package config

import (
	"fmt"
	"os"

	"github.com/joho/godotenv"
)

// Config holds all configuration values for the application.
// Each field maps to an environment variable defined in .env.
type Config struct {
	// Server settings
	Port        string // PORT — the port the HTTP server listens on
	Environment string // ENVIRONMENT — dev, stage, or prod

	// Database settings
	DBHost     string // DB_HOST
	DBPort     string // DB_PORT
	DBUser     string // DB_USER
	DBPassword string // DB_PASSWORD
	DBName     string // DB_NAME
	DBSSLMode  string // DB_SSLMODE
}

// LoadConfig reads the .env file and returns a populated Config struct.
// It returns an error if the .env file is missing or a required variable is empty.
func LoadConfig() (*Config, error) {
	// Load .env file into environment variables
	err := godotenv.Load()
	if err != nil {
		return nil, fmt.Errorf("error loading .env file: %w", err)
	}

	// Build the config from environment variables
	cfg := &Config{
		Port:        getEnv("PORT", "4000"),
		Environment: getEnv("ENVIRONMENT", "dev"),
		DBHost:      getEnv("DB_HOST", ""),
		DBPort:      getEnv("DB_PORT", "5432"),
		DBUser:      getEnv("DB_USER", ""),
		DBPassword:  getEnv("DB_PASSWORD", ""),
		DBName:      getEnv("DB_NAME", ""),
		DBSSLMode:   getEnv("DB_SSLMODE", "disable"),
	}

	// Validate that critical database fields are not empty
	if cfg.DBHost == "" || cfg.DBUser == "" || cfg.DBPassword == "" || cfg.DBName == "" {
		return nil, fmt.Errorf("missing required database configuration (DB_HOST, DB_USER, DB_PASSWORD, or DB_NAME)")
	}

	return cfg, nil
}

// DatabaseURL builds a PostgreSQL connection string from the config fields.
func (c *Config) DatabaseURL() string {
	return fmt.Sprintf(
		"postgres://%s:%s@%s:%s/%s?sslmode=%s",
		c.DBUser, c.DBPassword, c.DBHost, c.DBPort, c.DBName, c.DBSSLMode,
	)
}

// getEnv reads an environment variable or returns a default value.
func getEnv(key, defaultValue string) string {
	value := os.Getenv(key)
	if value == "" {
		return defaultValue
	}
	return value
}