From ddaffc5f3b3e7559926f2c162b9cd2ed18cf0a2f Mon Sep 17 00:00:00 2001
From: Lawrence Wang <l@lw.io>
Date: Mon, 19 Aug 2019 17:57:58 -0700
Subject: [PATCH] add instance cache to CdpManager

---
 packages/dai-plugin-mcd/src/CdpManager.js     | 38 ++++++++++++++++---
 .../dai-plugin-mcd/test/CdpManager.spec.js    |  8 +++-
 2 files changed, 39 insertions(+), 7 deletions(-)

diff --git a/packages/dai-plugin-mcd/src/CdpManager.js b/packages/dai-plugin-mcd/src/CdpManager.js
index 6599b4e57..5f3aa8c4a 100644
--- a/packages/dai-plugin-mcd/src/CdpManager.js
+++ b/packages/dai-plugin-mcd/src/CdpManager.js
@@ -45,8 +45,14 @@ export default class CdpManager extends LocalService {
   }
 
   async getCdp(id, options) {
+    const cacheEnabled = !has(options, 'cache') || options.cache;
+    let cdp = this._getFromInstanceCache(id, cacheEnabled);
+    if (cdp) return cdp;
+
     const ilk = bytesToString(await this._manager.ilks(id));
-    const cdp = new ManagedCdp(id, ilk, this, options);
+    cdp = new ManagedCdp(id, ilk, this, options);
+
+    this._putInInstanceCache(id, cdp, cacheEnabled);
     if (!has(options, 'prefetch') || options.prefetch) await cdp.prefetch();
     return cdp;
   }
@@ -78,25 +84,34 @@ export default class CdpManager extends LocalService {
   }
 
   @tracksTransactions
-  async open(ilk, { promise }) {
+  async open(ilk, { promise, cache = true }) {
     await this.get('proxy').ensureProxy({ promise });
     const op = this.proxyActions.open(
       this._managerAddress,
       stringToBytes(ilk),
       { dsProxy: true, promise }
     );
-    return ManagedCdp.create(await op, ilk, this);
+    const cdp = await ManagedCdp.create(await op, ilk, this);
+    this._putInInstanceCache(cdp.id, cdp, cache);
+    return cdp;
   }
 
   // ilk is required if the currency type corresponds to more than one ilk; if
   // it's omitted, it is inferred from lockAmount's currency type
   @tracksTransactions
-  async openLockAndDraw(ilk, lockAmount, drawAmount, { promise }) {
+  async openLockAndDraw(
+    ilk,
+    lockAmount,
+    drawAmount,
+    { promise, cache = true }
+  ) {
     const type = this.get(CDP_TYPE).getCdpType(lockAmount.type, ilk);
     const op = this.lockAndDraw(null, type.ilk, lockAmount, drawAmount, {
       promise
     });
-    return ManagedCdp.create(await op, type.ilk, this);
+    const cdp = await ManagedCdp.create(await op, type.ilk, this);
+    this._putInInstanceCache(cdp.id, cdp, cache);
+    return cdp;
   }
 
   @tracksTransactionsWithOptions({ numArguments: 5 })
@@ -267,6 +282,19 @@ export default class CdpManager extends LocalService {
       ? 'wei'
       : this.get(CDP_TYPE).getCdpType(amount.type).decimals;
   }
+
+  _getFromInstanceCache(id, enabled) {
+    if (!enabled) return;
+    if (!this._instanceCache) this._instanceCache = {};
+    const instance = this._instanceCache[id];
+    if (instance) return instance;
+  }
+
+  _putInInstanceCache(id, instance, enabled) {
+    if (!enabled) return;
+    if (!this._instanceCache) this._instanceCache = {};
+    this._instanceCache[id] = instance;
+  }
 }
 
 export function setMethod(isEth, id) {
diff --git a/packages/dai-plugin-mcd/test/CdpManager.spec.js b/packages/dai-plugin-mcd/test/CdpManager.spec.js
index 9919f937b..b70a57289 100644
--- a/packages/dai-plugin-mcd/test/CdpManager.spec.js
+++ b/packages/dai-plugin-mcd/test/CdpManager.spec.js
@@ -58,15 +58,19 @@ test('getCombinedDebtValue', async () => {
   expect(totalDebt).toEqual(MDAI(8));
 });
 
-test('getCdp looks up ilk', async () => {
+test('getCdp looks up ilk and has cache', async () => {
   const cdp = await cdpMgr.open('ETH-A');
   const sameCdp = await cdpMgr.getCdp(cdp.id);
   expect(sameCdp.ilk).toEqual(cdp.ilk);
+  expect(cdp).toBe(sameCdp);
+
+  const differentInstance = await cdpMgr.getCdp(cdp.id, { cache: false });
+  expect(differentInstance).not.toBe(cdp);
 });
 
 test('getCdp can disable prefetch', async () => {
   const cdp = await cdpMgr.open('ETH-A');
-  const sameCdp = await cdpMgr.getCdp(cdp.id, { prefetch: false });
+  const sameCdp = await cdpMgr.getCdp(cdp.id, { prefetch: false, cache: false });
   expect(sameCdp._urnInfoPromise).toBeUndefined();
 });