feat: add TOML config system with layered loading

Layers: defaults → ~/.config/gnoma/config.toml → .gnoma/config.toml
→ environment variables. Supports ${VAR} references in API keys,
GNOMA_PROVIDER/GNOMA_MODEL env overrides, alternative env var names
(ANTHROPICS_API_KEY, GOOGLE_API_KEY).

Custom Duration type for TOML string parsing. 6 tests.

go.mod

@@ -3,6 +3,7 @@ module somegit.dev/Owlibou/gnoma
 go 1.26.1
 
 require (
+	github.com/BurntSushi/toml v0.3.1
 	github.com/VikingOwl91/mistral-go-sdk v1.2.1
 	github.com/anthropics/anthropic-sdk-go v1.29.0
 	github.com/openai/openai-go v1.12.0

go.sum

@@ -5,6 +5,7 @@ cloud.google.com/go/auth v0.9.3 h1:VOEUIAADkkLtyfr3BLa3R8Ed/j6w1jTBmARx+wb5w5U=
 cloud.google.com/go/auth v0.9.3/go.mod h1:7z6VY+7h3KUdRov5F1i8NDP5ZzWKYmEPO842BgCsmTk=
 cloud.google.com/go/compute/metadata v0.5.0 h1:Zr0eK8JbFv6+Wi4ilXAR8FJ3wyNdpxHKJNPos6LTZOY=
 cloud.google.com/go/compute/metadata v0.5.0/go.mod h1:aHnloV2TPI38yx4s9+wAZhHykWvVCfu7hQbF+9CWoiY=
+github.com/BurntSushi/toml v0.3.1 h1:WXkYYl6Yr3qBf1K79EBnL4mak0OimBfB0XUf9Vl28OQ=
 github.com/BurntSushi/toml v0.3.1/go.mod h1:xHWCNGjB5oqiDr8zfno3MHue2Ht5sIBksp03qcyfWMU=
 github.com/VikingOwl91/mistral-go-sdk v1.2.1 h1:6OQMtOzJUFcvFUEtbX9VlglUPBn+dKOrQPnyoVKlpkA=
 github.com/VikingOwl91/mistral-go-sdk v1.2.1/go.mod h1:f4emNtHUx2zSqY3V0LBz6lNI1jE6q/zh+SEU+/hJ0i4=

internal/config/config.go

@@ -0,0 +1,39 @@
+package config
+
+import "time"
+
+// Config is the top-level configuration.
+type Config struct {
+	Provider   ProviderSection   `toml:"provider"`
+	Tools      ToolsSection      `toml:"tools"`
+}
+
+type ProviderSection struct {
+	Default     string            `toml:"default"`
+	Model       string            `toml:"model"`
+	MaxTokens   int64             `toml:"max_tokens"`
+	Temperature *float64          `toml:"temperature"`
+	APIKeys     map[string]string `toml:"api_keys"`
+	Endpoints   map[string]string `toml:"endpoints"`
+}
+
+type ToolsSection struct {
+	BashTimeout Duration `toml:"bash_timeout"`
+	MaxFileSize int64    `toml:"max_file_size"`
+}
+
+// Duration wraps time.Duration for TOML string parsing (e.g. "30s", "5m").
+type Duration time.Duration
+
+func (d *Duration) UnmarshalText(text []byte) error {
+	parsed, err := time.ParseDuration(string(text))
+	if err != nil {
+		return err
+	}
+	*d = Duration(parsed)
+	return nil
+}
+
+func (d Duration) Duration() time.Duration {
+	return time.Duration(d)
+}

internal/config/config_test.go

@@ -0,0 +1,165 @@
+package config
+
+import (
+	"os"
+	"path/filepath"
+	"testing"
+	"time"
+)
+
+func TestDefaults(t *testing.T) {
+	cfg := Defaults()
+	if cfg.Provider.Default != "mistral" {
+		t.Errorf("Provider.Default = %q, want mistral", cfg.Provider.Default)
+	}
+	if cfg.Provider.MaxTokens != 8192 {
+		t.Errorf("Provider.MaxTokens = %d", cfg.Provider.MaxTokens)
+	}
+	if cfg.Tools.BashTimeout.Duration() != 30*time.Second {
+		t.Errorf("Tools.BashTimeout = %v", cfg.Tools.BashTimeout)
+	}
+}
+
+func TestLoadTOML(t *testing.T) {
+	dir := t.TempDir()
+	path := filepath.Join(dir, "config.toml")
+
+	content := `
+[provider]
+default = "anthropic"
+model = "claude-sonnet-4"
+max_tokens = 16384
+
+[provider.api_keys]
+anthropic = "sk-test-123"
+
+[provider.endpoints]
+ollama = "http://myhost:11434/v1"
+
+[tools]
+bash_timeout = "60s"
+max_file_size = 2097152
+`
+	os.WriteFile(path, []byte(content), 0o644)
+
+	cfg := Defaults()
+	if err := loadTOML(&cfg, path); err != nil {
+		t.Fatalf("loadTOML: %v", err)
+	}
+
+	if cfg.Provider.Default != "anthropic" {
+		t.Errorf("Provider.Default = %q", cfg.Provider.Default)
+	}
+	if cfg.Provider.Model != "claude-sonnet-4" {
+		t.Errorf("Provider.Model = %q", cfg.Provider.Model)
+	}
+	if cfg.Provider.MaxTokens != 16384 {
+		t.Errorf("Provider.MaxTokens = %d", cfg.Provider.MaxTokens)
+	}
+	if cfg.Provider.APIKeys["anthropic"] != "sk-test-123" {
+		t.Errorf("APIKeys[anthropic] = %q", cfg.Provider.APIKeys["anthropic"])
+	}
+	if cfg.Provider.Endpoints["ollama"] != "http://myhost:11434/v1" {
+		t.Errorf("Endpoints[ollama] = %q", cfg.Provider.Endpoints["ollama"])
+	}
+	if cfg.Tools.BashTimeout.Duration() != 60*time.Second {
+		t.Errorf("Tools.BashTimeout = %v", cfg.Tools.BashTimeout)
+	}
+	if cfg.Tools.MaxFileSize != 2097152 {
+		t.Errorf("Tools.MaxFileSize = %d", cfg.Tools.MaxFileSize)
+	}
+}
+
+func TestLoadTOML_FileNotFound(t *testing.T) {
+	cfg := Defaults()
+	err := loadTOML(&cfg, "/nonexistent/config.toml")
+	if !os.IsNotExist(err) {
+		t.Errorf("expected os.IsNotExist, got %v", err)
+	}
+}
+
+func TestApplyEnv(t *testing.T) {
+	cfg := Defaults()
+
+	t.Setenv("MISTRAL_API_KEY", "sk-mistral-test")
+	t.Setenv("ANTHROPICS_API_KEY", "sk-anthro-test")
+	t.Setenv("GOOGLE_API_KEY", "goog-test")
+	t.Setenv("GNOMA_PROVIDER", "openai")
+	t.Setenv("GNOMA_MODEL", "gpt-4o-mini")
+
+	applyEnv(&cfg)
+
+	if cfg.Provider.APIKeys["mistral"] != "sk-mistral-test" {
+		t.Errorf("APIKeys[mistral] = %q", cfg.Provider.APIKeys["mistral"])
+	}
+	if cfg.Provider.APIKeys["anthropic"] != "sk-anthro-test" {
+		t.Errorf("APIKeys[anthropic] = %q (should pick ANTHROPICS_API_KEY)", cfg.Provider.APIKeys["anthropic"])
+	}
+	if cfg.Provider.APIKeys["google"] != "goog-test" {
+		t.Errorf("APIKeys[google] = %q (should pick GOOGLE_API_KEY)", cfg.Provider.APIKeys["google"])
+	}
+	if cfg.Provider.Default != "openai" {
+		t.Errorf("Provider.Default = %q, want openai (from GNOMA_PROVIDER)", cfg.Provider.Default)
+	}
+	if cfg.Provider.Model != "gpt-4o-mini" {
+		t.Errorf("Provider.Model = %q, want gpt-4o-mini (from GNOMA_MODEL)", cfg.Provider.Model)
+	}
+}
+
+func TestApplyEnv_EnvVarReference(t *testing.T) {
+	cfg := Defaults()
+	cfg.Provider.APIKeys["custom"] = "${MY_CUSTOM_KEY}"
+
+	t.Setenv("MY_CUSTOM_KEY", "resolved-value")
+
+	applyEnv(&cfg)
+
+	if cfg.Provider.APIKeys["custom"] != "resolved-value" {
+		t.Errorf("APIKeys[custom] = %q, want resolved-value", cfg.Provider.APIKeys["custom"])
+	}
+}
+
+func TestLayeredLoad(t *testing.T) {
+	// Set up global config
+	globalDir := t.TempDir()
+	gnomaDir := filepath.Join(globalDir, "gnoma")
+	os.MkdirAll(gnomaDir, 0o755)
+	os.WriteFile(filepath.Join(gnomaDir, "config.toml"), []byte(`
+[provider]
+default = "anthropic"
+max_tokens = 4096
+`), 0o644)
+
+	// Set up project config that overrides
+	projectDir := t.TempDir()
+	pGnomaDir := filepath.Join(projectDir, ".gnoma")
+	os.MkdirAll(pGnomaDir, 0o755)
+	os.WriteFile(filepath.Join(pGnomaDir, "config.toml"), []byte(`
+[provider]
+model = "claude-haiku"
+`), 0o644)
+
+	// Override XDG_CONFIG_HOME and working directory
+	t.Setenv("XDG_CONFIG_HOME", globalDir)
+	origDir, _ := os.Getwd()
+	os.Chdir(projectDir)
+	defer os.Chdir(origDir)
+
+	cfg, err := Load()
+	if err != nil {
+		t.Fatalf("Load: %v", err)
+	}
+
+	// Global: default = anthropic
+	if cfg.Provider.Default != "anthropic" {
+		t.Errorf("Default = %q, want anthropic (from global)", cfg.Provider.Default)
+	}
+	// Project: model = claude-haiku
+	if cfg.Provider.Model != "claude-haiku" {
+		t.Errorf("Model = %q, want claude-haiku (from project)", cfg.Provider.Model)
+	}
+	// Global: max_tokens = 4096
+	if cfg.Provider.MaxTokens != 4096 {
+		t.Errorf("MaxTokens = %d, want 4096 (from global)", cfg.Provider.MaxTokens)
+	}
+}

internal/config/defaults.go

@@ -0,0 +1,19 @@
+package config
+
+import "time"
+
+func Defaults() Config {
+	return Config{
+		Provider: ProviderSection{
+			Default:   "mistral",
+			Model:     "",
+			MaxTokens: 8192,
+			APIKeys:   make(map[string]string),
+			Endpoints: make(map[string]string),
+		},
+		Tools: ToolsSection{
+			BashTimeout: Duration(30 * time.Second),
+			MaxFileSize: 1 << 20, // 1MB
+		},
+	}
+}

internal/config/load.go

@@ -0,0 +1,105 @@
+package config
+
+import (
+	"fmt"
+	"os"
+	"path/filepath"
+	"strings"
+
+	"github.com/BurntSushi/toml"
+)
+
+// Load reads and merges config from all layers.
+// Order (lowest to highest priority):
+// 1. Defaults
+// 2. Global config: ~/.config/gnoma/config.toml
+// 3. Project config: .gnoma/config.toml
+// 4. Environment variables
+func Load() (*Config, error) {
+	cfg := Defaults()
+
+	// Layer 1: Global config
+	globalPath := globalConfigPath()
+	if err := loadTOML(&cfg, globalPath); err != nil && !os.IsNotExist(err) {
+		return nil, fmt.Errorf("loading global config %s: %w", globalPath, err)
+	}
+
+	// Layer 2: Project config
+	projectPath := projectConfigPath()
+	if err := loadTOML(&cfg, projectPath); err != nil && !os.IsNotExist(err) {
+		return nil, fmt.Errorf("loading project config %s: %w", projectPath, err)
+	}
+
+	// Layer 3: Environment variables
+	applyEnv(&cfg)
+
+	return &cfg, nil
+}
+
+func loadTOML(cfg *Config, path string) error {
+	data, err := os.ReadFile(path)
+	if err != nil {
+		return err
+	}
+	_, err = toml.Decode(string(data), cfg)
+	return err
+}
+
+func globalConfigPath() string {
+	// XDG_CONFIG_HOME or ~/.config
+	configDir := os.Getenv("XDG_CONFIG_HOME")
+	if configDir == "" {
+		home, _ := os.UserHomeDir()
+		configDir = filepath.Join(home, ".config")
+	}
+	return filepath.Join(configDir, "gnoma", "config.toml")
+}
+
+func projectConfigPath() string {
+	return filepath.Join(".gnoma", "config.toml")
+}
+
+func applyEnv(cfg *Config) {
+	envKeys := map[string]string{
+		"mistral":   "MISTRAL_API_KEY",
+		"anthropic": "ANTHROPIC_API_KEY",
+		"openai":    "OPENAI_API_KEY",
+		"google":    "GEMINI_API_KEY",
+	}
+	// Also check alternative names
+	altKeys := map[string][]string{
+		"anthropic": {"ANTHROPICS_API_KEY"},
+		"google":    {"GOOGLE_API_KEY"},
+	}
+
+	for provider, envVar := range envKeys {
+		if key := os.Getenv(envVar); key != "" {
+			cfg.Provider.APIKeys[provider] = key
+			continue
+		}
+		for _, alt := range altKeys[provider] {
+			if key := os.Getenv(alt); key != "" {
+				cfg.Provider.APIKeys[provider] = key
+				break
+			}
+		}
+	}
+
+	// Resolve ${VAR} references in configured API keys
+	for k, v := range cfg.Provider.APIKeys {
+		if strings.HasPrefix(v, "${") && strings.HasSuffix(v, "}") {
+			envName := v[2 : len(v)-1]
+			if resolved := os.Getenv(envName); resolved != "" {
+				cfg.Provider.APIKeys[k] = resolved
+			}
+		}
+	}
+
+	// Provider override
+	if p := os.Getenv("GNOMA_PROVIDER"); p != "" {
+		cfg.Provider.Default = p
+	}
+	if m := os.Getenv("GNOMA_MODEL"); m != "" {
+		cfg.Provider.Model = m
+	}
+}