From 6f2ea76232fc5226ef393d51d388f476fadd13ca Mon Sep 17 00:00:00 2001
From: Gregory Kurtzer <gmkurtzer@gmail.com>
Date: Fri, 15 Oct 2021 21:36:16 -0700
Subject: [PATCH] First version of the hostlist public package

---
 pkg/hostlist/hostlist.go | 80 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 80 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 00000000..3c821f87
--- /dev/null
+++ b/pkg/hostlist/hostlist.go
@@ -0,0 +1,80 @@
+package hostlist
+
+import (
+	"fmt"
+	"strconv"
+	"strings"
+	"unicode"
+)
+
+func toInt(i string) int {
+	ret, _ := strconv.Atoi(i)
+	return ret
+}
+
+func isDigit(s string) bool {
+	r := []rune(s)
+
+	for i := 0; i < len(r); i++ {
+		if !unicode.IsDigit(r[i]) {
+			return false
+		}
+	}
+
+	return true
+}
+
+func expand_iterate(list []string) ([]string, int) {
+	var ret []string
+	var count int
+
+	for _, i := range list {
+
+		bracketIndex1 := strings.Index(i, "[")
+		bracketIndex2 := strings.Index(i, "]")
+
+		if bracketIndex1 >= 0 && bracketIndex1 < bracketIndex2 {
+			prefix := i[:bracketIndex1]
+			suffix := i[bracketIndex2+1:]
+			ranges := strings.Split(i[bracketIndex1+1:bracketIndex2], ",")
+			count++
+
+			for _, r := range ranges {
+				iterate := strings.Split(r, "-")
+
+				if len(iterate) == 1 {
+					if !isDigit(iterate[0]) {
+						return ret, 0
+					} else {
+						ret = append(ret, prefix+iterate[0]+suffix)
+					}
+				} else if len(iterate) == 2 {
+					if !isDigit(iterate[0]) || !isDigit(iterate[1]) {
+						return ret, 0
+					} else {
+						sigfigures := len(iterate[0])
+						for i := toInt(iterate[0]); i <= toInt(iterate[1]); i++ {
+							ret = append(ret, fmt.Sprintf(`%s%.`+fmt.Sprintf("%d", sigfigures)+`d%s`, prefix, i, suffix))
+						}
+					}
+				}
+			}
+		}
+	}
+	return ret, count
+}
+
+func Expand(list []string) []string {
+	ret := list
+
+	for {
+		loop, count := expand_iterate(ret)
+
+		if count == 0 {
+			break
+		}
+		ret = loop
+	}
+
+	return ret
+}