# Swap

Uniswap v4's swap event improves token exchanges with enhanced efficiency and customization, allowing seamless ERC-20 trades with features like concentrated liquidity and adjustable fees, strengthening its DeFi role. The standard event emitted on swap is:

```solidity
event Swap(
    PoolId indexed id,
    address indexed sender,
    int128 amount0,
    int128 amount1,
    uint160 sqrtPriceX96,
    uint128 liquidity,
    int24 tick,
    uint24 fee
);
```

Where `amount0` and `amount1` are amounts of tokens that took part in swap, `sqrtPriceX96` is:

$$
\text{sqrtPriceX96} = \sqrt{\frac{\text{price of token1}}{\text{price of token0}}} \times 2^{96}
$$

`liquidity` is a liquidity in pool after the swap, [`tick`](https://support.uniswap.org/hc/en-us/articles/21069524840589-What-is-a-tick-when-providing-liquidity)`, fee` is a percentage of protocol fee.

To effectively monitor swap events on a pool, HookRank utilizes [The Graph](https://thegraph.com/) to continuously track  them on-chain and modify entities provided in [Tracked Data](/hookrank/hookrank-indexing/tracked-data.md).

On every Swap event emitted standard flow is executed in following order:

1. convert each token amount from decimal to integer value using number of decimals specified in [Tracked Data](/hookrank/hookrank-indexing/tracked-data.md#token) and revert a sign as specified in official Uniswap [article](https://uniswapfoundation.mirror.xyz/c7LDDTWhC2ry6gp0nGqcSKHvNHosJmhPQ-ZuIxqeB2I):\
   `amountDec = -(amount / decimals);`
2. calculate `abs()`for both amounts to be used in volume calculation further:\
   `amountAbs = abs(amountDec);`
3. calculate amount of each token in ETH and USD:\
   `amountETH = amountAbs * tokenPriceETH;`\
   `amountUSD = amountETH * ethPriceUSD;`
4. calculate the total swap amount in ETH and USD by accounting for only non-zero prices and dividing result by 2 as both input and output can\`t be counted as volume:

```typescript
const totalSwapAmount = 0;

if (price0USD > 0 && price1USD > 0) {
    totalSwapAmount = (price0USD * amount0Abs + price1USD * amount1Abs) / 2;
}

if (price0USD == 0 && price1USD > 0) {
    totalSwapAmount = price1USD * amount1Abs;
}

if (price0USD > 0 && price1USD == 0) {
    totalSwapAmount = price0USD * amount0Abs;
}
```

5. calculate the fees in ETH and USD by multiplying the fee values from the event with the totalSwapAmount in their respective currencies, then divide the result by 10^6 to with Uniswap percent [denominator](https://github.com/Uniswap/v4-core/blob/80311e34080fee64b6fc6c916e9a51a437d0e482/src/libraries/ProtocolFeeLibrary.sol#L15):\
   `fees = totalSwapAmount * fee / 10^6;`
6. update values of [Tracked Data](/hookrank/hookrank-indexing/tracked-data.md#poolmanager)
   * increment `txCount` by 1;
   * increment `totalVolumeETH` by `totalSwapAmount` in ETH;
   * increment `totalVolumeUSD by totalSwapAmount` in USD;
   * increment `totalFeesETH` by `fees` in ETH;
   * increment `totalFeesUSD` by `fees` in USD;
7. decrement [Tracked Data](/hookrank/hookrank-indexing/tracked-data.md#poolmanager) `totalValueLockedETH` by old [Tracked Data](/hookrank/hookrank-indexing/tracked-data.md#pool) `totalValueLockedETH` (it is needed to add new TVL later);
8. update values of [Tracked Data](/hookrank/hookrank-indexing/tracked-data.md#pool):
   * increment token volumes (`volumeToken0`, `volumeToken1`) by `amount0Abs,` `amount1Abs` respectively;
   * increment `volumeUSD` by `totalSwapAmountUSD;`
   * increment `feesUSD` by calculated `feesUSD;`
   * increment `txCount` by 1;
   * update `liquidity` with value from event;
   * update `tick` with value from event;
   * update `sqrtPrice` with value from event;
   * increment `totalValueLocked` for both tokens by amount respectively;
9. update for both tokens values of [Tracked Data](/hookrank/hookrank-indexing/tracked-data.md#token)
   * increment `volume` by `amountAbs;`
   * increment `totalValueLocked` by `amount`;
   * increment `volumeUSD` by `totalSwapAmountUSD;`
   * increment `feesUSD` by calculated `feesUSD;`
   * increment `txCount` by 1;
10. update [Tracked Data](/hookrank/hookrank-indexing/tracked-data.md#pool) rates:
    * update token prices to new prices calculated by standard AMM formula;
    * save `lastTx` value;
11. update [Tracked Data](/hookrank/hookrank-indexing/tracked-data.md#bundle)`ethPriceUSD` by new value fetched from native token pool;
12. update [Tracked Data](/hookrank/hookrank-indexing/tracked-data.md#token)`derivedETH` (token price in native currency) for both tokens;
13. update [Tracked Data](/hookrank/hookrank-indexing/tracked-data.md#pool) values affected by new USD rates:
    * `totalValueLockedETH:`\
      `totalValueLockedETH = totalValueLockedToken0 * token0DerivedETH + totalValueLockedToken1 * token1DerivedETH;`
    * `totalValueLockedUSD:`\
      `totalValueLockedUSD = totalValueLockedETH * ethPriceUSD;`
14. update [Tracked Data](/hookrank/hookrank-indexing/tracked-data.md#pool) gas values:
    * increment `gasAccumulatedBySwaps` by gas value from event;
    * increment `gasAccumulatedBySwapsInEth` by gas value from event times transaction gas price;
    * increment `swapsCount` by 1;
15. update [Tracked Data](/hookrank/hookrank-indexing/tracked-data.md#hook) values:
    * update `totalValueLocked` in ETH and USD by subtracting the pool's old `totalValueLocked` and adding new one (calculated with new prices);
    * increment `volumeUSD` by `totalSwapAmountUSD;`
    * increment `feesUSD` by calculated `feesUSD;`
    * increment `gasAccumulatedBySwaps` by gas value from event;
    * increment `gasAccumulatedBySwapsInEth` by gas value from event times transaction gas price;
    * increment `swapsCount` by 1;
16. increment [Tracked Data](/hookrank/hookrank-indexing/tracked-data.md#poolmanager) `totalValueLocked` by updated pool values;
17. increment [Tracked Data](/hookrank/hookrank-indexing/tracked-data.md#token) `totalValueLocked` by updated pool values;
18. update [Tracked Data](/hookrank/hookrank-indexing/tracked-data.md#uniswapdaydata), [Tracked Data](/hookrank/hookrank-indexing/tracked-data.md#pooldaydata), [Tracked Data](/hookrank/hookrank-indexing/tracked-data.md#poolhourdata), [Tracked Data](/hookrank/hookrank-indexing/tracked-data.md#tokendaydata) [Tracked Data](/hookrank/hookrank-indexing/tracked-data.md#tokenhourdata) with values calculated earlier;


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