From bf2e281787e303f29f5f06baf8779716b7b7b57f Mon Sep 17 00:00:00 2001
From: Matias Alejo Garcia <ematiu@gmail.com>
Date: Thu, 2 Nov 2017 10:35:34 -0300
Subject: [PATCH] WIP short address cache

---
 lib/common/defaults.js |  6 +++++
 lib/server.js          | 16 +++++++++--
 lib/storage.js         | 60 ++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 80 insertions(+), 2 deletions(-)

diff --git a/lib/common/defaults.js b/lib/common/defaults.js
index 30444b5..4181ef7 100644
--- a/lib/common/defaults.js
+++ b/lib/common/defaults.js
@@ -96,6 +96,12 @@ Defaults.CONFIRMATIONS_TO_START_CACHING = 6 * 6; // ~ 6hrs
 // Number of addresses from which tx history is enabled in a wallet
 Defaults.HISTORY_CACHE_ADDRESS_THRESOLD = 100;
 
+// Number of addresses from which balance in cache for a few seconds
+Defaults.BALANCE_CACHE_ADDRESS_THRESOLD = Defaults.HISTORY_CACHE_ADDRESS_THRESOLD;
+
+// Duration in seconds of the balance cache
+Defaults.BALANCE_CACHE_DURATION = 5
+
 // Cache time for blockchain height (in seconds)
 Defaults.BLOCKHEIGHT_CACHE_TIME = 10 * 60;
 
diff --git a/lib/server.js b/lib/server.js
index ac953f5..7f1ef7e 100644
--- a/lib/server.js
+++ b/lib/server.js
@@ -1243,11 +1243,18 @@ WalletService.prototype._totalizeUtxos = function(utxos) {
 
 WalletService.prototype._getBalanceFromAddresses = function(opts, cb, i) {
   var self = this;
-
   var opts = opts || {};
+  var isBig = opts.addresses.length > Default.BALANCE_CACHE_ADDRESS_THRESOLD;
 
   // This lock is to prevent server starvation on big wallets
   self._runLocked(cb, function(cb) {
+
+    if (isBig && self.storage.checkAndUseBalanceCache(addresses,cb))
+      log.info('Using UTXO Cache');
+      return;
+    }
+
+
     self._getUtxosForCurrentWallet({
       coin: opts.coin,
       addresses: opts.addresses
@@ -1271,7 +1278,12 @@ WalletService.prototype._getBalanceFromAddresses = function(opts, cb, i) {
       });
 
       balance.byAddress = _.values(byAddress);
-      return cb(null, balance);
+
+      if (isBig) {
+        return self.storage.storeBalanceCache(addresses, balance, cb);
+      } else {
+        return cb(null, balance);
+      }
     });
   });
 };
diff --git a/lib/storage.js b/lib/storage.js
index fe0ee75..3e6a691 100644
--- a/lib/storage.js
+++ b/lib/storage.js
@@ -7,6 +7,7 @@ var log = require('npmlog');
 log.debug = log.verbose;
 log.disableColor();
 var util = require('util');
+var Bitcore = require('bitcore-lib');
 
 var mongodb = require('mongodb');
 
@@ -1065,5 +1066,64 @@ Storage.prototype._dump = function(cb, fn) {
   });
 };
 
+
+Storage.prototype._addressHash = function(addresses) {
+  var all = addresses.join();
+  return Bitcore.crypto.Hash.ripemd160(new Buffer(all)).toString('hex');
+};
+
+Storage.prototype.checkAndUseBalanceCache = function(addresses, cb) {
+  var key = ths._addressHash(addresses);
+  var now = Date.now();
+
+  self.db.collection(collections.CACHE).findOne({
+    walletId: walletId,
+    type: 'balanceCache',
+    key: key,
+  }, function(err, ret) {
+    if (err) return cb(err);
+    if (!ret) return cb();
+
+    var validFor = ret.ts + Defauls.BALANCE_CACHE_DURATION * 1000 - now;
+
+    if (validFor > 0)  {
+      log.debug('','Using Balance Cache valid for %d ms more', validFor); 
+      return cb(null, ret.result);
+    }
+
+    return cb();
+
+    log.debug('','Balance cache expired, deleting'); 
+    self.db.collection(collections.CACHE).remove({
+      walletId: walletId,
+      type: 'balanceCache',
+      key: key,
+    }, {},  function() {
+    });
+  });
+});
+
+
+
+Storage.prototype.storeBalanceCache = function (addresses, balance, cb) {
+  var key = ths._addressHash(addresses);
+  var now = Date.now();
+
+  self.db.collection(collections.CACHE).update( { 
+    walletId: walletId,
+    type: 'balanceCache',
+    key: key,
+  }, {
+    "$set":
+    { 
+      ts: now,
+      result: balance,
+    }
+  }, {
+    w: 1,
+    upsert: true,
+  }, cb);
+};
+
 Storage.collections = collections;
 module.exports = Storage;