From bfd44fa7ef37519fa56972db0c6a715d54c9dad1 Mon Sep 17 00:00:00 2001
From: Tobias Kessels <tobiasoliverkessels@bundeswehr.org>
Date: Thu, 1 Aug 2024 16:13:12 +0200
Subject: [PATCH] Add gobetbeen.go as a golang replacement for between

---
 tools/go/gobetween/gobetween.go | 122 ++++++++++++++++++++++++++++++++
 1 file changed, 122 insertions(+)
 create mode 100644 tools/go/gobetween/gobetween.go

diff --git a/tools/go/gobetween/gobetween.go b/tools/go/gobetween/gobetween.go
new file mode 100644
index 0000000..c084486
--- /dev/null
+++ b/tools/go/gobetween/gobetween.go
@@ -0,0 +1,122 @@
+package main
+
+import (
+	"bufio"
+	"flag"
+	"fmt"
+	"log"
+	"os"
+	"regexp"
+	"strconv"
+	"strings"
+)
+
+func parseArgs(args []string) (int, int, string, error) {
+	var filename string
+	var start, length, end int
+	found := false
+
+	// Concatenate all arguments to a single string for easier parsing
+	joinedArgs := strings.Join(args, " ")
+
+	// Regular expression to match ranges and numbers
+	rangeRegex := regexp.MustCompile(`((\d+)?([ :,;-]))(\+)?(\d+)`)
+	range2Regex := regexp.MustCompile(`((\d+)([ :,;-]))`)
+	range3Regex := regexp.MustCompile(`(\+)?(\d+)`)
+
+	matches := rangeRegex.FindStringSubmatch(joinedArgs)
+
+	if matches != nil {
+		//check if start was defined
+		if matches[2] != "" {
+			start, _ = strconv.Atoi(matches[2]) // Convert start line to integer
+		} else {
+			start = 1
+		}
+		if matches[4] == "+" { // Check if it's a relative length
+			length, _ = strconv.Atoi(matches[5]) // Convert length to integer
+			end = start + length - 1
+		} else {
+			end, _ = strconv.Atoi(matches[5]) // Convert end line to integer
+		}
+		// Remove the matched part from the arguments
+		joinedArgs = strings.Replace(joinedArgs, matches[0], "", 1)
+		found = true
+	} else {
+		matches = range2Regex.FindStringSubmatch(joinedArgs)
+		if matches != nil {
+			start, _ = strconv.Atoi(matches[2]) // Convert start line to integer
+			end = -1
+			// Remove the matched part from the arguments
+			joinedArgs = strings.Replace(joinedArgs, matches[0], "", 1)
+			found = true
+		} else {
+			matches = range3Regex.FindStringSubmatch(joinedArgs)
+			if matches != nil {
+				if matches[1] == "+" { // Check if it's a relative length
+					length, _ := strconv.Atoi(matches[2]) // Convert length to integer
+					start = 1
+					end = start + length - 1
+				} else { // Otherwise convert it to an absolute length
+					start, _ = strconv.Atoi(matches[2]) // Convert start line to integer
+					end = -1
+					// Remove the matched part from the arguments
+				}
+				joinedArgs = strings.Replace(joinedArgs, matches[0], "", 1)
+				found = true
+			} else {
+				found = false
+				log.Fatal("No match found")
+			}
+		}
+	}
+
+	// Clean up and identify the filename, if present
+	joinedArgs = strings.TrimSpace(joinedArgs)
+	if joinedArgs != "" && !found {
+		// If we didn't find numbers, interpret the remaining as filename
+		filename = joinedArgs
+	} else if joinedArgs != "" {
+		// Otherwise, interpret any non-empty remaining part as filename
+		filename = joinedArgs
+	}
+
+	if !found {
+		return 0, 0, "", fmt.Errorf("no valid range or line number found")
+	}
+
+	return start, end, filename, nil
+}
+
+func main() {
+	flag.Parse()
+	args := flag.Args()
+
+	startIndex, endIndex, filename, err := parseArgs(args)
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "Error parsing arguments: %v\n", err)
+		os.Exit(1)
+	}
+
+	// Detemine the input source (file or stdin)
+	inputSource := os.Stdin
+	if filename != "" {
+		inputSource, err = os.Open(filename)
+		if err != nil {
+			log.Fatalf("Failed to open file: %v\n", err)
+		}
+		defer inputSource.Close()
+	}
+
+	scanner := bufio.NewScanner(inputSource)
+	//print all lines from line buner start to linenumber end unless linenumber end is -1
+	for i := 1; scanner.Scan(); i++ {
+		if startIndex <= i && (i <= endIndex || endIndex == -1) {
+			fmt.Println(scanner.Text())
+		}
+	}
+	if err := scanner.Err(); err != nil {
+		log.Fatal(err)
+	}
+
+}