package handlers

import (
	"encoding/json"
	"fmt"
	"os"
	"path/filepath"

	"FanslySync/structs"
	"FanslySync/utils"

	"github.com/wailsapp/wails/v2/pkg/logger"
)

// ConfigManager defines methods for accessing and persisting application configuration.
type ConfigManager interface {
	// GetConfig returns the current configuration. If forceReload is true,
	// it re-reads the file from disk even if a cached copy exists.
	GetConfig(forceReload bool) (*structs.Config, error)

	// LoadConfigOrCreate loads the config or, if the file doesn't exist,
	// creates a default config, saves it, and returns it.
	LoadConfigOrCreate() (*structs.Config, error)

	// SaveConfig writes the given config to disk and updates the in-memory cache.
	SaveConfig(config *structs.Config) error

	// GetConfigPath returns the filesystem path where the config is stored.
	GetConfigPath() string

	// ShouldMigrateOldAppConfig checks if the old app config file exists
	// and returns true if it should be migrated.
	ShouldMigrateOldAppConfig() (bool, error)

	// MigrateOldAppConfig migrates the old app config file to the new format.
	MigrateOldAppConfig() error
}

// FileConfigManager implements ConfigManager using a JSON file on disk
// with in-memory caching and custom logging.
type FileConfigManager struct {
	path   string
	config *structs.Config
	log    logger.Logger
}

func NewFileConfigManager(path string) (ConfigManager, error) {
	// Create our logger
	fileLogger, loggerCreateErr := utils.NewLogger("ConfigManager")
	if loggerCreateErr != nil {
		// Log the error and return nil
		return nil, loggerCreateErr
	}

	return &FileConfigManager{
		path: path,
		log:  fileLogger,
	}, nil
}

// GetConfigPath returns the path to the config file.
func (mgr *FileConfigManager) GetConfigPath() string {
	return mgr.path
}

func GetConfigPathForRuntime() (string, error) {
	dir, err := os.UserConfigDir()
	if err != nil {
		return "", err
	}
	return filepath.Join(dir, "FanslySync", "appconfig.json"), nil
}

// ShouldMigrateOldAppConfig checks for an existing legacy config.json and logs the result.
func (mgr *FileConfigManager) ShouldMigrateOldAppConfig() (bool, error) {
	mgr.log.Info("Checking for old config file")
	dir, err := os.UserConfigDir()
	if err != nil {
		mgr.log.Error(fmt.Sprintf("Error getting user config dir: %v", err))
		return false, err
	}

	oldConfigPath := filepath.Join(dir, "FanslySync", "config.json")
	if _, err := os.Stat(oldConfigPath); os.IsNotExist(err) {
		mgr.log.Info(fmt.Sprintf("No old config at %s", oldConfigPath))
		return false, nil
	} else if err != nil {
		mgr.log.Error(fmt.Sprintf("Error checking old config: %v", err))
		return false, err
	}

	mgr.log.Info(fmt.Sprintf("Old config exists at %s", oldConfigPath))
	return true, nil
}

// MigrateOldAppConfig reads the legacy config.json, converts it, saves the new format,
// and removes the old file, logging each step.
func (mgr *FileConfigManager) MigrateOldAppConfig() error {
	mgr.log.Info("Migrating old config file")
	dir, err := os.UserConfigDir()
	if err != nil {
		mgr.log.Error(fmt.Sprintf("Error getting user config dir: %v", err))
		return err
	}

	oldConfigPath := filepath.Join(dir, "FanslySync", "config.json")
	if _, err := os.Stat(oldConfigPath); os.IsNotExist(err) {
		mgr.log.Info("No old config to migrate")
		return nil
	} else if err != nil {
		mgr.log.Error(fmt.Sprintf("Error checking old config: %v", err))
		return err
	}

	data, err := os.ReadFile(oldConfigPath)
	if err != nil {
		mgr.log.Error(fmt.Sprintf("Error reading old config: %v", err))
		return err
	}

	var oldCfg structs.OldConfig
	if err := json.Unmarshal(data, &oldCfg); err != nil {
		mgr.log.Error(fmt.Sprintf("Error unmarshaling old config: %v", err))
		return err
	}

	newCfg := structs.NewConfigFromOld(&oldCfg)
	if err := mgr.SaveConfig(newCfg); err != nil {
		mgr.log.Error(fmt.Sprintf("Error saving new config: %v", err))
		return err
	}

	if err := os.Remove(oldConfigPath); err != nil {
		mgr.log.Error(fmt.Sprintf("Error removing old config: %v", err))
		return fmt.Errorf("could not remove old config file: %w", err)
	}

	mgr.log.Info("Migration complete; old config removed")
	return nil
}

// GetConfig loads the config from disk if forceReload is true or no cache exists.
// It logs each step and errors encountered.
func (mgr *FileConfigManager) GetConfig(forceReload bool) (*structs.Config, error) {
	mgr.log.Debug(fmt.Sprintf("GetConfig(forceReload=%v)", forceReload))
	if mgr.config != nil && !forceReload {
		mgr.log.Debug("Returning cached config")
		return mgr.config, nil
	}

	data, err := os.ReadFile(mgr.path)
	if err != nil {
		mgr.log.Error(fmt.Sprintf("Error reading config file: %v", err))
		return nil, err
	}

	var cfg structs.Config
	if err := json.Unmarshal(data, &cfg); err != nil {
		mgr.log.Error(fmt.Sprintf("Error unmarshaling config: %v", err))
		return nil, err
	}

	mgr.config = &cfg
	mgr.log.Info("Config loaded from disk. Cache updated.")
	mgr.log.Debug(fmt.Sprintf("Config: %+v", cfg))
	return mgr.config, nil
}

// LoadConfigOrCreate loads an existing config or creates/saves a default if none exists.
func (mgr *FileConfigManager) LoadConfigOrCreate() (*structs.Config, error) {
	cfg, err := mgr.GetConfig(false)
	if err == nil {
		mgr.log.Info("Existing config loaded")
		return cfg, nil
	}
	if os.IsNotExist(err) {
		mgr.log.Warning("Config missing; creating default")
		defaultCfg := structs.NewConfig()
		if saveErr := mgr.SaveConfig(defaultCfg); saveErr != nil {
			mgr.log.Error(fmt.Sprintf("Error saving default config: %v", saveErr))
			return nil, saveErr
		}
		mgr.log.Info("Default config created and saved")
		return defaultCfg, nil
	}
	mgr.log.Error(fmt.Sprintf("Error loading config: %v", err))
	return nil, err
}

// SaveConfig writes the config to disk, updates cache, and logs the process.
func (mgr *FileConfigManager) SaveConfig(cfg *structs.Config) error {
	mgr.log.Info(fmt.Sprintf("Saving config to %s", mgr.path))
	dir := filepath.Dir(mgr.path)
	if err := os.MkdirAll(dir, 0o755); err != nil {
		mgr.log.Error(fmt.Sprintf("Error creating config directory: %v", err))
		return fmt.Errorf("could not create config directory: %w", err)
	}

	data, err := json.MarshalIndent(cfg, "", "  ")
	if err != nil {
		mgr.log.Error(fmt.Sprintf("Error marshaling config: %v", err))
		return fmt.Errorf("could not marshal config: %w", err)
	}

	if err := os.WriteFile(mgr.path, data, 0o644); err != nil {
		mgr.log.Error(fmt.Sprintf("Error writing config file: %v", err))
		return fmt.Errorf("could not write config file: %w", err)
	}

	mgr.config = cfg
	mgr.log.Info("Config saved and cache updated")
	return nil
}