aethera/backend/internal/store/storage.go

package store

import (
	"encoding/json"
	"fmt"
	"os"
	"path/filepath"
	"strings"

	"github.com/google/uuid"
	"reichard.io/aethera/pkg/slices"
)

var _ Store = (*FileStore)(nil)

// Settings represents the application settings
type Settings struct {
	APIEndpoint             string `json:"api_endpoint,omitempty"`
	ImageEditSelector       string `json:"image_edit_selector,omitempty"`
	ImageGenerationSelector string `json:"image_generation_selector,omitempty"`
	TextGenerationSelector  string `json:"text_generation_selector,omitempty"`
}

// FileStore implements the Store interface using a file-based storage
type FileStore struct {
	filePath string
	chatDir  string
}

// NewFileStore creates a new FileStore with the specified file path
func NewFileStore(filePath string) (*FileStore, error) {
	// Derive Chat Directory
	chatDir := filepath.Join(filepath.Dir(filePath), "chats")

	// Ensure Chat Directory Exists
	if err := os.MkdirAll(chatDir, 0755); err != nil {
		return nil, fmt.Errorf("failed to create directory: %w", err)
	}

	return &FileStore{
		filePath: filePath,
		chatDir:  chatDir,
	}, nil
}

// GetSettings reads and returns the settings from the file
func (fs *FileStore) GetSettings() (*Settings, error) {
	data, err := os.ReadFile(fs.filePath)
	if err != nil {
		return &Settings{}, nil
	}

	var settings Settings
	err = json.Unmarshal(data, &settings)
	if err != nil {
		return nil, err
	}

	return &settings, nil
}

// SaveSettings saves the settings to the file
func (fs *FileStore) SaveSettings(settings *Settings) error {
	data, err := json.MarshalIndent(settings, "", "  ")
	if err != nil {
		return err
	}

	return os.WriteFile(fs.filePath, data, 0644)
}

// GetChat retrieves a chat from disk
func (fs *FileStore) GetChat(chatID uuid.UUID) (*Chat, error) {
	filePath := filepath.Join(fs.chatDir, chatID.String()+".json")

	data, err := os.ReadFile(filePath)
	if err != nil {
		if os.IsNotExist(err) {
			return nil, ErrChatNotFound
		}
		return nil, fmt.Errorf("failed to read chat: %w", err)
	}

	var chat Chat
	if err := json.Unmarshal(data, &chat); err != nil {
		return nil, fmt.Errorf("failed to unmarshal chat: %w", err)
	}

	return &chat, nil
}

// SaveChat creates or updates a chat and persists it to disk
func (fs *FileStore) SaveChat(c *Chat) error {
	c.ensureDefaults()
	return fs.saveChatSession(c)
}

// DeleteChat removes a chat from disk
func (fs *FileStore) DeleteChat(chatID uuid.UUID) error {
	filePath := filepath.Join(fs.chatDir, chatID.String()+".json")

	if _, err := os.Stat(filePath); os.IsNotExist(err) {
		return ErrChatNotFound
	}

	if err := os.Remove(filePath); err != nil {
		return fmt.Errorf("failed to delete chat: %w", err)
	}

	return nil
}

// ListChats returns all persisted chats
func (fs *FileStore) ListChats() ([]*Chat, error) {
	// Read Files
	entries, err := os.ReadDir(fs.chatDir)
	if err != nil {
		return nil, fmt.Errorf("failed to read chat directory: %w", err)
	}

	var chats []*Chat
	for _, entry := range entries {
		// Ensure JSON
		if entry.IsDir() || !strings.HasSuffix(entry.Name(), ".json") {
			continue
		}

		// Extract Chat ID
		rawChatID := strings.TrimSuffix(entry.Name(), ".json")
		chatID, err := uuid.Parse(rawChatID)
		if err != nil {
			return nil, fmt.Errorf("%w: invalid chat id %s", err, rawChatID)
		}

		// Read & Parse Chat
		chat, err := fs.GetChat(chatID)
		if err != nil {
			return nil, fmt.Errorf("%w: failed to read chat id %s", err, rawChatID)
		}

		chats = append(chats, chat)
	}

	return chats, nil
}

// SaveChatMessage creates or updates a chat message to a chat and persists it to disk
func (fs *FileStore) SaveChatMessage(m *Message) error {
	if m.ChatID == uuid.Nil {
		return ErrNilChatID
	}
	m.ensureDefaults()

	// Get Chat
	chat, err := fs.GetChat(m.ChatID)
	if err != nil {
		return err
	}

	// Find Existing
	existingMsg, found := slices.FindFirst(chat.Messages, func(item *Message) bool {
		return item.ID == m.ID
	})

	// Upsert
	if found {
		*existingMsg = *m
	} else {
		chat.Messages = append(chat.Messages, m)
	}

	// Save
	return fs.saveChatSession(chat)
}

// saveChatSession is a helper method to save a chat to disk
func (fs *FileStore) saveChatSession(session *Chat) error {
	filePath := filepath.Join(fs.chatDir, session.ID.String()+".json")

	data, err := json.MarshalIndent(session, "", "  ")
	if err != nil {
		return fmt.Errorf("failed to marshal chat: %w", err)
	}

	if err := os.WriteFile(filePath, data, 0644); err != nil {
		return fmt.Errorf("failed to write chat file: %w", err)
	}

	return nil
}