wdb-migration: handle edge case when wdb.addBlock is interrupted.

lib/wallet/migrations.js

@@ -925,9 +925,10 @@ class MigrateTXCountTimeIndex extends AbstractMigration {
 
     for await (const {key, value: rawBlockRecord} of rawBlockRecords) {
       const height = txlayout.b.decode(key)[0];
+      const hash = rawBlockRecord.slice(0, 32);
       const blockTime = encoding.readU32(rawBlockRecord, 32 + 4);
       const txCount = encoding.readU32(rawBlockRecord, 32 + 4 + 4);
-      const medianTime = await this.getMedianTime(height);
+      const medianTime = await this.getMedianTime(height, hash);
 
       const hashes = new BufferSet();
       let count = 0;
@@ -1158,27 +1159,44 @@ class MigrateTXCountTimeIndex extends AbstractMigration {
   /**
    * Get median time for the block.
    * @param {Number} height
+   * @param {Hash} lastHash
    * @returns {Promise<Number>}
    */
 
-  async getMedianTime(height) {
-    const getBlockTime = async (height) => {
-      const cache = this.blockTimeCache.get(height);
+  async getMedianTime(height, lastHash) {
+    const getBlockTime = async (bheight) => {
+      const cache = this.blockTimeCache.get(bheight);
 
       if (cache != null)
         return cache;
 
-      if (height < 0)
+      if (bheight < 0)
         return null;
 
-      const data = await this.ldb.get(this.layout.wdb.h.encode(height));
+      let time;
+      const data = await this.ldb.get(this.layout.wdb.h.encode(bheight));
 
-      if (!data)
-        return null;
+      if (!data) {
+        // Special case when txlayout.b exists, but txlayout.wdb.h does not.
+        // This can happen when walletDB is stopped during addBlock.
+        if (height !== bheight)
+          return null;
+
+        const header = await this.db.client.getBlockHeader(bheight);
+
+        if (!header)
+          return null;
 
-      const time = encoding.readU64(data, 32);
+        // double check hash.
+        if (header.hash !== lastHash.toString('hex'))
+          throw new Error('Bad block time response.');
+
+        time = header.time;
+      } else {
+        time = encoding.readU64(data, 32);
+      }
 
-      this.blockTimeCache.set(height, time);
+      this.blockTimeCache.set(bheight, time);
 
       return time;
     };