From 42fdb99c1fb6ec0af42167a2b3709a1fa14aa85a Mon Sep 17 00:00:00 2001
From: Andy Jansson <jansson.andy@gmail.com>
Date: Mon, 8 May 2017 19:38:15 +0200
Subject: [PATCH 1/4] Fix consecutive substractions

---
 src/__tests__/index.js | 13 +++++++++++++
 src/lib/reducer.js     |  4 ++--
 2 files changed, 15 insertions(+), 2 deletions(-)

diff --git a/src/__tests__/index.js b/src/__tests__/index.js
index a00f8df..c81ff8d 100644
--- a/src/__tests__/index.js
+++ b/src/__tests__/index.js
@@ -168,6 +168,19 @@ test(
   'calc(1px + 1)'
 )
 
+test(
+  'should reduce consecutive substractions (#24) (1)',
+  testFixture,
+  'calc(100% - 120px - 60px)',
+  'calc(100% - 180px)'
+)
+
+test(
+  'should reduce consecutive substractions (#24) (2)',
+  testFixture,
+  'calc(100% - 10px - 20px)',
+  'calc(100% - 30px)'
+)
 
 test(
   'should produce simpler result (postcss-calc#25) (1)',
diff --git a/src/lib/reducer.js b/src/lib/reducer.js
index 6f1d19f..1822e7d 100644
--- a/src/lib/reducer.js
+++ b/src/lib/reducer.js
@@ -115,12 +115,12 @@ function reduceAddSubExpression(node, precision) {
     // (something + value) + value => something + (value + value)
     // (something - value) + value => something - (value + value)
     // (something + value) - value => something + (value - value)
-    // (something - value) - value => something - (value - value)
+    // (something - value) - value => something - (value + value)
     else if (right.type === left.right.type) {
       node = Object.assign({ }, left)
       node.right = reduce({
         type: 'MathExpression',
-        operator: op,
+        operator: op === left.operator && op === '-' ? '+' : op,
         left: left.right,
         right: right
       }, precision)

From 76e6ea932644221788406e1343099959a98cb635 Mon Sep 17 00:00:00 2001
From: Andy Jansson <jansson.andy@gmail.com>
Date: Mon, 8 May 2017 20:53:16 +0200
Subject: [PATCH 2/4] Fix consecutive additions and substractions

---
 src/__tests__/index.js | 14 ++++++++++++++
 src/lib/reducer.js     | 29 ++++++++++++++++++++++-------
 2 files changed, 36 insertions(+), 7 deletions(-)

diff --git a/src/__tests__/index.js b/src/__tests__/index.js
index c81ff8d..169a054 100644
--- a/src/__tests__/index.js
+++ b/src/__tests__/index.js
@@ -42,6 +42,20 @@ test(
   '1ex'
 )
 
+test(
+  'should reduce additions and subtractions (1)',
+  testFixture,
+  'calc(100% - 10px + 20px)',
+  'calc(100% + 10px)'
+)
+
+test(
+  'should reduce additions and subtractions (2)',
+  testFixture,
+  'calc(100% + 10px - 20px)',
+  'calc(100% - 10px)'
+)
+
 test(
   'should ignore value surrounding calc function (1)',
   testFixture,
diff --git a/src/lib/reducer.js b/src/lib/reducer.js
index 1822e7d..879edc6 100644
--- a/src/lib/reducer.js
+++ b/src/lib/reducer.js
@@ -113,17 +113,32 @@ function reduceAddSubExpression(node, precision) {
       return reduce(node, precision)
     }
     // (something + value) + value => something + (value + value)
-    // (something - value) + value => something - (value + value)
+    // (something - value1) + value2 => something - (value2 - value1)
     // (something + value) - value => something + (value - value)
     // (something - value) - value => something - (value + value)
     else if (right.type === left.right.type) {
       node = Object.assign({ }, left)
-      node.right = reduce({
-        type: 'MathExpression',
-        operator: op === left.operator && op === '-' ? '+' : op,
-        left: left.right,
-        right: right
-      }, precision)
+      if (left.operator === '-') {
+        node.right = reduce({
+          type: 'MathExpression',
+          operator: op === left.operator ? '+' : '-',
+          left: right,
+          right: left.right
+        }, precision)
+        node.operator = op === left.operator ? '-' : '+';
+      }
+      else {
+        node.right = reduce({
+          type: 'MathExpression',
+          operator: op,
+          left: left.right,
+          right: right
+        }, precision)
+      }
+      if (node.right.value < 0) {
+        node.right.value *= -1;
+        node.operator = '-';
+      }
       return reduce(node, precision)
     }
   }

From c975de837075cc0c18df7044895534a44a3bf8c1 Mon Sep 17 00:00:00 2001
From: Andy Jansson <jansson.andy@gmail.com>
Date: Mon, 8 May 2017 21:14:28 +0200
Subject: [PATCH 3/4] fix for inverting operator on negative numbers

---
 src/lib/reducer.js | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/src/lib/reducer.js b/src/lib/reducer.js
index 879edc6..4d9b3d3 100644
--- a/src/lib/reducer.js
+++ b/src/lib/reducer.js
@@ -121,11 +121,11 @@ function reduceAddSubExpression(node, precision) {
       if (left.operator === '-') {
         node.right = reduce({
           type: 'MathExpression',
-          operator: op === left.operator ? '+' : '-',
+          operator: op === '-' ? '+' : '-',
           left: right,
           right: left.right
         }, precision)
-        node.operator = op === left.operator ? '-' : '+';
+        node.operator = op === '-' ? '-' : '+';
       }
       else {
         node.right = reduce({
@@ -137,7 +137,7 @@ function reduceAddSubExpression(node, precision) {
       }
       if (node.right.value < 0) {
         node.right.value *= -1;
-        node.operator = '-';
+        node.operator = node.operator === '-' ? '+' : '-';
       }
       return reduce(node, precision)
     }

From 4718d9b1262fb82c37a251396e4f341741e15a44 Mon Sep 17 00:00:00 2001
From: Andy Jansson <jansson.andy@gmail.com>
Date: Mon, 8 May 2017 21:19:07 +0200
Subject: [PATCH 4/4] Add additional test

---
 src/__tests__/index.js | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/src/__tests__/index.js b/src/__tests__/index.js
index 169a054..11fc629 100644
--- a/src/__tests__/index.js
+++ b/src/__tests__/index.js
@@ -42,6 +42,13 @@ test(
   '1ex'
 )
 
+test(
+  'should reduce simple calc (5)',
+  testFixture,
+  'calc(50px - (20px - 30px))',
+  '60px'
+)
+
 test(
   'should reduce additions and subtractions (1)',
   testFixture,