From 4fb6ac01403405c7ed2b6299a544362f3b467b15 Mon Sep 17 00:00:00 2001
From: Holger Obermaier <40787752+ho-ob@users.noreply.github.com>
Date: Tue, 29 Nov 2022 14:04:31 +0100
Subject: [PATCH] Add hostlist package

---
 pkg/hostlist/hostlist.go | 125 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 125 insertions(+)
 create mode 100644 pkg/hostlist/hostlist.go

diff --git a/pkg/hostlist/hostlist.go b/pkg/hostlist/hostlist.go
new file mode 100644
index 0000000..6ed5ae0
--- /dev/null
+++ b/pkg/hostlist/hostlist.go
@@ -0,0 +1,125 @@
+package hostlist
+
+import (
+	"fmt"
+	"regexp"
+	"sort"
+	"strconv"
+	"strings"
+)
+
+func Expand(in string) (result []string, err error) {
+
+	// Create ranges regular expression
+	reStNumber := "[[:digit:]]+"
+	reStRange := reStNumber + "-" + reStNumber
+	reStOptionalNumberOrRange := "(" + reStNumber + ",|" + reStRange + ",)*"
+	reStNumberOrRange := "(" + reStNumber + "|" + reStRange + ")"
+	reStBraceLeft := "[[]"
+	reStBraceRight := "[]]"
+	reStRanges := reStBraceLeft +
+		reStOptionalNumberOrRange +
+		reStNumberOrRange +
+		reStBraceRight
+	reRanges := regexp.MustCompile(reStRanges)
+
+	// Create host list regular expression
+	reStDNSChars := "[a-zA-Z0-9-]+"
+	reStPrefix := "^(" + reStDNSChars + ")"
+	reStOptionalSuffix := "(" + reStDNSChars + ")?"
+	re := regexp.MustCompile(reStPrefix + "([[][0-9,-]+[]])?" + reStOptionalSuffix)
+
+	// Remove all delimiters from the input
+	in = strings.TrimLeft(in, ", ")
+
+	for len(in) > 0 {
+		if v := re.FindStringSubmatch(in); v != nil {
+
+			// Remove matched part from the input
+			lenPrefix := len(v[0])
+			in = in[lenPrefix:]
+
+			// Remove all delimiters from the input
+			in = strings.TrimLeft(in, ", ")
+
+			// matched prefix, range and suffix
+			hlPrefix := v[1]
+			hlRanges := v[2]
+			hlSuffix := v[3]
+
+			// Single node without ranges
+			if hlRanges == "" {
+				result = append(result, hlPrefix)
+				continue
+			}
+
+			// Node with ranges
+			if v := reRanges.FindStringSubmatch(hlRanges); v != nil {
+
+				// Remove braces
+				hlRanges = hlRanges[1 : len(hlRanges)-1]
+
+				// Split host ranges at ,
+				for _, hlRange := range strings.Split(hlRanges, ",") {
+
+					// Split host range at -
+					RangeStartEnd := strings.Split(hlRange, "-")
+
+					// Range is only a single number
+					if len(RangeStartEnd) == 1 {
+						result = append(result, hlPrefix+RangeStartEnd[0]+hlSuffix)
+						continue
+					}
+
+					// Range has a start and an end
+					widthRangeStart := len(RangeStartEnd[0])
+					widthRangeEnd := len(RangeStartEnd[1])
+					iStart, _ := strconv.ParseUint(RangeStartEnd[0], 10, 64)
+					iEnd, _ := strconv.ParseUint(RangeStartEnd[1], 10, 64)
+					if iStart > iEnd {
+						return nil, fmt.Errorf("single range start is greater than end: %s", hlRange)
+					}
+
+					// Create print format string for range numbers
+					doPadding := widthRangeStart == widthRangeEnd
+					widthPadding := widthRangeStart
+					var formatString string
+					if doPadding {
+						formatString = "%0" + fmt.Sprint(widthPadding) + "d"
+					} else {
+						formatString = "%d"
+					}
+					formatString = hlPrefix + formatString + hlSuffix
+
+					// Add nodes from this range
+					for i := iStart; i <= iEnd; i++ {
+						result = append(result, fmt.Sprintf(formatString, i))
+					}
+				}
+			} else {
+				return nil, fmt.Errorf("not at hostlist range: %s", hlRanges)
+			}
+		} else {
+			return nil, fmt.Errorf("not a hostlist: %s", in)
+		}
+	}
+
+	if result != nil {
+		// sort
+		sort.Strings(result)
+
+		// uniq
+		previous := 1
+		for current := 1; current < len(result); current++ {
+			if result[current-1] != result[current] {
+				if previous != current {
+					result[previous] = result[current]
+				}
+				previous++
+			}
+		}
+		result = result[:previous]
+	}
+
+	return
+}