Update fetchEvents to write files per chunks

cli.js

@@ -618,6 +618,21 @@ function waitForTxReceipt({ txHash, attempts = 60, delay = 1000 }) {
   })
 }
 
+function initJson(file) {
+    return new Promise((resolve, reject) => {
+        fs.readFile(file, 'utf8', (error, data) => {
+            if (error) {
+                reject(error);
+            }
+            try {
+              resolve(JSON.parse(data));
+            } catch (error) {
+              resolve([]);
+            }
+        });
+    });
+};
+
 function loadCachedEvents({ type, currency, amount }) {
   try {
     const module = require(`./cache/${netName.toLowerCase()}/${type}s_${currency}_${amount}.json`)
@@ -641,8 +656,6 @@ function loadCachedEvents({ type, currency, amount }) {
 
 async function fetchEvents({ type, currency, amount}) {
     let leafIndex = -1
-    let events = [];
-    let fetchedEvents, chunks, targetBlock;
 
     if (type === "withdraw") {
       type = "withdrawal"
@@ -651,20 +664,21 @@ async function fetchEvents({ type, currency, amount}) {
     const cachedEvents = loadCachedEvents({ type, currency, amount })
     const startBlock = cachedEvents.lastBlock + 1
 
+    console.log("Loaded cached",amount,currency.toUpperCase(),type,"events for",startBlock,"block")
     console.log("Fetching",amount,currency.toUpperCase(),type,"events for",netName,"network")
 
-    async function fetchLatestEvents() {
+    async function syncEvents() {
-      targetBlock = await web3.eth.getBlockNumber();
+      try {
-      chunks = 1000;
+        let targetBlock = await web3.eth.getBlockNumber();
-      fetchedEvents = [];
+        let chunks = 1000;
         for (let i=startBlock; i < targetBlock; i+=chunks) {
+          let fetchedEvents = [];
+          async function fetchLatestEvents(i) {
             await tornadoContract.getPastEvents(capitalizeFirstLetter(type), {
                 fromBlock: i,
                 toBlock: i+chunks-1,
-        }).then(r => { fetchedEvents = fetchedEvents.concat(r); console.log("Fetched",amount,currency.toUpperCase(),type,"events from block:", i) }, err => { console.error(i + " failed fetching",type,"events from node", err) }).catch(console.log);
+            }).then(r => { fetchedEvents = fetchedEvents.concat(r); console.log("Fetched",amount,currency.toUpperCase(),type,"events from block:", i) }, err => { console.error(i + " failed fetching",type,"events from node", err); process.exit(1); }).catch(console.log);
           }
-    }
-    await fetchLatestEvents()
 
           async function mapDepositEvents() {
             fetchedEvents = fetchedEvents.map(({ blockNumber, transactionHash, returnValues }) => {
@@ -693,33 +707,43 @@ async function fetchEvents({ type, currency, amount}) {
           }
 
           async function mapLatestEvents() {
-      console.log("Mapping",amount,currency.toUpperCase(),type,"events, please wait")
             if (type === "deposit"){
               await mapDepositEvents();
             } else {
               await mapWithdrawEvents();
             }
           }
-    await mapLatestEvents();
-
-    console.log("Gathering cached events + collected events from node")
-
-    async function concatEvents() {
-      events = cachedEvents.events.concat(fetchedEvents)
-    }
-    await concatEvents();
-
-    console.log('Total events:', events.length)
 
           async function updateCache() {
             try {
-        await fs.writeFileSync(`./cache/${netName.toLowerCase()}/${type}s_${currency}_${amount}.json`, JSON.stringify(events, null, 2), 'utf8')
+              const fileName = `./cache/${netName.toLowerCase()}/${type}s_${currency}_${amount}.json`
-        console.log("Cache updated for Tornado",type,amount,currency,"instance successfully")
+              const localEvents = await initJson(fileName);
-      } catch (e) {
+              const events = localEvents.concat(fetchedEvents);
-        throw new Error('Writing cache file failed:',e)
+              await fs.writeFileSync(fileName, JSON.stringify(events, null, 2), 'utf8')
+            } catch (error) {
+              throw new Error('Writing cache file failed:',error)
             }
           }
+          await fetchLatestEvents(i);
+          await mapLatestEvents();
           await updateCache();
+        }
+      } catch (error) {
+        throw new Error("Error while updating cache")
+        process.exit(1)
+      }
+    }
+    await syncEvents();
+
+    async function loadUpdatedEvents() {
+      const fileName = `./cache/${netName.toLowerCase()}/${type}s_${currency}_${amount}.json`
+      const updatedEvents = await initJson(fileName);
+      const updatedBlock = updatedEvents[updatedEvents.length - 1].blockNumber
+      console.log("Cache updated for Tornado",type,amount,currency,"instance to block",updatedBlock,"successfully")
+      console.log('Total events:', updatedEvents.length)
+      return updatedEvents;
+    }
+    const events = await loadUpdatedEvents();
 
     return events
 }