Bootstrap milestone 0 and default API port 9999

internal/config/config.go

@@ -0,0 +1,68 @@
+package config
+
+import (
+	"fmt"
+	"os"
+	"strconv"
+	"time"
+)
+
+// Config holds process configuration loaded from environment variables.
+type Config struct {
+	HTTPAddr      string
+	ReadTimeout   time.Duration
+	WriteTimeout  time.Duration
+	ShutdownGrace time.Duration
+	DatabaseDSN   string
+	MigrationsDir string
+}
+
+func Load() (Config, error) {
+	readTimeout, err := envDuration("READ_TIMEOUT", 10*time.Second)
+	if err != nil {
+		return Config{}, err
+	}
+
+	writeTimeout, err := envDuration("WRITE_TIMEOUT", 15*time.Second)
+	if err != nil {
+		return Config{}, err
+	}
+
+	shutdownGrace, err := envDuration("SHUTDOWN_GRACE", 10*time.Second)
+	if err != nil {
+		return Config{}, err
+	}
+
+	return Config{
+		HTTPAddr:      envOrDefault("HTTP_ADDR", ":9999"),
+		ReadTimeout:   readTimeout,
+		WriteTimeout:  writeTimeout,
+		ShutdownGrace: shutdownGrace,
+		DatabaseDSN:   os.Getenv("DATABASE_DSN"),
+		MigrationsDir: envOrDefault("MIGRATIONS_DIR", "migrations"),
+	}, nil
+}
+
+func envOrDefault(key, fallback string) string {
+	if value := os.Getenv(key); value != "" {
+		return value
+	}
+	return fallback
+}
+
+func envDuration(key string, fallback time.Duration) (time.Duration, error) {
+	value := os.Getenv(key)
+	if value == "" {
+		return fallback, nil
+	}
+
+	seconds, err := strconv.Atoi(value)
+	if err != nil {
+		return 0, fmt.Errorf("%s must be an integer number of seconds: %w", key, err)
+	}
+	if seconds <= 0 {
+		return 0, fmt.Errorf("%s must be > 0", key)
+	}
+
+	return time.Duration(seconds) * time.Second, nil
+}