feat: bootstrap goaichat CLI and config system

internal/config/config.go

@@ -0,0 +1,127 @@
+package config
+
+import (
+	"errors"
+	"fmt"
+	"os"
+	"strings"
+
+	"gopkg.in/yaml.v3"
+)
+
+const (
+	envAPIKey = "GOAICHAT_API_KEY"
+	envAPIURL = "GOAICHAT_API_URL"
+)
+
+// Config captures runtime configuration for the Goaichat application.
+type Config struct {
+	API    APIConfig    `yaml:"api"`
+	Model  ModelConfig  `yaml:"model"`
+	Logging LoggingConfig `yaml:"logging"`
+	UI     UIConfig     `yaml:"ui"`
+}
+
+// APIConfig holds settings for connecting to the OpenAI-compatible API.
+type APIConfig struct {
+	URL string `yaml:"url"`
+	Key string `yaml:"key"`
+}
+
+// ModelConfig controls default model behaviour.
+type ModelConfig struct {
+	Name        string  `yaml:"name"`
+	Temperature float64 `yaml:"temperature"`
+	Stream      bool    `yaml:"stream"`
+}
+
+// LoggingConfig encapsulates logging preferences.
+type LoggingConfig struct {
+	Level string `yaml:"level"`
+}
+
+// UIConfig defines terminal rendering preferences.
+type UIConfig struct {
+	ShowTimestamps bool `yaml:"show_timestamps"`
+}
+
+// Load reads configuration from the provided path, falling back to defaults and
+// environment overrides.
+func Load(path string) (*Config, error) {
+	cfg := defaultConfig()
+
+	if path != "" {
+		if err := loadFile(path, &cfg); err != nil {
+			return nil, err
+		}
+	} else {
+		if err := loadFile("config.yaml", &cfg); err != nil && !errors.Is(err, os.ErrNotExist) {
+			return nil, err
+		}
+	}
+
+	applyEnvOverrides(&cfg)
+
+	if err := cfg.validate(); err != nil {
+		return nil, err
+	}
+
+	return &cfg, nil
+}
+
+func loadFile(path string, cfg *Config) error {
+	data, err := os.ReadFile(path)
+	if err != nil {
+		if errors.Is(err, os.ErrNotExist) {
+			return err
+		}
+		return fmt.Errorf("read config: %w", err)
+	}
+
+	if err := yaml.Unmarshal(data, cfg); err != nil {
+		return fmt.Errorf("parse config: %w", err)
+	}
+
+	return nil
+}
+
+func applyEnvOverrides(cfg *Config) {
+	if url := strings.TrimSpace(os.Getenv(envAPIURL)); url != "" {
+		cfg.API.URL = url
+	}
+	if key := strings.TrimSpace(os.Getenv(envAPIKey)); key != "" {
+		cfg.API.Key = key
+	}
+}
+
+func (c *Config) validate() error {
+	if strings.TrimSpace(c.API.URL) == "" {
+		return errors.New("api.url must be set")
+	}
+	if strings.TrimSpace(c.API.Key) == "" {
+		return errors.New("api.key must be set or GOAICHAT_API_KEY provided")
+	}
+	if c.Model.Temperature < 0 || c.Model.Temperature > 2 {
+		return fmt.Errorf("model.temperature must be between 0 and 2, got %f", c.Model.Temperature)
+	}
+	return nil
+}
+
+func defaultConfig() Config {
+	return Config{
+		API: APIConfig{
+			URL: "https://api.openai.com/v1",
+		},
+		Model: ModelConfig{
+			Name:        "gpt-4o-mini",
+			Temperature: 0.7,
+			Stream:      true,
+		},
+		Logging: LoggingConfig{
+			Level: "info",
+		},
+		UI: UIConfig{
+			ShowTimestamps: true,
+		},
+	}
+}