[wallet] deduplicate GetAvailableCredit logic

Author: jnewbery

src/wallet/wallet.cpp

@@ -1983,6 +1983,9 @@ CAmount CWalletTx::GetAvailableCredit(bool fUseCache, const isminefilter& filter
     if (filter == ISMINE_SPENDABLE) {
         cache = &nAvailableCreditCached;
         cache_used = &fAvailableCreditCached;
+    } else if (filter == ISMINE_WATCH_ONLY) {
+        cache = &nAvailableWatchCreditCached;
+        cache_used = &fAvailableWatchCreditCached;
     }
 
     if (fUseCache && cache_used && *cache_used) {
@@ -2025,31 +2028,7 @@ CAmount CWalletTx::GetImmatureWatchOnlyCredit(const bool fUseCache) const
 
 CAmount CWalletTx::GetAvailableWatchOnlyCredit(const bool fUseCache) const
 {
-    if (pwallet == nullptr)
-        return 0;
-
-    // Must wait until coinbase is safely deep enough in the chain before valuing it
-    if (IsCoinBase() && GetBlocksToMaturity() > 0)
-        return 0;
-
-    if (fUseCache && fAvailableWatchCreditCached)
-        return nAvailableWatchCreditCached;
-
-    CAmount nCredit = 0;
-    for (unsigned int i = 0; i < tx->vout.size(); i++)
-    {
-        if (!pwallet->IsSpent(GetHash(), i))
-        {
-            const CTxOut &txout = tx->vout[i];
-            nCredit += pwallet->GetCredit(txout, ISMINE_WATCH_ONLY);
-            if (!MoneyRange(nCredit))
-                throw std::runtime_error(std::string(__func__) + ": value out of range");
-        }
-    }
-
-    nAvailableWatchCreditCached = nCredit;
-    fAvailableWatchCreditCached = true;
-    return nCredit;
+    return GetAvailableCredit(fUseCache, ISMINE_WATCH_ONLY);
 }
 
 CAmount CWalletTx::GetChange() const