From fb9a357e1652b4d7d619f48f2315c863ff60152f Mon Sep 17 00:00:00 2001
From: Piotr Zawadzki <piotr.zawadzki@tomtom.com>
Date: Fri, 1 Nov 2019 23:26:34 +0100
Subject: [PATCH 1/3] Improve performance of writeFile  by reducing number of
 styles coversion (use weekMap)

---
 lib/xlsx/xform/style/styles-xform.js | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/lib/xlsx/xform/style/styles-xform.js b/lib/xlsx/xform/style/styles-xform.js
index e8b7235d7..97db808fe 100644
--- a/lib/xlsx/xform/style/styles-xform.js
+++ b/lib/xlsx/xform/style/styles-xform.js
@@ -82,6 +82,8 @@ class StylesXform extends BaseXform {
     // add default fills
     this._addFill({type: 'pattern', pattern: 'none'});
     this._addFill({type: 'pattern', pattern: 'gray125'});
+
+    this.weakMap = new Map()
   }
 
   render(xmlStream, model) {

From 1abe9bbcad7f2c8334db5cde1bedeff6cd00c60c Mon Sep 17 00:00:00 2001
From: Piotr Zawadzki <piotr.zawadzki@tomtom.com>
Date: Sat, 2 Nov 2019 16:26:01 +0100
Subject: [PATCH 2/3] Optimize generated excel with data validation - reduce
 number of entries (it makes excel opens generated file much faster)

---
 .../xform/sheet/data-validations-xform.js     | 54 +++++++++++++++++--
 1 file changed, 51 insertions(+), 3 deletions(-)

diff --git a/lib/xlsx/xform/sheet/data-validations-xform.js b/lib/xlsx/xform/sheet/data-validations-xform.js
index 1495165d3..b4a4b50dc 100644
--- a/lib/xlsx/xform/sheet/data-validations-xform.js
+++ b/lib/xlsx/xform/sheet/data-validations-xform.js
@@ -28,17 +28,65 @@ function assignBool(definedName, attributes, name, defaultValue) {
   }
 }
 
+function mergeDataValidations(model) {
+  const valueAddressesMap = new Map();
+  _.each(model, (value, address) => {
+    const key = JSON.stringify(value);
+    let mapPerColumn = valueAddressesMap.get(key);
+    if (!mapPerColumn) {
+      mapPerColumn = new Map();
+      valueAddressesMap.set(key, mapPerColumn);
+    }
+
+    const columnNo = address.match(/[A-Z]+/)[0];
+    const rowNo = parseInt(address.match(/\d+/)[0], 10);
+
+    let rowArray = mapPerColumn.get(columnNo);
+    if (!rowArray) {
+      rowArray = [];
+      mapPerColumn.set(columnNo, rowArray);
+    }
+    rowArray.push(rowNo);
+  });
+
+  const mergedResults = {};
+  valueAddressesMap.forEach((columnsMap, formulaeValue) => {
+    columnsMap.forEach((rows, columnNo) => {
+      const sortedRowNumbers = rows.sort((a, b) => a - b);
+      const arrayOfRanges = [];
+      sortedRowNumbers.forEach(rowNum => {
+        const previousNumber = arrayOfRanges.length > 0 ? arrayOfRanges[arrayOfRanges.length - 1].max : null;
+        if (previousNumber && previousNumber === rowNum - 1) {
+          arrayOfRanges[arrayOfRanges.length - 1].max = rowNum;
+        } else {
+          arrayOfRanges.push({min: rowNum, max: rowNum});
+        }
+      });
+      arrayOfRanges.forEach(range => {
+        if (range.min === range.max) {
+          mergedResults[`${columnNo}${range.min}`] = JSON.parse(formulaeValue);
+        } else {
+          mergedResults[`${columnNo}${range.min}:${columnNo}${range.max}`] = JSON.parse(formulaeValue);
+        }
+      });
+    });
+  });
+
+  return mergedResults;
+}
+
 class DataValidationsXform extends BaseXform {
   get tag() {
     return 'dataValidations';
   }
 
   render(xmlStream, model) {
-    const count = model && Object.keys(model).length;
+    const optimizedModel = mergeDataValidations(model);
+    const count = optimizedModel && Object.keys(optimizedModel).length;
     if (count) {
       xmlStream.openNode('dataValidations', {count});
 
-      _.each(model, (value, address) => {
+      _.each(optimizedModel, (value, address) => {
         xmlStream.openNode('dataValidation');
         if (value.type !== 'any') {
           xmlStream.addAttribute('type', value.type);
@@ -75,7 +123,7 @@ class DataValidationsXform extends BaseXform {
         (value.formulae || []).forEach((formula, index) => {
           xmlStream.openNode(`formula${index + 1}`);
           if (value.type === 'date') {
-            xmlStream.writeText(utils.dateToExcel(formula));
+            xmlStream.writeText(utils.dateToExcel(new Date(formula)));
           } else {
             xmlStream.writeText(formula);
           }

From 2c3acb726a985a33bc2bc80a3ff20c6cfb8eca8f Mon Sep 17 00:00:00 2001
From: Piotr Zawadzki <piotr.zawadzki@tomtom.com>
Date: Tue, 5 Nov 2019 10:24:30 +0100
Subject: [PATCH 3/3] StylesXform - use WeakMap instead Map

---
 lib/xlsx/xform/style/styles-xform.js | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lib/xlsx/xform/style/styles-xform.js b/lib/xlsx/xform/style/styles-xform.js
index 97db808fe..1c67edc8f 100644
--- a/lib/xlsx/xform/style/styles-xform.js
+++ b/lib/xlsx/xform/style/styles-xform.js
@@ -83,7 +83,7 @@ class StylesXform extends BaseXform {
     this._addFill({type: 'pattern', pattern: 'none'});
     this._addFill({type: 'pattern', pattern: 'gray125'});
 
-    this.weakMap = new Map()
+    this.weakMap = new WeakMap();
   }
 
   render(xmlStream, model) {