first commit

config.go

@@ -0,0 +1,93 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+// Copyright (C) 2026 Bryan Joshua Pedini
+
+package main
+
+import (
+	"fmt"
+	"os"
+	"strconv"
+)
+
+type Config struct {
+	PDNSAPIKey   string
+	ListenAddr   string
+	MySQLDSN     string
+	TablePrefix  string
+	PDNSServerID string
+	DefaultTTL   int
+	LogLevel     string
+	PUID         int
+	PGID         int
+}
+
+// LoadConfig reads configuration exclusively from environment variables.
+// Missing/invalid required variables are a fatal startup error.
+func LoadConfig() *Config {
+	c := &Config{
+		ListenAddr:   envOrDefault("LISTEN_ADDR", ":3000"),
+		TablePrefix:  envOrDefault("TABLE_PREFIX", "coredns_"),
+		PDNSServerID: envOrDefault("PDNS_SERVER_ID", "localhost"),
+		LogLevel:     envOrDefault("LOG_LEVEL", "info"),
+	}
+
+	c.PDNSAPIKey = requireEnv("PDNS_API_KEY")
+	c.MySQLDSN = requireEnv("MYSQL_DSN")
+
+	c.DefaultTTL = requirePositiveInt("DEFAULT_TTL", 120)
+
+	switch c.LogLevel {
+	case "debug", "info", "warn", "error":
+	default:
+		fatalf("invalid LOG_LEVEL %q: must be one of debug, info, warn, error", c.LogLevel)
+	}
+
+	c.PUID = requireInt("PUID")
+	c.PGID = requireInt("PGID")
+	if c.PUID == 0 || c.PGID == 0 {
+		fatalf("refusing to serve as root: PUID and PGID must both be non-zero")
+	}
+
+	return c
+}
+
+func envOrDefault(key, def string) string {
+	if v, ok := os.LookupEnv(key); ok && v != "" {
+		return v
+	}
+	return def
+}
+
+func requireEnv(key string) string {
+	v, ok := os.LookupEnv(key)
+	if !ok || v == "" {
+		fatalf("missing required environment variable: %s", key)
+	}
+	return v
+}
+
+func requireInt(key string) int {
+	v := requireEnv(key)
+	n, err := strconv.Atoi(v)
+	if err != nil {
+		fatalf("invalid %s: %q is not an integer", key, v)
+	}
+	return n
+}
+
+func requirePositiveInt(key string, def int) int {
+	v, ok := os.LookupEnv(key)
+	if !ok || v == "" {
+		return def
+	}
+	n, err := strconv.Atoi(v)
+	if err != nil || n <= 0 {
+		fatalf("invalid %s: %q is not a positive integer", key, v)
+	}
+	return n
+}
+
+func fatalf(format string, args ...any) {
+	fmt.Fprintf(os.Stderr, "config error: "+format+"\n", args...)
+	os.Exit(1)
+}