package platform

import (
	"encoding/json"
	"errors"
	"os"
	"path/filepath"
)

// DesktopConfig is the desktop-only preference set, persisted as JSON under the
// user config dir. json tags are the contract with the WebView settings page.
type DesktopConfig struct {
	ClipboardSyncEnabled bool   `json:"clipboard_sync_enabled"`
	LaunchAtLogin        bool   `json:"launch_at_login"`
	DeviceName           string `json:"device_name"`  // empty = use the hostname
	DownloadDir          string `json:"download_dir"` // empty = system Downloads dir
}

// ResolveDeviceName returns the persisted device name, or the hostname when the
// user hasn't renamed it. Persisting it Go-side is required because the WebView's
// localStorage doesn't survive restart on the wails:// scheme (see session.go).
func ResolveDeviceName() string {
	cfg, _ := LoadConfig()
	if cfg.DeviceName != "" {
		return cfg.DeviceName
	}
	if h, err := os.Hostname(); err == nil && h != "" {
		return h
	}
	return "cdrop-desktop"
}

// DefaultConfig is what a fresh install gets: clipboard sync on, no autostart.
func DefaultConfig() DesktopConfig {
	return DesktopConfig{ClipboardSyncEnabled: true, LaunchAtLogin: false}
}

// ResolveDownloadDir returns the directory received files land in: the user's
// configured override, or the system Downloads dir when unset.
func ResolveDownloadDir() string {
	cfg, _ := LoadConfig()
	if cfg.DownloadDir != "" {
		return cfg.DownloadDir
	}
	return DefaultDownloadDir()
}

// DefaultDownloadDir is ~/Downloads (the OS default download folder; its path is
// stable across locales on macOS/Windows). Falls back to the cwd if the home
// dir can't be resolved.
func DefaultDownloadDir() string {
	if home, err := os.UserHomeDir(); err == nil && home != "" {
		return filepath.Join(home, "Downloads")
	}
	return "."
}

// configPath is ~/Library/Application Support/cdrop/config.json on macOS
// (os.UserConfigDir resolves the per-OS base).
func configPath() (string, error) {
	dir, err := os.UserConfigDir()
	if err != nil {
		return "", err
	}
	return filepath.Join(dir, "cdrop", "config.json"), nil
}

// LoadConfig reads the persisted config, falling back to defaults when the file
// is absent or unreadable so the app always has a usable preference set.
func LoadConfig() (DesktopConfig, error) {
	p, err := configPath()
	if err != nil {
		return DefaultConfig(), err
	}
	data, err := os.ReadFile(p)
	if errors.Is(err, os.ErrNotExist) {
		return DefaultConfig(), nil
	}
	if err != nil {
		return DefaultConfig(), err
	}
	cfg := DefaultConfig()
	if err := json.Unmarshal(data, &cfg); err != nil {
		return DefaultConfig(), err
	}
	return cfg, nil
}

// SaveConfig writes the config atomically-ish (mkdir + write) under the user
// config dir.
func SaveConfig(cfg DesktopConfig) error {
	p, err := configPath()
	if err != nil {
		return err
	}
	if err := os.MkdirAll(filepath.Dir(p), 0o755); err != nil {
		return err
	}
	data, err := json.MarshalIndent(cfg, "", "  ")
	if err != nil {
		return err
	}
	return os.WriteFile(p, data, 0o644)
}