From 326b70dabe773c384e6f09cbe64d906a74a3bb29 Mon Sep 17 00:00:00 2001
From: Tom Kirkpatrick <tom@strike.me>
Date: Sun, 18 Feb 2024 09:04:21 +0000
Subject: [PATCH] Provide current block height data

---
 src/custom.d.ts |  1 +
 src/util.ts     | 49 +++++++++++++++++++++++++++++++++++++++++++++++--
 2 files changed, 48 insertions(+), 2 deletions(-)

diff --git a/src/custom.d.ts b/src/custom.d.ts
index 5e9cb80..9ac016f 100644
--- a/src/custom.d.ts
+++ b/src/custom.d.ts
@@ -16,6 +16,7 @@ type FeeByBlockTarget = {
 // Estimates represents the current block hash and fee by block target.
 type Estimates = {
   current_block_hash: string | null; // current block hash
+  current_block_height: number | null; // current block height
   fee_by_block_target: FeeByBlockTarget; // fee by block target (in sat/kb)
 };
 
diff --git a/src/util.ts b/src/util.ts
index fb59a6a..43da17d 100644
--- a/src/util.ts
+++ b/src/util.ts
@@ -35,22 +35,37 @@ export const FEE_MINIMUM = config.get<number>("settings.feeMinimum");
 export const CACHE_STDTTL = config.get<number>("cache.stdTTL");
 export const CACHE_CHECKPERIOD = config.get<number>("cache.checkperiod");
 
-// Constants
+// Primary URLs
 export const MEMPOOL_TIP_HASH_URL =
   MEMPOOL_BASE_URL && `${MEMPOOL_BASE_URL}/api/blocks/tip/hash`;
 export const ESPLORA_TIP_HASH_URL =
   ESPLORA_BASE_URL && `${ESPLORA_BASE_URL}/api/blocks/tip/hash`;
+
+export const MEMPOOL_TIP_HEIGHT_URL =
+  MEMPOOL_BASE_URL && `${MEMPOOL_BASE_URL}/api/blocks/tip/height`;
+export const ESPLORA_TIP_HEIGHT_URL =
+  ESPLORA_BASE_URL && `${ESPLORA_BASE_URL}/api/blocks/tip/height`;
+
 export const MEMPOOL_FEES_URL =
   MEMPOOL_BASE_URL && `${MEMPOOL_BASE_URL}/api/v1/fees/recommended`;
 export const ESPLORA_FEE_ESTIMATES_URL =
   ESPLORA_BASE_URL && `${ESPLORA_BASE_URL}/api/fee-estimates`;
 
+// Fallback URLs
 export const MEMPOOL_TIP_HASH_URL_FALLBACK =
   MEMPOOL_FALLBACK_BASE_URL &&
   `${MEMPOOL_FALLBACK_BASE_URL}/api/blocks/tip/hash`;
 export const ESPLORA_TIP_HASH_URL_FALLBACK =
   ESPLORA_FALLBACK_BASE_URL &&
   `${ESPLORA_FALLBACK_BASE_URL}/api/blocks/tip/hash`;
+
+export const MEMPOOL_TIP_HEIGHT_URL_FALLBACK =
+  MEMPOOL_FALLBACK_BASE_URL &&
+  `${MEMPOOL_FALLBACK_BASE_URL}/api/blocks/tip/height`;
+export const ESPLORA_TIP_HEIGHT_URL_FALLBACK =
+  ESPLORA_FALLBACK_BASE_URL &&
+  `${ESPLORA_FALLBACK_BASE_URL}/api/blocks/tip/height`;
+
 export const MEMPOOL_FEES_URL_FALLBACK =
   MEMPOOL_FALLBACK_BASE_URL &&
   `${MEMPOOL_FALLBACK_BASE_URL}/api/v1/fees/recommended`;
@@ -337,6 +352,33 @@ export async function fetchBlocksTipHash(): Promise<string | null> {
   return res0 || res1 || null;
 }
 
+/**
+ * Fetches the current block height.
+ */
+export async function fetchBlocksTipHeight(): Promise<number | null> {
+  const tasks = [
+    (MEMPOOL_TIP_HEIGHT_URL || MEMPOOL_TIP_HEIGHT_URL_FALLBACK) &&
+      fetchAndHandle(
+        MEMPOOL_TIP_HEIGHT_URL,
+        "text",
+        MEMPOOL_TIP_HEIGHT_URL_FALLBACK,
+      ),
+    (ESPLORA_TIP_HEIGHT_URL || ESPLORA_TIP_HEIGHT_URL_FALLBACK) &&
+      fetchAndHandle(
+        ESPLORA_TIP_HEIGHT_URL,
+        "text",
+        ESPLORA_TIP_HEIGHT_URL_FALLBACK,
+      ),
+  ].filter(Boolean);
+  const res = await Promise.allSettled(tasks);
+
+  let res0 = getValueFromFulfilledPromise(res[0]);
+  let res1 = getValueFromFulfilledPromise(res[1]);
+
+  const height = res0 || res1 || null;
+  return height ? Number(height) : null;
+}
+
 /**
  * Gets the current fee estimates from the cache or fetches them if they are not cached.
  */
@@ -353,12 +395,14 @@ export async function getEstimates(): Promise<Estimates> {
     await fetchEsploraData(),
     await fetchBitcoindData(),
     await fetchBlocksTipHash(),
+    await fetchBlocksTipHeight(),
   ];
-  const [result1, result2, result3, result4] = await Promise.allSettled(tasks);
+  const [result1, result2, result3, result4, result5] = await Promise.allSettled(tasks);
   const mempoolFeeEstimates = getValueFromFulfilledPromise(result1);
   const esploraFeeEstimates = getValueFromFulfilledPromise(result2);
   const bitcoindFeeEstimates = getValueFromFulfilledPromise(result3);
   const blocksTipHash = getValueFromFulfilledPromise(result4);
+  const blocksTipHeight = getValueFromFulfilledPromise(result5);
 
   // Get the minimum fee. If the mempool fee estimates are not available, use a default value of FEE_MINIMUM sat/vbyte as a safety net.
   const feeMinimum = (mempoolFeeEstimates?.minimumFee ?? FEE_MINIMUM) * 1000;
@@ -366,6 +410,7 @@ export async function getEstimates(): Promise<Estimates> {
 
   estimates = {
     current_block_hash: blocksTipHash,
+    current_block_height: blocksTipHeight,
     fee_by_block_target: calculateFees(
       mempoolFeeEstimates,
       esploraFeeEstimates,