Move substrate/consensus/tendermint to substrate/tendermint

substrate/tendermint/README.md

@@ -0,0 +1,52 @@
+# Tendermint
+
+An implementation of the Tendermint state machine in Rust.
+
+This is solely the state machine, intended to be mapped to any arbitrary system.
+It supports an arbitrary hash function, signature protocol, and block
+definition accordingly. It is not intended to work with the Cosmos SDK, solely
+be an implementation of the
+[academic protocol](https://arxiv.org/pdf/1807.04938.pdf).
+
+### Paper
+
+The [paper](https://arxiv.org/abs/1807.04938) describes the algorithm with
+pseudocode on page 6. This pseudocode is written as a series of conditions for
+advancement. This is extremely archaic, as its a fraction of the actually
+required code. This is due to its hand-waving away of data tracking, lack of
+comments (beyond the entire rest of the paper, of course), and lack of
+specification regarding faulty nodes.
+
+While the "hand-waving" is both legitimate and expected, as it's not the paper's
+job to describe a full message processing loop nor efficient variable handling,
+it does leave behind ambiguities and annoyances, not to mention an overall
+structure which cannot be directly translated. This section is meant to be a
+description of it as used for translation.
+
+The included pseudocode segments can be minimally described as follows:
+
+```
+01-09 Init
+10-10 StartRound(0)
+11-21 StartRound
+22-27 Fresh proposal
+28-33 Proposal building off a valid round with prevotes
+34-35 2f+1 prevote -> schedule timeout prevote
+36-43 First proposal with prevotes -> precommit Some
+44-46 2f+1 nil prevote -> precommit nil
+47-48 2f+1 precommit -> schedule timeout precommit
+49-54 First proposal with precommits -> finalize
+55-56 f+1 round > local round, jump
+57-60 on timeout propose
+61-64 on timeout prevote
+65-67 on timeout precommit
+```
+
+Remaining:
+
+```
+36-43 First proposal with prevotes -> precommit Some
+57-60 on timeout propose
+61-64 on timeout prevote
+65-67 on timeout precommit
+```