# Svelte and Dexie.js Integration Guide

This document provides a guide to integrating Svelte (with a focus on Runes) and Dexie.js for building reactive web applications. It covers key concepts and best practices for managing reactivity between Svelte components and the Dexie.js database.

## Svelte 5 Migration Guide

Svelte 5 introduces "runes" as a new way to manage reactivity. This is a major change from previous versions of Svelte, and it's important to understand the breaking changes before migrating.

### Key Breaking Changes

- **`let` is no longer reactive:** In Svelte 4, any `let` variable declared in the top-level scope of a component was automatically reactive. In Svelte 5, you must explicitly declare reactive state using the `$state` rune.
- **`$:` is replaced by `$derived` and `$effect`:** The `$` label is no longer used for reactive statements. Instead, you should use the `$derived` rune for computed values and the `$effect` rune for side effects.
- **`export let` is replaced by `$props`:** Component props are now declared using the `$props` rune, which provides a more flexible and explicit way to define component APIs.
- **Event handling:** The `on:` directive is replaced by event attributes (e.g., `onclick`). Component events are now handled using callback props instead of `createEventDispatcher`.
- **Slots are replaced by snippets:** The `<slot>` element is replaced by the `{#snippet ...}` block, which provides a more powerful and flexible way to pass content to components.

For a complete list of breaking changes, refer to the [Svelte 5 migration guide](https://svelte.dev/docs/svelte/v5-migration-guide).

## Dexie.js Quick Reference

Dexie.js is a lightweight, minimalistic wrapper for IndexedDB that makes it easier to work with client-side databases.

### Key Classes and Methods

- **`Dexie`:** The main class for creating and managing IndexedDB databases.
    - `new Dexie(databaseName)`: Creates a new database instance.
    - `version(versionNumber).stores({ ... })`: Defines the database schema.
- **`Table`:** Represents an object store (table) in the database.
    - `add(item)`: Adds a new item to the table.
    - `put(item)`: Adds or updates an item in the table.
    - `update(key, changes)`: Updates an existing item.
    - `delete(key)`: Deletes an item by its primary key.
    - `get(key)`: Retrieves an item by its primary key.
    - `where(index)`: Starts a query using an index.
    - `toArray()`: Retrieves all items from the table as an array.
- **`Collection`:** Represents a collection of items resulting from a query.
    - `toArray()`: Retrieves all items in the collection as an array.
    - `first()`: Retrieves the first item in the collection.
    - `last()`: Retrieves the last item in the collection.
    - `each(callback)`: Iterates over each item in the collection.
    - `modify(changes)`: Updates all items in the collection.
    - `delete()`: Deletes all items in the collection.

For a complete list of API methods, refer to the [Dexie.js API Reference](https://dexie.org/docs/API-Reference).

## Integrating Svelte Runes and Dexie.js

The combination of Svelte Runes and Dexie.js allows for the creation of highly reactive and efficient web applications.

### The `liveQuery` Function

Dexie.js provides a `liveQuery` function that returns an observable of the query result. This observable can be used to automatically update the UI whenever the data in the database changes.

### Using `liveQuery` with Svelte Runes

To use `liveQuery` with Svelte Runes, you can create a custom readable store that wraps the `liveQuery` observable. This store can then be used in your Svelte components to display and interact with the data.

**1. Create a `liveQuery` store:**

```typescript
import { liveQuery } from 'dexie';
import { readable } from 'svelte/store';
import { db } from './db'; // Your Dexie database instance

export function createLiveQueryStore<T>(query: () => T | Promise<T>) {
    return readable<T | undefined>(undefined, (set) => {
        const subscription = liveQuery(query).subscribe({
            next: (result) => set(result),
            error: (error) => console.error(error)
        });
        return () => subscription.unsubscribe();
    });
}
```

**2. Use the `createLiveQueryStore` in your component:**

```html
<script>
    import { createLiveQueryStore } from './stores';
    import { db } from './db';

    const friends = createLiveQueryStore(() => db.friends.toArray());
</script>

<ul>
    {#if $friends} {#each $friends as friend}
    <li>{friend.name}</li>
    {/each} {/if}
</ul>
```

The `createLiveQueryStore` function creates a readable store that automatically updates whenever the data in the `friends` table changes. The `$friends` variable in the component will always contain the latest data from the database.

## Current Data Flow in `ae_journals` Module

The `ae_journals` module currently uses a manual, API-first caching strategy. It does not use Dexie.js's `liveQuery` function for reactivity.

### Data Flow

1.  **Fetch from API:** The `load_ae_obj_id__journal` and `load_ae_obj_li__journal` functions are used to fetch data from the API.
2.  **Process Data:** The `process_ae_obj__journal_props` and `process_ae_obj__journal_entry_props` functions are used to process the data before it's saved to the database. This includes parsing Markdown, creating temporary sorting fields, and combining passcodes.
3.  **Save to IndexedDB:** The `db_save_ae_obj_li__ae_obj` function is used to save the processed data to the `journal` and `journal_entry` tables in the `ae_journals_db` IndexedDB database.
4.  **Manual Store Updates:** The Svelte stores in `src/lib/ae_journals/ae_journals_stores.ts` are manually updated with the fetched data.

### Future Improvements

The current implementation could be improved by refactoring it to use Dexie.js's `liveQuery` function. This would simplify the code, reduce boilerplate, and improve the reactivity of the application. By using `liveQuery`, the UI would automatically update whenever the data in the IndexedDB database changes, without the need for manual store updates.
