create separate service for short term tx & block caching

frontend/src/app/services/cache.service.ts

@@ -0,0 +1,105 @@
+import { Injectable } from '@angular/core';
+import { firstValueFrom, Subject, Subscription} from 'rxjs';
+import { Transaction } from '../interfaces/electrs.interface';
+import { BlockExtended } from '../interfaces/node-api.interface';
+import { StateService } from './state.service';
+import { ApiService } from './api.service';
+
+const BLOCK_CACHE_SIZE = 50;
+const KEEP_RECENT_BLOCKS = 50;
+
+@Injectable({
+  providedIn: 'root'
+})
+export class CacheService {
+  loadedBlocks$ = new Subject<BlockExtended>();
+  tip: number = 0;
+
+  txCache: { [txid: string]: Transaction } = {};
+
+  blockCache: { [height: number]: BlockExtended } = {};
+  blockLoading: { [height: number]: boolean } = {};
+  copiesInBlockQueue: { [height: number]: number } = {};
+  blockPriorities: number[] = [];
+
+  constructor(
+    private stateService: StateService,
+    private apiService: ApiService,
+  ) {
+    this.stateService.blocks$.subscribe(([block]) => {
+      this.addBlockToCache(block);
+      this.clearBlocks();
+    });
+    this.stateService.chainTip$.subscribe((height) => {
+      this.tip = height;
+    });
+  }
+
+  setTxCache(transactions) {
+    this.txCache = {};
+    transactions.forEach(tx => {
+      this.txCache[tx.txid] = tx;
+    });
+  }
+ 
+  getTxFromCache(txid) {
+    if (this.txCache && this.txCache[txid]) {
+      return this.txCache[txid];
+    } else {
+      return null;
+    }
+  }
+
+  addBlockToCache(block: BlockExtended) {
+    this.blockCache[block.height] = block;
+    this.bumpBlockPriority(block.height);
+  }
+
+  async loadBlock(height) {
+    if (!this.blockCache[height] && !this.blockLoading[height]) {
+      const chunkSize = 10;
+      const maxHeight = Math.ceil(height / chunkSize) * chunkSize;
+      for (let i = 0; i < chunkSize; i++) {
+        this.blockLoading[maxHeight - i] = true;
+      }
+      const result = await firstValueFrom(this.apiService.getBlocks$(maxHeight));
+      for (let i = 0; i < chunkSize; i++) {
+        delete this.blockLoading[maxHeight - i];
+      }
+      if (result && result.length) {
+        result.forEach(block => {
+          this.addBlockToCache(block);
+          this.loadedBlocks$.next(block);
+        });
+      }
+      this.clearBlocks();
+    } else {
+      this.bumpBlockPriority(height);
+    }
+  }
+
+  // increase the priority of a block, to delay removal
+  bumpBlockPriority(height) {
+    this.blockPriorities.push(height);
+    this.copiesInBlockQueue[height] = (this.copiesInBlockQueue[height] || 0) + 1;
+  }
+
+  // remove lowest priority blocks from the cache
+  clearBlocks() {
+    while (Object.keys(this.blockCache).length > (BLOCK_CACHE_SIZE + KEEP_RECENT_BLOCKS) && this.blockPriorities.length > KEEP_RECENT_BLOCKS) {
+      const height = this.blockPriorities.shift();
+      if (this.copiesInBlockQueue[height] > 1) {
+        this.copiesInBlockQueue[height]--;
+      } else if ((this.tip - height) < KEEP_RECENT_BLOCKS) {
+        this.bumpBlockPriority(height);
+      } else {
+        delete this.blockCache[height];
+        delete this.copiesInBlockQueue[height];
+      }
+    }
+  }
+
+  getCachedBlock(height) {
+    return this.blockCache[height];
+  }
+}

frontend/src/app/services/state.service.ts

@@ -1,6 +1,6 @@
 import { Inject, Injectable, PLATFORM_ID, LOCALE_ID } from '@angular/core';
 import { ReplaySubject, BehaviorSubject, Subject, fromEvent, Observable } from 'rxjs';
-import { Block, Transaction } from '../interfaces/electrs.interface';
+import { Transaction } from '../interfaces/electrs.interface';
 import { IBackendInfo, MempoolBlock, MempoolBlockWithTransactions, MempoolBlockDelta, MempoolInfo, Recommendedfees, ReplacedTransaction, TransactionStripped } from '../interfaces/websocket.interface';
 import { BlockExtended, DifficultyAdjustment, OptimizedMempoolStats } from '../interfaces/node-api.interface';
 import { Router, NavigationStart } from '@angular/router';
@@ -119,8 +119,6 @@ export class StateService {
   timeLtr: BehaviorSubject<boolean>;
   hideFlow: BehaviorSubject<boolean>;
 
-  txCache: { [txid: string]: Transaction } = {};
-
   constructor(
     @Inject(PLATFORM_ID) private platformId: any,
     @Inject(LOCALE_ID) private locale: string,
@@ -275,28 +273,12 @@ export class StateService {
     return this.network === 'liquid' || this.network === 'liquidtestnet';
   }
 
-  setTxCache(transactions) {
-    this.txCache = {};
-    transactions.forEach(tx => {
-      this.txCache[tx.txid] = tx;
-    });
-  }
-
-  getTxFromCache(txid) {
-    if (this.txCache && this.txCache[txid]) {
-      return this.txCache[txid];
-    } else {
-    return null;
-    }
-  }
-
   resetChainTip() {
     this.latestBlockHeight = -1;
     this.chainTip$.next(-1);
   }
 
   updateChainTip(height) {
-    console.log('updating chain tip to ', height);
     if (height > this.latestBlockHeight) {
       this.latestBlockHeight = height;
       this.chainTip$.next(height);