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/***************************************************************************************************
Each level on a SMTInsert has a state.
The state of the level depends on the state of te botom level and on `xor` and
`is0` signals.
`isOldLev` 1 when is the level where oldLeaf is.
`xor` signal is 0 if the index bit at the current level is the same in the old
and the new index, and 1 if it is different.
`is0` signal, is 1 if we are inserting in an empty leaf and 0 if we are inserting
in a leaf that contains an element.
The states are:
top: While the index bits of the old and new insex in the top level is the same, whe are in the top state.
old0 and old1: When the we reach insert level, we go to old0 and old1 states
according to `is0` signal.
btn: Once in old1 we go to btn until xor=1
new1: This level is reached when xor=1. Here is where we insert the hash of the
old and the new trees with just one element.
na: Not appliable. After inserting it, we go to the na level.
Fnction
fnc[0] fnc[1]
0 0 NOP
0 1 UPDATE
1 0 INSERT
1 1 DELETE
###########
# #
┌────────────────────────────▶# upd #─────────────────────┐
│ ## ## │
│ ######### │
levIns=1 │ │
fnc[0]=0 │ │ any
│ │
│ │
│ │
│ ########### │
│ levIns=1 # # │
levIns=0 │ is0=1 ┌────────────▶# old0 #────────┐ │ any
┌─────┐ │ fnc[0]=1│ ## ## │ │ ┌──────┐
│ │ │ │ ######### │ any │ │ │
│ ▼ │ │ │ ▼ ▼ │
│ ########### │ │ ########### │
│ # # ────────────┘ └────────▶# #│
└──# top # # na #
## ## ────┐ ┌──▶## ##
######### │ │ #########
│ │
│ ########### ########### │ any
levIns=1 │ # # xor=1 # # │
is0=0 └───▶# old1 #─────────────▶# new1 #──┘
fnc[0]=1 ## ## ## ##
#########│ #########
│ ▲
└───┐ ┌─────┘
xor=0 │ ###########│ xor=1
│ # #
▼# btn #
## ##
#########◀───────┐
│ │
│ │
└────────────┘
xor=0
***************************************************************************************************/
template SMTInsertSM() {
signal input xor;
signal input is0;
signal input levIns;
signal input fnc[2];
signal input prev_top;
signal input prev_old0;
signal input prev_old1;
signal input prev_bot;
signal input prev_new1;
signal input prev_na;
signal input prev_upd;
signal output st_top;
signal output st_old0;
signal output st_old1;
signal output st_bot;
signal output st_new1;
signal output st_na;
signal output st_upd;
signal aux1;
signal aux2;
aux1 <== prev_top * levIns;
aux2 <== aux1*is0;
st_top <== prev_top - aux1 // prev_top * (1-levIns) =
// = prev_top - aux1;
st_old0 <== aux2 * fnc[0]; // (prev_top * levIns * is0)*fnc[0] = aux2
st_old1 <== (aux1 - aux2)*fnc[0]; // (prev_top * levIns * (1-is0))*fnc[0] =
// = (aux1 * (1-is0))*fnc[0] =
// = (aux1 - aux2) * fnc[0]
st_new1 <== (prev_old1 + prev_bot)*xor // prev_old1*xor + prev_bot*xor =
// = (prev_old1 + prev_bot)*xor;
st_bot <== -st_new1 + prev_old1 + prev_bot // prev_old1*(1-xor) + prev_bot*(1-xor) =
// = - prev_old1*xor -prev_bot*xor + prev_old1 + prev_bot =
// = -st_new1 + prev_old1 + prev_bot
st_na <== prev_new1 + prev_old0 + prev_na + prev_upd;
st_upd <== aux1*(1-fnc[0]); // prev_top*levIns*(1-fnc[0]) =
// = aux1 * (1-fnc[0])
}