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+
+peers wrap connections with given clients (any transport type). each peer can
+be talking about multiple feeds. state consists of which feeds, what the remote
+has (feed, bitmap), and what chunks (feed, index) have been requested
+("in-flight"). connection logic runs in threads, passes back and forth entire
+messages in channels.
+
+ ConnCommand
+ Send(DatNetMessage)
+ Terminate()
+
+ ConnReply
+ Received(DatNetMessage)
+ Disconnected()
+
+A synchronizer event loop has local feeds (storage) and a bunch of peers. Extra
+state includes mode configuration, feeds, "wanted" bitmap for each feed.
+Callbacks for certain feed events allow for extension (eg, hyperdrive stuff).
+Needs a timer event.
+
+Use chan and chan-signal for now (MPSC style)... tokio will be the future but
+seems too unstable for now. mio is too low-level to use on it's own (eg, no
+timers, no threads). Use two threads per peer: a "main" thread that does
+connection setup, `chan_select`, and blocking writes, and a "reader" thread
+that does blocking reads of entire messages (writing either into the main
+thread or skipping straight to the output channel). Got this pattern from the
+`rusty_torrent` package. Need to set some write timeout. Synchronizer handles
+cleanup if peer isn't replying/heartbeating.
+
+Probably want a dedicated discovery thread/worker in the future, but for now
+just do it synchronously and connect to up to N peers to start.
+
+Synchronize will select on:
+
+ signal
+ graceful shutdown
+ unified_inbound
+ feed: depends on state; ignore for now
+ handshake: error, close connection?
+ have, info: update PeerState bitmap
+ unhave, info, want, unwant: ignore for now
+ request: depends on state; read from storage
+ cancel: ignore for now
+ data: write to storage, clear pending; send new request
+ tick
+ check peer states, kill if too slow
+ dump status to command line
+
+Synchronize needs state:
+- "tried" peers, so we don't retry in a loop if they fail
+
+Synchronize options:
+- whether or not to hook signals
+
+Where does drive logic live? Plugin, via callback, to Synchronize? Let's just
+fold it in to synchronizer for now, as a mode flag.
diff --git a/notes/refs.md b/notes/refs.md
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+
+Decent "Original" Bittorrent client description:
+
+https://github.com/mgp/coding-in-the-real-world/blob/master/manuscript/bittorrent-client-case-study.md
+