feat: widget loading animations polish (#3232)

* create use best trade hook for widgets

* update comment in hook file

* add loading states to input / output fields

* update to not use imports from app

* remove custom loading component

* update var name and syncing detection logic

* fix USD div type

* simplify loading css, small changes

src/lib/components/Swap/Input.tsx

 import { Trans } from '@lingui/macro'
 import { useUSDCValue } from 'hooks/useUSDCPrice'
+import { useAtomValue } from 'jotai/utils'
+import { loadingOpacityCss } from 'lib/css/loading'
 import { useSwapAmount, useSwapCurrency, useSwapInfo } from 'lib/hooks/swap'
 import { usePrefetchCurrencyColor } from 'lib/hooks/useCurrencyColor'
-import { Field } from 'lib/state/swap'
+import { Field, independentFieldAtom } from 'lib/state/swap'
 import styled, { ThemedText } from 'lib/theme'
 import { useMemo } from 'react'
+import { TradeState } from 'state/routing/types'
 import { formatCurrencyAmount } from 'utils/formatCurrencyAmount'
 
 import Column from '../Column'
@@ -12,6 +15,10 @@ import Row from '../Row'
 import TokenImg from '../TokenImg'
 import TokenInput from './TokenInput'
 
+const LoadingSpan = styled.span<{ $loading: boolean }>`
+  ${loadingOpacityCss};
+`
+
 const InputColumn = styled(Column)<{ approved?: boolean }>`
   margin: 0.75em;
   position: relative;
@@ -28,6 +35,7 @@ interface InputProps {
 
 export default function Input({ disabled }: InputProps) {
   const {
+    trade: { state: tradeState },
     currencyBalances: { [Field.INPUT]: balance },
     currencyAmounts: { [Field.INPUT]: inputCurrencyAmount },
   } = useSwapInfo()
@@ -39,6 +47,13 @@ export default function Input({ disabled }: InputProps) {
   // extract eagerly in case of reversal
   usePrefetchCurrencyColor(swapInputCurrency)
 
+  const isTradeLoading = useMemo(
+    () => TradeState.LOADING === tradeState || TradeState.SYNCING === tradeState,
+    [tradeState]
+  )
+  const isDependentField = useAtomValue(independentFieldAtom) !== Field.INPUT
+  const isLoading = isDependentField && isTradeLoading
+
   //TODO(ianlapham): mimic logic from app swap page
   const mockApproved = true
 
@@ -63,10 +78,11 @@ export default function Input({ disabled }: InputProps) {
         onMax={onMax}
         onChangeInput={updateSwapInputAmount}
         onChangeCurrency={updateSwapInputCurrency}
+        loading={isLoading}
       >
         <ThemedText.Body2 color="secondary">
           <Row>
-            <span>{inputUSDC ? `$${inputUSDC.toFixed(2)}` : '-'}</span>
+            <LoadingSpan $loading={isLoading}>{inputUSDC ? `$${inputUSDC.toFixed(2)}` : '-'}</LoadingSpan>
             {balance && (
               <ThemedText.Body2 color={inputCurrencyAmount?.greaterThan(balance) ? 'error' : undefined}>
                 Balance: <span style={{ userSelect: 'text' }}>{formatCurrencyAmount(balance, 4)}</span>

src/lib/components/Swap/Output.tsx

@@ -3,11 +3,13 @@ import { useUSDCValue } from 'hooks/useUSDCPrice'
 import { atom } from 'jotai'
 import { useAtomValue } from 'jotai/utils'
 import BrandedFooter from 'lib/components/BrandedFooter'
+import { loadingOpacityCss } from 'lib/css/loading'
 import { useSwapAmount, useSwapCurrency, useSwapInfo } from 'lib/hooks/swap'
 import useCurrencyColor from 'lib/hooks/useCurrencyColor'
-import { Field } from 'lib/state/swap'
+import { Field, independentFieldAtom } from 'lib/state/swap'
 import styled, { DynamicThemeProvider, ThemedText } from 'lib/theme'
 import { ReactNode, useMemo } from 'react'
+import { TradeState } from 'state/routing/types'
 import { computeFiatValuePriceImpact } from 'utils/computeFiatValuePriceImpact'
 import { formatCurrencyAmount } from 'utils/formatCurrencyAmount'
 
@@ -17,6 +19,10 @@ import TokenInput from './TokenInput'
 
 export const colorAtom = atom<string | undefined>(undefined)
 
+const LoadingSpan = styled.span<{ $loading: boolean }>`
+  ${loadingOpacityCss};
+`
+
 const OutputColumn = styled(Column)<{ hasColor: boolean | null }>`
   background-color: ${({ theme }) => theme.module};
   border-radius: ${({ theme }) => theme.borderRadius - 0.25}em;
@@ -40,6 +46,7 @@ interface OutputProps {
 
 export default function Output({ disabled, children }: OutputProps) {
   const {
+    trade: { state: tradeState },
     currencyBalances: { [Field.OUTPUT]: balance },
     currencyAmounts: { [Field.INPUT]: inputCurrencyAmount, [Field.OUTPUT]: outputCurrencyAmount },
   } = useSwapInfo()
@@ -47,6 +54,15 @@ export default function Output({ disabled, children }: OutputProps) {
   const [swapOutputAmount, updateSwapOutputAmount] = useSwapAmount(Field.OUTPUT)
   const [swapOutputCurrency, updateSwapOutputCurrency] = useSwapCurrency(Field.OUTPUT)
 
+  //loading status of the trade
+  const isTradeLoading = useMemo(
+    () => TradeState.LOADING === tradeState || TradeState.SYNCING === tradeState,
+    [tradeState]
+  )
+
+  const isDependentField = useAtomValue(independentFieldAtom) !== Field.OUTPUT
+  const isLoading = isDependentField && isTradeLoading
+
   const overrideColor = useAtomValue(colorAtom)
   const dynamicColor = useCurrencyColor(swapOutputCurrency)
   const color = overrideColor || dynamicColor
@@ -83,10 +99,11 @@ export default function Output({ disabled, children }: OutputProps) {
           disabled={disabled}
           onChangeInput={updateSwapOutputAmount}
           onChangeCurrency={updateSwapOutputCurrency}
+          loading={isLoading}
         >
           <ThemedText.Body2 color="secondary">
             <Row>
-              <span>{usdc}</span>
+              <LoadingSpan $loading={isLoading}>{usdc}</LoadingSpan>
               {balance && (
                 <span>
                   Balance: <span style={{ userSelect: 'text' }}>{formatCurrencyAmount(balance, 4)}</span>

src/lib/components/Swap/TokenInput.tsx

 import { Trans } from '@lingui/macro'
 import { Currency } from '@uniswap/sdk-core'
+import { loadingOpacityCss } from 'lib/css/loading'
 import styled, { keyframes, ThemedText } from 'lib/theme'
 import { FocusEvent, ReactNode, useCallback, useRef, useState } from 'react'
 
@@ -13,7 +14,7 @@ const TokenInputRow = styled(Row)`
   grid-template-columns: 1fr;
 `
 
-const ValueInput = styled(DecimalInput)`
+const ValueInput = styled(DecimalInput)<{ $loading: boolean }>`
   color: ${({ theme }) => theme.primary};
 
   :hover:not(:focus-within) {
@@ -23,6 +24,8 @@ const ValueInput = styled(DecimalInput)`
   :hover:not(:focus-within)::placeholder {
     color: ${({ theme }) => theme.onHover(theme.secondary)};
   }
+
+  ${loadingOpacityCss}
 `
 
 const delayedFadeIn = keyframes`
@@ -50,6 +53,7 @@ interface TokenInputProps {
   onMax?: () => void
   onChangeInput: (input: string) => void
   onChangeCurrency: (currency: Currency) => void
+  loading?: boolean
   children: ReactNode
 }
 
@@ -60,6 +64,7 @@ export default function TokenInput({
   onMax,
   onChangeInput,
   onChangeCurrency,
+  loading,
   children,
 }: TokenInputProps) {
   const max = useRef<HTMLButtonElement>(null)
@@ -70,6 +75,7 @@ export default function TokenInput({
       setShowMax(false)
     }
   }, [])
+
   return (
     <Column gap={0.25}>
       <TokenInputRow gap={0.5} onBlur={onBlur}>
@@ -79,6 +85,7 @@ export default function TokenInput({
             onFocus={onFocus}
             onChange={onChangeInput}
             disabled={disabled || !currency}
+            $loading={Boolean(loading)}
           ></ValueInput>
         </ThemedText.H2>
         {showMax && (

src/lib/css/loading.ts

+import { css } from 'lib/theme'
+
+// need to use $loading as `loading` is a reserved prop
+export const loadingOpacityCss = css<{ $loading: boolean }>`
+  filter: ${({ $loading }) => ($loading ? 'grayscale(1)' : 'none')};
+  opacity: ${({ $loading }) => ($loading ? '0.4' : '1')};
+  transition: opacity 0.2s ease-in-out;
+`

src/lib/hooks/swap/useBestTrade.ts

@@ -78,13 +78,15 @@ export function useBestTrade(
 
   const debouncing =
     (amountSpecified && debouncedAmount && amountSpecified !== debouncedAmount) ||
-    (debouncedOtherCurrency && otherCurrency && debouncedOtherCurrency !== otherCurrency)
+    (amountSpecified && debouncedOtherCurrency && otherCurrency && debouncedOtherCurrency !== otherCurrency)
 
-  const syncing = isTradeDebouncing({
-    amounts: [amountFromLatestTrade, debouncedAmount],
-    indepdenentCurrencies: [currencyFromTrade, debouncedOtherCurrency],
-    dependentCurrencies: [otherCurrencyFromTrade, otherCurrency],
-  })
+  const syncing =
+    amountSpecified &&
+    isTradeDebouncing({
+      amounts: [amountFromLatestTrade, amountSpecified],
+      indepdenentCurrencies: [currencyFromTrade, amountSpecified?.currency],
+      dependentCurrencies: [otherCurrencyFromTrade, debouncedOtherCurrency],
+    })
 
   const useFallback = !syncing && clientSORTrade.state === TradeState.NO_ROUTE_FOUND