From 0230f95001875039995c6f68a3adc80f85ce0eea Mon Sep 17 00:00:00 2001
From: Mononaut <github@monospace.live>
Date: Mon, 8 Jan 2024 22:33:11 +0000
Subject: [PATCH] Fix bad coinbase price url, switch to median prices

---
 backend/src/tasks/price-feeds/coinbase-api.ts |  4 ++--
 backend/src/tasks/price-updater.ts            | 14 ++++++++++----
 2 files changed, 12 insertions(+), 6 deletions(-)

diff --git a/backend/src/tasks/price-feeds/coinbase-api.ts b/backend/src/tasks/price-feeds/coinbase-api.ts
index 424ac8867..d2c6d063a 100644
--- a/backend/src/tasks/price-feeds/coinbase-api.ts
+++ b/backend/src/tasks/price-feeds/coinbase-api.ts
@@ -5,14 +5,14 @@ class CoinbaseApi implements PriceFeed {
   public name: string = 'Coinbase';
   public currencies: string[] = ['USD', 'EUR', 'GBP'];
 
-  public url: string = 'https://api.coinbase.com/v2/prices/spot?currency=';
+  public url: string = 'https://api.coinbase.com/v2/prices/BTC-{CURRENCY}/spot';
   public urlHist: string = 'https://api.exchange.coinbase.com/products/BTC-{CURRENCY}/candles?granularity={GRANULARITY}';
 
   constructor() {
   }
 
   public async $fetchPrice(currency): Promise<number> {
-    const response = await query(this.url + currency);
+    const response = await query(this.url.replace('{CURRENCY}', currency));
     if (response && response['data'] && response['data']['amount']) {
       return parseInt(response['data']['amount'], 10);
     } else {
diff --git a/backend/src/tasks/price-updater.ts b/backend/src/tasks/price-updater.ts
index fd799fb87..0d5ca5958 100644
--- a/backend/src/tasks/price-updater.ts
+++ b/backend/src/tasks/price-updater.ts
@@ -23,6 +23,14 @@ export interface PriceHistory {
   [timestamp: number]: ApiPrice;
 }
 
+function getMedian(arr: number[]): number {
+  const sortedArr = arr.slice().sort((a, b) => a - b);
+  const mid = Math.floor(sortedArr.length / 2);
+  return sortedArr.length % 2 !== 0
+      ? sortedArr[mid]
+      : (sortedArr[mid - 1] + sortedArr[mid]) / 2;
+}
+
 class PriceUpdater {
   public historyInserted = false;
   private timeBetweenUpdatesMs = 360_0000 / config.MEMPOOL.PRICE_UPDATES_PER_HOUR;
@@ -173,7 +181,7 @@ class PriceUpdater {
       if (prices.length === 0) {
         this.latestPrices[currency] = -1;
       } else {
-        this.latestPrices[currency] = Math.round((prices.reduce((partialSum, a) => partialSum + a, 0)) / prices.length);
+        this.latestPrices[currency] = Math.round(getMedian(prices));
       }
     }
 
@@ -300,9 +308,7 @@ class PriceUpdater {
         if (grouped[time][currency].length === 0) {
           continue;
         }
-        prices[currency] = Math.round((grouped[time][currency].reduce(
-          (partialSum, a) => partialSum + a, 0)
-        ) / grouped[time][currency].length);
+        prices[currency] = Math.round(getMedian(grouped[time][currency]));
       }
       await PricesRepository.$savePrices(parseInt(time, 10), prices);
       ++totalInserted;