package config

import (
	"encoding/json"
	"fmt"
	"log"
	"os"
	"sync"
)

type Config struct {
	Backend struct {
		Port string `json:"port"`
		Host string `json:"host"`
		Auth struct {
			Required bool   `json:"required"`
			Key      string `json:"key"`
		} `json:"auth"`
		Database struct {
			Versions struct {
				Path string `json:"path"`
			} `json:"versions"`
			Bulletins struct {
				Path string `json:"path"`
			} `json:"bulletins"`
			Themes struct {
				Path string `json:"path"`
			} `json:"themes"`
			ThemesFiles struct {
				Path string `json:"path"`
			} `json:"themes_files"`
		} `json:"database"`
		Casdoor struct {
			Endpoint     string `json:"endpoint"`
			ClientID     string `json:"client_id"`
			ClientSecret string `json:"client_secret"`
			Certificate  string `json:"certificate"`
			Organization string `json:"organization"`
			Application  string `json:"application"`
		} `json:"casdoor"`
	} `json:"backend"`

	Frontend struct {
		Port   string `json:"port"`
		Host   string `json:"host"`
		Static struct {
			Path string `json:"path"`
		} `json:"static"`
	} `json:"frontend"`
}

var (
	instance *Config
	once     sync.Once
	loadErr  error
)

func createDefaultConfig() *Config {
	config := &Config{}
	config.Backend.Port = "8080"
	config.Backend.Host = "127.0.0.1"
	config.Backend.Auth.Required = false
	config.Backend.Auth.Key = "null"
	config.Backend.Database.Versions.Path = "./backend/data/versions.db"
	config.Backend.Database.Bulletins.Path = "./backend/data/bulletins.db"
	config.Backend.Database.Themes.Path = "./backend/data/themes.db"
	config.Backend.Database.ThemesFiles.Path = "./backend/data/themes_files"

	config.Backend.Casdoor.Endpoint = "http://127.0.0.1:8000"
	config.Backend.Casdoor.ClientID = ""
	config.Backend.Casdoor.ClientSecret = ""
	config.Backend.Casdoor.Certificate = ""
	config.Backend.Casdoor.Organization = "autolibrary"
	config.Backend.Casdoor.Application = "marketplace"

	config.Frontend.Port = "3000"
	config.Frontend.Host = "127.0.0.1"
	config.Frontend.Static.Path = "./frontend/dist"

	return config
}

func LoadConfig(configPath string, allowDefaults bool) (*Config, error) {
	once.Do(func() {
		data, err := os.ReadFile(configPath)
		if err != nil {
			loadErr = err
			return
		}
		cfg := createDefaultConfig()
		if err := json.Unmarshal(data, &cfg); err != nil {
			loadErr = fmt.Errorf("decode config %q: %w", configPath, err)
			return
		}
		if cfg == nil {
			loadErr = fmt.Errorf("config %q must be a JSON object", configPath)
			return
		}
		instance = cfg
	})
	if loadErr != nil {
		if !allowDefaults {
			return nil, loadErr
		}
		log.Printf("[W] using default config: %v", loadErr)
		return createDefaultConfig(), nil
	}
	log.Printf("[I] config loaded successfully from: %s", configPath)
	return instance, nil
}

func GetConfig() *Config {
	if instance == nil {
		return createDefaultConfig()
	}
	return instance
}