Read scheduled rewards from spark-rewards (#606)

* add read scheduled rewards from `spark-rewards`

* rename

* service now returns `0`

lib/rewards.js

@@ -1,4 +1,5 @@
 import timers from 'node:timers/promises'
+import assert from 'node:assert/strict'
 
 /**
  * @param {object} args
@@ -11,10 +12,13 @@ export const runUpdateRewardsLoop = async ({ contracts, ethAddress, onMetrics })
     while (!contracts.length) {
       await timers.setTimeout(1000)
     }
-    const contractRewards = await Promise.all(contracts.map(async contract => {
-      return getScheduledRewardsWithFallback(contract, ethAddress)
-    }))
-    const totalRewards = contractRewards.reduce((a, b) => a + b, 0n)
+    const rewards = await Promise.all([
+      ...contracts.map(async contract => {
+        return getContractScheduledRewardsWithFallback(contract, ethAddress)
+      }),
+      getOffchainScheduledRewardsWithFallback(ethAddress)
+    ])
+    const totalRewards = rewards.reduce((a, b) => a + b, 0n)
     onMetrics({ rewardsScheduledForAddress: totalRewards })
 
     const delay = 10 * 60 * 1000 // 10 minutes
@@ -23,7 +27,21 @@ export const runUpdateRewardsLoop = async ({ contracts, ethAddress, onMetrics })
   }
 }
 
-async function getScheduledRewardsWithFallback (contract, ethAddress) {
+async function getOffchainScheduledRewardsWithFallback (ethAddress) {
+  try {
+    const res = await fetch(
+      `https://spark-rewards.fly.dev/scheduled-rewards/${ethAddress}`
+    )
+    const json = await res.json()
+    assert(typeof json === 'string')
+    return BigInt(json)
+  } catch (err) {
+    console.error('Failed to get scheduled rewards:', err.stack)
+    return 0n
+  }
+}
+
+async function getContractScheduledRewardsWithFallback (contract, ethAddress) {
   try {
     return await contract.rewardsScheduledFor(ethAddress)
   } catch (err) {