Fix the fetching of exchange rates

packages/mobile/src/exchange/reducer.ts

@@ -3,7 +3,7 @@ import { Actions, ActionTypes } from 'src/exchange/actions'
 import { getRehydratePayload, REHYDRATE, RehydrateAction } from 'src/redux/persist-helper'
 import { RootState } from 'src/redux/reducers'
 
-export const MAX_HISTORY_RETENTION = 30 * 24 * 3600 * 1000 // (ms) ~ 180 days
+export const MAX_HISTORY_RETENTION = 30 * 24 * 3600 * 1000 // (ms) ~ 30 days
 export const ADDRESS_LENGTH = 42
 
 export interface ExchangeRatePair {

packages/mobile/src/firebase/saga.ts

@@ -100,55 +100,62 @@ function celoGoldExchangeRateHistoryChannel(lastTimeUpdated: number) {
   }
 
   const now = Date.now()
+  // timestamp + 1 is used because .startAt is inclusive
+  const startAt = Math.max(lastTimeUpdated + 1, now - MAX_HISTORY_RETENTION)
 
   return eventChannel((emit: any) => {
-    const emitter = (snapshot: FirebaseDatabaseTypes.DataSnapshot) => {
+    const singleItemEmitter = (snapshot: FirebaseDatabaseTypes.DataSnapshot) => {
+      emit([snapshot.val()])
+    }
+    let cancelFunction = () => {}
+    const listenForNewElements = (newElementsStartAt: number) => {
+      cancelFunction = firebase
+        .database()
+        .ref(`${EXCHANGE_RATES}/cGLD/cUSD`)
+        .orderByChild('timestamp')
+        .startAt(newElementsStartAt)
+        .on('child_added', singleItemEmitter, errorCallback)
+    }
+    const fullListEmitter = (snapshot: FirebaseDatabaseTypes.DataSnapshot) => {
       const result: ExchangeRate[] = []
       snapshot.forEach((childSnapshot: FirebaseDatabaseTypes.DataSnapshot) => {
         result.push(childSnapshot.val())
         return undefined
       })
-      emit(result)
+      if (result.length) {
+        emit(result)
+        listenForNewElements(result[result.length - 1].timestamp + 1)
+      } else {
+        listenForNewElements(startAt)
+      }
     }
 
-    // timestamp + 1 is used because .startAt is inclusive
-    const startAt = lastTimeUpdated + 1 || now - MAX_HISTORY_RETENTION
-
-    const onValueChange = firebase
+    firebase
       .database()
       .ref(`${EXCHANGE_RATES}/cGLD/cUSD`)
       .orderByChild('timestamp')
       .startAt(startAt)
-      .on(VALUE_CHANGE_HOOK, emitter, errorCallback)
-
-    const cancel = () => {
-      firebase
-        .database()
-        .ref(`${EXCHANGE_RATES}/cGLD/cUSD`)
-        .orderByChild('timestamp')
-        .startAt(startAt)
-        .off(VALUE_CHANGE_HOOK, onValueChange)
-    }
+      .once(VALUE_CHANGE_HOOK, fullListEmitter, errorCallback)
 
-    return cancel
+    return cancelFunction
   })
 }
 
 export function* subscribeToCeloGoldExchangeRateHistory() {
   yield call(waitForFirebaseAuth)
   const history = yield select(exchangeHistorySelector)
-  const chan = yield call(celoGoldExchangeRateHistoryChannel, history.lastTimeUpdated)
+  const channel = yield call(celoGoldExchangeRateHistoryChannel, history.lastTimeUpdated)
   try {
     while (true) {
-      const exchangeRates = yield take(chan)
+      const exchangeRates = yield take(channel)
       const now = getRemoteTime()
       yield put(updateCeloGoldExchangeRateHistory(exchangeRates, now))
     }
   } catch (error) {
     Logger.error(`${TAG}@subscribeToCeloGoldExchangeRateHistory`, error)
   } finally {
     if (yield cancelled()) {
-      chan.close()
+      channel.close()
     }
   }
 }

packages/mobile/src/redux/migrations.test.ts

@@ -1,4 +1,5 @@
 import { DEFAULT_DAILY_PAYMENT_LIMIT_CUSD } from 'src/config'
+import { initialState as exchangeInitialState } from 'src/exchange/reducer'
 import { CicoProviderNames } from 'src/fiatExchanges/reducer'
 import { migrations } from 'src/redux/migrations'
 import { v0Schema, v1Schema, v2Schema, v7Schema, v8Schema, vNeg1Schema } from 'test/schemas'
@@ -177,4 +178,25 @@ describe('Redux persist migrations', () => {
     expect(migratedSchema.app.bitfyUrl).toBeUndefined()
     expect(migratedSchema.app.flowBtcUrl).toBeUndefined()
   })
+  it('works for v11 to v12', () => {
+    const appStub = 'dont delete please'
+    const exchangeStub = 'also dont delete please'
+    const stub = {
+      exchange: {
+        otherExchangeProps: exchangeStub,
+        history: {
+          celoGoldExchangeRates: [1, 2, 3],
+          aggregatedExchangeRates: [4, 5, 6],
+          granularity: 0,
+          range: 0,
+          lastTimeUpdated: 100,
+        },
+      },
+      app: appStub,
+    }
+    const migratedSchema = migrations[12](stub)
+    expect(migratedSchema.app).toEqual(appStub)
+    expect(migratedSchema.exchange.otherExchangeProps).toEqual(exchangeStub)
+    expect(migratedSchema.exchange.history).toEqual(exchangeInitialState.history)
+  })
 })

packages/mobile/src/redux/migrations.ts

@@ -1,5 +1,6 @@
 import _ from 'lodash'
 import { DEFAULT_DAILY_PAYMENT_LIMIT_CUSD } from 'src/config'
+import { initialState as exchangeInitialState } from 'src/exchange/reducer'
 import { providersDisplayInfo } from 'src/fiatExchanges/reducer'
 import { AddressToDisplayNameType } from 'src/identity/reducer'
 
@@ -166,4 +167,14 @@ export const migrations = {
       app: _.omit(state.app, 'pontoEnabled', 'kotaniEnabled', 'bitfyUrl', 'flowBtcUrl'),
     }
   },
+  12: (state: any) => {
+    // Removing the exchange rate history because it's very likely that it's repeated a bunch of times.
+    return {
+      ...state,
+      exchange: {
+        ...state.exchange,
+        history: { ...exchangeInitialState.history },
+      },
+    }
+  },
 }

packages/mobile/src/redux/store.ts

@@ -18,7 +18,7 @@ let lastEventTime = Date.now()
 
 const persistConfig: any = {
   key: 'root',
-  version: 11, // default is -1, increment as we make migrations
+  version: 12, // default is -1, increment as we make migrations
   keyPrefix: `reduxStore-`, // the redux-persist default is `persist:` which doesn't work with some file systems.
   storage: FSStorage(),
   blacklist: ['geth', 'networkInfo', 'alert', 'fees', 'recipients', 'imports'],