# GRU Formulas NFT

**Contract**: `archive/solidity/contracts/nft/GRUFormulasNFT.sol`  
**Standard**: ERC-721

---

## Overview

The GRU Formulas NFT mints up to three token types, each depicting a GRU-related monetary formula as an on-chain SVG graphic.

## Token ID Mapping

| Token ID | Formula        | Name / Description |
|----------|----------------|--------------------|
| **0**    | Money Supply   | GRU monetary layers: **1 M00 = 5 M0 = 25 M1** (base M00, collateral M0, credit M1). See `GRUConstants.sol`. |
| **1**    | Money Velocity | Equation of exchange: **M × V = P × Y** (money supply × velocity = price level × output). |
| **2**    | Money Multiplier | **m = Reserve / Supply = 1.0** — no fractional reserve; enforced in ComplianceGuard and ISO4217W tokens. |

## Minting

- Only addresses with `MINTER_ROLE` can mint.
- `mint(to, tokenId)` with `tokenId` 0, 1, or 2.
- There are exactly three NFTs: tokenId 0, 1, and 2 (one per formula). Each tokenId can be minted once; the recipient receives that formula’s graphic.

## Metadata

- `tokenURI(tokenId)` returns a data URI: `data:application/json;base64,<base64(JSON)>`.
- The JSON includes `name`, `description`, and `image`.
- The `image` field is a data URI with an on-chain SVG: `data:image/svg+xml;base64,<base64(SVG)>`.
- No off-chain or IPFS dependency; all graphics are on-chain.

## Deployment

Deploy with an admin address (receives `DEFAULT_ADMIN_ROLE` and `MINTER_ROLE`). Grant `MINTER_ROLE` to any additional minters as needed.

```bash
forge create archive/solidity/contracts/nft/GRUFormulasNFT.sol:GRUFormulasNFT --constructor-args <ADMIN_ADDRESS> --rpc-url $RPC_URL --private-key $PRIVATE_KEY
```

## References

- GRU layers: `contracts/vault/libraries/GRUConstants.sol`
- Money multiplier validation: `contracts/iso4217w/ComplianceGuard.sol`, `docs/OPERATIONS_RUNBOOK.md`
