Add price impact indicator to the trade component (#765)

* WIP

* calculate price impact by subtracting tokens fiat values

* get and use spotPrice for price impact calculation, use Decimal

* set impact to 0 if input and output values are undefined

* move price impact to a new component

* turn price impact value color to red if grater than 5

* add tooltip to price impact and slippage

* removed fiat price

* change formula

* remove console.log

* don't block add liquidity button

* typos

* proper text alignment

Co-authored-by: mihaisc <mihai@oceanprotocol.com>
Co-authored-by: Matthias Kretschmann <m@kretschmann.io>

src/components/organisms/AssetActions/Pool/index.tsx

@@ -367,7 +367,7 @@ export default function Pool(): ReactElement {
                 style="primary"
                 size="small"
                 onClick={() => setShowAdd(true)}
-                disabled={isInPurgatory || !isAssetNetwork}
+                disabled={isInPurgatory}
               >
                 Add Liquidity
               </Button>

src/components/organisms/AssetActions/Trade/PriceImpact.module.css

@@ -0,0 +1,24 @@
+.priceImpact {
+  font-size: var(--font-size-small);
+  border-top: 1px solid var(--border-color);
+  margin-left: -2rem;
+  margin-right: -2rem;
+  padding: calc(var(--spacer) / 4) var(--spacer);
+  color: var(--color-secondary);
+  display: grid;
+  grid-template-columns: 1fr 1fr;
+  gap: calc(var(--spacer) / 3);
+}
+
+.priceImpact strong {
+  font-weight: var(--font-weight-base);
+  text-align: right;
+}
+
+.alert {
+  color: var(--brand-alert-red);
+}
+
+.number {
+  font-weight: var(--font-weight-bold);
+}

src/components/organisms/AssetActions/Trade/PriceImpact.tsx

@@ -0,0 +1,65 @@
+import React, { ReactElement, useEffect, useState } from 'react'
+import Decimal from 'decimal.js'
+import Tooltip from '../../../atoms/Tooltip'
+import styles from './PriceImpact.module.css'
+
+export default function PriceImpact({
+  totalValue,
+  tokenAmount,
+  spotPrice
+}: {
+  /// how much the user actually pays (doesn't matter witch token it is)
+  totalValue: string
+  /// how many tokens the user trades (doesn't matter witch token it is)
+  tokenAmount: string
+  /// the spot price of the traded token (doesn't matter witch token it is))
+  spotPrice: string
+}): ReactElement {
+  const [priceImpact, setPriceImpact] = useState<string>('0')
+
+  async function getPriceImpact(
+    totalValue: string,
+    tokenAmount: string,
+    spotPrice: string
+  ) {
+    const dtotalValue = new Decimal(totalValue)
+    const dTokenAmount = new Decimal(tokenAmount)
+    const dSpotPrice = new Decimal(spotPrice)
+    let priceImpact = Decimal.abs(
+      dtotalValue.div(dTokenAmount.times(dSpotPrice)).minus(1)
+    ).mul(100)
+    if (priceImpact.isNaN()) priceImpact = new Decimal(0)
+    return priceImpact.toDecimalPlaces(2, Decimal.ROUND_DOWN)
+  }
+
+  useEffect(() => {
+    if (!totalValue || !tokenAmount || !spotPrice) {
+      setPriceImpact('0')
+      return
+    }
+
+    async function init() {
+      const newPriceImpact = await getPriceImpact(
+        totalValue,
+        tokenAmount,
+        spotPrice
+      )
+      setPriceImpact(newPriceImpact.toString())
+    }
+    init()
+  }, [totalValue, tokenAmount, spotPrice])
+
+  return (
+    <div className={styles.priceImpact}>
+      <strong>Price impact</strong>
+      <div>
+        <span
+          className={`${styles.number} ${
+            parseInt(priceImpact) > 5 && styles.alert
+          }`}
+        >{`${priceImpact}%`}</span>
+        <Tooltip content="The difference between the market price and estimated price due to trade size." />
+      </div>
+    </div>
+  )
+}

src/components/organisms/AssetActions/Trade/Slippage.module.css

@@ -4,13 +4,15 @@
   margin-left: -2rem;
   margin-right: -2rem;
   padding: calc(var(--spacer) / 4) var(--spacer);
-  text-align: center;
   color: var(--color-secondary);
+  display: grid;
+  grid-template-columns: 1fr 1fr;
+  gap: calc(var(--spacer) / 3);
 }
 
 .slippage strong {
   font-weight: var(--font-weight-base);
-  color: var(--font-color-heading);
+  text-align: right;
 }
 
 .title {
@@ -25,6 +27,4 @@
 .slippage select {
   width: fit-content;
   display: inline-block;
-  margin-left: calc(var(--spacer) / 4);
-  margin-right: calc(var(--spacer) / 4);
 }

src/components/organisms/AssetActions/Trade/Slippage.tsx

@@ -1,7 +1,8 @@
 import { FormikContextType, useFormikContext } from 'formik'
-import React, { ChangeEvent, ReactElement, useEffect, useState } from 'react'
+import React, { ChangeEvent, ReactElement } from 'react'
 import { FormTradeData, slippagePresets } from '../../../../models/FormTrade'
 import InputElement from '../../../atoms/Input/InputElement'
+import Tooltip from '../../../atoms/Tooltip'
 import styles from './Slippage.module.css'
 
 export default function Slippage(): ReactElement {
@@ -14,9 +15,9 @@ export default function Slippage(): ReactElement {
   }
 
   return (
-    <>
     <div className={styles.slippage}>
-        <strong>Expected price impact</strong>
+      <strong>Slippage Tolerance</strong>
+      <div>
         <InputElement
           name="slippage"
           type="select"
@@ -27,7 +28,8 @@ export default function Slippage(): ReactElement {
           value={values.slippage}
           onChange={handleChange}
         />
+        <Tooltip content="Your transaction will revert if the price changes unfavorably by more than this percentage." />
+      </div>
     </div>
-    </>
   )
 }

src/components/organisms/AssetActions/Trade/Swap.tsx

@@ -10,6 +10,7 @@ import Output from './Output'
 import Slippage from './Slippage'
 import { FormTradeData, TradeItem } from '../../../../models/FormTrade'
 import { useOcean } from '../../../../providers/Ocean'
+import PriceImpact from './PriceImpact'
 
 export default function Swap({
   ddo,
@@ -47,6 +48,11 @@ export default function Swap({
     validateForm
   }: FormikContextType<FormTradeData> = useFormikContext()
 
+  /// Values used for calculation of price impact
+  const [spotPrice, setSpotPrice] = useState<string>()
+  const [totalValue, setTotalValue] = useState<string>()
+  const [tokenAmount, setTokenAmount] = useState<string>()
+  ///
   useEffect(() => {
     if (!ddo || !balance || !values || !price) return
 
@@ -106,16 +112,63 @@ export default function Swap({
   }
 
   const handleValueChange = async (name: string, value: number) => {
-    const newValue =
-      name === 'ocean'
-        ? values.type === 'sell'
-          ? await ocean.pool.getDTNeeded(price.address, value.toString())
-          : await ocean.pool.getDTReceived(price.address, value.toString())
-        : values.type === 'sell'
-        ? await ocean.pool.getOceanReceived(price.address, value.toString())
-        : await ocean.pool.getOceanNeeded(price.address, value.toString())
+    let tokenIn = ''
+    let tokenOut = ''
+    let newValue
 
-    setFieldValue(name === 'ocean' ? 'datatoken' : 'ocean', newValue)
+    if (name === 'ocean') {
+      if (values.type === 'sell') {
+        newValue = await ocean.pool.getDTNeeded(price.address, value.toString())
+
+        setTotalValue(newValue)
+        setTokenAmount(value.toString())
+
+        tokenIn = ddo.dataToken
+        tokenOut = ocean.pool.oceanAddress
+      } else {
+        newValue = await ocean.pool.getDTReceived(
+          price.address,
+          value.toString()
+        )
+
+        setTotalValue(value.toString())
+        setTokenAmount(newValue)
+        tokenIn = ocean.pool.oceanAddress
+        tokenOut = ddo.dataToken
+      }
+    } else {
+      if (values.type === 'sell') {
+        newValue = await ocean.pool.getOceanReceived(
+          price.address,
+          value.toString()
+        )
+
+        setTotalValue(value.toString())
+        setTokenAmount(newValue)
+        tokenIn = ddo.dataToken
+        tokenOut = ocean.pool.oceanAddress
+      } else {
+        newValue = await ocean.pool.getOceanNeeded(
+          price.address,
+          value.toString()
+        )
+
+        setTotalValue(newValue)
+        setTokenAmount(value.toString())
+        tokenIn = ocean.pool.oceanAddress
+        tokenOut = ddo.dataToken
+      }
+    }
+
+    await setFieldValue(name === 'ocean' ? 'datatoken' : 'ocean', newValue)
+
+    const spotPrice = await ocean.pool.getSpotPrice(
+      price.address,
+      tokenIn,
+      tokenOut
+    )
+
+    setSpotPrice(spotPrice)
     validateForm()
   }
 
@@ -139,6 +192,11 @@ export default function Swap({
 
       <Output dtSymbol={dtItem.token} poolAddress={price?.address} />
 
+      <PriceImpact
+        totalValue={totalValue}
+        tokenAmount={tokenAmount}
+        spotPrice={spotPrice}
+      />
       <Slippage />
     </div>
   )

src/utils/subgraph.ts

@@ -410,6 +410,21 @@ export async function getPrice(asset: DDO): Promise<BestPrice> {
   return bestPrice
 }
 
+export async function getSpotPrice(asset: DDO): Promise<number> {
+  const poolVariables = {
+    datatokenAddress: asset?.dataToken.toLowerCase()
+  }
+  const queryContext = getQueryContext(Number(asset.chainId))
+
+  const poolPriceResponse: OperationResult<AssetsPoolPrice> = await fetchData(
+    AssetPoolPriceQuerry,
+    poolVariables,
+    queryContext
+  )
+
+  return poolPriceResponse.data.pools[0].spotPrice
+}
+
 export async function getAssetsBestPrices(
   assets: DDO[]
 ): Promise<AssetListPrices[]> {