# ISO-4217 Currency Support

This document explains ISO-4217 currency support and XAU triangulation.

## Overview

The ISOCurrencyManager supports all ISO-4217 currencies with XAU triangulation for conversions.

## Supported Currencies

All major currencies are supported:

- USD (US Dollar)
- EUR (Euro)
- GBP (British Pound)
- JPY (Japanese Yen)
- CNY (Chinese Yuan)
- And all other ISO-4217 currencies

## Registration

Register a currency:

```solidity
isoCurrencyManager.registerCurrency(
    "USD",           // Currency code
    usdtAddress,     // Token address (or address(0) if not tokenized)
    2000e18          // XAU rate: 1 oz XAU = 2000 USD
);
```

## Conversion

Convert between currencies via XAU:

```solidity
uint256 eurAmount = isoCurrencyManager.convertViaXAU(
    "USD",      // From currency
    "EUR",      // To currency
    2000e18     // Amount
);
```

## XAU Triangulation

All conversions go through XAU:

1. Convert source currency to XAU
2. Convert XAU to target currency

This ensures consistent pricing across all currency pairs.

## Tokenized vs Non-Tokenized

- **Tokenized**: Currency has on-chain token representation (e.g., USDT for USD)
- **Non-Tokenized**: Currency exists only as a code (e.g., EUR without on-chain token)

Both types are supported and can be converted via XAU triangulation.