Code frameworks
Recipe: clamp a value
Keep a value inside a range with math.max and math.min.
Goal
Stop HP from going below zero when a Keeper takes damage.
The change
Read the current value, then write the clamped result.
rules/hurt.ts
export function hurt(self: ElementRef, amount: number): void {
const hp: number = element.var(self, "hp") as number;
ledger.set(self, "hp", math.max(0, hp - amount));
}- Line 2 Read the current HP.
- Line 3 math.max keeps the result at 0 or above. Write the final value with ledger.set.
Use math.min(limit, value) to keep a value at or below a limit.
A limit can be another field. To keep Sanity at or below a max_sanity field, read both and write math.min(max_sanity, sanity + amount). The heal rule in the quickstart does this with max_hp. Test the capped step.
Test it
The rule now sets a value, so the expected write is ledger.set instead of ledger.add. Add a step that would go below zero.
scenarios/heal.json
"actions": [
{
"action": "hurt",
"parameters": { "amount": 6 },
"expectedWrites": [{ "op": "ledger.set", "key": "hp", "value": 4 }]
},
{
"action": "hurt",
"parameters": { "amount": 20 },
"expectedWrites": [{ "op": "ledger.set", "key": "hp", "value": 0 }]
},
{
"action": "heal",
"parameters": { "amount": 3 },
"expectedWrites": [{ "op": "ledger.set", "key": "hp", "value": 3 }]
}
]- Lines 7-11 Take 6 damage: 10 minus 6 is 4.
- Lines 12-16 A hit of 20 would go below zero. The rule writes 0.
- Lines 17-21 Heal 3 from 0.