Meta-Transactions (Gasless)

// 1. Delegate (builds and signs the transaction off-chain)
const { signedDelegateAction, payload } = userNear
  .transaction("user.near")
  .functionCall("game.near", "move", { x: 1, y: 2 })
  .delegate()

// Inspect locally (Typed Object)
console.log("User signed for:", signedDelegateAction.delegateAction.receiverId)

// 3. Send the PAYLOAD to your API (Base64 String)
await fetch("https://api.mygame.com/relay", {
  method: "POST",
  headers: { "Content-Type": "application/json" },
  body: JSON.stringify({ payload }),
})

import { Near, decodeSignedDelegateAction } from "near-kit"

const relayer = new Near({
  network: "testnet",
  privateKey: process.env.RELAYER_KEY,
})

app.post("/relay", async (req, res) => {
  try {
    const { payload } = req.body

    // 1. Decode the Base64 string back into a Typed Object
    const userAction = decodeSignedDelegateAction(payload)

    // 2. SECURITY: Inspect the object before paying for it!
    // access the inner details via .delegateAction
    const innerAction = userAction.delegateAction

    // Example Check: Only allow calls to "game.near"
    if (innerAction.receiverId !== "game.near") {
      return res.status(400).send("Invalid target contract")
    }

    // 3. Submit to the Network
    // The relayer wraps the user's action in its own transaction
    const result = await relayer
      .transaction("relayer.near")
      .signedDelegateAction(userAction)
      .send()

    res.json({ hash: result.transaction.hash })
  } catch (e) {
    console.error(e)
    res.status(500).send("Relay failed")
  }
})