package ui

import (
	"errors"
	"os"
	"sync"
	"time"

	"git.wxccs.org/iceking2nd/winauth-go/internal/config"
	"git.wxccs.org/iceking2nd/winauth-go/internal/global"
)

// store wraps the on-disk YAML config plus the in-memory passphrase.
// All writes go through an async, coalescing worker: callers Push() and
// the worker debounces rapid bursts (e.g. HOTP code clicks) into a single
// disk write.
//
// passphrase is held in memory for the lifetime of the process. We do not
// attempt to zero it after use — Go's garbage collector may move strings
// around freely, so secure-erase is largely placebo and would only buy a
// false sense of security. We instead enforce that it is never logged.
type store struct {
	path string

	mu         sync.Mutex
	passphrase []byte
	encrypted  bool

	// Top-level user preferences kept alongside entries so save() can
	// roundtrip them without requiring the UI to rebuild a full Config.
	language        string
	theme           string
	autoLockMinutes int
	minimizeToTray  bool

	// dirty signals a save is pending. The worker reads & resets it.
	dirty       bool
	snapshotFn  func() []config.Entry
	pendingErr  error
	saveTrigger chan struct{}

	// onError is called from the save goroutine when a write fails.
	// The caller is responsible for marshalling back to the UI thread.
	onError func(error)
}

// Preferences returns the persisted top-level prefs. UI code reads these
// after Load to seed dialog defaults.
func (s *store) Preferences() (language, theme string, autoLockMinutes int, minimizeToTray bool) {
	s.mu.Lock()
	defer s.mu.Unlock()
	return s.language, s.theme, s.autoLockMinutes, s.minimizeToTray
}

// SetPreferences updates the persisted top-level prefs and schedules a
// save. Callers pass the current value for each field — there is no
// per-field "leave unchanged" sentinel.
func (s *store) SetPreferences(language, theme string, autoLockMinutes int, minimizeToTray bool) {
	s.mu.Lock()
	s.language = language
	s.theme = theme
	s.autoLockMinutes = autoLockMinutes
	s.minimizeToTray = minimizeToTray
	s.mu.Unlock()
	s.Push()
}

// newStore initializes a store and starts the background save worker.
// snapshotFn is invoked whenever a save runs; it must return a freshly
// copied entries slice (the worker holds no UI locks). onError is called
// asynchronously from the worker goroutine on save failures.
func newStore(path string, snapshotFn func() []config.Entry, onError func(error)) *store {
	s := &store{
		path:        path,
		snapshotFn:  snapshotFn,
		onError:     onError,
		saveTrigger: make(chan struct{}, 1),
	}
	go s.run()
	return s
}

// Load reads the YAML file at path. If the file does not exist, returns
// (nil, nil) — the caller should treat that as an empty config. If the
// file is encrypted, passphrase must be valid; otherwise ErrPasswordRequired
// or ErrPasswordWrong is returned.
//
// On success the store's passphrase + encrypted flag are updated.
func (s *store) Load(passphrase []byte) (*config.Config, error) {
	const fn = "internal.ui.store.Load"
	logger := global.Log.WithField("func", fn).WithField("path", s.path)

	if _, err := os.Stat(s.path); errors.Is(err, os.ErrNotExist) {
		logger.Debug("config file does not exist; starting empty")
		s.mu.Lock()
		s.passphrase = nil
		s.encrypted = false
		s.mu.Unlock()
		return nil, nil
	}

	// First load: peek the header (no passphrase) to learn encrypted-ness.
	cfg, err := config.LoadYAML(s.path, passphrase)
	if err != nil {
		switch {
		case errors.Is(err, config.ErrPasswordRequired):
			return cfg, ErrPasswordRequired
		case errors.Is(err, config.ErrPasswordWrong):
			return cfg, ErrPasswordWrong
		default:
			return nil, err
		}
	}
	s.mu.Lock()
	s.passphrase = passphrase
	s.encrypted = cfg.Encrypted
	s.language = cfg.Language
	s.theme = cfg.Theme
	s.autoLockMinutes = cfg.AutoLockMinutes
	s.minimizeToTray = cfg.MinimizeToTray
	s.mu.Unlock()
	logger.WithField("entries", len(cfg.Entries)).Debug("config loaded into store")
	return cfg, nil
}

// Sentinel errors returned by store.Load to signal the password UI path.
// We re-export config's sentinels here so the UI layer doesn't need to
// import internal/config directly.
var (
	ErrPasswordRequired = config.ErrPasswordRequired
	ErrPasswordWrong    = config.ErrPasswordWrong
)

// SetPassword updates the in-memory passphrase. An empty value disables
// encryption on the next save. The change is queued for save immediately.
func (s *store) SetPassword(pw []byte) {
	s.mu.Lock()
	s.passphrase = pw
	s.encrypted = len(pw) > 0
	s.mu.Unlock()
	s.Push()
}

// Encrypted reports whether the store will encrypt the next write.
func (s *store) Encrypted() bool {
	s.mu.Lock()
	defer s.mu.Unlock()
	return s.encrypted
}

// Push schedules a save. Calls within ~300ms of each other coalesce into
// a single write.
func (s *store) Push() {
	s.mu.Lock()
	s.dirty = true
	s.mu.Unlock()
	select {
	case s.saveTrigger <- struct{}{}:
	default:
	}
}

// LastError returns the most recent save error, if any.
func (s *store) LastError() error {
	s.mu.Lock()
	defer s.mu.Unlock()
	return s.pendingErr
}

func (s *store) run() {
	const fn = "internal.ui.store.run"
	for range s.saveTrigger {
		// debounce: wait briefly to coalesce bursts
		time.Sleep(300 * time.Millisecond)
		s.mu.Lock()
		if !s.dirty {
			s.mu.Unlock()
			continue
		}
		s.dirty = false
		pw := append([]byte(nil), s.passphrase...)
		enc := s.encrypted
		lang := s.language
		theme := s.theme
		autoLock := s.autoLockMinutes
		minToTray := s.minimizeToTray
		s.mu.Unlock()

		entries := s.snapshotFn()
		cfg := &config.Config{
			Version:         1,
			Language:        lang,
			Theme:           theme,
			AutoLockMinutes: autoLock,
			MinimizeToTray:  minToTray,
			Encrypted:       enc,
			Entries:         entries,
		}
		if err := config.SaveYAML(cfg, s.path, pw); err != nil {
			global.Log.WithField("func", fn).WithError(err).Error("save failed")
			s.mu.Lock()
			s.pendingErr = err
			s.mu.Unlock()
			if s.onError != nil {
				s.onError(err)
			}
			continue
		}
		s.mu.Lock()
		s.pendingErr = nil
		s.mu.Unlock()
	}
}