Estimate staking fees

sdk/src/lib/contracts/bitcoin-depositor.ts

@@ -9,6 +9,45 @@ export type DecodedExtraData = {
   referral: number
 }
 
+/**
+ * Represents the tBTC network minting fees.
+ */
+type TBTCMintingFees = {
+  /**
+   * The tBTC treasury fee taken from each deposit and transferred to the
+   * treasury upon sweep proof submission. Is calculated based on the initial
+   * funding transaction amount.
+   */
+  treasuryFee: bigint
+  /**
+   * The tBTC optimistic minting fee, Is calculated AFTER the treasury fee is
+   * cut.
+   */
+  optimisticMintingFee: bigint
+  /**
+   * Maximum amount of BTC transaction fee that can
+   * be incurred by each swept deposit being part of the given sweep
+   * transaction.
+   */
+  depositTxMaxFee: bigint
+}
+
+/**
+ * Represents the Acre network staking fees.
+ */
+type AcreStakingFees = {
+  /**
+   * The Acre network depositor fee taken from each deposit and transferred to
+   * the treasury upon stake request finalization.
+   */
+  depositorFee: bigint
+}
+
+export type StakingFees = {
+  tbtc: TBTCMintingFees
+  acre: AcreStakingFees
+}
+
 /**
  * Interface for communication with the AcreBitcoinDepositor on-chain contract.
  */
@@ -35,4 +74,12 @@ export interface BitcoinDepositor extends DepositorProxy {
    * @param extraData Encoded extra data.
    */
   decodeExtraData(extraData: string): DecodedExtraData
+
+  /**
+   * Estimates the staking fees based on the provided amount.
+   * @param amountToStake Amount to stake in 1e8 satoshi precision.
+   * @returns Staking fees grouped by tBTC and Acre networks in 1e18 tBTC token
+   *          precision.
+   */
+  estimateStakingFees(amountToStake: bigint): Promise<StakingFees>
 }

sdk/src/lib/ethereum/bitcoin-depositor.ts

@@ -7,12 +7,14 @@ import {
   isAddress,
   solidityPacked,
   zeroPadBytes,
+  Contract,
 } from "ethers"
 import {
   ChainIdentifier,
   DecodedExtraData,
   BitcoinDepositor,
   DepositReceipt,
+  StakingFees,
 } from "../contracts"
 import { BitcoinRawTxVectors } from "../bitcoin"
 import { EthereumAddress } from "./address"
@@ -26,6 +28,11 @@ import { EthereumNetwork } from "./network"
 
 import SepoliaBitcoinDepositor from "./artifacts/sepolia/AcreBitcoinDepositor.json"
 
+type TbtcDepositParameters = {
+  depositTreasuryFeeDivisor: bigint
+  depositTxMaxFee: bigint
+}
+
 /**
  * Ethereum implementation of the BitcoinDepositor.
  */
@@ -36,6 +43,15 @@ class EthereumBitcoinDepositor
   extends EthersContractWrapper<AcreBitcoinDepositorTypechain>
   implements BitcoinDepositor
 {
+  /**
+   * Multiplier to convert satoshi to tBTC token units.
+   */
+  readonly #satoshiMultiplier = 10n ** 10n
+
+  #tbtcBridgeDepositsParameters: TbtcDepositParameters | undefined
+
+  #tbtcOptimisticMintingFeeDivisor: bigint | undefined
+
   constructor(config: EthersContractConfig, network: EthereumNetwork) {
     let artifact: EthersContractDeployment
 
@@ -128,6 +144,102 @@ class EthereumBitcoinDepositor
 
     return { staker, referral }
   }
+
+  /**
+   * @see {BitcoinDepositor#estimateStakingFees}
+   */
+  async estimateStakingFees(amountToStake: bigint): Promise<StakingFees> {
+    const {
+      depositTreasuryFeeDivisor,
+      depositTxMaxFee,
+      optimisticMintingFeeDivisor,
+    } = await this.#getTbtcMintingFeesParameters()
+
+    const treasuryFee =
+      depositTreasuryFeeDivisor > 0
+        ? amountToStake / depositTreasuryFeeDivisor
+        : 0n
+
+    // Both deposit amount and treasury fee are in the 1e8 satoshi precision.
+    // We need to convert them to the 1e18 TBTC precision.
+    const amountSubTreasury =
+      (amountToStake - treasuryFee) * this.#satoshiMultiplier
+
+    const optimisticMintingFee =
+      optimisticMintingFeeDivisor > 0
+        ? amountSubTreasury / optimisticMintingFeeDivisor
+        : 0n
+
+    const depositorFeeDivisor = await this.instance.depositorFeeDivisor()
+    // Compute depositor fee. The fee is calculated based on the initial funding
+    // transaction amount, before the tBTC protocol network fees were taken.
+    const depositorFee =
+      depositorFeeDivisor > 0n
+        ? (amountToStake * this.#satoshiMultiplier) / depositorFeeDivisor
+        : 0n
+
+    return {
+      tbtc: {
+        treasuryFee: treasuryFee * this.#satoshiMultiplier,
+        optimisticMintingFee,
+        depositTxMaxFee: depositTxMaxFee * this.#satoshiMultiplier,
+      },
+      acre: {
+        depositorFee,
+      },
+    }
+  }
+
+  async #getTbtcMintingFeesParameters(): Promise<
+    TbtcDepositParameters & { optimisticMintingFeeDivisor: bigint }
+  > {
+    const depositParameters = await this.#getTbtcDepositParameters()
+    const optimisticMintingFeeDivisor =
+      await this.#getTbtcOptimisticMintingFeeDivisor()
+
+    return {
+      ...depositParameters,
+      optimisticMintingFeeDivisor,
+    }
+  }
+
+  async #getTbtcDepositParameters(): Promise<TbtcDepositParameters> {
+    if (this.#tbtcBridgeDepositsParameters) {
+      return this.#tbtcBridgeDepositsParameters
+    }
+
+    const bridgeAddress = await this.instance.bridge()
+
+    const bridge = new Contract(bridgeAddress, [
+      "function depositsParameters()",
+    ])
+
+    const depositsParameters =
+      (await bridge.depositsParameters()) as TbtcDepositParameters
+
+    this.#tbtcBridgeDepositsParameters = depositsParameters
+
+    return depositsParameters
+  }
+
+  async #getTbtcOptimisticMintingFeeDivisor(): Promise<bigint> {
+    if (this.#tbtcOptimisticMintingFeeDivisor) {
+      return this.#tbtcOptimisticMintingFeeDivisor
+    }
+
+    const vaultAddress = await this.getTbtcVaultChainIdentifier()
+
+    const vault = new Contract(`0x${vaultAddress.identifierHex}`, [
+      "function optimisticMintingFeeDivisor()",
+    ])
+
+    const optimisticMintingFeeDivisor =
+      (await vault.optimisticMintingFeeDivisor()) as bigint
+
+    this.#tbtcOptimisticMintingFeeDivisor = optimisticMintingFeeDivisor
+
+    return optimisticMintingFeeDivisor
+  }
 }
 
 export { EthereumBitcoinDepositor, packRevealDepositParameters }

sdk/src/lib/utils/index.ts

@@ -1,3 +1,4 @@
 export * from "./hex"
 export * from "./ethereum-signer"
 export * from "./backoff"
+export * from "./satoshi-converter"

sdk/src/lib/utils/satoshi-converter.ts

@@ -0,0 +1,11 @@
+const BTC_DECIMALS = 8n
+
+// eslint-disable-next-line import/prefer-default-export
+export function toSatoshi(amount: bigint, fromPrecision: bigint = 18n) {
+  const SATOSHI_MULTIPLIER = 10n ** (fromPrecision - BTC_DECIMALS)
+
+  const remainder = amount % SATOSHI_MULTIPLIER
+  const satoshis = (amount - remainder) / SATOSHI_MULTIPLIER
+
+  return satoshis
+}

sdk/src/modules/staking/index.ts

@@ -1,7 +1,21 @@
 import { ChainIdentifier, TBTC } from "@keep-network/tbtc-v2.ts"
-import { AcreContracts, DepositorProxy } from "../../lib/contracts"
+import {
+  AcreContracts,
+  DepositorProxy,
+  StakingFees as StakingFeesByNetwork,
+} from "../../lib/contracts"
 import { ChainEIP712Signer } from "../../lib/eip712-signer"
 import { StakeInitialization } from "./stake-initialization"
+import { toSatoshi } from "../../lib/utils"
+
+/**
+ * Represents all total staking fees grouped by network.
+ */
+export type TotalStakingFees = {
+  tbtc: bigint
+  acre: bigint
+  total: bigint
+}
 
 /**
  * Module exposing features related to the staking.
@@ -78,6 +92,33 @@ class StakingModule {
   estimatedBitcoinBalance(identifier: ChainIdentifier) {
     return this.#contracts.stBTC.assetsBalanceOf(identifier)
   }
+
+  /**
+   * Estimates the staking fees based on the provided amount.
+   * @param amountToStake Amount to stake in satoshi.
+   * @returns Staking fees grouped by tBTC and Acre networks in 1e8 satoshi
+   *          precision and total staking fees value.
+   */
+  async estimateStakingFees(amount: bigint): Promise<TotalStakingFees> {
+    const { acre: acreFees, tbtc: tbtcFees } =
+      await this.#contracts.bitcoinDepositor.estimateStakingFees(amount)
+
+    const sumFeesByNetwork = <
+      T extends StakingFeesByNetwork["tbtc"] | StakingFeesByNetwork["acre"],
+    >(
+      fees: T,
+    ) => Object.values(fees).reduce((reducer, fee) => reducer + fee, 0n)
+
+    const tbtc = toSatoshi(sumFeesByNetwork(tbtcFees))
+
+    const acre = toSatoshi(sumFeesByNetwork(acreFees))
+
+    return {
+      tbtc,
+      acre,
+      total: tbtc + acre,
+    }
+  }
 }
 
 export { StakingModule, StakeInitialization }