Just another update

Task/Find-common-directory-path/Go/find-common-directory-path.go

@@ -1,65 +1,59 @@
 package main
 
-import(
+import (
 	"fmt"
+	"os"
 	"path"
-	"strings"
 )
 
-func CommonPrefix(sep string, paths ...string) (string) {
+func CommonPrefix(sep byte, paths ...string) string {
 	// Handle special cases.
 	switch len(paths) {
-		case 0:
-			return ""
-		case 1:
-			return path.Clean(paths[0])
+	case 0:
+		return ""
+	case 1:
+		return path.Clean(paths[0])
 	}
 
+	// Note, we treat string as []byte, not []rune as is often
+	// done in Go. (And sep as byte, not rune). This is because
+	// most/all supported OS' treat paths as string of non-zero
+	// bytes. A filename may be displayed as a sequence of Unicode
+	// runes (typically encoded as UTF-8) but paths are
+	// not required to be valid UTF-8 or in any normalized form
+	// (e.g. "é" (U+00C9) and "é" (U+0065,U+0301) are different
+	// file names.
 	c := []byte(path.Clean(paths[0]))
 
-	// Ignore the first path since it's already in c.
-	for _, v := range(paths[1:]) {
-		// Clean up each path before testing it.
-		v = path.Clean(v)
+	// We add a trailing sep to handle the case where the
+	// common prefix directory is included in the path list
+	// (e.g. /home/user1, /home/user1/foo, /home/user1/bar).
+	// path.Clean will have cleaned off trailing / separators with
+	// the exception of the root directory, "/" (in which case we
+	// make it "//", but this will get fixed up to "/" bellow).
+	c = append(c, sep)
 
-		// Get the length of the shorter slice.
-		shorter := len(v)
-		if len(v) > len(c) {
-			shorter = len(c)
+	// Ignore the first path since it's already in c
+	for _, v := range paths[1:] {
+		// Clean up each path before testing it
+		v = path.Clean(v) + string(sep)
+
+		// Find the first non-common byte and truncate c
+		if len(v) < len(c) {
+			c = c[:len(v)]
 		}
-
-		// Find the first non-common character and copy up to it into c.
-		for i := 0; i < shorter; i++ {
+		for i := 0; i < len(c); i++ {
 			if v[i] != c[i] {
-				c = c[0:i]
+				c = c[:i]
 				break
 			}
 		}
 	}
 
-	// Correct for problem caused by prepending the actual common path to the
-	// list of paths searched through.
-	for _, v := range(paths) {
-		if len(v) > len(c) {
-			if strings.HasPrefix(v, string(c)) {
-				if len(v) > len(c) + len(sep) {
-					if v[len(c):len(c)+len(sep)] == sep {
-						c = append(c, []byte(sep)...)
-						break
-					}
-				}
-			}
-		}
-	}
-
-	// Remove trailing non-seperator characters.
-	for i := len(c)-1; i >= 0; i-- {
-		if i + len(sep) > len(c) {
-			continue
-		}
-
-		if string(c[i:i+len(sep)]) == sep {
-			c = c[0:i]
+	// Remove trailing non-separator characters and the final separator
+	for i := len(c) - 1; i >= 0; i-- {
+		if c[i] == sep {
+			c = c[:i]
 			break
 		}
 	}
@@ -68,10 +62,18 @@ func CommonPrefix(sep string, paths ...string) (string) {
 }
 
 func main() {
-	c := CommonPrefix("/",
+	c := CommonPrefix(os.PathSeparator,
+		//"/home/user1/tmp",
 		"/home/user1/tmp/coverage/test",
 		"/home/user1/tmp/covert/operator",
 		"/home/user1/tmp/coven/members",
+		"/home//user1/tmp/coventry",
+		"/home/user1/././tmp/covertly/foo",
+		"/home/bob/../user1/tmp/coved/bar",
 	)
-	fmt.Printf("%v\n", c)
+	if c == "" {
+		fmt.Println("No common path")
+	} else {
+		fmt.Println("Common path:", c)
+	}
 }