Dialectic.Backend/internal/config/config.go

// Package config loads runtime configuration from environment variables.
//
// Conventions:
//   - 12-factor: every config knob is an env var; no config files.
//   - Sensible dev defaults for local docker-compose; prod sets via env.
//   - Sensitive values (DB password, system api key) are *required* in
//     prod; LoadFromEnv() fails fast if absent and ENV_MODE != "dev".
package config

import (
	"fmt"
	"os"
	"strings"
)

type Config struct {
	// "dev" | "prod". Dev relaxes required-field checks and enables a
	// dev-mode auth bypass token. Prod requires every sensitive field.
	Mode string

	// HTTP server bind. e.g. "0.0.0.0:8090".
	HTTPAddr string

	// CORS allowed origins (comma-separated; "*" allowed only in dev).
	CORSAllowOrigins []string

	// MySQL DSN parts.
	DBHost     string
	DBPort     string
	DBName     string
	DBUser     string
	DBPassword string

	// Auth.
	//
	// SystemAPIKey: Phase-1 system key for posting to announce channels
	// in Fabric. Mirrored here so Dialectic backend itself can post topic
	// announcements via Fabric's POST /channels/:id/messages with
	// x-fabric-system-key header.
	//
	// AgentAPIKeyPepper: HMAC pepper for hashing agent API keys at rest
	// (we store sha256(pepper || raw) not the raw key). Rotating the
	// pepper invalidates all keys — that's intentional, an emergency
	// kill switch.
	//
	// OIDCDevBypassToken: dev-mode only. If set AND Mode == "dev", a
	// browser request with header `x-dev-bypass: <token>` bypasses OIDC
	// and is treated as user "dev-operator" with role "dialectic-admin".
	// Prod ignores this even if set.
	SystemAPIKey       string
	AgentAPIKeyPepper  string
	OIDCDevBypassToken string

	// OIDC issuer URL (Keycloak realm endpoint). e.g.
	// https://auth.hangman-lab.top/realms/hangman-lab
	// Phase 2C ships this as configured-but-not-verified; Phase 4 wires
	// real JWKS validation.
	OIDCIssuer   string
	OIDCClientID string
}

func LoadFromEnv() (*Config, error) {
	c := &Config{
		Mode:               getenv("ENV_MODE", "dev"),
		HTTPAddr:           getenv("HTTP_ADDR", "0.0.0.0:8090"),
		CORSAllowOrigins:   splitCSV(getenv("CORS_ALLOW_ORIGINS", "*")),
		DBHost:             getenv("DB_HOST", "127.0.0.1"),
		DBPort:             getenv("DB_PORT", "3306"),
		DBName:             getenv("DB_NAME", "dialectic"),
		DBUser:             getenv("DB_USER", "dialectic"),
		DBPassword:         os.Getenv("DB_PASSWORD"),
		SystemAPIKey:       os.Getenv("SYSTEM_API_KEY"),
		AgentAPIKeyPepper:  os.Getenv("AGENT_API_KEY_PEPPER"),
		OIDCDevBypassToken: os.Getenv("OIDC_DEV_BYPASS_TOKEN"),
		OIDCIssuer:         os.Getenv("OIDC_ISSUER"),
		OIDCClientID:       os.Getenv("OIDC_CLIENT_ID"),
	}

	if c.Mode != "dev" && c.Mode != "prod" {
		return nil, fmt.Errorf("ENV_MODE must be dev|prod, got %q", c.Mode)
	}

	if c.Mode == "prod" {
		var missing []string
		if c.DBPassword == "" {
			missing = append(missing, "DB_PASSWORD")
		}
		if c.AgentAPIKeyPepper == "" {
			missing = append(missing, "AGENT_API_KEY_PEPPER")
		}
		if c.OIDCIssuer == "" {
			missing = append(missing, "OIDC_ISSUER")
		}
		if c.OIDCClientID == "" {
			missing = append(missing, "OIDC_CLIENT_ID")
		}
		if len(missing) > 0 {
			return nil, fmt.Errorf("prod mode requires env: %s", strings.Join(missing, ", "))
		}
		// In prod, "*" CORS is never accepted.
		for _, o := range c.CORSAllowOrigins {
			if o == "*" {
				return nil, fmt.Errorf("prod mode forbids CORS_ALLOW_ORIGINS='*'")
			}
		}
	}

	return c, nil
}

func (c *Config) IsDev() bool { return c.Mode == "dev" }

func (c *Config) DSN() string {
	// MySQL DSN: user:pass@tcp(host:port)/dbname?params
	return fmt.Sprintf(
		"%s:%s@tcp(%s:%s)/%s?parseTime=true&charset=utf8mb4&collation=utf8mb4_unicode_ci",
		c.DBUser, c.DBPassword, c.DBHost, c.DBPort, c.DBName,
	)
}

func getenv(key, fallback string) string {
	if v := os.Getenv(key); v != "" {
		return v
	}
	return fallback
}

func splitCSV(s string) []string {
	if s == "" {
		return nil
	}
	parts := strings.Split(s, ",")
	out := make([]string, 0, len(parts))
	for _, p := range parts {
		p = strings.TrimSpace(p)
		if p != "" {
			out = append(out, p)
		}
	}
	return out
}