Direct x chain bridging

cross-chain/base/contracts/BaseGateway.sol

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+pragma solidity ^0.8.17;
+
+import "./lib/wormhole-solidity-sdk/interfaces/IWormholeRelayer.sol";
+// import BitcoinTx from tBTC
+// import Deposit from tBTC
+
+contract BaseGateway {
+    uint256 constant GAS_LIMIT = 50_000; // TODO: check this value
+
+    IWormholeRelayer public immutable wormholeRelayer;
+
+    constructor(address _wormholeRelayer) {
+        wormholeRelayer = IWormholeRelayer(_wormholeRelayer);
+    }
+
+    // targetChain: Ethereum with a chain ID 2
+    // targetAddress: address of the Base Depositor contract on Ethereum
+    function revealDeposit(
+        uint16 targetChain, // Ethereum
+        address targetAddress, // BaseDepositor
+        BitcoinTx.Info calldata fundingTx,
+        Deposit.DepositRevealInfo calldata reveal
+    ) external {
+        // Cost of requesting a message to be sent to
+        // chain 'targetChain' with a gasLimit of 'GAS_LIMIT'
+        uint256 cost = quoteCrossChainDelivery(targetChain);
+        require(msg.value == cost);
+
+        wormholeRelayer.sendPayloadToEvm{value: cost}(
+            targetChain,
+            targetAddress,
+            abi.encode(fundingTx, reveal, msg.sender), // payload
+            0, // no receiver value needed since we're just passing a message
+            GAS_LIMIT
+        );
+
+        // emit revealDeposit(params...)
+    }
+
+    // targetChain: Ethereum with a chain ID 2
+    // targetAddress: address of the Base Redemption contract on Ethereum
+    function requestRedemption(
+      uint16 targetChain, // Ethereum
+      address targetAddress, // BaseRedeemer
+      bytes20 walletPubKeyHash,
+      BitcoinTx.UTXO calldata mainUtxo,
+      bytes calldata redeemerOutputScript,
+      uint64 amount
+    ) external {
+        // Relayer calls L2WormholeGateway.sendTBTC to send the canonical TBTC to the redeemer from L2 -> L1
+
+        // Cost of requesting a message to be sent to
+        // chain 'targetChain' with a gasLimit of 'GAS_LIMIT'
+        uint256 cost = quoteCrossChainDelivery(targetChain);
+        require(msg.value == cost);
+
+        wormholeRelayer.sendPayloadToEvm{value: cost}(
+            targetChain,
+            targetAddress,
+            abi.encode(walletPubKeyHash, mainUtxo, redeemerOutputScript, amount, msg.sender), // payload
+            0, // no receiver value needed since we're just passing a message
+            GAS_LIMIT
+        );
+
+        // emit request redemption event
+    }
+
+    function quoteCrossChainDelivery(uint16 targetChain) public view returns (uint256 cost) {
+        (cost,) = wormholeRelayer.quoteEVMDeliveryPrice(targetChain, 0, GAS_LIMIT);
+    }
+}