Section FixM.
Variable M : SBTM.
Notation X := 1.
Notation "⦇" := 2.
Notation "⦈" := 3.
Notation tt := 4.
Notation ff := 5.
Notation "!! b" := (if b then tt else ff) (at level 1).
Definition enc_state (q : Fin.t (S (num_states M))) := ((S ff) + proj1_sig (Fin.to_nat q)).
Notation "! p" := (enc_state p) (at level 1).
Fixpoint all_fins (n : nat) : list (Fin.t n) :=
match n with
| 0 => nil
| S n => Fin.F1 :: map Fin.FS (all_fins n)
end.
Definition all_states {B} f : list B := flat_map f (all_fins (S (num_states M))).
Definition all_syms {B} f : list B := [f tt ; f ff].
Definition encode_sym (o : option bool) := match o with None => X | Some true => tt | Some false => ff end.
Definition encode_trans (c : option (state M * option bool * move)) (q : Fin.t (S (num_states M))) : option (nat * nat * nat * move) :=
option_map (fun '(s,o,m) => (!q, !s, encode_sym o, m)) c.
Definition rules q₁ : list (list nat * list nat):=
match encode_trans (trans M (q₁, None)) q₁ with
| Some (q₁, q₂, X, Lmove) => all_syms (fun l => ([l;q₁;X], [q₂;l])) ++ [([⦇;q₁;X],[⦇;q₂;X])]
| Some (q₁, q₂, X, Nmove) => [([q₁;X], [q₂;X])]
| Some (q₁, q₂, X, Rmove) => all_syms (fun r => ([q₁;X;r], [q₂;r])) ++ [([q₁;X;⦈],[q₂;X;⦈])]
| Some (q₁, q₂, c, Lmove) => all_syms (fun l => ([l;q₁;X], [q₂;l;c])) ++ [([⦇;q₁;X],[⦇;q₂;X;c])]
| Some (q₁, q₂, c, Nmove) => [([q₁;X], [q₂;c])]
| Some (q₁, q₂, c, Rmove) => all_syms (fun r => ([q₁;X;r], [c;q₂;r])) ++ [([q₁;X;⦈],[c;q₂;X;⦈])]
| None => []
end ++
let a := tt in
match encode_trans (trans M (q₁, Some true)) q₁ with
| Some (q₁, q₂, X, Lmove) => all_syms (fun l => ([l;q₁;a], [q₂;l;a])) ++ [([⦇;q₁;a],[⦇;q₂;X;a])]
| Some (q₁, q₂, X, Nmove) => [([q₁;a], [q₂;a])]
| Some (q₁, q₂, X, Rmove) => all_syms (fun r => ([q₁;a;r], [a;q₂;r])) ++ [([q₁;a;⦈],[a;q₂;X;⦈])]
| Some (q₁, q₂, c, Lmove) => all_syms (fun l => ([l;q₁;a], [q₂;l;c])) ++ [([⦇;q₁;a],[⦇;q₂;X;c])]
| Some (q₁, q₂, c, Rmove) => all_syms (fun r => ([q₁;a;r], [c;q₂;r])) ++ [([q₁;a;⦈],[c;q₂;X;⦈])]
| Some (q₁, q₂, c, Nmove) => [([q₁;a], [q₂;c])]
| None => []
end ++
let a := ff in
match encode_trans (trans M (q₁, Some false)) q₁ with
| Some (q₁, q₂, X, Lmove) => all_syms (fun l => ([l;q₁;a], [q₂;l;a])) ++ [([⦇;q₁;a],[⦇;q₂;X;a])]
| Some (q₁, q₂, X, Rmove) => all_syms (fun r => ([q₁;a;r], [a;q₂;r])) ++ [([q₁;a;⦈],[a;q₂;X;⦈])]
| Some (q₁, q₂, X, Nmove) => [([q₁;a], [q₂;a])]
| Some (q₁, q₂, c, Lmove) => all_syms (fun l => ([l;q₁;a], [q₂;l;c])) ++ [([⦇;q₁;a],[⦇;q₂;X;c])]
| Some (q₁, q₂, c, Rmove) => all_syms (fun r => ([q₁;a;r], [c;q₂;r])) ++ [([q₁;a;⦈],[c;q₂;X;⦈])]
| Some (q₁, q₂, c, Nmove) => [([q₁;a], [q₂;c])]
| None => []
end.
Definition R : SR.SRS nat := all_states rules.
Definition enc_conf '(ls, o, rs) (q : Fin.t (S (num_states M))) : list nat :=
[⦇] ++ map (fun b : bool => !!b) (rev ls) ++ [!q] ++ [encode_sym o] ++ map (fun b : bool => !!b) rs ++ [⦈].

Lemma rev_sim t q z :
SR.rew R (enc_conf t q) z -> exists q' w m, trans M (q, curr t) = Some (q', w, m) /\ z = enc_conf (mv m (wr w t)) q'.