From 0811b653bd20f08f98b6412e587f8b2360d6e55c Mon Sep 17 00:00:00 2001
From: Lucas Barrena <lucasbarrena98@gmail.com>
Date: Mon, 14 Aug 2023 14:12:11 -0300
Subject: [PATCH] Allow modifying next.value

---
 index.js    |  5 ++---
 test/cas.js | 56 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 58 insertions(+), 3 deletions(-)

diff --git a/index.js b/index.js
index 9079b68..1434026 100644
--- a/index.js
+++ b/index.js
@@ -741,7 +741,6 @@ class Batch {
       value
     }
     key = enc(encoding.key, key)
-    value = enc(encoding.value, value)
 
     const stack = []
 
@@ -768,7 +767,7 @@ class Batch {
           if (cas && !(await cas((await node.getKeyNode(mid)).final(encoding), newNode))) return this._unlockMaybe()
 
           node.setKey(mid, target)
-          return this._append(root, seq, key, value)
+          return this._append(root, seq, key, enc(encoding.value, newNode.value))
         }
 
         if (c < 0) e = mid
@@ -798,7 +797,7 @@ class Batch {
       }
     }
 
-    return this._append(root, seq, key, value)
+    return this._append(root, seq, key, enc(encoding.value, newNode.value))
   }
 
   async del (key, opts) {
diff --git a/test/cas.js b/test/cas.js
index 101f0f4..72bdcfc 100644
--- a/test/cas.js
+++ b/test/cas.js
@@ -2,6 +2,62 @@ const test = require('brittle')
 const b4a = require('b4a')
 const { create } = require('./helpers')
 
+test('cas - swap with a new value', async function (t) {
+  const db = create({ valueEncoding: 'json' })
+
+  await db.put('/a', 0, {
+    cas: function (prev, next) {
+      t.is(prev, null)
+      t.alike(next, { seq: 1, key: '/a', value: 0 })
+      return next
+    }
+  })
+
+  t.alike(await db.get('/a'), { seq: 1, key: '/a', value: 0 })
+
+  await db.put('/a', 99, {
+    cas: function (prev, next) {
+      t.alike(prev, { seq: 1, key: '/a', value: 0 })
+      t.alike(next, { seq: 2, key: '/a', value: 99 })
+      next.value = prev.value + 1 // Overwrites so it's not 99 anymore
+      return next
+    }
+  })
+
+  t.alike(await db.get('/a'), { seq: 2, key: '/a', value: 1 })
+
+  await db.put('/a', 99, {
+    cas: function (prev, next) {
+      t.alike(prev, { seq: 2, key: '/a', value: 1 })
+      t.alike(next, { seq: 3, key: '/a', value: 99 })
+      next.value = prev.value + 1
+      return next
+    }
+  })
+
+  t.alike(await db.get('/a'), { seq: 3, key: '/a', value: 2 })
+})
+
+test('cas - should not swap', async function (t) {
+  t.plan(4)
+
+  const db = create({ valueEncoding: 'json' })
+
+  await db.put('/a', 1)
+
+  t.alike(await db.get('/a'), { seq: 1, key: '/a', value: 1 })
+
+  await db.put('/a', 2, {
+    cas: function (prev, next) {
+      t.alike(prev, { seq: 1, key: '/a', value: 1 })
+      t.alike(next, { seq: 2, key: '/a', value: 2 })
+      return null
+    }
+  })
+
+  t.alike(await db.get('/a'), { seq: 1, key: '/a', value: 1 })
+})
+
 test('cas is called when prev does not exists', async function (t) {
   t.plan(6)