# @jqhtml/core

Core runtime library for JQHTML v2 - jQuery-first component framework.

## Installation

```bash
npm install @jqhtml/core jquery
```

## Module Structure

The core package exports two separate entry points:

### Main Runtime (Production)
```javascript
import { Component, jqhtml } from '@jqhtml/core';
```

### Debug Utilities (Development Only)
```javascript
import { showDebugOverlay, hideDebugOverlay } from '@jqhtml/core/debug';
```

The debug module is kept separate to avoid including debug code in production bundles. It provides:
- Visual debug overlay with performance profiling
- Component flash visualization
- Lifecycle logging
- Slow render detection

## Overview

The core package provides:
- Component base class with 5-stage lifecycle
- Lifecycle manager for phase coordination
- Component registry for dynamic instantiation
- Instruction processor for template rendering
- jQuery plugin integration
- Template rendering with data bindings

## Quick Start

### Basic Component

```javascript
import { Component } from '@jqhtml/core';

class UserCard extends Component {
  async init() {
    // Quick setup, hide elements
    this.$.addClass('loading');
  }
  
  async load() {
    // Fetch data (runs in parallel with siblings)
    this.data.user = await fetch('/api/user').then(r => r.json());
  }
  
  async render() {
    // Create DOM structure
    this.$.html(`
      <div class="card">
        <h2>${this.data.user.name}</h2>
        <p>${this.data.user.email}</p>
      </div>
    `);
  }
  
  async ready() {
    // Component fully initialized
    this.$.removeClass('loading');
  }
}
```

### Using jQuery Plugin

```javascript
// Create component on existing element
$('#user-container').component(UserCard, { userId: 123 });

// Get component instance
const card = $('#user-container').component();
```

## Component Lifecycle

Components follow a multi-stage lifecycle with automatic re-rendering:

1. **constructor** - Instance creation, jQuery element setup (`this.data` is `{}`)
2. **render** - Create initial DOM structure (top-down, atomic/synchronous operation)
3. **create** - Quick setup after DOM creation (bottom-up, siblings parallel)
4. **load** - Fetch data (bottom-up, fully parallel, **ABSOLUTELY NO DOM MODIFICATIONS**)
5. **render** (automatic) - Re-render if data changed during load (empties DOM first)
6. **create** (automatic) - Re-setup if component was re-rendered
7. **ready** - Fully initialized (bottom-up, siblings parallel)
8. **destroy** - Cleanup when removed

### Critical: NO DOM Modifications in load()

**The requirement that `on_load()` must not modify the DOM is ABSOLUTE.** This is not a guideline but a strict architectural requirement. Violating this will cause rendering issues and race conditions.

**Data Initialization Timeline:**
- Before `load()`: `this.data = {}` (empty object)
- After `load()`: `this.data` contains fetched data (remains `{}` if no data loaded)

### Correct Patterns for Loading States

If you need to show different DOM states before and after loading, use these patterns:

**Pattern 1: Conditional Rendering in Template**
```jqhtml
<Define:UserProfile>
  <div class="user-profile">
    <% if (Object.keys(this.data).length === 0): %>
      <!-- Show loading state (no data loaded yet) -->
      <div class="loading">
        <div class="spinner"></div>
        <p>Loading user profile...</p>
      </div>
    <% else: %>
      <!-- Show loaded content -->
      <h2><%= this.data.user?.name || 'Unknown User' %></h2>
      <p><%= this.data.user?.bio || 'No bio available' %></p>
    <% endif; %>
  </div>
</Define:UserProfile>
```

**Pattern 2: DOM Changes in create() and ready()**
```javascript
class DataComponent extends Component {
  async on_create() {
    // Set loading state in the DOM during create phase
    this.$id('status').addClass('loading').text('Loading...');
  }

  async on_load() {
    // ONLY fetch data - NO DOM modifications here!
    this.data.user = await fetch('/api/user').then(r => r.json());
  }

  async on_ready() {
    // Update DOM after data is loaded
    this.$id('status').removeClass('loading').text('Loaded');
    this.$id('username').text(this.data.user.name);
  }
}
```

**NEVER do this:**
```javascript
class BadComponent extends Component {
  async on_load() {
    // ❌ WRONG - DOM modification in load()
    this.$id('status').text('Loading...');  // VIOLATION!

    this.data.user = await fetch('/api/user').then(r => r.json());

    // ❌ WRONG - More DOM modification
    this.$id('status').text('Loaded');  // VIOLATION!
  }
}
```

**Important:** The `render()` method is atomic and essentially synchronous - it empties the DOM and rebuilds it in a single operation. While marked `async` for technical reasons, it completes immediately without yielding control.

### Phase Batching

All components complete each phase before moving to the next:
- Parents render before children
- Children create/load/ready before parents
- Siblings execute in parallel where safe

### Automatic Re-rendering

After the `load` phase, if `this.data` has changed, the component automatically:
1. Calls `render()` again (which empties the DOM with `$.empty()` first)
2. Calls `create()` again to re-setup the new DOM
3. Then proceeds to `ready()`

This ensures components can fetch data and re-render with that data seamlessly.

### Controlling Re-rendering

By default, components automatically re-render if `this.data` changes during `load()`:

```javascript
class DataComponent extends Component {
  async on_load() {
    // If this modifies this.data, component will re-render
    this.data.user = await fetch('/api/user').then(r => r.json());
  }

  // Override to customize re-render logic
  should_rerender() {
    // Default: returns true if JSON.stringify(this.data) changed
    // Override for custom logic:
    return this.data.user && !this.data.cached;
  }
}
```

### Manual Re-rendering

You can manually re-render a component at any time:

```javascript
class InteractiveComponent extends Component {
  async handleUpdate(newData) {
    // Update data
    this.data = { ...this.data, ...newData };

    // Manually re-render (atomic operation)
    await this.render();

    // Optionally re-initialize (call create/ready as needed)
    await this.on_create();  // Re-setup event handlers
    await this.on_ready();   // Re-initialize component state
  }

  // Lifecycle manipulation methods
  redraw() {
    // Synchronously re-renders with current data
  }

  async reload_data() {
    // Re-fetches data via on_load(), then redraws
  }

  async reinitialize() {
    // Full lifecycle reset from stage 0
  }

  destroy() {
    // Cleanup component and children
  }
}
```

**Note:** The re-render process:
1. Empties the component's DOM with `this.$.empty()`
2. Calls `render()` to rebuild the DOM atomically
3. For automatic re-renders, calls `create()` again for the new DOM
4. Finally calls `ready()`
5. For manual re-renders, you control which lifecycle methods to call

## Scoped IDs

Components use `_cid` for scoped element selection:

```javascript
class TabsComponent extends Component {
  async render() {
    this.$.html(`
      <button id="tab1:${this._cid}">Tab 1</button>
      <button id="tab2:${this._cid}">Tab 2</button>
      <div id="content:${this._cid}"></div>
    `);
  }
  
  selectTab(tabId) {
    // Use $id() for scoped selection
    this.$id('tab1').removeClass('active');
    this.$id('tab2').removeClass('active');
    this.$id(tabId).addClass('active');
  }
}
```

## Template Integration

The core runtime processes templates compiled by `@jqhtml/parser`:

```javascript
import { render_template, with_template } from '@jqhtml/core';

// Template function (usually generated by parser)
const template = function(data, args, content) {
  const _output = [];
  _output.push({tag: ["h1", {"data-bind-text": "title"}, false]});
  _output.push({tag: ["h1", {}, true]});
  return [_output, this];
};

// Component with template
class Article extends Component {
  async on_render() {
    await render_template(this, template);
  }
}

// Or use mixin
const Article = with_template(template)(Component);
```

## Attribute Rules

JQHTML has specific rules for attribute quoting and value passing:
- **@ Event attributes**: MUST be unquoted (pass function references)
  Example: `@click=this.handleClick`
- **$ Data attributes**: Can be quoted OR unquoted (flexible)
  Example: `$id="my-id"` or `$data=this.complexObject`
- **Regular HTML attributes**: MUST be quoted (strings only)
  Example: `class="container <%= this.args.theme %>"`

See [ATTRIBUTE_RULES.md](../../docs/ATTRIBUTE_RULES.md) for comprehensive documentation.

## Data Bindings

Templates support reactive data bindings:

- `:text="expression"` - Update text content
- `:value="expression"` - Form input values
- `:class="{active: isActive}"` - Dynamic classes
- `:style="{color: textColor}"` - Dynamic styles
- `@click=handler` - Event handlers (unquoted)

## Browser Bundle

For browser usage without a build tool:

```html
<script src="https://code.jquery.com/jquery-3.7.1.min.js"></script>
<script src="jqhtml-bundle.js"></script>
<script>
  const { Component } = JQHTML;

  class MyComponent extends Component {
    // ...
  }
</script>
```

## Lifecycle Event Callbacks

JQHTML provides a `.on()` method for registering callbacks that fire after lifecycle events complete. This is useful for external code that needs to know when a component reaches a certain state.

### Supported Events

- `'render'` - Fires after the render phase completes
- `'create'` - Fires after the create phase completes
- `'load'` - Fires after the load phase completes
- `'ready'` - Fires after the ready phase completes (component fully initialized)

### Usage

```javascript
// Get component instance and register callback
const component = $('#my-component').component();

component.on('ready', (comp) => {
  console.log('Component is ready!', comp);
  // Access component data, DOM, etc.
});

// If the event already occurred, callback fires immediately
// AND still registers for future occurrences (e.g., on re-render)
```

### Behavior

1. **Immediate Execution**: If the lifecycle event has already occurred when you register the callback, it fires immediately
2. **Future Events**: The callback also registers for future occurrences of the same event (useful for re-renders)
3. **Multiple Callbacks**: You can register multiple callbacks for the same event
4. **Error Safety**: Errors in callbacks are caught and logged without breaking the component
5. **Validation**: Only lifecycle events are allowed; other event names trigger a console error

### Example: Wait for Component to be Ready

```javascript
// Register callback before or after component initialization
$('#user-profile').component().on('ready', (component) => {
  // Component is fully initialized, data is loaded
  console.log('User data:', component.data.user);

  // Safe to access all DOM elements
  component.$id('email').addClass('verified');
});
```

### Example: Track Multiple Lifecycle Events

```javascript
const component = $('#dashboard').component();

component
  .on('render', () => console.log('Dashboard rendered'))
  .on('create', () => console.log('Dashboard created'))
  .on('load', () => console.log('Dashboard data loaded'))
  .on('ready', () => console.log('Dashboard ready'));
```

### Example: Invalid Event (Error)

```javascript
// This will log an error to console
$('#my-component').component().on('click', callback);
// Error: Component.on() only supports lifecycle events: render, create, load, ready
```

### Note on Re-renders

When a component re-renders (manually or automatically after `load()`), lifecycle events fire again:

```javascript
const component = $('#widget').component();

component.on('render', () => {
  console.log('Widget rendered');
  // Fires on initial render AND every re-render
});

// Later, trigger re-render
await component.render();  // "Widget rendered" logs again
```

## API Reference

### Component Class

- `constructor(element, args)` - Create component instance
- `async render()` - Create DOM structure
- `async init()` - Quick setup phase
- `async load()` - Data fetching phase
- `async ready()` - Final initialization
- `destroy()` - Cleanup
- `should_rerender()` - Control re-rendering after load
- `emit(event, data)` - Emit jQuery events
- `on(event, callback)` - Register lifecycle event callback
- `$id(localId)` - Get scoped jQuery element
- `id(localId)` - Get scoped component instance
- `parent()` - Get parent component
- `children()` - Get direct child components
- `find(selector)` - Find descendant components

### jQuery Plugin

- `$(el).component()` - Get component instance
- `$(el).component(Class, args)` - Create component
- `$.jqhtml.register(name, Class)` - Register component
- `$.jqhtml.create(name, args)` - Create by name

### Template Functions

- `render_template(component, template)` - Render template
- `with_template(template)` - Component mixin
- `process_instructions(instructions, target, context)` - Process instruction array

## Component and Template Registration Flexibility

JQHTML provides complete flexibility in how you define components - you can use JavaScript classes, `.jqhtml` template files, both, or neither. The framework automatically handles all combinations:

### All Possible Combinations

1. **Both JS Class and .jqhtml Template** (Standard approach)
   ```javascript
   // UserCard.js
   class UserCard extends Jqhtml_Component {
     async load() {
       this.data.user = await fetch('/api/user').then(r => r.json());
     }
   }
   jqhtml.register_component('UserCard', UserCard);
   ```
   ```html
   <!-- UserCard.jqhtml -->
   <Define:UserCard>
     <div class="card">
       <h2><%= this.data.user.name %></h2>
     </div>
   </Define:UserCard>
   ```
   **Result**: Uses your custom class logic + your custom template

2. **.jqhtml Template Only** (No JS class needed)
   ```html
   <!-- SimpleWidget.jqhtml -->
   <Define:SimpleWidget>
     <div class="widget">
       Hello, <%= this.args.name %>!
     </div>
   </Define:SimpleWidget>
   ```
   **Result**: Uses default `Jqhtml_Component` class + your template. Perfect for presentational components that don't need custom logic.

3. **JS Class Only** (No .jqhtml template)
   ```javascript
   class DynamicComponent extends Jqhtml_Component {
     async render() {
       this.$.html(`<div>Rendered at ${Date.now()}</div>`);
     }
   }
   jqhtml.register_component('DynamicComponent', DynamicComponent);
   ```
   **Result**: Uses your class + default passthrough template. Useful when you want full programmatic control.

4. **Neither Class nor Template** (Passthrough)
   ```html
   <!-- In your JQHTML file -->
   <FooBar>
     <p>This content just passes through!</p>
   </FooBar>
   ```
   **Result**: Uses default `Jqhtml_Component` class + default passthrough template. Acts as a simple wrapper that renders its inner content.

### How It Works

When you use `<ComponentName>`:
- **JS Class Resolution**: Looks for registered class, falls back to `Jqhtml_Component`
- **Template Resolution**: Looks for registered template by class, then by name, then uses default passthrough
- **Default Passthrough Template**: Simply renders the component's inner HTML as-is

This means you can start simple and progressively add complexity:
```html
<!-- Start with just markup -->
<UserBadge>Basic HTML content</UserBadge>

<!-- Later, add a .jqhtml template for consistent styling -->
<Define:UserBadge>
  <div class="badge"><%= this.args.username %></div>
</Define:UserBadge>

<!-- Finally, add JS class for complex behavior -->
class UserBadge extends Jqhtml_Component {
  async load() { /* fetch user data */ }
}
```

## Laravel Integration

This package includes a Laravel bridge for error handling and source map support. After installing via npm, you can load it directly from `node_modules` in your Laravel application:

```php
// In app/Providers/AppServiceProvider.php
public function register()
{
    $jqhtmlBridge = base_path('node_modules/@jqhtml/core/laravel-bridge/autoload.php');
    if (file_exists($jqhtmlBridge)) {
        require_once $jqhtmlBridge;
    }
}
```

See [laravel-bridge/LARAVEL_INTEGRATION.md](./laravel-bridge/LARAVEL_INTEGRATION.md) for complete integration instructions.

## Development

```bash
# Install dependencies
npm install

# Build TypeScript
npm run build

# Run tests
npm test

# Watch mode
npm run watch
```

## License

MIT