feat(config): add multiple server instances support

- Add ServersConfig and ServerInstanceConfig structs
- Support configuring multiple named server instances
- Add global timeout defaults with per-instance overrides
- Add TLS configuration options (SSL cert/key, self-signed, AutoTLS)
- Add validation for server configurations
- Add helper methods for applying defaults and getting default server
- Add conversion helper to avoid import cycles

pkg/config/manager_test.go

@@ -34,8 +34,8 @@ func TestDefaultValues(t *testing.T) {
 		got      interface{}
 		expected interface{}
 	}{
-		{"server.addr", cfg.Server.Addr, ":8080"},
-		{"server.shutdown_timeout", cfg.Server.ShutdownTimeout, 30 * time.Second},
+		{"servers.default_server", cfg.Servers.DefaultServer, "default"},
+		{"servers.shutdown_timeout", cfg.Servers.ShutdownTimeout, 30 * time.Second},
 		{"tracing.enabled", cfg.Tracing.Enabled, false},
 		{"tracing.service_name", cfg.Tracing.ServiceName, "resolvespec"},
 		{"cache.provider", cfg.Cache.Provider, "memory"},
@@ -46,6 +46,18 @@ func TestDefaultValues(t *testing.T) {
 		{"middleware.rate_limit_burst", cfg.Middleware.RateLimitBurst, 200},
 	}
 
+	// Test default server instance
+	defaultServer, ok := cfg.Servers.Instances["default"]
+	if !ok {
+		t.Fatal("Default server instance not found")
+	}
+	if defaultServer.Port != 8080 {
+		t.Errorf("default server port: got %d, want 8080", defaultServer.Port)
+	}
+	if defaultServer.Name != "default" {
+		t.Errorf("default server name: got %s, want default", defaultServer.Name)
+	}
+
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
 			if tt.got != tt.expected {
@@ -57,12 +69,12 @@ func TestDefaultValues(t *testing.T) {
 
 func TestEnvironmentVariableOverrides(t *testing.T) {
 	// Set environment variables
-	os.Setenv("RESOLVESPEC_SERVER_ADDR", ":9090")
+	os.Setenv("RESOLVESPEC_SERVERS_INSTANCES_DEFAULT_PORT", "9090")
 	os.Setenv("RESOLVESPEC_TRACING_ENABLED", "true")
 	os.Setenv("RESOLVESPEC_CACHE_PROVIDER", "redis")
 	os.Setenv("RESOLVESPEC_LOGGER_DEV", "true")
 	defer func() {
-		os.Unsetenv("RESOLVESPEC_SERVER_ADDR")
+		os.Unsetenv("RESOLVESPEC_SERVERS_INSTANCES_DEFAULT_PORT")
 		os.Unsetenv("RESOLVESPEC_TRACING_ENABLED")
 		os.Unsetenv("RESOLVESPEC_CACHE_PROVIDER")
 		os.Unsetenv("RESOLVESPEC_LOGGER_DEV")
@@ -84,7 +96,6 @@ func TestEnvironmentVariableOverrides(t *testing.T) {
 		got      interface{}
 		expected interface{}
 	}{
-		{"server.addr", cfg.Server.Addr, ":9090"},
 		{"tracing.enabled", cfg.Tracing.Enabled, true},
 		{"cache.provider", cfg.Cache.Provider, "redis"},
 		{"logger.dev", cfg.Logger.Dev, true},
@@ -97,11 +108,17 @@ func TestEnvironmentVariableOverrides(t *testing.T) {
 			}
 		})
 	}
+
+	// Test server port override
+	defaultServer := cfg.Servers.Instances["default"]
+	if defaultServer.Port != 9090 {
+		t.Errorf("server port: got %d, want 9090", defaultServer.Port)
+	}
 }
 
 func TestProgrammaticConfiguration(t *testing.T) {
 	mgr := NewManager()
-	mgr.Set("server.addr", ":7070")
+	mgr.Set("servers.instances.default.port", 7070)
 	mgr.Set("tracing.service_name", "test-service")
 
 	cfg, err := mgr.GetConfig()
@@ -109,8 +126,8 @@ func TestProgrammaticConfiguration(t *testing.T) {
 		t.Fatalf("Failed to get config: %v", err)
 	}
 
-	if cfg.Server.Addr != ":7070" {
-		t.Errorf("server.addr: got %s, want :7070", cfg.Server.Addr)
+	if cfg.Servers.Instances["default"].Port != 7070 {
+		t.Errorf("server port: got %d, want 7070", cfg.Servers.Instances["default"].Port)
 	}
 
 	if cfg.Tracing.ServiceName != "test-service" {
@@ -148,8 +165,8 @@ func TestWithOptions(t *testing.T) {
 	}
 
 	// Set environment variable with custom prefix
-	os.Setenv("MYAPP_SERVER_ADDR", ":5000")
-	defer os.Unsetenv("MYAPP_SERVER_ADDR")
+	os.Setenv("MYAPP_SERVERS_INSTANCES_DEFAULT_PORT", "5000")
+	defer os.Unsetenv("MYAPP_SERVERS_INSTANCES_DEFAULT_PORT")
 
 	if err := mgr.Load(); err != nil {
 		t.Fatalf("Failed to load config: %v", err)
@@ -160,7 +177,432 @@ func TestWithOptions(t *testing.T) {
 		t.Fatalf("Failed to get config: %v", err)
 	}
 
-	if cfg.Server.Addr != ":5000" {
-		t.Errorf("server.addr: got %s, want :5000", cfg.Server.Addr)
+	if cfg.Servers.Instances["default"].Port != 5000 {
+		t.Errorf("server port: got %d, want 5000", cfg.Servers.Instances["default"].Port)
+	}
+}
+
+func TestServersConfig(t *testing.T) {
+	mgr := NewManager()
+	if err := mgr.Load(); err != nil {
+		t.Fatalf("Failed to load config: %v", err)
+	}
+
+	cfg, err := mgr.GetConfig()
+	if err != nil {
+		t.Fatalf("Failed to get config: %v", err)
+	}
+
+	// Test default server exists
+	if cfg.Servers.DefaultServer != "default" {
+		t.Errorf("Expected default_server to be 'default', got %s", cfg.Servers.DefaultServer)
+	}
+
+	// Test default instance
+	defaultServer, ok := cfg.Servers.Instances["default"]
+	if !ok {
+		t.Fatal("Default server instance not found")
+	}
+
+	if defaultServer.Port != 8080 {
+		t.Errorf("Expected default port 8080, got %d", defaultServer.Port)
+	}
+
+	if defaultServer.Name != "default" {
+		t.Errorf("Expected default name 'default', got %s", defaultServer.Name)
+	}
+
+	if defaultServer.Description != "Default HTTP server" {
+		t.Errorf("Expected description 'Default HTTP server', got %s", defaultServer.Description)
+	}
+}
+
+func TestMultipleServerInstances(t *testing.T) {
+	mgr := NewManager()
+
+	// Add additional server instances (default instance exists from defaults)
+	mgr.Set("servers.default_server", "api")
+	mgr.Set("servers.instances.api.name", "api")
+	mgr.Set("servers.instances.api.host", "0.0.0.0")
+	mgr.Set("servers.instances.api.port", 8080)
+	mgr.Set("servers.instances.admin.name", "admin")
+	mgr.Set("servers.instances.admin.host", "localhost")
+	mgr.Set("servers.instances.admin.port", 8081)
+
+	cfg, err := mgr.GetConfig()
+	if err != nil {
+		t.Fatalf("Failed to get config: %v", err)
+	}
+
+	// Should have default + api + admin = 3 instances
+	if len(cfg.Servers.Instances) < 2 {
+		t.Errorf("Expected at least 2 server instances, got %d", len(cfg.Servers.Instances))
+	}
+
+	// Verify api instance
+	apiServer, ok := cfg.Servers.Instances["api"]
+	if !ok {
+		t.Fatal("API server instance not found")
+	}
+	if apiServer.Port != 8080 {
+		t.Errorf("Expected API port 8080, got %d", apiServer.Port)
+	}
+
+	// Verify admin instance
+	adminServer, ok := cfg.Servers.Instances["admin"]
+	if !ok {
+		t.Fatal("Admin server instance not found")
+	}
+	if adminServer.Port != 8081 {
+		t.Errorf("Expected admin port 8081, got %d", adminServer.Port)
+	}
+
+	// Validate default server
+	if err := cfg.Servers.Validate(); err != nil {
+		t.Errorf("Server config validation failed: %v", err)
+	}
+
+	// Get default
+	defaultSrv, err := cfg.Servers.GetDefault()
+	if err != nil {
+		t.Fatalf("Failed to get default server: %v", err)
+	}
+	if defaultSrv.Name != "api" {
+		t.Errorf("Expected default server 'api', got '%s'", defaultSrv.Name)
+	}
+}
+
+func TestExtensionsField(t *testing.T) {
+	mgr := NewManager()
+
+	// Set custom extensions
+	mgr.Set("extensions.custom_feature.enabled", true)
+	mgr.Set("extensions.custom_feature.api_key", "test-key")
+	mgr.Set("extensions.another_extension.timeout", "5s")
+
+	cfg, err := mgr.GetConfig()
+	if err != nil {
+		t.Fatalf("Failed to get config: %v", err)
+	}
+
+	if cfg.Extensions == nil {
+		t.Fatal("Extensions should not be nil")
+	}
+
+	// Verify extensions are accessible
+	customFeature := mgr.Get("extensions.custom_feature")
+	if customFeature == nil {
+		t.Error("custom_feature extension not found")
+	}
+
+	// Verify via config manager methods
+	if !mgr.GetBool("extensions.custom_feature.enabled") {
+		t.Error("Expected custom_feature.enabled to be true")
+	}
+
+	if mgr.GetString("extensions.custom_feature.api_key") != "test-key" {
+		t.Error("Expected api_key to be 'test-key'")
+	}
+}
+
+func TestServerInstanceValidation(t *testing.T) {
+	tests := []struct {
+		name      string
+		instance  ServerInstanceConfig
+		expectErr bool
+	}{
+		{
+			name: "valid basic config",
+			instance: ServerInstanceConfig{
+				Name: "test",
+				Port: 8080,
+			},
+			expectErr: false,
+		},
+		{
+			name: "invalid port - too high",
+			instance: ServerInstanceConfig{
+				Name: "test",
+				Port: 99999,
+			},
+			expectErr: true,
+		},
+		{
+			name: "invalid port - zero",
+			instance: ServerInstanceConfig{
+				Name: "test",
+				Port: 0,
+			},
+			expectErr: true,
+		},
+		{
+			name: "empty name",
+			instance: ServerInstanceConfig{
+				Name: "",
+				Port: 8080,
+			},
+			expectErr: true,
+		},
+		{
+			name: "conflicting TLS options",
+			instance: ServerInstanceConfig{
+				Name:          "test",
+				Port:          8080,
+				SelfSignedSSL: true,
+				AutoTLS:       true,
+			},
+			expectErr: true,
+		},
+		{
+			name: "incomplete SSL cert config",
+			instance: ServerInstanceConfig{
+				Name:    "test",
+				Port:    8080,
+				SSLCert: "/path/to/cert.pem",
+				// Missing SSLKey
+			},
+			expectErr: true,
+		},
+		{
+			name: "AutoTLS without domains",
+			instance: ServerInstanceConfig{
+				Name:    "test",
+				Port:    8080,
+				AutoTLS: true,
+				// Missing AutoTLSDomains
+			},
+			expectErr: true,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			err := tt.instance.Validate()
+			if tt.expectErr && err == nil {
+				t.Error("Expected validation error, got nil")
+			}
+			if !tt.expectErr && err != nil {
+				t.Errorf("Expected no error, got: %v", err)
+			}
+		})
+	}
+}
+
+func TestApplyGlobalDefaults(t *testing.T) {
+	globals := ServersConfig{
+		ShutdownTimeout: 30 * time.Second,
+		DrainTimeout:    25 * time.Second,
+		ReadTimeout:     10 * time.Second,
+		WriteTimeout:    10 * time.Second,
+		IdleTimeout:     120 * time.Second,
+	}
+
+	instance := ServerInstanceConfig{
+		Name: "test",
+		Port: 8080,
+	}
+
+	// Apply global defaults
+	instance.ApplyGlobalDefaults(globals)
+
+	// Check that defaults were applied
+	if instance.ShutdownTimeout == nil || *instance.ShutdownTimeout != 30*time.Second {
+		t.Error("ShutdownTimeout not applied correctly")
+	}
+	if instance.DrainTimeout == nil || *instance.DrainTimeout != 25*time.Second {
+		t.Error("DrainTimeout not applied correctly")
+	}
+	if instance.ReadTimeout == nil || *instance.ReadTimeout != 10*time.Second {
+		t.Error("ReadTimeout not applied correctly")
+	}
+	if instance.WriteTimeout == nil || *instance.WriteTimeout != 10*time.Second {
+		t.Error("WriteTimeout not applied correctly")
+	}
+	if instance.IdleTimeout == nil || *instance.IdleTimeout != 120*time.Second {
+		t.Error("IdleTimeout not applied correctly")
+	}
+
+	// Test that explicit overrides are not replaced
+	customTimeout := 60 * time.Second
+	instance2 := ServerInstanceConfig{
+		Name:            "test2",
+		Port:            8081,
+		ShutdownTimeout: &customTimeout,
+	}
+
+	instance2.ApplyGlobalDefaults(globals)
+
+	if instance2.ShutdownTimeout == nil || *instance2.ShutdownTimeout != 60*time.Second {
+		t.Error("Custom ShutdownTimeout was overridden")
+	}
+}
+
+func TestPathsConfig(t *testing.T) {
+	mgr := NewManager()
+	if err := mgr.Load(); err != nil {
+		t.Fatalf("Failed to load config: %v", err)
+	}
+
+	cfg, err := mgr.GetConfig()
+	if err != nil {
+		t.Fatalf("Failed to get config: %v", err)
+	}
+
+	// Test default paths exist
+	if !cfg.Paths.Has("data_dir") {
+		t.Error("Expected data_dir path to exist")
+	}
+	if !cfg.Paths.Has("config_dir") {
+		t.Error("Expected config_dir path to exist")
+	}
+	if !cfg.Paths.Has("logs_dir") {
+		t.Error("Expected logs_dir path to exist")
+	}
+	if !cfg.Paths.Has("temp_dir") {
+		t.Error("Expected temp_dir path to exist")
+	}
+
+	// Test Get method
+	dataDir, err := cfg.Paths.Get("data_dir")
+	if err != nil {
+		t.Errorf("Failed to get data_dir: %v", err)
+	}
+	if dataDir != "./data" {
+		t.Errorf("Expected data_dir to be './data', got '%s'", dataDir)
+	}
+
+	// Test GetOrDefault
+	existing := cfg.Paths.GetOrDefault("data_dir", "/default/path")
+	if existing != "./data" {
+		t.Errorf("Expected existing path, got '%s'", existing)
+	}
+
+	nonExisting := cfg.Paths.GetOrDefault("nonexistent", "/default/path")
+	if nonExisting != "/default/path" {
+		t.Errorf("Expected default path, got '%s'", nonExisting)
+	}
+}
+
+func TestPathsConfigMethods(t *testing.T) {
+	pc := PathsConfig{
+		"base": "/var/myapp",
+		"data": "/var/myapp/data",
+	}
+
+	// Test Get
+	path, err := pc.Get("base")
+	if err != nil {
+		t.Errorf("Failed to get path: %v", err)
+	}
+	if path != "/var/myapp" {
+		t.Errorf("Expected '/var/myapp', got '%s'", path)
+	}
+
+	// Test Get non-existent
+	_, err = pc.Get("nonexistent")
+	if err == nil {
+		t.Error("Expected error for non-existent path")
+	}
+
+	// Test Set
+	pc.Set("new_path", "/new/location")
+	newPath, err := pc.Get("new_path")
+	if err != nil {
+		t.Errorf("Failed to get newly set path: %v", err)
+	}
+	if newPath != "/new/location" {
+		t.Errorf("Expected '/new/location', got '%s'", newPath)
+	}
+
+	// Test Has
+	if !pc.Has("base") {
+		t.Error("Expected 'base' path to exist")
+	}
+	if pc.Has("nonexistent") {
+		t.Error("Expected 'nonexistent' path to not exist")
+	}
+
+	// Test List
+	names := pc.List()
+	if len(names) != 3 {
+		t.Errorf("Expected 3 paths, got %d", len(names))
+	}
+
+	// Test Join
+	joined, err := pc.Join("base", "subdir", "file.txt")
+	if err != nil {
+		t.Errorf("Failed to join paths: %v", err)
+	}
+	expected := "/var/myapp/subdir/file.txt"
+	if joined != expected {
+		t.Errorf("Expected '%s', got '%s'", expected, joined)
+	}
+}
+
+func TestPathsConfigEnvironmentVariables(t *testing.T) {
+	// Set environment variables for paths
+	os.Setenv("RESOLVESPEC_PATHS_DATA_DIR", "/custom/data")
+	os.Setenv("RESOLVESPEC_PATHS_LOGS_DIR", "/custom/logs")
+	defer func() {
+		os.Unsetenv("RESOLVESPEC_PATHS_DATA_DIR")
+		os.Unsetenv("RESOLVESPEC_PATHS_LOGS_DIR")
+	}()
+
+	mgr := NewManager()
+	if err := mgr.Load(); err != nil {
+		t.Fatalf("Failed to load config: %v", err)
+	}
+
+	cfg, err := mgr.GetConfig()
+	if err != nil {
+		t.Fatalf("Failed to get config: %v", err)
+	}
+
+	// Test environment variable override of existing default path
+	dataDir, err := cfg.Paths.Get("data_dir")
+	if err != nil {
+		t.Errorf("Failed to get data_dir: %v", err)
+	}
+	if dataDir != "/custom/data" {
+		t.Errorf("Expected '/custom/data', got '%s'", dataDir)
+	}
+
+	// Test another environment variable override
+	logsDir, err := cfg.Paths.Get("logs_dir")
+	if err != nil {
+		t.Errorf("Failed to get logs_dir: %v", err)
+	}
+	if logsDir != "/custom/logs" {
+		t.Errorf("Expected '/custom/logs', got '%s'", logsDir)
+	}
+}
+
+func TestPathsConfigProgrammatic(t *testing.T) {
+	mgr := NewManager()
+
+	// Set custom paths programmatically
+	mgr.Set("paths.custom_dir", "/my/custom/dir")
+	mgr.Set("paths.cache_dir", "/var/cache/myapp")
+
+	cfg, err := mgr.GetConfig()
+	if err != nil {
+		t.Fatalf("Failed to get config: %v", err)
+	}
+
+	// Verify custom paths
+	customDir, err := cfg.Paths.Get("custom_dir")
+	if err != nil {
+		t.Errorf("Failed to get custom_dir: %v", err)
+	}
+	if customDir != "/my/custom/dir" {
+		t.Errorf("Expected '/my/custom/dir', got '%s'", customDir)
+	}
+
+	cacheDir, err := cfg.Paths.Get("cache_dir")
+	if err != nil {
+		t.Errorf("Failed to get cache_dir: %v", err)
+	}
+	if cacheDir != "/var/cache/myapp" {
+		t.Errorf("Expected '/var/cache/myapp', got '%s'", cacheDir)
 	}
 }