Expose the difficulty adjustment information in an API #622 (#628)

* Added difficulty adjustment information API

* Added Difficulty API in API docs frontend

* Added link to API

* Updated the API implementation of difficulty-adjustment

* Updated API End Point in frontend

* Updated sample API response in frontend

backend/package-lock.json

@@ -2820,8 +2820,7 @@
     "ws": {
       "version": "7.4.6",
       "resolved": "https://registry.npmjs.org/ws/-/ws-7.4.6.tgz",
-      "integrity": "sha512-YmhHDO4MzaDLB+M9ym/mDA5z0naX8j7SIlT8f8z+I0VtzsRbekxEutHSme7NPS2qE8StCYQNUnfWdXta/Yu85A==",
+      "integrity": "sha512-YmhHDO4MzaDLB+M9ym/mDA5z0naX8j7SIlT8f8z+I0VtzsRbekxEutHSme7NPS2qE8StCYQNUnfWdXta/Yu85A=="
-      "requires": {}
     },
     "yallist": {
       "version": "4.0.0",

backend/src/index.ts

@@ -248,6 +248,7 @@ class Server {
         .get(config.MEMPOOL.API_URL_PREFIX + 'address/:address/txs', routes.getAddressTransactions)
         .get(config.MEMPOOL.API_URL_PREFIX + 'address/:address/txs/chain/:txId', routes.getAddressTransactions)
         .get(config.MEMPOOL.API_URL_PREFIX + 'address-prefix/:prefix', routes.getAddressPrefix)
+        .get(config.MEMPOOL.API_URL_PREFIX + 'difficulty-adjustment', routes.getDifficultyChange)
       ;
     }
   }

backend/src/routes.ts

@@ -666,6 +666,46 @@ class Routes {
   public getTransactionOutspends(req: Request, res: Response) {
     res.status(501).send('Not implemented');
   }
+
+  public getDifficultyChange(req: Request, res: Response) {
+    try {
+      const now = new Date().getTime() / 1000;
+      const DATime=blocks.getLastDifficultyAdjustmentTime();
+      const diff = now - DATime;
+      const blockHeight=blocks.getCurrentBlockHeight();
+      const blocksInEpoch = blockHeight % 2016;
+      const estimatedBlocks = Math.round(diff / 60 / 10);
+      const difficultyChange = (600 / (diff / blocksInEpoch ) - 1) * 100;
+
+      const timeAvgDiff = difficultyChange * 0.1;
+
+      let timeAvgMins = 10;
+      if (timeAvgDiff > 0 ){
+        timeAvgMins -= Math.abs(timeAvgDiff);
+      } else {
+        timeAvgMins += Math.abs(timeAvgDiff);
+      }
+
+      const remainingBlocks = 2016 - blocksInEpoch;
+      const timeAvgSeconds = timeAvgMins * 60;
+      const remainingTime = remainingBlocks * timeAvgSeconds;
+      const estimatedRetargetDate=(remainingTime + now);
+      const totalTime=estimatedRetargetDate-DATime;
+      const progressPercent=100-((remainingTime*100)/totalTime);
+
+      const result={
+        progressPercent,
+        difficultyChange,
+        estimatedRetargetDate,
+        remainingBlocks,
+        remainingTime,
+      }
+      res.json(result);
+
+    } catch (e) {
+      res.status(500).send(e.message || e);
+    }
+  }
 }
 
 export default new Routes();

frontend/angular.json

@@ -1,5 +1,8 @@
 {
   "$schema": "./node_modules/@angular/cli/lib/config/schema.json",
+  "cli": {
+    "analytics": "ed0ff723-05da-4a22-b43d-692b797b5243"
+  },
   "version": 1,
   "newProjectRoot": "projects",
   "projects": {

frontend/src/app/components/api-docs/api-docs.component.html

@@ -823,6 +823,23 @@
       </ng-template>
     </li>
 
+    <li *ngIf="network.val !== 'bisq'" [ngbNavItem]="8">
+      <a ngbNavLink i18n="api-docs.tab.difficulty|API Docs tab for Difficulty">Difficulty</a>
+      <ng-template ngbNavContent >
+        <div class="difficulty">
+          <div class="endpoint">
+            <div class="subtitle" i18n="Api docs endpoint">Endpoint</div>
+            <a href="{{ network.val === '' ? '' : '/' + network.val }}/api/difficulty-adjustment" target="_blank">GET {{ network.val === '' ? '' : '/' + network.val }}/api/difficulty-adjustment</a>
+          </div>
+          <div class="description">
+            <div class="subtitle" i18n>Description</div>
+              <div i18n>Returns details about difficulty adjustment.</div>
+          </div> 
+          <app-code-template [code]="code.difficulty" [network]="network.val" ></app-code-template>
+        </div>
+      </ng-template>
+    </li>
+
   </ul>
 
   <div [ngbNavOutlet]="nav" class="mt-2"></div>

frontend/src/app/components/api-docs/api-docs.component.scss

@@ -69,4 +69,8 @@ li.nav-item {
 }
 .websocket {
   padding: 15px;
+}
+
+.difficulty {
+  padding: 15px;
 }

frontend/src/app/components/api-docs/api-docs.component.ts

@@ -1125,7 +1125,24 @@ responseSample: `{
         curl: ``,
       },
       responseSample: ``,
-    }
+    },
+
+     difficulty: {
+      codeSample: {
+        esModule:``,
+        commonJS:``,
+        curl: `curl -X GET "https://mempool.space/api/difficulty-adjustment"`,
+      },
+      responseSample: `{
+        progressPercent: 18.55392610846515,
+        difficultyChange: -1.2440503501069622,
+        estimatedRetargetDate: 1627400849.2000492,
+        remainingBlocks: 1642,
+        remainingTime: 997456.3840492539
+          
+}`,
+    },
+    
   };
 
   constructor(

frontend/src/app/components/api-docs/code-template.component.scss

@@ -71,6 +71,10 @@ li.nav-item {
   padding: 15px;
 }
 
+.difficulty {
+  padding: 15px;
+}
+
 .links {
   margin-bottom: 5px;
   a {