generate empty workbook if no data to add

.gitignore

@@ -5,4 +5,8 @@
 json2excel
 
 # Ignore test data
-*.json
+*.json
+
+# Ignore Mac DS_Store files
+.DS_Store
+**/.DS_Store

README.md

@@ -14,3 +14,14 @@ It expects that the json input is formatted as an object containing an array of
 | freezeTopRow | true | Freezes the first row of the Excel worksheet |
 | autofilter | true | Sets the auto filter on the first row |
 | autowidth | true | Automatically set the column width to fit contents |
+| overwriteFile | false | Overwrite any existing output file instead of modifying in-place |
+
+## Advanced configuration
+
+Advanced settings can be provided via a top level json key named "config". Here is a table of options that can be set via this config key.
+
+| Key     | Example Value | Description               |
+|---------------|---------------|---------------------------|
+| keyOrder | "Column3,Column1,Column2"| Comma separated list of column names in the desired order |
+| overwriteFile | true | Boolean indicating whether output file should be overwritten if it already exists |
+| parentNode | "results" | Specify an alternate starting key for the spreadsheet data than just the first non-config key. Useful with json structures with multiple top-level keys |

cmd/main/main.go

@@ -6,6 +6,8 @@ import (
 	"fmt"
 	"log"
 	"os"
+	"reflect"
+	"strings"
 	"time"
 	"unicode/utf8"
 
@@ -15,9 +17,17 @@ import (
 
 // Initial concept from https://stackoverflow.com/q/68621039
 
+type Config struct {
+	keyOrder       map[int]string
+	parentOverride string
+}
+
+var config Config
+
 func main() {
 	//jsonFile := "test.json"
 	parentNode := "input"
+	configNode := "config"
 	//worksheetName := "Sheet2"
 	//outputFilename := "test.xlsx"
 
@@ -54,6 +64,115 @@ func main() {
 	// Truncate worksheetName to the maximum 31 characters
 	worksheetName = TruncateString(worksheetName, 31)
 
+	// Read the json input file
+	if fileExists(inputJson) {
+		s, err = os.ReadFile(inputJson)
+		if err != nil {
+			panic(err)
+		}
+	} else {
+		fmt.Printf("Input JSON file '%s' does not exist.\n", inputJson)
+		os.Exit(1)
+	}
+
+	// Unmarshal the json into an orderedmap to preserve the ordering of json structure
+	o := orderedmap.New()
+	err = json.Unmarshal([]byte(s), &o)
+	if err != nil {
+		error := fmt.Sprintf("JSON Unmarshal error %s\n", err)
+		panic(error)
+	}
+
+	// Assume that our content is within the first top-level key
+	topLevel := o.Keys()
+	fmt.Printf("Found %d top-level keys in json data\n", len(topLevel))
+	for i, key := range topLevel {
+		fmt.Printf("[%d] : %s\n", i, key)
+	}
+
+	// Check for config embedded in json
+	if strings.EqualFold(topLevel[0], configNode) && len(topLevel) > 1 {
+		fmt.Printf("Found configNode as toplevel json key, setting parentNode as '%s'\n", topLevel[1])
+		parentNode = topLevel[1]
+
+		config.keyOrder = make(map[int]string)
+
+		// Get a reference to the top level node we specified earlier
+		configInterface, ok := o.Get(configNode)
+		if !ok {
+			fmt.Printf("Missing key for multitype array when reading embedded config")
+		}
+
+		// Get an interface that we can work with to access the sub elements
+		// This doesn't seem necessary for some reason - maybe because there's only one level of depth to the configNode
+		//configSlice := configInterface
+		//fmt.Printf("%v\n", configSlice)
+
+		// Get the keys for the first element so we know what config options have been specified
+		configMap := configInterface.(orderedmap.OrderedMap)
+		configKeys := configMap.Keys()
+
+		// Parse each key into our config struct
+		for _, key := range configKeys {
+			if strings.EqualFold(key, "keyOrder") {
+				fmt.Printf("Found config element for keyOrder\n")
+				e, _ := configMap.Get(key)
+				for i, e := range strings.Split(e.(string), ",") {
+					config.keyOrder[i] = e
+				}
+				fmt.Printf("Column order is now : '%v'\n", config.keyOrder)
+			} else if strings.EqualFold(key, "overwriteFile") {
+				fmt.Printf("Found config element for overwriting output file\n")
+				e, _ := configMap.Get(key)
+				overwriteFile = e.(bool)
+			} else if strings.EqualFold(key, "parentNode") {
+				fmt.Printf("Found config element for forcing parent key for spreadsheet data\n")
+				e, _ := configMap.Get(key)
+				config.parentOverride = e.(string)
+			}
+		}
+	} else if strings.EqualFold(topLevel[0], configNode) {
+		error := "Only found config in first level of json keys"
+		panic(error)
+	} else {
+		fmt.Printf("Detected toplevel json key as: '%s'\n", topLevel[0])
+		parentNode = topLevel[0]
+	}
+
+	if config.parentOverride != "" {
+		fmt.Printf("Overriding parent node to '%s'\n", config.parentOverride)
+		parentNode = config.parentOverride
+	}
+
+	// Get a reference to the top level node we specified earlier
+	vislice, ok := o.Get(parentNode)
+	if !ok {
+		fmt.Printf("Missing key for multitype array")
+	}
+
+	// Get an interface that we can work with to access the sub elements
+	vslice := vislice.([]interface{})
+
+	if len(vslice) < 1 {
+		// There was no data but lets just log that and close off the empty workbook
+		fmt.Printf("No data found contained in top-level json key '%s', no work to do.\n", parentNode)
+		// Close off the file
+		if err := xlsx.SaveAs(outputFilename); err != nil {
+			log.Fatal(err)
+		}
+		return
+	}
+
+	// Check that the first element is what we expected
+	if _, ok := vslice[0].(orderedmap.OrderedMap); !ok {
+		error := fmt.Sprintf("Type of first vslice element is not an ordered map. It appears to be '%v'\n", reflect.TypeOf(vslice[0]))
+		panic(error)
+	}
+	// Get the keys for the first element so we know what the column names will be
+	columnMap := vslice[0].(orderedmap.OrderedMap)
+	//fmt.Printf("First vslice element is an ordered map\n")
+	columnNames := columnMap.Keys()
+
 	// Check if xlsx file exists already, and if it does then open and append data
 	if fileExists(outputFilename) {
 		if overwriteFile {
@@ -74,41 +193,6 @@ func main() {
 		xlsx = createWorkbook(worksheetName, outputFilename)
 	}
 
-	// Read the json input file
-	if fileExists(inputJson) {
-		s, err = os.ReadFile(inputJson)
-		if err != nil {
-			panic(err)
-		}
-	} else {
-		fmt.Printf("Input JSON file '%s' does not exist.\n", inputJson)
-		os.Exit(1)
-	}
-
-	// Unmarshal the json into an orderedmap to preserve the ordering of json structure
-	o := orderedmap.New()
-	err = json.Unmarshal([]byte(s), &o)
-	if err != nil {
-		fmt.Printf("JSON Unmarshal error %s\n", err)
-	}
-
-	// Assume that our content is within the first top-level key
-	topLevel := o.Keys()
-	fmt.Printf("Detected toplevel json key as: '%s'\n", topLevel[0])
-	parentNode = topLevel[0]
-
-	// Get a reference to the top level node we specified earlier
-	vislice, ok := o.Get(parentNode)
-	if !ok {
-		fmt.Printf("Missing key for multitype array")
-	}
-	// Get an interface that we can work with to access the sub elements
-	vslice := vislice.([]interface{})
-
-	// Get the keys for the first element so we know what the column names will be
-	columnMap := vslice[0].(orderedmap.OrderedMap)
-	columnNames := columnMap.Keys()
-
 	// Run code to add column names to the first row of the workbook
 	createHeadingRow(xlsx, worksheetName, columnNames)
 
@@ -178,23 +262,37 @@ func main() {
 		// Each iteration should start back at column 1
 		column = 1
 
-		// Print each key-value pair contained in this slice
+		// Get the key-value pairs contained in this slice
 		vmap := v.(orderedmap.OrderedMap)
 		k := vmap.Keys()
 
-		for j := range k {
-			//a = string(asciiValue)
-			//cell = a + strconv.Itoa(2+i)
-			cell, _ = excelize.CoordinatesToCellName(column, row)
+		if len(config.keyOrder) > 0 {
+			// If we have a specified order for the values then use that
 
-			e, _ := vmap.Get(k[j])
-			//fmt.Printf("Setting cell %s to value %v\n", cell, e)
-			xlsx.SetCellValue(worksheetName, cell, e)
+			for j := 0; j < len(config.keyOrder); j++ {
+				cell, _ = excelize.CoordinatesToCellName(column, row)
 
-			// Move to the next column
-			//asciiValue++
-			column++
+				e, _ := vmap.Get(config.keyOrder[j])
+				//fmt.Printf("Setting cell %s to value %v\n", cell, e)
+				xlsx.SetCellValue(worksheetName, cell, e)
+
+				// Move to the next column
+				column++
+			}
+		} else {
+			// Otherwise use the order the json was in
+			for j := range k {
+				cell, _ = excelize.CoordinatesToCellName(column, row)
+
+				e, _ := vmap.Get(k[j])
+				//fmt.Printf("Setting cell %s to value %v\n", cell, e)
+				xlsx.SetCellValue(worksheetName, cell, e)
+
+				// Move to the next column
+				column++
+			}
 		}
+
 		//fmt.Printf("k: %v\n", k)
 
 		// Move to next row
@@ -314,19 +412,37 @@ func modifyWorkbook(worksheetName string, outputFilename string) *excelize.File
 }
 
 func createHeadingRow(xlsx *excelize.File, worksheetName string, columnNames []string) {
-	fmt.Printf("Creating excel workbook with following headings : '%v'\n", columnNames)
 	var cell string
 	row := 1
 	column := 1
 
-	// Add the header row
-	for i := 0; i < len(columnNames); i++ {
-		cell, _ = excelize.CoordinatesToCellName(column, row)
-		fmt.Printf("Setting cell %s to value %s\n", cell, columnNames[i])
-		xlsx.SetCellValue(worksheetName, cell, columnNames[i])
-		//xlsx.SetCellStyle(worksheetName, cell, cell, headerStyle)
-		column++
+	if len(config.keyOrder) > 0 {
+		fmt.Printf("Creating excel workbook with heading order as per config key-order\n")
+		// Check that the number of specified columns matches input data
+		if len(config.keyOrder) != len(columnNames) {
+			error := fmt.Sprintf("Column order specified in json key-order but mismatch found in json data. %d specifed columns does not match %d found columns.", len(config.keyOrder), len(columnNames))
+			panic(error)
+		}
+
+		// Iterate the map and add the columns as per that order
+		for i := 0; i < len(config.keyOrder); i++ {
+			cell, _ = excelize.CoordinatesToCellName(column, row)
+			fmt.Printf("Setting cell %s to value %s at index %d\n", cell, config.keyOrder[i], i)
+			xlsx.SetCellValue(worksheetName, cell, config.keyOrder[i])
+			column++
+		}
+	} else {
+		fmt.Printf("Creating excel workbook with following headings : '%v'\n", columnNames)
+		// Add the header row
+		for i := 0; i < len(columnNames); i++ {
+			cell, _ = excelize.CoordinatesToCellName(column, row)
+			fmt.Printf("Setting cell %s to value %s\n", cell, columnNames[i])
+			xlsx.SetCellValue(worksheetName, cell, columnNames[i])
+			//xlsx.SetCellStyle(worksheetName, cell, cell, headerStyle)
+			column++
+		}
 	}
+
 }
 
 // Taken from https://github.com/qax-os/excelize/issues/92#issuecomment-821578446
@@ -344,7 +460,7 @@ func SetColAutoWidth(xlsx *excelize.File, sheetName string) error {
 				largestWidth = cellWidth
 			}
 		}
-		fmt.Printf("SetColAutoWidth calculated largest width is '%d'\n", largestWidth)
+		fmt.Printf("SetColAutoWidth calculated largest width for column index '%d' is '%d'\n", idx, largestWidth)
 		name, err := excelize.ColumnNumberToName(idx + 1)
 		if err != nil {
 			return err