refactor: extract utilities, fix SCP port parsing, add terminal resize

- Extract shared helpers (parseUserHostPath, path helpers, fatalError, etc.)
  into util.go to eliminate duplication across args.go, config.go, sftp.go, ssh.go
- Fix SCP -P port value being incorrectly treated as local file path
- Add mergeConfig to centralize config merging logic in SCP/rsync modes
- Add dynamic terminal resizing with platform-specific signal handling
- Add cleanRemotePath for Git Bash path conversion detection
- Fix -u flag default: use empty string with applyUserDefault instead of "root"

Co-Authored-By: Claude Opus 4.6 <[email protected]>

Author: chuccp

.gitignore

@@ -34,3 +34,6 @@ go.work.sum
 /.idea
 *.config
 *.log
+/test_dir
+/dltest
+*.txt

args.go

@@ -22,46 +22,9 @@ type ParsedCommand struct {
 	SCPArgs []string // scp arguments
 }
 
-// parseUserHostPath parses user@host:path format, supporting IPv6
-// returns user, host, path
-func parseUserHostPath(arg string) (user, host, remotePath string) {
-	atIdx := strings.Index(arg, "@")
-	if atIdx <= 0 {
-		return "", "", ""
-	}
-	user = arg[:atIdx]
-	remainder := arg[atIdx+1:]
-
-	// check if IPv6 address (starts with [)
-	if strings.HasPrefix(remainder, "[") {
-		// IPv6 format: [::1]:path or [2001:db8::1]:path
-		closeBracket := strings.Index(remainder, "]")
-		if closeBracket > 0 {
-			host = remainder[:closeBracket+1] // including square brackets
-			// check if there is a path after ]:
-			if closeBracket+1 < len(remainder) && remainder[closeBracket+1] == ':' {
-				remotePath = remainder[closeBracket+2:]
-			}
-		}
-	} else {
-		// IPv4 or hostname: host:path
-		colonIdx := strings.Index(remainder, ":")
-		if colonIdx > 0 {
-			host = remainder[:colonIdx]
-			remotePath = remainder[colonIdx+1:]
-		} else {
-			host = remainder
-		}
-	}
-	return user, host, remotePath
-}
-
 // parseSSHArgs parses ssh-style arguments (user@host or -p port user@host)
 func parseSSHArgs(args []string) (*Config, string) {
-	config := &Config{
-		User: "root",
-		Port: "22",
-	}
+	config := newDefaultConfig()
 	var command string
 
 	i := 0
@@ -99,7 +62,7 @@ func parseSSHArgs(args []string) (*Config, string) {
 		}
 		// remaining args as command
 		if config.Host != "" {
-			command = strings.Join(args[i:], " ")
+			command = joinArgs(args[i:])
 			break
 		}
 		i++
@@ -110,10 +73,7 @@ func parseSSHArgs(args []string) (*Config, string) {
 
 // parseSCPArgs parses scp command arguments
 func parseSCPArgs(args []string) (*Config, []string) {
-	config := &Config{
-		User: "root",
-		Port: "22",
-	}
+	config := newDefaultConfig()
 	var scpArgs []string
 
 	i := 0
@@ -126,7 +86,6 @@ func parseSCPArgs(args []string) (*Config, []string) {
 		if arg == "-P" && i+1 < len(args) {
 			// scp uses uppercase -P for port
 			config.Port = args[i+1]
-			scpArgs = append(scpArgs, "-P", args[i+1])
 			i += 2
 			continue
 		}
@@ -140,12 +99,7 @@ func parseSCPArgs(args []string) (*Config, []string) {
 			continue
 		}
 		if strings.Contains(arg, "@") && strings.Contains(arg, ":") {
-			// user@host:path format (supports IPv6)
-			user, host, _ := parseUserHostPath(arg)
-			if user != "" && host != "" {
-				config.User = user
-				config.Host = host
-			}
+			config.setUserHostFromArg(arg)
 		}
 		scpArgs = append(scpArgs, arg)
 		i++
@@ -156,10 +110,7 @@ func parseSCPArgs(args []string) (*Config, []string) {
 
 // parseRsyncArgs parses rsync command arguments
 func parseRsyncArgs(args []string) (*Config, []string) {
-	config := &Config{
-		User: "root",
-		Port: "22",
-	}
+	config := newDefaultConfig()
 	var rsyncArgs []string
 
 	i := 0
@@ -180,18 +131,16 @@ func parseRsyncArgs(args []string) (*Config, []string) {
 			continue
 		}
 		if strings.HasPrefix(arg, "-p") && len(arg) > 2 {
-			// -p22 format port
-			config.Port = arg[2:]
-			i++
-			continue
+			// -p22 format port (only match if followed by digits)
+			portPart := arg[2:]
+			if isAllDigits(portPart) {
+				config.Port = portPart
+				i++
+				continue
+			}
 		}
 		if strings.Contains(arg, "@") && strings.Contains(arg, ":") {
-			// user@host:path format (supports IPv6)
-			user, host, _ := parseUserHostPath(arg)
-			if user != "" && host != "" {
-				config.User = user
-				config.Host = host
-			}
+			config.setUserHostFromArg(arg)
 		}
 		rsyncArgs = append(rsyncArgs, arg)
 		i++

config.go

@@ -17,6 +17,81 @@ type Config struct {
 	StrictHostKey bool   // whether to verify host key
 }
 
+// newDefaultConfig creates a Config with default values
+func newDefaultConfig() *Config {
+	return &Config{
+		User: "root",
+		Port: "22",
+	}
+}
+
+// applyUserDefault sets the user to "root" if empty
+func applyUserDefault(cfg *Config) {
+	if cfg.User == "" {
+		cfg.User = "root"
+	}
+}
+
+// setUserHostFromArg parses user@host:path format and sets config fields
+func (c *Config) setUserHostFromArg(arg string) {
+	user, host, _ := parseUserHostPath(arg)
+	if user != "" && host != "" {
+		c.User = user
+		c.Host = host
+	}
+}
+
+// validate checks that the  config has required fields
+func (c *Config) validate() error {
+	if c.Host == "" {
+		return fmt.Errorf("host address not specified")
+	}
+	if c.Password == "" && c.KeyPath == "" {
+		return fmt.Errorf("no authentication method provided (password or key required)")
+	}
+	return nil
+}
+
+// mergeConfig merges non-empty fields from src into dst,
+// then applies command-line overrides and user default
+func mergeConfig(dst, src *Config, pass, keyPath, host, user, port string) {
+	// inherit from source (config file)
+	if src != nil {
+		if src.Password != "" {
+			dst.Password = src.Password
+		}
+		if src.KeyPath != "" {
+			dst.KeyPath = src.KeyPath
+		}
+		if src.User != "" {
+			dst.User = src.User
+		}
+		if src.Host != "" {
+			dst.Host = src.Host
+		}
+		if src.Port != "" {
+			dst.Port = src.Port
+		}
+	}
+	// command-line overrides
+	if pass != "" {
+		dst.Password = pass
+	}
+	if keyPath != "" {
+		dst.KeyPath = keyPath
+	}
+	if host != "" {
+		dst.Host = host
+	}
+	if user != "" {
+		dst.User = user
+	}
+	if port != "" && port != "22" {
+		dst.Port = port
+	}
+	applyUserDefault(dst)
+}
+
 // parseConfigFile parses a config file (format: key: value)
 func parseConfigFile(filename string) (*Config, error) {
 	file, err := os.Open(filename)
@@ -25,10 +100,7 @@ func parseConfigFile(filename string) (*Config, error) {
 	}
 	defer file.Close()
 
-	config := &Config{
-		Port: "22",
-		User: "root",
-	}
+	config := newDefaultConfig()
 
 	scanner := bufio.NewScanner(file)
 	for scanner.Scan() {
@@ -80,4 +152,4 @@ func readPasswordFile(filename string) (string, error) {
 // getEnvPassword gets password from environment variable
 func getEnvPassword() string {
 	return os.Getenv("SSHPASS")
-}
+}