Add core modules (SSH args parser, cache, resolver, NetBox client) with tests

internal/ssh/args.go

@@ -0,0 +1,109 @@
+package ssh
+
+import "strings"
+
+// flagsWithArg lists all SSH flags that consume the following argument.
+var flagsWithArg = map[byte]bool{
+	'b': true, 'c': true, 'D': true, 'E': true, 'e': true,
+	'F': true, 'I': true, 'i': true, 'J': true, 'L': true,
+	'l': true, 'm': true, 'o': true, 'O': true, 'p': true,
+	'Q': true, 'R': true, 'S': true, 'w': true, 'W': true,
+}
+
+// ParsedArgs holds the result of parsing SSH arguments.
+type ParsedArgs struct {
+	Host    string // hostname without the user@ prefix
+	User    string // empty if not specified
+	DestIdx int    // index in Args where [user@]host sits
+	Args    []string
+}
+
+// Parse scans SSH arguments and extracts the destination ([user@]host).
+// Returns nil if no destination is found.
+func Parse(args []string) *ParsedArgs {
+	i := 0
+	for i < len(args) {
+		arg := args[i]
+
+		// "--" ends option processing
+		if arg == "--" {
+			i++
+			break
+		}
+
+		if strings.HasPrefix(arg, "-") && len(arg) > 1 {
+			flag := arg[1]
+			if flagsWithArg[flag] {
+				if len(arg) > 2 {
+					// argument is attached, e.g. -p2222
+					i++
+				} else {
+					// argument is the next element, e.g. -p 2222
+					i += 2
+				}
+			} else {
+				i++
+			}
+			continue
+		}
+
+		// first non-flag argument is the destination
+		host, user := splitUserHost(arg)
+		return &ParsedArgs{
+			Host:    host,
+			User:    user,
+			DestIdx: i,
+			Args:    args,
+		}
+	}
+
+	// handle arguments after "--"
+	if i < len(args) {
+		host, user := splitUserHost(args[i])
+		return &ParsedArgs{
+			Host:    host,
+			User:    user,
+			DestIdx: i,
+			Args:    args,
+		}
+	}
+
+	return nil
+}
+
+// ReplaceHost returns a copy of args with the destination replaced by newHost,
+// preserving any user@ prefix.
+func ReplaceHost(args []string, destIdx int, newHost string) []string {
+	result := make([]string, len(args))
+	copy(result, args)
+
+	original := args[destIdx]
+	if at := strings.Index(original, "@"); at != -1 {
+		result[destIdx] = original[:at+1] + newHost
+	} else {
+		result[destIdx] = newHost
+	}
+	return result
+}
+
+// HasUserFlag reports whether a user was specified via -l in args.
+// Used to avoid overriding an explicit -l with the configured default user.
+func HasUserFlag(args []string) bool {
+	for i, a := range args {
+		if a == "-l" && i+1 < len(args) {
+			return true
+		}
+		// handle attached form: -lroot
+		if len(a) > 2 && a[0] == '-' && a[1] == 'l' {
+			return true
+		}
+	}
+	return false
+}
+
+func splitUserHost(dest string) (host, user string) {
+	if at := strings.Index(dest, "@"); at != -1 {
+		return dest[at+1:], dest[:at]
+	}
+	return dest, ""
+}