package config

import (
	_ "embed"
	"errors"
	"fmt"
	"maps"
	"os"
	"path/filepath"
	"reflect"

	"github.com/go-viper/mapstructure/v2"
	"github.com/spf13/viper"
	"gopkg.in/yaml.v3"
)

func DefaultPath() string {
	dir, err := os.UserConfigDir()
	if err != nil {
		dir = "."
	}
	return filepath.Join(dir, "proton-vpn-tui", "config.yaml")
}

func Load(path string) error {
	var defaults map[string]any
	if err := yaml.Unmarshal(defaultConfig, &defaults); err != nil {
		return fmt.Errorf("default config: %w", err)
	}
	for k, v := range flatten("", defaults) {
		viper.SetDefault(k, v)
	}

	viper.SetConfigType("yaml")
	viper.SetConfigFile(path)
	if err := viper.ReadInConfig(); err != nil {
		if !errors.Is(err, os.ErrNotExist) {
			return err
		}
	}

	Global = &Config{}
	hook := viper.DecodeHook(mapstructure.ComposeDecodeHookFunc(
		stringToKeyBindingHook,
		mapstructure.StringToTimeDurationHookFunc(),
	))
	if err := viper.Unmarshal(Global, hook); err != nil {
		return err
	}
	fillHelp(reflect.ValueOf(&Global.Keybindings))
	return nil
}

func WriteDefaultConfig(path string) error {
	if err := os.MkdirAll(filepath.Dir(path), 0o750); err != nil {
		return fmt.Errorf("create config dir: %w", err)
	}
	if err := os.WriteFile(path, defaultConfig, 0o600); err != nil {
		return fmt.Errorf("write config: %w", err)
	}
	return nil
}

func flatten(prefix string, m map[string]any) map[string]any {
	out := make(map[string]any)
	for k, v := range m {
		key := k
		if prefix != "" {
			key = prefix + "." + k
		}
		if nested, ok := v.(map[string]any); ok {
			maps.Copy(out, flatten(key, nested))
		} else {
			out[key] = v
		}
	}
	return out
}