first commit

internal/config/config.go

@@ -0,0 +1,215 @@
+package config
+
+import (
+	"fmt"
+	"log/slog"
+	"net/netip"
+	"os"
+	"strconv"
+	"strings"
+	"time"
+)
+
+const defaultTrustedProxyCIDRs = "127.0.0.1/32,::1/128"
+
+type Config struct {
+	Addr              string
+	TrustProxyHeaders bool
+	TrustedProxyCIDRs []netip.Prefix
+	ReadHeaderTimeout time.Duration
+	ReadTimeout       time.Duration
+	WriteTimeout      time.Duration
+	IdleTimeout       time.Duration
+	ShutdownTimeout   time.Duration
+	MaxHeaderBytes    int
+	LogLevel          slog.Level
+	LogFormat         string
+}
+
+func Load() (Config, error) {
+	trustProxyHeaders, err := envBool("TRUST_PROXY_HEADERS", false)
+	if err != nil {
+		return Config{}, err
+	}
+
+	trustedProxyCIDRs, err := envPrefixes("TRUSTED_PROXY_CIDRS", defaultTrustedProxyCIDRs)
+	if err != nil {
+		return Config{}, err
+	}
+
+	readHeaderTimeout, err := envDuration("READ_HEADER_TIMEOUT", 5*time.Second)
+	if err != nil {
+		return Config{}, err
+	}
+
+	readTimeout, err := envDuration("READ_TIMEOUT", 10*time.Second)
+	if err != nil {
+		return Config{}, err
+	}
+
+	writeTimeout, err := envDuration("WRITE_TIMEOUT", 10*time.Second)
+	if err != nil {
+		return Config{}, err
+	}
+
+	idleTimeout, err := envDuration("IDLE_TIMEOUT", 60*time.Second)
+	if err != nil {
+		return Config{}, err
+	}
+
+	shutdownTimeout, err := envDuration("SHUTDOWN_TIMEOUT", 5*time.Second)
+	if err != nil {
+		return Config{}, err
+	}
+
+	maxHeaderBytes, err := envInt("MAX_HEADER_BYTES", 1<<20)
+	if err != nil {
+		return Config{}, err
+	}
+
+	logLevel, err := envLogLevel("LOG_LEVEL", slog.LevelInfo)
+	if err != nil {
+		return Config{}, err
+	}
+
+	logFormat, err := envLogFormat("LOG_FORMAT", "text")
+	if err != nil {
+		return Config{}, err
+	}
+
+	return Config{
+		Addr:              envString("ADDR", ":8080"),
+		TrustProxyHeaders: trustProxyHeaders,
+		TrustedProxyCIDRs: trustedProxyCIDRs,
+		ReadHeaderTimeout: readHeaderTimeout,
+		ReadTimeout:       readTimeout,
+		WriteTimeout:      writeTimeout,
+		IdleTimeout:       idleTimeout,
+		ShutdownTimeout:   shutdownTimeout,
+		MaxHeaderBytes:    maxHeaderBytes,
+		LogLevel:          logLevel,
+		LogFormat:         logFormat,
+	}, nil
+}
+
+func envString(name, fallback string) string {
+	value := strings.TrimSpace(os.Getenv(name))
+	if value == "" {
+		return fallback
+	}
+
+	return value
+}
+
+func envBool(name string, fallback bool) (bool, error) {
+	value := strings.TrimSpace(os.Getenv(name))
+	if value == "" {
+		return fallback, nil
+	}
+
+	parsed, err := strconv.ParseBool(value)
+	if err != nil {
+		return false, fmt.Errorf("%s must be a boolean value: %w", name, err)
+	}
+
+	return parsed, nil
+}
+
+func envDuration(name string, fallback time.Duration) (time.Duration, error) {
+	value := strings.TrimSpace(os.Getenv(name))
+	if value == "" {
+		return fallback, nil
+	}
+
+	parsed, err := time.ParseDuration(value)
+	if err != nil {
+		return 0, fmt.Errorf("%s must be a duration like 5s or 1m: %w", name, err)
+	}
+
+	if parsed <= 0 {
+		return 0, fmt.Errorf("%s must be greater than zero", name)
+	}
+
+	return parsed, nil
+}
+
+func envInt(name string, fallback int) (int, error) {
+	value := strings.TrimSpace(os.Getenv(name))
+	if value == "" {
+		return fallback, nil
+	}
+
+	parsed, err := strconv.Atoi(value)
+	if err != nil {
+		return 0, fmt.Errorf("%s must be an integer: %w", name, err)
+	}
+
+	if parsed <= 0 {
+		return 0, fmt.Errorf("%s must be greater than zero", name)
+	}
+
+	return parsed, nil
+}
+
+func envPrefixes(name, fallback string) ([]netip.Prefix, error) {
+	value := strings.TrimSpace(os.Getenv(name))
+	if value == "" {
+		value = fallback
+	}
+
+	parts := strings.Split(value, ",")
+	prefixes := make([]netip.Prefix, 0, len(parts))
+
+	for _, part := range parts {
+		part = strings.TrimSpace(part)
+		if part == "" {
+			continue
+		}
+
+		if prefix, err := netip.ParsePrefix(part); err == nil {
+			prefixes = append(prefixes, prefix.Masked())
+			continue
+		}
+
+		addr, err := netip.ParseAddr(part)
+		if err != nil {
+			return nil, fmt.Errorf("%s contains invalid CIDR or IP %q: %w", name, part, err)
+		}
+
+		prefixes = append(prefixes, netip.PrefixFrom(addr, addr.BitLen()))
+	}
+
+	if len(prefixes) == 0 {
+		return nil, fmt.Errorf("%s must contain at least one CIDR or IP", name)
+	}
+
+	return prefixes, nil
+}
+
+func envLogLevel(name string, fallback slog.Level) (slog.Level, error) {
+	value := strings.TrimSpace(os.Getenv(name))
+	if value == "" {
+		return fallback, nil
+	}
+
+	var level slog.Level
+	if err := level.UnmarshalText([]byte(strings.ToUpper(value))); err != nil {
+		return 0, fmt.Errorf("%s must be debug, info, warn, or error: %w", name, err)
+	}
+
+	return level, nil
+}
+
+func envLogFormat(name, fallback string) (string, error) {
+	value := strings.ToLower(strings.TrimSpace(os.Getenv(name)))
+	if value == "" {
+		return fallback, nil
+	}
+
+	switch value {
+	case "text", "json":
+		return value, nil
+	default:
+		return "", fmt.Errorf("%s must be text or json", name)
+	}
+}