fix: Precision loss for gas calculation of HTS system contracts v2 (#…

…15446)

Signed-off-by: Stanimir Stoyanov <stanimir.stoyanov@limechain.tech>

hedera-node/hedera-config/src/main/java/com/hedera/node/config/data/ContractsConfig.java

@@ -85,6 +85,10 @@ public record ContractsConfig(
                 boolean systemContractUpdateCustomFeesEnabled,
         @ConfigProperty(value = "systemContract.tokenInfo.v2.enabled", defaultValue = "false") @NetworkProperty
                 boolean systemContractTokenInfoV2Enabled,
+        @ConfigProperty(value = "systemContract.precisionLossFixForGas.enabled", defaultValue = "true") @NetworkProperty
+                boolean isGasPrecisionLossFixEnabled,
+        @ConfigProperty(value = "systemContract.canonicalViewGas.enabled", defaultValue = "true") @NetworkProperty
+                boolean isCanonicalViewGasEnabled,
         @ConfigProperty(value = "evm.version.dynamic", defaultValue = "false") @NetworkProperty
                 boolean evmVersionDynamic,
         @ConfigProperty(value = "evm.allowCallsToNonContractAccounts", defaultValue = "true") @NetworkProperty

hedera-node/hedera-smart-contract-service-impl/src/main/java/com/hedera/node/app/service/contract/impl/exec/QueryModule.java

@@ -39,6 +39,7 @@
 import com.hedera.node.app.service.contract.impl.state.ProxyWorldUpdater;
 import com.hedera.node.app.service.contract.impl.state.ScopedEvmFrameStateFactory;
 import com.hedera.node.app.spi.workflows.QueryContext;
+import com.hedera.node.config.data.ContractsConfig;
 import com.hedera.node.config.data.HederaConfig;
 import dagger.Binds;
 import dagger.Module;
@@ -57,8 +58,9 @@ static HederaConfig provideHederaConfig(@NonNull final QueryContext context) {
 
     @Provides
     @QueryScope
-    static TinybarValues provideTinybarValues(@NonNull final ExchangeRate exchangeRate) {
-        return TinybarValues.forQueryWith(exchangeRate);
+    static TinybarValues provideTinybarValues(
+            @NonNull final ExchangeRate exchangeRate, @NonNull final QueryContext context) {
+        return TinybarValues.forQueryWith(exchangeRate, context.configuration().getConfigData(ContractsConfig.class));
     }
 
     @Provides

hedera-node/hedera-smart-contract-service-impl/src/main/java/com/hedera/node/app/service/contract/impl/exec/TransactionModule.java

@@ -91,8 +91,13 @@ static FeatureFlags provideFeatureFlags(@NonNull final TransactionProcessor proc
     static TinybarValues provideTinybarValues(
             @TopLevelResourcePrices @NonNull final FunctionalityResourcePrices topLevelResourcePrices,
             @ChildTransactionResourcePrices @NonNull final FunctionalityResourcePrices childTransactionResourcePrices,
-            @NonNull final ExchangeRate exchangeRate) {
-        return TinybarValues.forTransactionWith(exchangeRate, topLevelResourcePrices, childTransactionResourcePrices);
+            @NonNull final ExchangeRate exchangeRate,
+            @NonNull final HandleContext context) {
+        return TinybarValues.forTransactionWith(
+                exchangeRate,
+                context.configuration().getConfigData(ContractsConfig.class),
+                topLevelResourcePrices,
+                childTransactionResourcePrices);
     }
 
     @Provides

hedera-node/hedera-smart-contract-service-impl/src/main/java/com/hedera/node/app/service/contract/impl/exec/gas/CustomGasCalculator.java

@@ -79,8 +79,8 @@ public long logOperationGasCost(
         final var hevmGasCost = gasCostOfStoring(
                 logSize(numTopics, dataLength),
                 lifetime,
-                tinybarValues.topLevelTinybarRbhPrice(),
-                tinybarValues.topLevelTinybarGasPrice());
+                tinybarValues.topLevelTinycentRbhPrice(),
+                tinybarValues.topLevelTinycentGasPrice());
 
         return Math.max(evmGasCost, hevmGasCost);
     }
@@ -104,15 +104,15 @@ public long getEdSignatureVerificationSystemContractGasCost() {
 
     /**
      * Logically, would return the gas cost of storing the given number of bytes for the given number of seconds,
-     * given the relative prices of a byte-hour and a gas unit in tinybar.
+     * given the relative prices of a byte-hour and a gas unit in tinycent.
      *
      * <p>But for differential testing, ignores the {@code numBytes} and returns the gas cost of storing just a
      * single byte for the given number of seconds.
      *
      * @param numBytes ignored
      * @param lifetime the number of seconds to store a single byte
-     * @param rbhPrice the price of a byte-hour in tinybar
-     * @param gasPrice the price of a gas unit in tinybar
+     * @param rbhPrice the price of a byte-hour in tinycent
+     * @param gasPrice the price of a gas unit in tinycent
      * @return the gas cost of storing a single byte for the given number of seconds
      */
     private static long gasCostOfStoring(

hedera-node/hedera-smart-contract-service-impl/src/main/java/com/hedera/node/app/service/contract/impl/exec/gas/DispatchType.java

@@ -57,6 +57,7 @@ public enum DispatchType {
     WIPE_NFT(HederaFunctionality.TOKEN_ACCOUNT_WIPE, TOKEN_NON_FUNGIBLE_UNIQUE),
     UPDATE(HederaFunctionality.TOKEN_UPDATE, DEFAULT),
     UTIL_PRNG(HederaFunctionality.UTIL_PRNG, DEFAULT),
+    TOKEN_INFO(HederaFunctionality.TOKEN_GET_INFO, DEFAULT),
     UPDATE_TOKEN_CUSTOM_FEES(HederaFunctionality.TOKEN_FEE_SCHEDULE_UPDATE, DEFAULT);
 
     private final HederaFunctionality functionality;

hedera-node/hedera-smart-contract-service-impl/src/main/java/com/hedera/node/app/service/contract/impl/exec/gas/SystemContractGasCalculator.java

@@ -16,6 +16,7 @@
 
 package com.hedera.node.app.service.contract.impl.exec.gas;
 
+import static com.hedera.node.app.service.contract.impl.utils.ConversionUtils.FEE_SCHEDULE_UNITS_PER_TINYCENT;
 import static java.util.Objects.requireNonNull;
 
 import com.hedera.hapi.node.base.AccountID;
@@ -29,6 +30,12 @@
 public class SystemContractGasCalculator {
     private static final long FIXED_VIEW_GAS_COST = 100L;
 
+    // This represents the predefined gas price which is $0.000_000_0852 per unit of gas.
+    // 852_000 = $0.000_000_0852 * 100(cents per dollars) * 100_000_000 (tiny cents per cents) * 1000 (Fee schedule
+    // units
+    // per tiny cents). For more info -> https://hedera.com/blog/rolling-smart-contract-hedera-api-fees-into-gas-fees
+    private static final long FIXED_TINY_CENT_GAS_PRICE_COST = 852_000L;
+
     private final TinybarValues tinybarValues;
     private final CanonicalDispatchPrices dispatchPrices;
     private final ToLongBiFunction<TransactionBody, AccountID> feeCalculator;
@@ -57,68 +64,85 @@ public long gasRequirement(
             @NonNull final AccountID payer) {
         requireNonNull(body);
         requireNonNull(dispatchType);
-        return gasRequirement(body, payer, canonicalPriceInTinybars(dispatchType));
+        requireNonNull(payer);
+        // isGasPrecisionLossFixEnabled is a temporary feature flag that will be removed in the future.
+        if (!tinybarValues.isGasPrecisionLossFixEnabled()) {
+            return gasRequirementOldWithPrecisionLoss(body, payer, canonicalPriceInTinybars(dispatchType));
+        }
+        return gasRequirementWithTinycents(body, payer, dispatchPrices.canonicalPriceInTinycents(dispatchType));
     }
 
     /**
-     * Given a transaction body whose dispatch gas requirement must be at least equivalent to a given minimum
-     * amount of tinybars, returns the gas requirement for the transaction to be dispatched.
-     *
-     * @param body the transaction body to be dispatched
+     * Compares the canonical price and the feeCalculator's calculated price and uses the maximum of the two to
+     * calculate the gas requirement and returns it.
+     * @param body the transaction body
      * @param payer the payer of the transaction
-     * @param minimumPriceInTinybars the minimum equivalent tinybar cost of the dispatch
-     * @return the gas requirement for the transaction to be dispatched
+     * @param minimumPriceInTinycents the minimum price in tiny cents
+     * @return the gas requirement for the transaction
      */
-    public long gasRequirement(
-            @NonNull final TransactionBody body, @NonNull final AccountID payer, final long minimumPriceInTinybars) {
-        final var nominalPriceInTinybars = feeCalculator.applyAsLong(body, payer);
-        final var priceInTinybars = Math.max(minimumPriceInTinybars, nominalPriceInTinybars);
-        return asGasRequirement(priceInTinybars);
+    public long gasRequirementWithTinycents(
+            @NonNull final TransactionBody body, @NonNull final AccountID payer, final long minimumPriceInTinycents) {
+        // If not enabled, make the calculation using the old method.
+        if (!tinybarValues.isGasPrecisionLossFixEnabled()) {
+            return gasRequirementOldWithPrecisionLoss(body, payer, minimumPriceInTinycents);
+        }
+        final var computedPriceInTinybars = feeCalculator.applyAsLong(body, payer);
+        final var priceInTinycents =
+                Math.max(minimumPriceInTinycents, tinybarValues.asTinycents(computedPriceInTinybars));
+        // For the rare cases where computedPrice > minimumPriceInTinycents:
+        // Precision loss may occur as we convert between tinyBars and tinycents, but it is typically negligible.
+        // The minimal computed price is > 1e6 tinycents, ensuring enough precision.
+        // In most cases, the gas difference is zero.
+        // In scenarios where we compare significant price fluctuations (200x, 100x), the gas difference should still be
+        // unlikely to exceed 0 gas.
+        return gasRequirementFromTinycents(priceInTinycents, tinybarValues.childTransactionTinycentGasPrice());
     }
 
     /**
-     * Given a transaction body whose, returns the gas requirement for the transaction to be
-     * dispatched using the gas price of the top-level HAPI operation and no markup.
+     * Returns the gas price for the top-level HAPI operation.
      *
-     * @param body the transaction body to be dispatched
-     * @param payer the payer of the transaction
-     * @return the gas requirement for the transaction to be dispatched
+     * @return the gas price for the top-level HAPI operation in tinyBars.
      */
-    public long topLevelGasRequirement(@NonNull final TransactionBody body, @NonNull final AccountID payer) {
-        return feeCalculator.applyAsLong(body, payer) / tinybarValues.topLevelTinybarGasPrice();
+    public long topLevelGasPriceInTinyBars() {
+        return tinybarValues.topLevelTinybarGasPriceFullPrecision();
     }
 
     /**
-     * Returns the gas price for the top-level HAPI operation.
+     * Estimates the gas requirement for a view operation.
+     * The minimum gas requirement is 100 gas.
+     * For all view operations, the gas requirement is determined using the canonical gas value
+     * for the TOKEN_INFO dispatch type, as specified in the canonical-prices.json.
+     * The TOKEN_INFO operation is representative of view operations.
      *
-     * @return the gas price for the top-level HAPI operation
+     * @return the gas requirement for a view operation
      */
-    public long topLevelGasPrice() {
-        return tinybarValues.topLevelTinybarGasPrice();
+    public long viewGasRequirement() {
+        // isCanonicalViewGasEnabled is a temporary feature flag that will be removed in the future.
+        if (!tinybarValues.isCanonicalViewGasEnabled()) {
+            return FIXED_VIEW_GAS_COST;
+        }
+        final var gasRequirement = gasRequirementFromTinycents(
+                dispatchPrices.canonicalPriceInTinycents(DispatchType.TOKEN_INFO), FIXED_TINY_CENT_GAS_PRICE_COST);
+        return Math.max(FIXED_VIEW_GAS_COST, gasRequirement);
     }
 
     /**
      * Given a dispatch type, returns the canonical gas requirement for that dispatch type.
      * Useful when providing a ballpark gas requirement in the absence of a valid
      * transaction body for the dispatch type.
+     * Used for non-query operations.
      *
      * @param dispatchType the dispatch type
      * @return the canonical gas requirement for that dispatch type
      */
     public long canonicalGasRequirement(@NonNull final DispatchType dispatchType) {
-        return asGasRequirement(canonicalPriceInTinybars(dispatchType));
-    }
-
-    /**
-     * Although mono-service compares the fixed {@code 100 gas} cost to the implied gas requirement of a
-     * stand-in {@link com.hedera.hapi.node.transaction.TransactionGetRecordQuery}, this stand-in query's
-     * cost will be less than {@code 100 gas} at any exchange rate that sustains the existence of the network.
-     * So for simplicity, we drop that comparison and just return the fixed {@code 100 gas} cost.
-     *
-     * @return the minimum gas requirement for a view query
-     */
-    public long viewGasRequirement() {
-        return FIXED_VIEW_GAS_COST;
+        // isGasPrecisionLossFixEnabled is a temporary feature flag that will be removed in the future.
+        if (!tinybarValues.isGasPrecisionLossFixEnabled()) {
+            return asGasRequirement(canonicalPriceInTinybars(dispatchType));
+        }
+        return gasRequirementFromTinycents(
+                dispatchPrices.canonicalPriceInTinycents(dispatchType),
+                tinybarValues.childTransactionTinycentGasPrice());
     }
 
     /**
@@ -127,9 +151,14 @@ public long viewGasRequirement() {
      * @param dispatchType the dispatch type
      * @return the canonical price for that dispatch type
      */
-    public long canonicalPriceInTinybars(@NonNull final DispatchType dispatchType) {
+    public long canonicalPriceInTinycents(@NonNull final DispatchType dispatchType) {
         requireNonNull(dispatchType);
-        return tinybarValues.asTinybars(dispatchPrices.canonicalPriceInTinycents(dispatchType));
+        // If not enabled, return the price in TinyBars.
+        // This is directly used only in ClassicTransfersCall. However, it is easier to place the feature flag here.
+        if (!tinybarValues.isGasPrecisionLossFixEnabled()) {
+            return canonicalPriceInTinybars(dispatchType);
+        }
+        return dispatchPrices.canonicalPriceInTinycents(dispatchType);
     }
 
     /**
@@ -139,7 +168,7 @@ public long canonicalPriceInTinybars(@NonNull final DispatchType dispatchType) {
      * @param payer the payer account
      * @return the canonical price for that dispatch
      */
-    public long canonicalPriceInTinybars(@NonNull final TransactionBody body, @NonNull final AccountID payer) {
+    public long feeCalculatorPriceInTinyBars(@NonNull final TransactionBody body, @NonNull final AccountID payer) {
         return feeCalculator.applyAsLong(body, payer);
     }
 
@@ -154,15 +183,65 @@ public long gasCostInTinybars(final long gas) {
     }
 
     /**
-     * Given a tinybar price, returns the equivalent gas requirement at the current gas price.
+     * Calculates the gas requirement for an operation based on the provided tinycents price and gas price.
+     * The calculation rounds up the result to the nearest gas unit and then adds 20% to the computed gas
+     * requirement to account for the premium of executing a HAPI operation within the EVM.
      *
-     * @param tinybarPrice the tinybar price
-     * @return the equivalent gas requirement at the current gas price
+     * @param tinycentsPrice the price of the operation in tinycents
+     * @param gasPriceInCents the current gas price in cents
+     * @return the computed gas requirement for the operation
      */
+    private long gasRequirementFromTinycents(long tinycentsPrice, final long gasPriceInCents) {
+        final var gasRequirement =
+                (tinycentsPrice + gasPriceInCents - 1) * FEE_SCHEDULE_UNITS_PER_TINYCENT / gasPriceInCents;
+        return gasRequirement + (gasRequirement / 5);
+    }
+
+    /**
+     * After feature flag isGasPrecisionLossFixEnabled is removed, this method should be removed.
+     * @deprecated
+     */
+    @Deprecated(since = "Precision loss fix was implemented in PR #14842", forRemoval = true)
+    public long topLevelGasPrice() {
+        return tinybarValues.topLevelTinybarGasPrice();
+    }
+
+    /**
+     * After feature flag isGasPrecisionLossFixEnabled is removed, this method should be removed.
+     * @deprecated
+     */
+    @Deprecated(since = "Precision loss fix was implemented in PR #14842", forRemoval = true)
+    public long canonicalPriceInTinybars(@NonNull final DispatchType dispatchType) {
+        requireNonNull(dispatchType);
+        return tinybarValues.asTinybars(dispatchPrices.canonicalPriceInTinycents(dispatchType));
+    }
+
+    /**
+     * After feature flag isGasPrecisionLossFixEnabled is removed, this method should be removed.
+     * @deprecated
+     */
+    @Deprecated(since = "Precision loss fix was implemented in PR #14842", forRemoval = true)
+    public long gasRequirementOldWithPrecisionLoss(
+            @NonNull final TransactionBody body, @NonNull final AccountID payer, final long minimumPriceInTinybars) {
+        final var nominalPriceInTinybars = feeCalculator.applyAsLong(body, payer);
+        final var priceInTinybars = Math.max(minimumPriceInTinybars, nominalPriceInTinybars);
+        return asGasRequirement(priceInTinybars);
+    }
+
+    /**
+     * After feature flag isGasPrecisionLossFixEnabled is removed, this method should be removed.
+     * @deprecated
+     */
+    @Deprecated(since = "Precision loss fix was implemented in PR #14842", forRemoval = true)
     private long asGasRequirement(final long tinybarPrice) {
         return asGasRequirement(tinybarPrice, tinybarValues.childTransactionTinybarGasPrice());
     }
 
+    /**
+     * After feature flag isGasPrecisionLossFixEnabled is removed, this method should be removed.
+     * @deprecated
+     */
+    @Deprecated(since = "Precision loss fix was implemented in PR #14842", forRemoval = true)
     private long asGasRequirement(final long tinybarPrice, final long gasPrice) {
         // We round up to the nearest gas unit, and then add 20% to account for the premium
         // of doing a HAPI operation from inside the EVM