package config

import (
	"fmt"
	"log"
	"os"
	"strings"

	"github.com/spf13/viper"
)

// Config holds all configuration for the application.
type Config struct {
	Database DatabaseConfig `mapstructure:"database"`
	Server   ServerConfig   `mapstructure:"server"`
}

// DatabaseConfig holds database connection configuration.
type DatabaseConfig struct {
	User     string `mapstructure:"user"`
	Password string `mapstructure:"password"`
	Dbname   string `mapstructure:"dbname"`
	Host     string `mapstructure:"host"`
	Port     int    `mapstructure:"port"`
	Sslmode  string `mapstructure:"sslmode"`
}

// ServerConfig holds server-specific configuration.
type ServerConfig struct {
	Address string `mapstructure:"address"`
}

// Load reads configuration from file and environment variables.
func Load() (*Config, error) {
	// 0. Configuration for environment variables
	viper.SetEnvPrefix("APP") // Variables must start with "APP_" (e.g., APP_SERVER_ADDRESS)

	// 1. Base configuration file
	viper.SetConfigName("config") // config.yaml
	viper.SetConfigType("yaml")
	viper.AddConfigPath(".")

	// Read the base file. Don't stop if it's not found.
	if err := viper.ReadInConfig(); err != nil {
		if _, ok := err.(viper.ConfigFileNotFoundError); !ok {
			return nil, fmt.Errorf("error reading base config file config.yaml: %w", err)
		}
	}

	// 2. Override with environment-specific file (via APP_ENV)
	if env := os.Getenv("APP_ENV"); env != "" {
		viper.SetConfigName("config." + env) // e.g., config.prod.yaml
		if err := viper.MergeInConfig(); err != nil {
			log.Printf("Warning: could not load config file for environment '%s': %v", env, err)
		}
	}

	viper.SetEnvKeyReplacer(strings.NewReplacer(".", "_"))
	viper.AutomaticEnv()

	var cfg Config
	if err := viper.Unmarshal(&cfg); err != nil {
		return nil, fmt.Errorf("unable to decode config into struct: %w", err)
	}

	return &cfg, nil
}