kt-coroutines-example2.kt

data class Event(val name: String = "", val data: String = "")

fun getEventsFlow(): Flow<Event> = flow {
    val url = "https://hacker-news.firebaseio.com/v0/updates.json"

    // Gets HttpURLConnection. Blocking function.  Should run in background
    val conn = (URL(url).openConnection() as HttpURLConnection).also {
        it.setRequestProperty("Accept", "text/event-stream") // set this Header to stream
        it.doInput = true // enable inputStream
    }

    conn.connect() // Blocking function. Should run in background

    val inputReader = conn.inputStream.bufferedReader()

    var event = Event()

    // run forever
    while (true) {
        val line = inputReader.readLine() // Blocking function. Read stream until \n is found
        
        when {
            line.startsWith("event:") -> { // get event name
                event = event.copy(name = line.substring(6).trim())
            }
            line.startsWith("data:") -> { // get data
                event = event.copy(data = line.substring(5).trim())
            }
            line.isEmpty() -> { // empty line, finished block. Emit the event
                emit(event)
                event = Event()
            }
        }
    }
}