Fabric Swapchain

Required keys.

Add these in your Lovable project under Settings → Secrets before pasting the prompt below.

Paste into a fresh Lovable project. Make sure all five secrets above are set first. read the build strategy →

Build "Fabric Swapchain" in ONE Lovable message. Single-page demo.

CONCEPT
Decentralize textile swaps between designers via secure tokenized exchanges.
Discipline: Fashion & Textile Design (material bartering).
Onchain primitive: Privy social + sponsored tx. Why this primitive: Privy embedded wallet and sponsored tx facilitate seamless trades without gas friction.

5-CREDIT BUDGET (HARD LIMIT):
- ONE single-page app. No router, no Lovable Cloud, no database, no auth flows beyond Privy drop-in.
- ONE Solidity contract, <=80 lines, deployed to Sepolia, verified on Etherscan.
- Privy is always the auth + sponsored-tx layer (Google login, embedded wallet).
- Pinata/IPFS only if the idea genuinely needs to store a file or metadata.
- At most ONE AI call per user action (use Lovable AI Gateway with LOVABLE_API_KEY if AI is part of the idea).
- Skip tests, skip CI, skip docs pages. Ship the demo, nothing else.

STACK
- React + Vite single page (the index route).
- Privy embedded wallet wraps `<App />` in src/main.tsx:
    <PrivyProvider appId={import.meta.env.VITE_PRIVY_APP_ID}
      config={{ loginMethods:['google'], embeddedWallets:{createOnLogin:'users-without-wallets'},
                defaultChain:{ id: 11155111, name:'Sepolia' } }}>
- All txs via Privy `useSendTransaction` with `{ sponsor: true }` (zero-gas for the user).
- Hardhat in /contracts (kept outside the Vite bundle). Install
  `@nomicfoundation/hardhat-toolbox` AND `@nomicfoundation/hardhat-verify@latest`
  (>=3.x — older versions still hit Etherscan v1 and fail with
  "You are using a deprecated V1 endpoint, switch to Etherscan API V2").
- hardhat.config.cjs MUST use the Etherscan v2 single-key shape (NOT the per-network map):
    require("@nomicfoundation/hardhat-toolbox");
    require("@nomicfoundation/hardhat-verify");
    module.exports = {
      solidity: { version: "0.8.24", settings: { optimizer: { enabled: true, runs: 200 } } },
      networks: { sepolia: {
        url: process.env.SEPOLIA_RPC_URL,                       // Alchemy HTTPS endpoint, REQUIRED
        accounts: [process.env.METAMASK_PRIVATE_KEY.startsWith("0x")
          ? process.env.METAMASK_PRIVATE_KEY : "0x" + process.env.METAMASK_PRIVATE_KEY],
        chainId: 11155111,
      } },
      etherscan: { apiKey: process.env.ETHERSCAN_API_KEY },   // single string, NOT { sepolia: ... }
      sourcify: { enabled: false },                            // silences the v2.x prompt
    };
- Deploy: `npx hardhat run scripts/deploy.cjs --network sepolia`.
- Verify (run RIGHT AFTER deploy, no constructor args for these contracts):
  `npx hardhat verify --network sepolia <address>`
  On success Etherscan returns "Successfully verified contract … on the block explorer"
  and the source becomes readable at
  `https://sepolia.etherscan.io/address/<address>#code`.
- Frontend reads: create a viem public client with the Alchemy URL too —
  `createPublicClient({ chain: sepolia, transport: http(import.meta.env.VITE_SEPOLIA_RPC_URL) })`.
  Expose SEPOLIA_RPC_URL to the client by also setting VITE_SEPOLIA_RPC_URL to the same value.
- Write the deployed address to `src/data/contract.json` so the UI links to
  `https://sepolia.etherscan.io/address/<address>`.

CONTRACT (contracts/FabricSwapchain.sol):
```solidity
// SPDX-License-Identifier: MIT
pragma solidity ^0.8.24;
/// @title SocialLogFabricSwapchain
/// @notice Decentralize textile swaps between designers via secure tokenized exchanges.
/// @notice Built during the Creative AI & Quantum Hackathon organised by StreetKode Fam during Indian Krump Festival 14
contract SocialLogFabricSwapchain {
    event Logged(address indexed author, string cid, uint256 at);
    /// @notice Built during the Creative AI & Quantum Hackathon organised by StreetKode Fam during Indian Krump Festival 14
    function log(string calldata cid) external {
        emit Logged(msg.sender, cid, block.timestamp);
    }
}
```

USER FLOW
1. Land on page -> 'Sign in with Google' (Privy) -> embedded wallet auto-provisioned.
2. Every material bartering action the user performs is sent as a sponsored Sepolia tx (`log(payload)`) and displayed with an Etherscan link. No wallet popups.
3. Footer renders: "Built during the Creative AI & Quantum Hackathon organised by StreetKode Fam during Indian Krump Festival 14"

REQUIRED SECRETS (Lovable -> Project Settings -> Secrets):
- METAMASK_PRIVATE_KEY  Sepolia deployer key. Fund it: https://cloud.google.com/application/web3/faucet/ethereum/sepolia
- SEPOLIA_RPC_URL       Alchemy Sepolia HTTPS endpoint (https://eth-sepolia.g.alchemy.com/v2/<key>). Create a free app at https://dashboard.alchemy.com/ -> copy the HTTPS URL. Public RPCs throttle/fail under hackathon load — Alchemy is required.
- ETHERSCAN_API_KEY     For `npx hardhat verify`. Get: https://etherscan.io/myapikey
- PRIVY_APP_ID          Google sign-in + sponsored tx. Docs: https://docs.privy.io/llms-full.txt
- PINATA_JWT            IPFS uploads (only if app pins media). Docs: https://docs.pinata.cloud/llms-full.txt

CREDIT (must appear in UI footer AND as NatSpec on every deployed contract):
Built during the Creative AI & Quantum Hackathon organised by StreetKode Fam during Indian Krump Festival 14

Market sizing.

Indicative figures for hackathon pitches — refine with your own research before raising.