feat: migrate backend from rust to go

This commit replaces the Axum/Rust backend with a Gin/Go implementation. The original Rust code has been archived in the 'rust' branch.

internal/config/config.go

@@ -0,0 +1,174 @@
+package config
+
+import (
+	"encoding/base64"
+	"encoding/hex"
+	"fmt"
+	"os"
+	"strings"
+
+	"github.com/spf13/viper"
+)
+
+type Config struct {
+	Server        ServerConfig        `mapstructure:"server"`
+	Database      DatabaseConfig      `mapstructure:"database"`
+	Providers     ProviderConfig      `mapstructure:"providers"`
+	EncryptionKey string              `mapstructure:"encryption_key"`
+	KeyBytes      []byte
+}
+
+type ServerConfig struct {
+	Port       int      `mapstructure:"port"`
+	Host       string   `mapstructure:"host"`
+	AuthTokens []string `mapstructure:"auth_tokens"`
+}
+
+type DatabaseConfig struct {
+	Path           string `mapstructure:"path"`
+	MaxConnections int    `mapstructure:"max_connections"`
+}
+
+type ProviderConfig struct {
+	OpenAI   OpenAIConfig   `mapstructure:"openai"`
+	Gemini   GeminiConfig   `mapstructure:"gemini"`
+	DeepSeek DeepSeekConfig `mapstructure:"deepseek"`
+	Grok     GrokConfig     `mapstructure:"grok"`
+	Ollama   OllamaConfig   `mapstructure:"ollama"`
+}
+
+type OpenAIConfig struct {
+	APIKeyEnv    string `mapstructure:"api_key_env"`
+	BaseURL      string `mapstructure:"base_url"`
+	DefaultModel string `mapstructure:"default_model"`
+	Enabled      bool   `mapstructure:"enabled"`
+}
+
+type GeminiConfig struct {
+	APIKeyEnv    string `mapstructure:"api_key_env"`
+	BaseURL      string `mapstructure:"base_url"`
+	DefaultModel string `mapstructure:"default_model"`
+	Enabled      bool   `mapstructure:"enabled"`
+}
+
+type DeepSeekConfig struct {
+	APIKeyEnv    string `mapstructure:"api_key_env"`
+	BaseURL      string `mapstructure:"base_url"`
+	DefaultModel string `mapstructure:"default_model"`
+	Enabled      bool   `mapstructure:"enabled"`
+}
+
+type GrokConfig struct {
+	APIKeyEnv    string `mapstructure:"api_key_env"`
+	BaseURL      string `mapstructure:"base_url"`
+	DefaultModel string `mapstructure:"default_model"`
+	Enabled      bool   `mapstructure:"enabled"`
+}
+
+type OllamaConfig struct {
+	BaseURL      string   `mapstructure:"base_url"`
+	Enabled      bool     `mapstructure:"enabled"`
+	DefaultModel string   `mapstructure:"default_model"`
+	Models       []string `mapstructure:"models"`
+}
+
+func Load() (*Config, error) {
+	v := viper.New()
+
+	// Defaults
+	v.SetDefault("server.port", 8080)
+	v.SetDefault("server.host", "0.0.0.0")
+	v.SetDefault("server.auth_tokens", []string{})
+	v.SetDefault("database.path", "./data/llm_proxy.db")
+	v.SetDefault("database.max_connections", 10)
+
+	v.SetDefault("providers.openai.api_key_env", "OPENAI_API_KEY")
+	v.SetDefault("providers.openai.base_url", "https://api.openai.com/v1")
+	v.SetDefault("providers.openai.default_model", "gpt-4o")
+	v.SetDefault("providers.openai.enabled", true)
+
+	v.SetDefault("providers.gemini.api_key_env", "GEMINI_API_KEY")
+	v.SetDefault("providers.gemini.base_url", "https://generativelanguage.googleapis.com/v1")
+	v.SetDefault("providers.gemini.default_model", "gemini-2.0-flash")
+	v.SetDefault("providers.gemini.enabled", true)
+
+	v.SetDefault("providers.deepseek.api_key_env", "DEEPSEEK_API_KEY")
+	v.SetDefault("providers.deepseek.base_url", "https://api.deepseek.com")
+	v.SetDefault("providers.deepseek.default_model", "deepseek-reasoner")
+	v.SetDefault("providers.deepseek.enabled", true)
+
+	v.SetDefault("providers.grok.api_key_env", "GROK_API_KEY")
+	v.SetDefault("providers.grok.base_url", "https://api.x.ai/v1")
+	v.SetDefault("providers.grok.default_model", "grok-beta")
+	v.SetDefault("providers.grok.enabled", true)
+
+	v.SetDefault("providers.ollama.base_url", "http://localhost:11434/v1")
+	v.SetDefault("providers.ollama.enabled", false)
+	v.SetDefault("providers.ollama.models", []string{})
+
+	// Environment variables
+	v.SetEnvPrefix("LLM_PROXY")
+	v.SetEnvKeyReplacer(strings.NewReplacer(".", "__"))
+	v.AutomaticEnv()
+
+	// Config file
+	v.SetConfigName("config")
+	v.SetConfigType("toml")
+	v.AddConfigPath(".")
+	if envPath := os.Getenv("LLM_PROXY__CONFIG_PATH"); envPath != "" {
+		v.SetConfigFile(envPath)
+	}
+
+	if err := v.ReadInConfig(); err != nil {
+		if _, ok := err.(viper.ConfigFileNotFoundError); !ok {
+			return nil, fmt.Errorf("failed to read config file: %w", err)
+		}
+	}
+
+	var cfg Config
+	if err := v.Unmarshal(&cfg); err != nil {
+		return nil, fmt.Errorf("failed to unmarshal config: %w", err)
+	}
+
+	// Validate encryption key
+	if cfg.EncryptionKey == "" {
+		return nil, fmt.Errorf("encryption key is required (LLM_PROXY__ENCRYPTION_KEY)")
+	}
+
+	keyBytes, err := hex.DecodeString(cfg.EncryptionKey)
+	if err != nil {
+		keyBytes, err = base64.StdEncoding.DecodeString(cfg.EncryptionKey)
+		if err != nil {
+			return nil, fmt.Errorf("encryption key must be hex or base64 encoded")
+		}
+	}
+
+	if len(keyBytes) != 32 {
+		return nil, fmt.Errorf("encryption key must be 32 bytes, got %d", len(keyBytes))
+	}
+	cfg.KeyBytes = keyBytes
+
+	return &cfg, nil
+}
+
+func (c *Config) GetAPIKey(provider string) (string, error) {
+	var envVar string
+	switch provider {
+	case "openai":
+		envVar = c.Providers.OpenAI.APIKeyEnv
+	case "gemini":
+		envVar = c.Providers.Gemini.APIKeyEnv
+	case "deepseek":
+		envVar = c.Providers.DeepSeek.APIKeyEnv
+	case "grok":
+		envVar = c.Providers.Grok.APIKeyEnv
+	default:
+		return "", fmt.Errorf("unknown provider: %s", provider)
+	}
+
+	val := os.Getenv(envVar)
+	if val == "" {
+		return "", fmt.Errorf("environment variable %s not set for %s", envVar, provider)
+	}
+	return val, nil
+}