Enhancement: Empty config

When user starts kportal for the first time, and there is no config file,
kportal should create an empty config file with default values and empty
forwarding rules, so that user can easily edit the config file and add their
own rules.

cmd/kportal/main.go

@@ -1,6 +1,7 @@
 package main
 
 import (
+	"bufio"
 	"context"
 	"flag"
 	"fmt"
@@ -49,6 +50,23 @@ var (
 	appVersion    = "0.1.0" // Set via ldflags during build
 )
 
+// promptCreateConfig asks the user if they want to create a new config file.
+// Returns true if the user answers yes, false otherwise.
+func promptCreateConfig(path string) bool {
+	fmt.Printf("Configuration file not found: %s\n", path)
+	fmt.Print("Would you like to create an empty configuration? [Y/n] ")
+
+	reader := bufio.NewReader(os.Stdin)
+	response, err := reader.ReadString('\n')
+	if err != nil {
+		return false
+	}
+
+	response = strings.TrimSpace(strings.ToLower(response))
+	// Empty response (just Enter) defaults to yes
+	return response == "" || response == "y" || response == "yes"
+}
+
 func main() {
 	flag.Parse()
 
@@ -173,14 +191,38 @@ func main() {
 
 	// Load configuration
 	cfg, err := config.LoadConfig(*configFile)
+	configIsNew := false
 	if err != nil {
-		fmt.Fprintf(os.Stderr, "Error loading config: %v\n", err)
-		os.Exit(1)
+		if err == config.ErrConfigNotFound {
+			// Config file doesn't exist - offer to create it
+			if !promptCreateConfig(*configFile) {
+				os.Exit(0)
+			}
+			// Create empty config file
+			if err := config.CreateEmptyConfigFile(*configFile); err != nil {
+				fmt.Fprintf(os.Stderr, "Error creating config file: %v\n", err)
+				os.Exit(1)
+			}
+			fmt.Printf("Created %s\n", *configFile)
+			fmt.Println("Use 'n' in the UI to add port forwards, or edit the file manually.")
+			fmt.Println()
+
+			// Load the newly created config
+			cfg, err = config.LoadConfig(*configFile)
+			if err != nil {
+				fmt.Fprintf(os.Stderr, "Error loading config: %v\n", err)
+				os.Exit(1)
+			}
+			configIsNew = true
+		} else {
+			fmt.Fprintf(os.Stderr, "Error loading config: %v\n", err)
+			os.Exit(1)
+		}
 	}
 
-	// Validate configuration
+	// Validate configuration (allow empty configs for newly created files)
 	validator := config.NewValidator()
-	if errs := validator.ValidateConfig(cfg); len(errs) > 0 {
+	if errs := validator.ValidateConfigWithOptions(cfg, configIsNew || cfg.IsEmpty()); len(errs) > 0 {
 		fmt.Fprint(os.Stderr, config.FormatValidationErrors(errs))
 		os.Exit(1)
 	}

internal/config/config.go

@@ -2,6 +2,7 @@ package config
 
 import (
 	"bytes"
+	"errors"
 	"fmt"
 	"os"
 	"strings"
@@ -10,6 +11,9 @@ import (
 	"gopkg.in/yaml.v3"
 )
 
+// ErrConfigNotFound is returned when the configuration file does not exist
+var ErrConfigNotFound = fmt.Errorf("config file not found")
+
 const (
 	// maxConfigSize is the maximum allowed configuration file size (10MB)
 	maxConfigSize = 10 * 1024 * 1024
@@ -282,6 +286,9 @@ func LoadConfig(path string) (*Config, error) {
 	// Validate file size before reading
 	fileInfo, err := os.Stat(path)
 	if err != nil {
+		if errors.Is(err, os.ErrNotExist) {
+			return nil, ErrConfigNotFound
+		}
 		return nil, fmt.Errorf("failed to stat config file: %w", err)
 	}
 
@@ -337,3 +344,58 @@ func (c *Config) GetAllForwards() []Forward {
 
 	return forwards
 }
+
+// NewEmptyConfig returns a minimal empty configuration with no forwards.
+// This is used when creating a new config file for the first time.
+func NewEmptyConfig() *Config {
+	return &Config{
+		Contexts: []Context{},
+	}
+}
+
+// IsEmpty returns true if the configuration has no forwards defined.
+func (c *Config) IsEmpty() bool {
+	return len(c.Contexts) == 0 || len(c.GetAllForwards()) == 0
+}
+
+// CreateEmptyConfigFile creates a new empty configuration file at the given path.
+// Returns an error if the file already exists or cannot be created.
+func CreateEmptyConfigFile(path string) error {
+	// Check if file already exists
+	if _, err := os.Stat(path); err == nil {
+		return fmt.Errorf("config file already exists: %s", path)
+	} else if !errors.Is(err, os.ErrNotExist) {
+		return fmt.Errorf("failed to check config file: %w", err)
+	}
+
+	cfg := NewEmptyConfig()
+	data, err := yaml.Marshal(cfg)
+	if err != nil {
+		return fmt.Errorf("failed to marshal empty config: %w", err)
+	}
+
+	// Add a helpful comment header
+	header := `# kportal configuration file
+# Add port forwards using the 'n' key in the TUI, or manually add them below.
+#
+# Example forward:
+#   contexts:
+#     - name: my-cluster
+#       namespaces:
+#         - name: default
+#           forwards:
+#             - resource: service/my-service
+#               protocol: tcp
+#               port: 8080
+#               localPort: 8080
+#
+`
+	content := header + string(data)
+
+	// Write with restrictive permissions (0600)
+	if err := os.WriteFile(path, []byte(content), 0600); err != nil {
+		return fmt.Errorf("failed to write config file: %w", err)
+	}
+
+	return nil
+}

internal/config/config_test.go

@@ -97,7 +97,7 @@ func TestLoadConfig_FileNotFound(t *testing.T) {
 	cfg, err := LoadConfig("/non/existent/path/.kportal.yaml")
 	assert.Error(t, err, "LoadConfig should fail with non-existent file")
 	assert.Nil(t, cfg, "config should be nil on error")
-	assert.Contains(t, err.Error(), "failed to stat config file", "error should mention stat failure")
+	assert.Equal(t, ErrConfigNotFound, err, "should return ErrConfigNotFound")
 }
 
 func TestForward_ID(t *testing.T) {
@@ -397,3 +397,123 @@ func TestHTTPLogSpec_UnmarshalYAML(t *testing.T) {
 		})
 	}
 }
+
+func TestNewEmptyConfig(t *testing.T) {
+	cfg := NewEmptyConfig()
+	assert.NotNil(t, cfg, "NewEmptyConfig should return non-nil config")
+	assert.Empty(t, cfg.Contexts, "NewEmptyConfig should have empty contexts")
+	assert.True(t, cfg.IsEmpty(), "NewEmptyConfig should be considered empty")
+}
+
+func TestConfig_IsEmpty(t *testing.T) {
+	tests := []struct {
+		name     string
+		config   *Config
+		expected bool
+	}{
+		{
+			name:     "nil contexts",
+			config:   &Config{},
+			expected: true,
+		},
+		{
+			name:     "empty contexts slice",
+			config:   &Config{Contexts: []Context{}},
+			expected: true,
+		},
+		{
+			name: "context with empty namespaces",
+			config: &Config{
+				Contexts: []Context{
+					{Name: "test", Namespaces: []Namespace{}},
+				},
+			},
+			expected: true,
+		},
+		{
+			name: "context with namespace but no forwards",
+			config: &Config{
+				Contexts: []Context{
+					{
+						Name: "test",
+						Namespaces: []Namespace{
+							{Name: "default", Forwards: []Forward{}},
+						},
+					},
+				},
+			},
+			expected: true,
+		},
+		{
+			name: "config with forward",
+			config: &Config{
+				Contexts: []Context{
+					{
+						Name: "test",
+						Namespaces: []Namespace{
+							{
+								Name: "default",
+								Forwards: []Forward{
+									{Resource: "pod/app", Port: 8080, LocalPort: 8080},
+								},
+							},
+						},
+					},
+				},
+			},
+			expected: false,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			assert.Equal(t, tt.expected, tt.config.IsEmpty())
+		})
+	}
+}
+
+func TestCreateEmptyConfigFile(t *testing.T) {
+	tmpDir := t.TempDir()
+	configPath := filepath.Join(tmpDir, ".kportal.yaml")
+
+	// Create empty config file
+	err := CreateEmptyConfigFile(configPath)
+	assert.NoError(t, err, "CreateEmptyConfigFile should succeed")
+
+	// Verify file exists
+	_, err = os.Stat(configPath)
+	assert.NoError(t, err, "config file should exist")
+
+	// Verify file is readable and parseable
+	cfg, err := LoadConfig(configPath)
+	assert.NoError(t, err, "should be able to load created config")
+	assert.NotNil(t, cfg, "config should not be nil")
+	assert.True(t, cfg.IsEmpty(), "created config should be empty")
+
+	// Verify file permissions (0600)
+	info, _ := os.Stat(configPath)
+	assert.Equal(t, os.FileMode(0600), info.Mode().Perm(), "file should have 0600 permissions")
+
+	// Verify file contains helpful header
+	content, _ := os.ReadFile(configPath)
+	assert.Contains(t, string(content), "# kportal configuration file", "should contain header comment")
+	assert.Contains(t, string(content), "Example forward", "should contain example")
+}
+
+func TestCreateEmptyConfigFile_AlreadyExists(t *testing.T) {
+	tmpDir := t.TempDir()
+	configPath := filepath.Join(tmpDir, ".kportal.yaml")
+
+	// Create existing file
+	err := os.WriteFile(configPath, []byte("existing content"), 0644)
+	assert.NoError(t, err)
+
+	// Try to create config file - should fail
+	err = CreateEmptyConfigFile(configPath)
+	assert.Error(t, err, "CreateEmptyConfigFile should fail when file exists")
+	assert.Contains(t, err.Error(), "already exists")
+
+	// Verify original content is preserved
+	content, _ := os.ReadFile(configPath)
+	assert.Equal(t, "existing content", string(content))
+}

internal/config/validator.go

@@ -37,6 +37,13 @@ func NewValidator() *Validator {
 
 // ValidateConfig validates the entire configuration and returns all errors found.
 func (v *Validator) ValidateConfig(cfg *Config) []ValidationError {
+	return v.ValidateConfigWithOptions(cfg, false)
+}
+
+// ValidateConfigWithOptions validates configuration with configurable strictness.
+// When allowEmpty is true, empty configurations (no contexts/forwards) are allowed.
+// This is useful for newly created config files where the user will add forwards via the TUI.
+func (v *Validator) ValidateConfigWithOptions(cfg *Config, allowEmpty bool) []ValidationError {
 	var errs []ValidationError
 
 	if cfg == nil {
@@ -46,6 +53,12 @@ func (v *Validator) ValidateConfig(cfg *Config) []ValidationError {
 		}}
 	}
 
+	// If empty configs are allowed and this config is empty, skip structure validation
+	if allowEmpty && cfg.IsEmpty() {
+		// Still validate health check and reliability if present (they don't require forwards)
+		return errs
+	}
+
 	// Validate structure
 	errs = append(errs, v.validateStructure(cfg)...)
 

internal/config/validator_test.go

@@ -972,3 +972,141 @@ func TestIsAlphanumeric(t *testing.T) {
 		})
 	}
 }
+
+func TestValidator_ValidateConfigWithOptions(t *testing.T) {
+	validator := NewValidator()
+
+	tests := []struct {
+		name         string
+		config       *Config
+		allowEmpty   bool
+		expectErrors bool
+	}{
+		{
+			name:         "empty config - strict mode",
+			config:       &Config{Contexts: []Context{}},
+			allowEmpty:   false,
+			expectErrors: true,
+		},
+		{
+			name:         "empty config - allow empty",
+			config:       &Config{Contexts: []Context{}},
+			allowEmpty:   true,
+			expectErrors: false,
+		},
+		{
+			name:         "nil contexts - allow empty",
+			config:       &Config{},
+			allowEmpty:   true,
+			expectErrors: false,
+		},
+		{
+			name: "context with no forwards - allow empty",
+			config: &Config{
+				Contexts: []Context{
+					{
+						Name: "dev",
+						Namespaces: []Namespace{
+							{Name: "default", Forwards: []Forward{}},
+						},
+					},
+				},
+			},
+			allowEmpty:   true,
+			expectErrors: false,
+		},
+		{
+			name: "valid config - strict mode",
+			config: &Config{
+				Contexts: []Context{
+					{
+						Name: "dev-cluster",
+						Namespaces: []Namespace{
+							{
+								Name: "default",
+								Forwards: []Forward{
+									{
+										Resource:      "pod/my-app",
+										Protocol:      "tcp",
+										Port:          8080,
+										LocalPort:     8080,
+										contextName:   "dev-cluster",
+										namespaceName: "default",
+									},
+								},
+							},
+						},
+					},
+				},
+			},
+			allowEmpty:   false,
+			expectErrors: false,
+		},
+		{
+			name: "valid config - allow empty (should still validate)",
+			config: &Config{
+				Contexts: []Context{
+					{
+						Name: "dev-cluster",
+						Namespaces: []Namespace{
+							{
+								Name: "default",
+								Forwards: []Forward{
+									{
+										Resource:      "pod/my-app",
+										Protocol:      "tcp",
+										Port:          8080,
+										LocalPort:     8080,
+										contextName:   "dev-cluster",
+										namespaceName: "default",
+									},
+								},
+							},
+						},
+					},
+				},
+			},
+			allowEmpty:   true,
+			expectErrors: false,
+		},
+		{
+			name: "invalid forward in non-empty config - allow empty still validates",
+			config: &Config{
+				Contexts: []Context{
+					{
+						Name: "dev-cluster",
+						Namespaces: []Namespace{
+							{
+								Name: "default",
+								Forwards: []Forward{
+									{
+										Resource:      "pod/my-app",
+										Protocol:      "tcp",
+										Port:          0, // Invalid port
+										LocalPort:     8080,
+										contextName:   "dev-cluster",
+										namespaceName: "default",
+									},
+								},
+							},
+						},
+					},
+				},
+			},
+			allowEmpty:   true,
+			expectErrors: true,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			errs := validator.ValidateConfigWithOptions(tt.config, tt.allowEmpty)
+
+			if tt.expectErrors {
+				assert.NotEmpty(t, errs, "expected validation errors")
+			} else {
+				assert.Empty(t, errs, "expected no validation errors, got: %v", errs)
+			}
+		})
+	}
+}

internal/forward/manager.go

@@ -169,8 +169,10 @@ func (m *Manager) Start(cfg *config.Config) error {
 	// Get all forwards from config
 	forwards := cfg.GetAllForwards()
 
+	// Empty config is valid - user can add forwards later via TUI
 	if len(forwards) == 0 {
-		return fmt.Errorf("no forwards configured")
+		log.Printf("No forwards configured - use 'n' to add forwards")
+		return nil
 	}
 
 	// Check port availability before starting

internal/forward/manager_test.go

@@ -124,8 +124,8 @@ func TestManager_Start_EmptyForwards(t *testing.T) {
 
 	cfg := &config.Config{}
 	err = manager.Start(cfg)
-	assert.Error(t, err)
-	assert.Contains(t, err.Error(), "no forwards configured")
+	// Empty config is now valid - allows users to add forwards via TUI
+	assert.NoError(t, err)
 }
 
 // TestManager_Reload_NilConfig tests reloading with nil config