@@ -359,3 +359,117 @@ export const closestRateForTimestamp = (
359359 }
360360 return bestRate
361361}
362+
363+ /**
364+ * Fetches exchange rates for a specific fiat currency on demand.
365+ * This is used when the user wants to view rates in a currency other than their default.
366+ */
367+ export function fetchExchangeRatesForFiat (
368+ fiatCurrencyCode : string
369+ ) : ThunkAction < Promise < void > > {
370+ return async ( dispatch , getState ) => {
371+ const state = getState ( )
372+ const { account } = state . core
373+ const { currencyWallets } = account
374+ const now = Date . now ( )
375+ const yesterday = getYesterdayDateRoundDownHour ( now ) . toISOString ( )
376+
377+ // Build asset pairs for the requested fiat currency
378+ const assetPairs : AssetPair [ ] = [ ]
379+ const pairExpiration = now + ONE_MONTH
380+ const rateExpiration = now + ONE_DAY
381+
382+ // If the fiat isn't dollars, get its price relative to USD
383+ if ( fiatCurrencyCode !== 'iso:USD' ) {
384+ assetPairs . push ( {
385+ currency_pair : `iso:USD_${ fiatCurrencyCode } ,
386+ date : undefined ,
387+ expiration : pairExpiration
388+ } )
389+ }
390+
391+ // Get rates for all wallet assets
392+ for ( const walletId of Object . keys ( currencyWallets ) ) {
393+ const wallet = currencyWallets [ walletId ]
394+ const { currencyCode } = wallet . currencyInfo
395+
396+ // Get the primary asset's prices for today
397+ assetPairs . push ( {
398+ currency_pair : `${ currencyCode } ${ fiatCurrencyCode } ,
399+ date : undefined ,
400+ expiration : pairExpiration
401+ } )
402+
403+ // Do the same for any tokens
404+ for ( const tokenId of wallet . enabledTokenIds ) {
405+ const token = wallet . currencyConfig . allTokens [ tokenId ]
406+ if ( token == null ) continue
407+ if ( token . currencyCode === currencyCode ) continue
408+ assetPairs . push ( {
409+ currency_pair : `${ token . currencyCode } ${ fiatCurrencyCode } ,
410+ date : undefined ,
411+ expiration : pairExpiration
412+ } )
413+ }
414+ }
415+
416+ // Fetch rates from server in batches
417+ const newRates : ExchangeRateCache = { }
418+ for ( let i = 0 ; i < assetPairs . length ; i += RATES_SERVER_MAX_QUERY_SIZE ) {
419+ const query = assetPairs . slice ( i , i + RATES_SERVER_MAX_QUERY_SIZE )
420+
421+ const options = {
422+ method : 'POST' ,
423+ headers : { 'Content-Type' : 'application/json' } ,
424+ body : JSON . stringify ( { data : query } )
425+ }
426+
427+ try {
428+ const response = await fetchRates ( 'v2/exchangeRates' , options )
429+ if ( response . ok ) {
430+ const json = await response . json ( )
431+ const cleanedRates = asRatesResponse ( json )
432+ for ( const rate of cleanedRates . data ) {
433+ const { currency_pair : currencyPair , exchangeRate, date } = rate
434+ const isHistorical = now - new Date ( date ) . valueOf ( ) > HOUR_MS
435+ const key = isHistorical ? `${ currencyPair } ${ date } : currencyPair
436+
437+ if ( exchangeRate != null ) {
438+ newRates [ key ] = {
439+ expiration : rateExpiration ,
440+ rate : parseFloat ( exchangeRate )
441+ }
442+ }
443+ }
444+ }
445+ } catch ( error : unknown ) {
446+ console . log (
447+ `fetchExchangeRatesForFiat error querying rates server ${ String (
448+ error
449+ ) } `
450+ )
451+ }
452+ }
453+
454+ // Merge with existing rates
455+ const mergedRates = { ...exchangeRateCache ?. rates , ...newRates }
456+ const { exchangeRates, exchangeRatesMap } = buildGuiRates (
457+ mergedRates ,
458+ yesterday
459+ )
460+
461+ // Update Redux state
462+ dispatch ( {
463+ type : 'EXCHANGE_RATES/UPDATE_EXCHANGE_RATES' ,
464+ data : {
465+ exchangeRates,
466+ exchangeRatesMap
467+ }
468+ } )
469+
470+ // Update the in-memory cache if it exists
471+ if ( exchangeRateCache != null ) {
472+ exchangeRateCache . rates = mergedRates
473+ }
474+ }
475+ }
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