GIX-1890: Add min to disburse based on moduation

frontend/src/lib/components/neuron-detail/actions/SpawnNeuronButton.svelte

@@ -3,7 +3,7 @@
   import { E8S_PER_ICP } from "$lib/constants/icp.constants";
   import {
     MIN_NEURON_STAKE,
-    SPAWN_VARIANCE_PERCENTAGE,
+    MATURITY_MODULATION_VARIANCE_PERCENTAGE,
   } from "$lib/constants/neurons.constants";
   import { i18n } from "$lib/stores/i18n";
   import { formatNumber, formatPercentage } from "$lib/utils/format.utils";
@@ -49,17 +49,22 @@
         $i18n.neuron_detail.spawn_neuron_disabled_tooltip,
         {
           $amount: formatNumber(
-            MIN_NEURON_STAKE / E8S_PER_ICP / SPAWN_VARIANCE_PERCENTAGE,
+            MIN_NEURON_STAKE /
+              E8S_PER_ICP /
+              MATURITY_MODULATION_VARIANCE_PERCENTAGE,
             { minFraction: 4, maxFraction: 4 }
           ),
           $min: formatNumber(MIN_NEURON_STAKE / E8S_PER_ICP, {
             minFraction: 0,
             maxFraction: 0,
           }),
-          $varibility: formatPercentage(SPAWN_VARIANCE_PERCENTAGE, {
-            minFraction: 0,
-            maxFraction: 0,
-          }),
+          $varibility: formatPercentage(
+            MATURITY_MODULATION_VARIANCE_PERCENTAGE,
+            {
+              minFraction: 0,
+              maxFraction: 0,
+            }
+          ),
         }
       )}
     >
@@ -69,3 +74,4 @@
     </Tooltip>
   {/if}
 </TestIdWrapper>
+MATURITY_MODULATION_VARIANCE_PERCENTAGEMATURITY_MODULATION_VARIANCE_PERCENTAGE

frontend/src/lib/constants/neurons.constants.ts

@@ -6,7 +6,7 @@ import { E8S_PER_ICP } from "./icp.constants";
 export const MAX_NEURONS_MERGED = 2;
 export const MIN_NEURON_STAKE = E8S_PER_ICP;
 export const MAX_CONCURRENCY = 10;
-export const SPAWN_VARIANCE_PERCENTAGE = 0.95;
+export const MATURITY_MODULATION_VARIANCE_PERCENTAGE = 0.95;
 // Neuron ids are random u64. Max digits of a u64 is 20.
 export const MAX_NEURON_ID_DIGITS = 20;
 

frontend/src/lib/modals/sns/neurons/SnsDisburseMaturityModal.svelte

@@ -5,7 +5,10 @@
   import type { SnsNeuron, SnsNeuronId } from "@dfinity/sns";
   import type { Principal } from "@dfinity/principal";
   import { disburseMaturity as disburseMaturityService } from "$lib/services/sns-neurons.services";
-  import { formattedMaturity } from "$lib/utils/sns-neuron.utils";
+  import {
+    formattedMaturity,
+    minimumAmountToDisburseMaturity,
+  } from "$lib/utils/sns-neuron.utils";
   import DisburseMaturityModal from "$lib/modals/neurons/DisburseMaturityModal.svelte";
   import { snsProjectMainAccountStore } from "$lib/derived/sns/sns-project-accounts.derived";
   import { shortenWithMiddleEllipsis } from "$lib/utils/format.utils";
@@ -28,10 +31,10 @@
   let token: IcrcTokenMetadata | undefined;
   $: token = $tokensStore[rootCanisterId.toText()]?.token;
 
-  // 99% of users will disburse more than the transaction fee.
-  // We don't want a possible error fetching the fee to disrupt the whole flow.
-  let minimumAmountE8s = 0n;
-  $: minimumAmountE8s = token?.fee ?? 0n;
+  let minimumAmountE8s: bigint;
+  // Token is loaded with all the projects from the aggregator.
+  // Therefore, if the user made it here, it's present.
+  $: minimumAmountE8s = minimumAmountToDisburseMaturity(token?.fee ?? 0n);
 
   const dispatcher = createEventDispatcher();
   const close = () => dispatcher("nnsClose");

frontend/src/lib/utils/neuron.utils.ts

@@ -12,9 +12,9 @@ import {
 import {
   AGE_MULTIPLIER,
   DISSOLVE_DELAY_MULTIPLIER,
+  MATURITY_MODULATION_VARIANCE_PERCENTAGE,
   MAX_NEURONS_MERGED,
   MIN_NEURON_STAKE,
-  SPAWN_VARIANCE_PERCENTAGE,
   TOPICS_TO_FOLLOW_NNS,
 } from "$lib/constants/neurons.constants";
 import { DEPRECATED_TOPICS } from "$lib/constants/proposals.constants";
@@ -499,7 +499,10 @@ export const isEnoughMaturityToSpawn = ({
   const maturitySelected = Math.floor(
     (Number(fullNeuron.maturityE8sEquivalent) * percentage) / 100
   );
-  return maturitySelected >= MIN_NEURON_STAKE / SPAWN_VARIANCE_PERCENTAGE;
+  return (
+    maturitySelected >=
+    MIN_NEURON_STAKE / MATURITY_MODULATION_VARIANCE_PERCENTAGE
+  );
 };
 
 export const isSpawning = (neuron: NeuronInfo): boolean =>

frontend/src/lib/utils/sns-neuron.utils.ts

@@ -1,3 +1,4 @@
+import { MATURITY_MODULATION_VARIANCE_PERCENTAGE } from "$lib/constants/neurons.constants";
 import {
   HOTKEY_PERMISSIONS,
   MANAGE_HOTKEY_PERMISSIONS,
@@ -981,3 +982,11 @@ export const totalDisbursingMaturity = ({
     (acc, disbursement) => acc + disbursement.amount_e8s,
     BigInt(0)
   );
+
+/**
+ * The governance canister checks that the amount to disburse in the worst case (of the maturity modulation) is bigger than the transaction fee.
+ *
+ * Source: https://sourcegraph.com/github.com/dfinity/ic/-/blob/rs/sns/governance/src/governance.rs?L1651
+ */
+export const minimumAmountToDisburseMaturity = (fee: bigint): bigint =>
+  BigInt(Math.round(Number(fee) / MATURITY_MODULATION_VARIANCE_PERCENTAGE));

frontend/src/tests/lib/utils/sns-neuron.utils.spec.ts

@@ -47,6 +47,7 @@ import {
   isUserHotkey,
   isVesting,
   minNeuronSplittable,
+  minimumAmountToDisburseMaturity,
   needsRefresh,
   neuronAge,
   nextMemo,
@@ -2492,4 +2493,14 @@ describe("sns-neuron utils", () => {
       expect(totalDisbursingMaturity(neuron)).toBe(0n);
     });
   });
+
+  describe("minimumAmountToDisburseMaturity", () => {
+    it("returns worst case of maturity modulation", () => {
+      expect(minimumAmountToDisburseMaturity(10_000n)).toBe(10526n);
+    });
+
+    it("returns 0 if fee is 0", () => {
+      expect(minimumAmountToDisburseMaturity(0n)).toBe(0n);
+    });
+  });
 });