From cbbda23e014e1684788268bebbb4050ea361650e Mon Sep 17 00:00:00 2001
From: Kovid Goyal <kovid@kovidgoyal.net>
Date: Sun, 18 Sep 2022 19:31:24 +0530
Subject: [PATCH] Utility code to find longest common prefix/suffix and to
 quote strings for various shells

---
 tools/utils/longest-common.go      | 79 ++++++++++++++++++++++++++++++
 tools/utils/longest-common_test.go | 21 ++++++++
 tools/utils/shell.go               | 26 ++++++++++
 3 files changed, 126 insertions(+)
 create mode 100644 tools/utils/longest-common.go
 create mode 100644 tools/utils/longest-common_test.go
 create mode 100644 tools/utils/shell.go

diff --git a/tools/utils/longest-common.go b/tools/utils/longest-common.go
new file mode 100644
index 000000000..1551395b0
--- /dev/null
+++ b/tools/utils/longest-common.go
@@ -0,0 +1,79 @@
+// License: GPLv3 Copyright: 2022, Kovid Goyal, <kovid at kovidgoyal.net>
+
+package utils
+
+import (
+	"fmt"
+	"math"
+)
+
+var _ = fmt.Print
+
+func slice_iter(strs []string) func() (string, bool) {
+	i := 0
+	limit := len(strs)
+	return func() (string, bool) {
+		if i < limit {
+			i++
+			return strs[i-1], false
+		}
+		return "", true
+	}
+}
+
+// Prefix returns the longest common prefix of the provided strings
+func Prefix(strs []string) string {
+	return LongestCommon(slice_iter(strs), true)
+}
+
+// Suffix returns the longest common suffix of the provided strings
+func Suffix(strs []string) string {
+	return LongestCommon(slice_iter(strs), false)
+}
+
+func min(a ...int) int {
+	ans := math.MaxInt
+	for _, x := range a {
+		if x < ans {
+			ans = x
+		}
+	}
+	return ans
+}
+
+func LongestCommon(next func() (string, bool), prefix bool) string {
+	xfix, done := next()
+	if xfix == "" || done {
+		return ""
+	}
+	for {
+		q, done := next()
+		if done {
+			break
+		}
+		q_len := len(q)
+		xfix_len := len(xfix)
+		max_len := min(q_len, xfix_len)
+		if max_len == 0 {
+			return ""
+		}
+		if prefix {
+			for i := 0; i < max_len; i++ {
+				if xfix[i] != q[i] {
+					xfix = xfix[:i]
+					break
+				}
+			}
+		} else {
+			for i := 0; i < max_len; i++ {
+				xi := xfix_len - i - 1
+				si := q_len - i - 1
+				if xfix[xi] != q[si] {
+					xfix = xfix[xi+1:]
+					break
+				}
+			}
+		}
+	}
+	return xfix
+}
diff --git a/tools/utils/longest-common_test.go b/tools/utils/longest-common_test.go
new file mode 100644
index 000000000..5f8d656cf
--- /dev/null
+++ b/tools/utils/longest-common_test.go
@@ -0,0 +1,21 @@
+// License: GPLv3 Copyright: 2022, Kovid Goyal, <kovid at kovidgoyal.net>
+
+package utils
+
+import (
+	"fmt"
+	"testing"
+)
+
+var _ = fmt.Print
+
+func TestLongestCommon(t *testing.T) {
+	p := func(expected string, items ...string) {
+		actual := Prefix(items)
+		if actual != expected {
+			t.Fatalf("Failed with %#v\nExpected: %#v\nActual:   %#v", items, expected, actual)
+		}
+	}
+	p("abc", "abc", "abcd")
+	p("", "abc", "xy")
+}
diff --git a/tools/utils/shell.go b/tools/utils/shell.go
new file mode 100644
index 000000000..a415897cb
--- /dev/null
+++ b/tools/utils/shell.go
@@ -0,0 +1,26 @@
+// License: GPLv3 Copyright: 2022, Kovid Goyal, <kovid at kovidgoyal.net>
+
+package utils
+
+import (
+	"fmt"
+	"strings"
+)
+
+var _ = fmt.Print
+
+// Quotes arbitrary strings for bash, dash and zsh
+func QuoteStringForSH(x string) string {
+	parts := strings.Split(x, "'")
+	for i, p := range parts {
+		parts[i] = "'" + p + "'"
+	}
+	return strings.Join(parts, "\"'\"")
+}
+
+// Quotes arbitrary strings for fish
+func QuoteStringForFish(x string) string {
+	x = strings.ReplaceAll(x, "\\", "\\\\")
+	x = strings.ReplaceAll(x, "'", "\\'")
+	return "'" + x + "'"
+}