Cliff Vesting

A pure vesting calculator, demoing the p/moul/x/daily/cliffvesting library.

A 12-month grant with a 3-month cliff

1200 tokens, Start = 0, Cliff = 3, End = 12.

month	vested	unvested	%
0	0	1200	0%
1	0	1200	0%
2	0	1200	0% ← nothing yet
3	300	900	25% ← cliff
4	400	800	33%
5	500	700	41%
6	600	600	50%
7	700	500	58%
8	800	400	66%
9	900	300	75%
10	1000	200	83%
11	1100	100	91%
12	1200	0	100% ← fully vested

The cliff is a step, not a ramp: at month 3 a quarter of the term has elapsed, so 300 tokens unlock at once. After that it accrues linearly.

Claiming

The library tracks no balances, so the caller supplies what has already been claimed:

at month	already claimed	claimable
6	0	600
6	300	300
6	600	0
12	600	600

Integer rounding

All arithmetic is integer, no float ever reaches consensus state. Rounding is down, so nobody is ever paid more than they earned, and the final instalment collects the remainder.

1000 over 3 periods:

t	vested
0	0
1	333
2	666
3	1000

333 + 333 + 334, and the end is exactly 1000, never 999.

Bug 1: a rate truncated to zero

When the total is smaller than the duration, computing a per-tick rate first truncates it to zero and nothing ever vests. Multiplying before dividing keeps it honest. 7 tokens over 1000 ticks:

t	vested
100	0
150	1
500	3
1000	7

Bug 2: a product that leaves int64

Multiplying first is only safe if the product fits. Over a term measured in seconds, total * elapsed passes 2^63 for any grant above about 146,036 whole coins, and a wrapped int64 is still a valid int64: v0 of this library returned a negative vested amount and nothing signalled it. v1 routes the product through a 128-bit intermediate.

A real two-year schedule, 1789225200 to 1852383600, at the halfway mark:

grant	vested at halfway	expected
100000000000	50000000000	50000000000
146037000000	73018500000	73018500000
318720000000000	159360000000000	159360000000000