From 00fd0e3b14dc5dda21451b38eee2f56a6f9994a8 Mon Sep 17 00:00:00 2001
From: Jaco <jacogr@gmail.com>
Date: Thu, 29 Apr 2021 10:45:03 +0300
Subject: [PATCH] Allow forks on explorer (no Babe), adjust EventsContext
 (#5161)

---
 packages/page-explorer/src/index.tsx |   5 --
 packages/react-query/src/Events.tsx  | 127 ++++++++++++++-------------
 2 files changed, 67 insertions(+), 65 deletions(-)

diff --git a/packages/page-explorer/src/index.tsx b/packages/page-explorer/src/index.tsx
index 283ad205f1..a7acd6ef5d 100644
--- a/packages/page-explorer/src/index.tsx
+++ b/packages/page-explorer/src/index.tsx
@@ -7,7 +7,6 @@ import React, { useContext, useRef } from 'react';
 import { Route, Switch } from 'react-router';
 
 import Tabs from '@polkadot/react-components/Tabs';
-import { useApi } from '@polkadot/react-hooks';
 import { BlockAuthorsContext, EventsContext } from '@polkadot/react-query';
 
 import BlockInfo from './BlockInfo';
@@ -22,11 +21,8 @@ interface Props {
   newEvents?: KeyedEvent[];
 }
 
-const HIDDESN_NOBABE = ['forks'];
-
 function ExplorerApp ({ basePath, className }: Props): React.ReactElement<Props> {
   const { t } = useTranslation();
-  const { api } = useApi();
   const { lastHeaders } = useContext(BlockAuthorsContext);
   const events = useContext(EventsContext);
 
@@ -55,7 +51,6 @@ function ExplorerApp ({ basePath, className }: Props): React.ReactElement<Props>
     <main className={className}>
       <Tabs
         basePath={basePath}
-        hidden={api.query.babe ? undefined : HIDDESN_NOBABE}
         items={itemsRef.current}
       />
       <Switch>
diff --git a/packages/react-query/src/Events.tsx b/packages/react-query/src/Events.tsx
index 18e61fb4e1..33762b104c 100644
--- a/packages/react-query/src/Events.tsx
+++ b/packages/react-query/src/Events.tsx
@@ -1,12 +1,15 @@
 // Copyright 2017-2021 @polkadot/react-query authors & contributors
 // SPDX-License-Identifier: Apache-2.0
 
+import type { ApiPromise } from '@polkadot/api';
+import type { Vec } from '@polkadot/types';
+import type { EventRecord } from '@polkadot/types/interfaces';
 import type { IndexedEvent, KeyedEvent } from './types';
 
-import React, { useEffect, useState } from 'react';
+import React, { useEffect, useRef, useState } from 'react';
 
-import { useApi } from '@polkadot/react-hooks';
-import { stringToU8a } from '@polkadot/util';
+import { useApi, useCall } from '@polkadot/react-hooks';
+import { stringify, stringToU8a } from '@polkadot/util';
 import { xxhashAsHex } from '@polkadot/util-crypto';
 
 type Events = KeyedEvent[];
@@ -15,71 +18,75 @@ interface Props {
   children: React.ReactNode;
 }
 
+interface PrevHashes {
+  block: string | null;
+  event: string | null;
+}
+
 const MAX_EVENTS = 75;
 
 const EventsContext: React.Context<Events> = React.createContext<Events>([]);
 
+async function manageEvents (api: ApiPromise, prev: PrevHashes, records: Vec<EventRecord>, setState: React.Dispatch<React.SetStateAction<Events>>): Promise<void> {
+  const newEvents: IndexedEvent[] = records
+    .map((record, index) => ({ indexes: [index], record }))
+    .filter(({ record: { event: { method, section } } }) =>
+      section !== 'system' &&
+      (method !== 'Deposit' || !['balances', 'treasury'].includes(section)) &&
+      (section !== 'inclusion' || !['CandidateBacked', 'CandidateIncluded'].includes(method))
+    )
+    .reduce((combined: IndexedEvent[], e): IndexedEvent[] => {
+      const prev = combined.find(({ record: { event: { method, section } } }) =>
+        e.record.event.section === section &&
+        e.record.event.method === method
+      );
+
+      if (prev) {
+        prev.indexes.push(...e.indexes);
+      } else {
+        combined.push(e);
+      }
+
+      return combined;
+    }, [])
+    .reverse();
+  const newEventHash = xxhashAsHex(stringToU8a(stringify(newEvents)));
+
+  if (newEventHash !== prev.event && newEvents.length) {
+    prev.event = newEventHash;
+
+    // retrieve the last header, this will map to the current state
+    const header = await api.rpc.chain.getHeader(records.createdAtHash);
+    const blockNumber = header.number.unwrap();
+    const blockHash = header.hash.toHex();
+
+    if (blockHash !== prev.block) {
+      prev.block = blockHash;
+
+      setState((events) => [
+        ...newEvents.map(({ indexes, record }): KeyedEvent => ({
+          blockHash,
+          blockNumber,
+          indexes,
+          key: `${blockNumber.toNumber()}-${blockHash}-${indexes.join('.')}`,
+          record
+        })),
+        // remove all events for the previous same-height blockNumber
+        ...events.filter((p) => !p.blockNumber?.eq(blockNumber))
+      ].slice(0, MAX_EVENTS));
+    }
+  }
+}
+
 function EventsBase ({ children }: Props): React.ReactElement<Props> {
-  const { api } = useApi();
+  const { api, isApiReady } = useApi();
   const [state, setState] = useState<Events>([]);
+  const records = useCall<Vec<EventRecord>>(isApiReady && api.query.system.events);
+  const prevHashes = useRef({ block: null, event: null });
 
   useEffect((): void => {
-    // No unsub, global context - destroyed on app close
-    api.isReady.then((): void => {
-      let prevBlockHash: string | null = null;
-      let prevEventHash: string | null = null;
-
-      api.query.system.events((records): void => {
-        const newEvents: IndexedEvent[] = records
-          .map((record, index) => ({ indexes: [index], record }))
-          .filter(({ record: { event: { method, section } } }) =>
-            section !== 'system' &&
-            (method !== 'Deposit' || !['balances', 'treasury'].includes(section)) &&
-            (section !== 'inclusion' || !['CandidateBacked', 'CandidateIncluded'].includes(method))
-          )
-          .reduce((combined: IndexedEvent[], e): IndexedEvent[] => {
-            const prev = combined.find(({ record: { event: { method, section } } }) => e.record.event.section === section && e.record.event.method === method);
-
-            if (prev) {
-              prev.indexes.push(...e.indexes);
-            } else {
-              combined.push(e);
-            }
-
-            return combined;
-          }, [])
-          .reverse();
-        const newEventHash = xxhashAsHex(stringToU8a(JSON.stringify(newEvents)));
-
-        if (newEventHash !== prevEventHash && newEvents.length) {
-          prevEventHash = newEventHash;
-
-          // retrieve the last header, this will map to the current state
-          api.rpc.chain.getHeader().then((header): void => {
-            const blockNumber = header.number.unwrap();
-            const blockHash = header.hash.toHex();
-
-            if (blockHash !== prevBlockHash) {
-              prevBlockHash = blockHash;
-
-              setState((events) => [
-                ...newEvents.map(({ indexes, record }): KeyedEvent => ({
-                  blockHash,
-                  blockNumber,
-                  indexes,
-                  key: `${blockNumber.toNumber()}-${blockHash}-${indexes.join('.')}`,
-                  record
-                })),
-                // remove all events for the previous same-height blockNumber
-                ...events.filter((p) => !p.blockNumber?.eq(blockNumber))
-              ].slice(0, MAX_EVENTS));
-            }
-          }).catch(console.error);
-        }
-      }).catch(console.error);
-    }).catch(console.error);
-  // eslint-disable-next-line react-hooks/exhaustive-deps
-  }, []);
+    records && manageEvents(api, prevHashes.current, records, setState).catch(console.error);
+  }, [api, prevHashes, records, setState]);
 
   return (
     <EventsContext.Provider value={state}>