package shell

import (
	"encoding/json"
	"errors"
	"io/fs"
	"os"
	"path/filepath"
	"sync"
)

// Settings is what the desktop app keeps between runs. The client's own
// state (sessions, keys) lives in the webview's storage, not here.
type Settings struct {
	// Homeserver is the base URL new sign-ins go to, e.g.
	// https://matrix.example.org. Empty until the first-run page has asked.
	Homeserver string `json:"homeserver,omitempty"`
	// TrayHintShown is set once the app has said, the first time its
	// window was closed, that it keeps running in the tray.
	TrayHintShown bool `json:"tray_hint_shown,omitempty"`
}

// Store reads and writes Settings as a JSON file.
type Store struct {
	path string
	mu   sync.Mutex
}

// NewStore returns a store backed by the file at path. The file and its
// directory are created on the first Save.
func NewStore(path string) *Store { return &Store{path: path} }

// Load returns the saved settings, or the zero value when there are none.
func (s *Store) Load() (Settings, error) {
	s.mu.Lock()
	defer s.mu.Unlock()
	var st Settings
	b, err := os.ReadFile(s.path)
	if errors.Is(err, fs.ErrNotExist) {
		return st, nil
	}
	if err != nil {
		return st, err
	}
	return st, json.Unmarshal(b, &st)
}

// Save writes the settings, replacing the file atomically.
func (s *Store) Save(st Settings) error {
	s.mu.Lock()
	defer s.mu.Unlock()
	b, err := json.MarshalIndent(st, "", "  ")
	if err != nil {
		return err
	}
	if err := os.MkdirAll(filepath.Dir(s.path), 0o700); err != nil {
		return err
	}
	tmp := s.path + ".tmp"
	if err := os.WriteFile(tmp, append(b, '\n'), 0o600); err != nil {
		return err
	}
	return os.Rename(tmp, s.path)
}