// Copyright (c) 2026 Storm Dragon
// SPDX-License-Identifier: GPL-3.0-or-later

package tentacle

import (
	"bytes"
	"encoding/json"
	"errors"
	"os"
	"path/filepath"
	"syscall"

	"git.stormux.org/storm/cthulhu/internal/interaction"
)

// PageValues contains only host-validated declarative preferences. Active speech
// overrides and quick-setting selections are deliberately never restored here.
type PageValues map[string]map[string]map[string]interaction.Value

type PageStore struct {
	Path     string
	original []byte
	loaded   bool
}

func (store *PageStore) Load() (PageValues, error) {
	store.loaded = false
	data, err := read_registry(store.Path)
	if err != nil {
		return nil, err
	}
	values := PageValues{}
	if data != nil {
		if validate_json(data) != nil {
			return nil, ErrProtocol
		}
		if err := json.Unmarshal(data, &values); err != nil || values == nil {
			return nil, ErrProtocol
		}
	}
	store.original, store.loaded = data, true
	return values, nil
}

func (store *PageStore) Save(values PageValues) error {
	if !store.loaded {
		return errors.New("tentacle preferences were not loaded successfully")
	}
	data, err := json.Marshal(values)
	if err != nil {
		return err
	}
	if len(data) > MaxFrameBytes {
		return ErrLimit
	}
	directory := filepath.Dir(store.Path)
	if err := os.MkdirAll(directory, 0700); err != nil {
		return err
	}
	lock, err := os.OpenFile(store.Path+".lock", os.O_CREATE|os.O_RDWR|syscall.O_NOFOLLOW|syscall.O_NONBLOCK, 0600)
	if err != nil {
		return err
	}
	defer lock.Close()
	if info, err := lock.Stat(); err != nil || !info.Mode().IsRegular() {
		return errors.New("tentacle preferences lock must be a regular file")
	}
	if err := syscall.Flock(int(lock.Fd()), syscall.LOCK_EX|syscall.LOCK_NB); err != nil {
		return errors.New("tentacle preferences are being edited")
	}
	defer syscall.Flock(int(lock.Fd()), syscall.LOCK_UN)
	current, err := read_registry(store.Path)
	if err != nil {
		return err
	}
	if !bytes.Equal(current, store.original) || (current == nil) != (store.original == nil) {
		return errors.New("tentacle preferences changed outside the reader")
	}
	file, err := os.CreateTemp(directory, ".tentacle-preferences-*")
	if err != nil {
		return err
	}
	defer os.Remove(file.Name())
	defer file.Close()
	if _, err := file.Write(data); err != nil {
		return err
	}
	if err := file.Sync(); err != nil {
		return err
	}
	if err := file.Close(); err != nil {
		return err
	}
	dir, err := os.Open(directory)
	if err != nil {
		return err
	}
	defer dir.Close()
	if err := os.Rename(file.Name(), store.Path); err != nil {
		return err
	}
	store.original = data
	return dir.Sync()
}