built converter

Will probably need to spend more time in the future rebuilding regex to
check for only scientific notation.

main.go

@@ -0,0 +1,145 @@
+package main
+
+import (
+	"bufio"
+	"fmt"
+	"os"
+	"regexp"
+	"strconv"
+	"strings"
+
+	"github.com/pterm/pterm"
+	"github.com/schollz/progressbar/v3"
+)
+
+func main() {
+	// Set Welcome Header
+	// pterm.DefaultHeader.WithBackgroundStyle(pterm.NewStyle(pterm.BgCyan)).WithTextStyle(pterm.NewStyle(pterm.FgBlack)).Println("Welcome to Checkdigit Calculator")
+
+	pterm.DefaultSection.Printfln(pterm.Cyan("Welcome to Scientific Notation Converter"))
+
+	// Check what directory the commandline is on when the program is launched.
+	directory, err := os.Getwd()
+	Error(err)
+
+	// Get name of file to be processed.
+	args := os.Args[1:]
+
+	var input string
+
+	if len(args) > 0 {
+		input = args[0]
+	} else {
+		pterm.Printf(pterm.LightGreen("What is the name of the file in this directory?: "))
+		reader := bufio.NewReader(os.Stdin)
+		input, err = reader.ReadString('\n')
+		Error(err)
+	}
+
+	// Create upcs array and push all upc strings into it
+	input = strings.TrimSpace(input)
+	file, err := os.Open(input)
+	Error(err)
+	var upcs []string
+	scanner := bufio.NewScanner(file)
+	for scanner.Scan() {
+		upcs = append(upcs, scanner.Text())
+	}
+	err = file.Close()
+	Error(err)
+	if scanner.Err() != nil {
+		fmt.Println(scanner.Err())
+	}
+
+	// Create gtins array that will eventually be returned
+	var gtins []string
+
+	// Using regex compile so the program stays fast
+	regex, err := regexp.Compile("^[^0-9]")
+	Error(err)
+
+	checkBar := progressbar.NewOptions(len(upcs),
+		progressbar.OptionEnableColorCodes(true),
+		progressbar.OptionSetDescription("[cyan][1/2][reset] Converting Scientific Notation Number..."),
+		progressbar.OptionUseANSICodes(true),
+		progressbar.OptionSetTheme(progressbar.Theme{
+			Saucer:        "[green]=[reset]",
+			SaucerHead:    "[green]>[reset]",
+			SaucerPadding: " ",
+			BarStart:      "[",
+			BarEnd:        "]",
+		}))
+
+	for _, upc := range upcs {
+		checkForNonStartingNumber := regex.MatchString(upc)
+
+		if checkForNonStartingNumber {
+			gtins = append(gtins, upc)
+			continue
+		}
+
+		// Split scientific notation at the e+ point
+		upcArray := strings.Split(upc, "e+")
+
+		fmt.Println(upcArray)
+
+		// Create separate variables for the split values
+		workingUpc := upcArray[0]
+		upcENumber := upcArray[1]
+
+		// At one to the scientific notation length to allow for the decimal point to be removed
+		upcLength, err := strconv.Atoi(upcENumber)
+		Error(err)
+		upcLength = upcLength + 1
+
+		// Remove the decimal point
+		workingUpc = strings.ReplaceAll(workingUpc, ".", "")
+
+		// Append 0 to UPC to match notation length
+		for len(workingUpc) < upcLength {
+			workingUpc = workingUpc + "0"
+		}
+
+		upc = workingUpc
+
+		gtins = append(gtins, upc)
+		checkBar.Add(1)
+	}
+
+	answerBar := progressbar.NewOptions(len(gtins),
+		progressbar.OptionEnableColorCodes(true),
+		progressbar.OptionSetDescription("[cyan][2/2][reset] Writing answers into file..."),
+		progressbar.OptionUseANSICodes(true),
+		progressbar.OptionClearOnFinish(),
+		progressbar.OptionSetTheme(progressbar.Theme{
+			Saucer:        "[green]=[reset]",
+			SaucerHead:    "[green]>[reset]",
+			SaucerPadding: " ",
+			BarStart:      "[",
+			BarEnd:        "]",
+		}))
+
+	// Check if answer.txt already exists and if so, delete it
+	if _, err := os.Stat(directory + "/answer.txt"); err == nil {
+		e := os.Remove(directory + "/answer.txt")
+		Error(e)
+	}
+
+	// Create new answer.txt
+	answerFile, err := os.Create(directory + "/answer.txt")
+	Error(err)
+
+	defer answerFile.Close()
+
+	// Fill the answers.txt file
+	for _, gtin := range gtins {
+		_, err := answerFile.WriteString(gtin + "\n")
+		Error(err)
+		answerBar.Add(1)
+	}
+
+	// Print Success message and exit
+	pterm.Printf("\n")
+	pterm.Success.Println("The answer.txt file has been successfully generated with check digits.")
+	os.Exit(0)
+}