package config

import (
	"errors"
	"fmt"
	"os"
	"strings"

	"github.com/joho/godotenv"
)

// DefaultEnvFile is loaded automatically when it exists.
const DefaultEnvFile = ".env"

// LoadDotEnv loads KEY=VALUE pairs from the file named by ENV_FILE, or from
// .env in the current directory when ENV_FILE is unset.
//
// Variables that already exist in the process environment are never
// overwritten, so exported shell variables take precedence over the file.
// A missing default .env is ignored; an explicitly configured ENV_FILE must
// exist and be readable.
func LoadDotEnv() error {
	if path := strings.TrimSpace(os.Getenv("ENV_FILE")); path != "" {
		return LoadEnvFile(path)
	}

	if err := godotenv.Load(DefaultEnvFile); err != nil {
		if errors.Is(err, os.ErrNotExist) {
			return nil
		}
		return fmt.Errorf("load env file %s: %w", DefaultEnvFile, err)
	}
	return nil
}

// LoadEnvFile loads KEY=VALUE pairs from an explicit file. Existing process
// variables are not overwritten. The file must exist and be readable.
func LoadEnvFile(path string) error {
	path = strings.TrimSpace(path)
	if path == "" {
		return errors.New("env file path must not be empty")
	}
	if err := godotenv.Load(path); err != nil {
		return fmt.Errorf("load env file %s: %w", path, err)
	}
	return nil
}