git ssb

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  OUR_SEQ, THEIR_SEQ, THEM_RECV, US_RECV
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  onRecieveValidMessage: //after we have processed the message.
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    if(OUR_SEQ > THEIR_SEQ && THEM_RECV)
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      send(msg)
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    else if(OUR_SEQ < THEIR_SEQ && US_RECV)
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      send({id: msg.author, seq: msg.sequence}) //OPTIONAL, don't have to do this every time
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  onReceiveMessage:
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    if(OUR_SEQ > msg.sequence)
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      send({id: msg.author, seq: - OUR_SEQ}) //tell them to stop sending.
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                                             //else, validate the message and continue.
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  onRecieveNote:
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    if(note.seq < 0 && THEM_RECV) {
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      THEM_RECV = false //they have asked us to stop sending this feed to them.
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    }
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    if(Math.abs(note.seq) > OUR_SEQ) {
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      US_RECV = true
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      send({id: note.id, seq: OUR_SEQ})
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    }
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  onBeginReplication:
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    for(var id in feeds)
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      send({id: id, seq: feed[id].seq})
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  //okay I feel satisfied that is the correct logic
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  //but how do I make this FSM pull?
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  //I know, functional style state
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  //For each peer, for each feed keep the state of:
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  remote = {requested: Seq, sent: Seq, ready: msg|null, sending: bool, receiving: bool} //sending to, receiving from
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  //also keep a map of local = {id: seq}
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  //then I think all events can be handled sync
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  READ:
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    if ready!= null, the puller takes `ready` then sets it to `null`
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    if ready was a msg, this also triggers retriving the next msg, if this feed.sent < local[id]
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    if ready was a note, it's just sent without triggering anything.
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  RECEIVE_MSG: //receive a message from this peer, before it's validated.
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    remote.requested = msg.sequence //always remember they are up to this sequence.
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    if(msg.seq <= local[msg.author]) //if we already know about this message
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      if(remote.receiving) {
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        remote.ready = {id, seq: - local[id]} //tell them we do not need this feed.
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        remote.receiving = false
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      }
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      if(!remote.receiving) {
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        we have asked them to stop sending, but they havn't got the note yet.
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        anyway, remember they know this sequence.
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        remote.requested = msg.sequence
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      }
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      else if(remote.sending) {
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        this is an error, they should never send to us if we are sending.
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        if this ever happens it's a programmer error. maybe should tell them to top sending?
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        you might receive a 
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      }
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    RECEIVE_NOTE:
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      if(remote.sending) {
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        if(note.seq < 0) //stop sending
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          remote.sending = false, remote.ready = null, remote.requested = abs(note.seq)
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      }
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      else if(!remote.receiving) {
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        if(abs(note.seq) > local[id]) //if this is the fastest peer for this feed, ask them to send.
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      }
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