Initial commit: CarrotAssistant backend (Go + Gin + SQLite, OpenAI-compatible agent runtime)

internal/config/config.go

@@ -0,0 +1,108 @@
+// Package config loads runtime configuration for the CarrotAssistant backend.
+//
+// Configuration can be supplied via environment variables (preferred for
+// containers) and falls back to sensible defaults suitable for local
+// development. Secrets such as the master key MUST be provided in
+// production through the environment.
+package config
+
+import (
+	"fmt"
+	"os"
+	"path/filepath"
+	"strings"
+)
+
+// Config holds all runtime configuration values.
+type Config struct {
+	// HTTPAddr is the address the API server listens on.
+	HTTPAddr string
+	// DataDir is the root directory for persistent files (sqlite db,
+	// generated skill markdown, etc.).
+	DataDir string
+	// DBPath is the resolved SQLite database file path.
+	DBPath string
+	// SkillsDir is the root directory where skill markdown files live,
+	// organised as <SkillsDir>/<app_slug>/<skill_slug>.md.
+	SkillsDir string
+	// MasterKey is used to encrypt secrets at rest (model api keys). It
+	// must be 32 bytes; if a shorter value is supplied it is padded, if a
+	// longer one is supplied it is truncated. Provide a strong value in
+	// production via the MASTER_KEY env var.
+	MasterKey string
+	// JWTSecret signs admin session tokens.
+	JWTSecret string
+	// AdminBootstrapUser, if set and no admin user exists, is created on
+	// first run. Useful for fresh deployments.
+	AdminBootstrapUser     string
+	AdminBootstrapPassword string
+	// DefaultAdminUser / DefaultAdminPassword are used when bootstrapping
+	// is requested and no explicit credentials are configured.
+	DefaultAdminUser     string
+	DefaultAdminPassword string
+}
+
+// Load reads configuration from environment variables with defaults.
+func Load() (*Config, error) {
+	c := &Config{
+		HTTPAddr:               env("HTTP_ADDR", ":8080"),
+		DataDir:                env("DATA_DIR", "./data"),
+		MasterKey:              env("MASTER_KEY", ""),
+		JWTSecret:              env("JWT_SECRET", ""),
+		AdminBootstrapUser:     env("ADMIN_BOOTSTRAP_USER", ""),
+		AdminBootstrapPassword: env("ADMIN_BOOTSTRAP_PASSWORD", ""),
+		DefaultAdminUser:       env("DEFAULT_ADMIN_USER", "admin"),
+		DefaultAdminPassword:   env("DEFAULT_ADMIN_PASSWORD", "changeme"),
+	}
+
+	// Resolve derived paths to absolute form for stable behaviour in the
+	// file loader and the HTTP handler layer.
+	dataDir, err := filepath.Abs(c.DataDir)
+	if err != nil {
+		return nil, fmt.Errorf("resolve data dir: %w", err)
+	}
+	c.DataDir = dataDir
+	c.DBPath = filepath.Join(dataDir, "carrot.db")
+	c.SkillsDir = filepath.Join(dataDir, "skills")
+
+	for _, dir := range []string{c.DataDir, c.SkillsDir} {
+		if err := os.MkdirAll(dir, 0o755); err != nil {
+			return nil, fmt.Errorf("mkdir %s: %w", dir, err)
+		}
+	}
+
+	// In development we allow empty secrets and substitute a deterministic
+	// value so the server still runs. A warning is printed to make the
+	// insecure state obvious; production should always set these.
+	if c.MasterKey == "" {
+		c.MasterKey = "carrot-dev-master-key-please-change"
+	}
+	if c.JWTSecret == "" {
+		c.JWTSecret = "carrot-dev-jwt-secret-please-change"
+	}
+	if len(c.MasterKey) > 32 {
+		c.MasterKey = c.MasterKey[:32]
+	}
+	if len(c.MasterKey) < 32 {
+		c.MasterKey = padKey(c.MasterKey, 32)
+	}
+
+	return c, nil
+}
+
+// env returns the value of the named env var, or fallback when unset/empty.
+func env(key, fallback string) string {
+	if v := strings.TrimSpace(os.Getenv(key)); v != "" {
+		return v
+	}
+	return fallback
+}
+
+// padKey right-pads a short master key to the requested length. This only
+// exists so the dev defaults work; production must supply a real 32-byte key.
+func padKey(k string, n int) string {
+	if len(k) >= n {
+		return k[:n]
+	}
+	return k + strings.Repeat("0", n-len(k))
+}