: existing.id + "/undo",
    type: "Undo",
    actor: ACTOR,
    object: {
      id: existing.id,
      type: "Follow",
      actor: ACTOR,
      object: handle,
    },
  });

  // delete the following reference from the database
  deleteFollowing(handle);

  return new Response("", { status: 204 })
}