# Spry Framework - Important Details

## Component Basics

### Template DOM is NOT Persisted
- The template is fresh on every request
- Any state set via setters (like `title`, `completed`) is NOT available in `handle_action()`
- Always use `prepare()` to fetch data from store and set up the template

### The `prepare()` Method
- Called automatically before serialization
- Use this to fetch data from stores and populate the template
- Centralizes data fetching logic in one place

```vala
public override async void prepare() throws Error {
    var item = store.get_by_id(_item_id);
    if (item == null) return;
    
    this["title"].text_content = item.title;
    this["button"].text_content = item.completed ? "Undo" : "Done";
}
```

### The `prepare_once()` Method
- Called only once before the first `prepare()` call
- Useful for one-time initialization that should not repeat on every render
- Runs before `prepare()` in the same request lifecycle

```vala
public override async void prepare_once() throws Error {
    // One-time setup, e.g., loading initial data
    initial_data = yield fetch_initial_data();
}
```

### The `handle_action()` Method
- Called when HTMX requests trigger an action
- Modify state in stores, then let `prepare()` handle template updates
- For delete with `hx-swap="delete"`, just return (no content needed)

```vala
public async override void handle_action(string action) throws Error {
    var id = get_id_from_query_params();
    _item_id = id; // Set for prepare()
    
    switch (action) {
        case "Toggle":
            store.toggle(id);
            break; // prepare() will be called automatically
        case "Delete":
            store.remove(id);
            return; // HTMX removes element via hx-swap="delete"
    }
}
```

## Real-Time Updates with Continuations (SSE)

### Overview

The continuation feature allows a Component to send real-time updates to the client via Server-Sent Events (SSE). This is useful for:
- Long-running task progress reporting
- Real-time status updates
- Live data streaming

### The `continuation()` Method

Override `continuation(ContinuationContext context)` to send SSE events:

```vala
public async override void continuation(ContinuationContext continuation_context) throws Error {
    for (int i = 0; i <= 100; i += 10) {
        percent = i;
        status = @"Processing... $(i)%";
        
        // Send fragment updates to the client
        yield continuation_context.send_fragment("progress", "progress-bar");
        yield continuation_context.send_fragment("status", "status");
        
        Timeout.add(500, () => {
            continuation.callback();
            return false;
        });
        yield;
    }
    
    status = "Complete!";
    yield continuation_context.send_fragment("status", "status");
}
```

### The `continuation_canceled()` Method

Called when the client disconnects from the SSE stream:

```vala
public async override void continuation_canceled() throws Error {
    // Clean up resources when client disconnects
    cleanup_task();
}
```

### ContinuationContext API

| Method | Description |
|--------|-------------|
| `send_fragment(event_type, sid)` | Send a fragment (by `sid`) as an SSE event with the given event type |
| `send_json(event_type, node)` | Send JSON data as an SSE event |
| `send_string(event_type, data)` | Send raw string data as an SSE event |
| `send_full_update(event_type)` | Send the entire component document |
| `send_event(event)` | Send a custom `SseEvent` |

### The `spry-continuation` Attribute

Add `spry-continuation` to an element to enable SSE:

```vala
public override string markup { get {
    return """
    <div spry-continuation>
        <div class="progress-bar" sid="progress-bar" sse-swap="progress">
            0%
        </div>
        <div class="status" sid="status" sse-swap="status">
            Initializing...
        </div>
    </div>
    """;
}}
```

The `spry-continuation` attribute is shorthand for:
- `hx-ext="sse"` - Enable HTMX SSE extension
- `sse-connect="(auto-generated-endpoint)"` - Connect to the SSE endpoint
- `sse-close="_spry-close"` - Close event name

### The `sse-swap` Attribute

Use `sse-swap="eventname"` on child elements to specify which SSE event type should swap the content:

```html
<div sid="progress-bar" sse-swap="progress">...</div>
<div sid="status" sse-swap="status">...</div>
```

When `continuation_context.send_fragment("progress", "progress-bar")` is called, the fragment with `sid="progress-bar"` is sent as an SSE event with type "progress", and HTMX swaps it into the element listening for that event type.

### Required Scripts for SSE

Include the HTMX SSE extension in your markup:

```html
<script spry-res="htmx.js"></script>
<script spry-res="htmx-sse.js"></script>
```

## HTMX Integration

### Declarative Attributes

#### `spry-action` - Declare HTMX Actions
- `spry-action=":ActionName"` - Action on same component (e.g., `:Toggle`)
- `spry-action="ComponentName:ActionName"` - Action on different component (cross-component)

#### `spry-target` - Scoped Targeting (within same component)
- `spry-target="sid"` - Targets element by its `sid` attribute
- Only works within the SAME component
- Automatically generates proper `hx-target` with unique IDs

#### `hx-target` - Global Targeting (cross-component)
- Use `hx-target="#id"` to target elements anywhere on the page
- Requires the target element to have an `id` attribute (not just `sid`)

#### `hx-swap` - Swap Strategies
- `hx-swap="outerHTML"` - Replace entire target element (prevents nesting)
- `hx-swap="delete"` - Remove target element (no response content needed)

### Out-of-Band Swaps with `spry-global` and `add_globals_from()`

Update multiple elements on the page with a single response using `spry-global`:

```vala
// 1. Add spry-global to elements that may need OOB updates
// 2. Use prepare() to fetch data from store - no manual property setting needed!

class HeaderComponent : Component {
    private TodoStore todo_store = inject<TodoStore>();
    
    public override string markup { get {
        return """
        <div class="card" id="header" spry-global="header">
            <h1>Todo App</h1>
            <div sid="total"></div>
        </div>
        """;
    }}
    
    // prepare() fetches data from store automatically
    public override async void prepare() throws Error {
        this["total"].text_content = todo_store.count().to_string();
    }
}

// 3. Inject the component and pass it to add_globals_from()

class ItemComponent : Component {
    private HeaderComponent header = inject<HeaderComponent>();
    
    public override string markup { get {
        return """
        <div sid="item">...</div>
        """;
    }}
    
    public async override void handle_action(string action) throws Error {
        store.toggle(id);
        // Add header globals for OOB swap (header's prepare() fetches stats)
        add_globals_from(header);
    }
}
```

The `spry-global="key"` attribute:
- Automatically adds `hx-swap-oob="true"` when the element appears in a response
- HTMX finds the existing element on the page and swaps it in place
- Use `add_globals_from(component)` to append spry-global elements from another component
- The component's `prepare()` method is called automatically to populate data

### Passing Data with `hx-vals`

Since template DOM is not persisted, use `hx-vals` to pass data:

```vala
// In prepare() - set on parent element, inherited by children
this["item"].set_attribute("hx-vals", @"{\"id\":$_item_id}");

// In handle_action()
var id_str = http_context.request.query_params.get_any_or_default("id");
var id = int.parse(id_str);
```

**Note**: `hx-vals` is inherited by child elements, so set it on the parent div rather than individual buttons.

## Declarative Expression Attributes

### Expression Attributes (`*-expr`)

Use `*-expr` attributes to dynamically set any attribute based on component properties:

```vala
class ProgressComponent : Component {
    public int percent { get; set; }
    
    public override string markup { get {
        return """
        <div class="progress-bar" 
             content-expr='format("%i%%", this.percent)' 
             style-width-expr='format("%i%%", this.percent)'>
            0%
        </div>
        """;
    }}
}
```

Expression attribute patterns:
- `content-expr="expression"` - Set text/HTML content
- `class-expr="expression"` - Set CSS classes
- `style-expr="expression"` - Set inline styles (e.g., `style-width-expr`)
- `any-attr-expr="expression"` - Set any attribute dynamically

### Conditional Class Expressions

For `class-*` attributes, boolean expressions add/remove the class:

```html
<div class-completed-expr="this.is_completed">Item</div>
```

If `this.is_completed` is `true`, the `completed` class is added.

### Conditional Rendering with `spry-if`

Use `spry-if`, `spry-else-if`, and `spry-else` for conditional rendering:

```html
<div spry-if="this.is_admin">Admin Panel</div>
<div spry-else-if="this.is_moderator">Moderator Panel</div>
<div spry-else>User Panel</div>
```

### Loop Rendering with `spry-per-*`

Use `spry-per-{varname}="expression"` to iterate over collections:

```html
<div spry-per-task="this.tasks">
    <span content-expr="task.name"></span>
</div>
```

The variable name after `spry-per-` (e.g., `task`) becomes available in nested expressions.

### Static Resources with `spry-res`

Use `spry-res` to reference Spry's built-in static resources:

```html
<script spry-res="htmx.js"></script>
<script spry-res="htmx-sse.js"></script>
```

This resolves to `/_spry/res/{resource-name}` automatically.

## IoC Composition

### Registration Patterns

```vala
// State as singleton
application.add_singleton<AppState>();

// Factory as scoped
application.add_scoped<ComponentFactory>();

// Components as transient
application.add_transient<MyComponent>();
```

### Dependency Injection

Use `inject<T>()` in field initializers:

```vala
class MyComponent : Component {
    private TodoStore store = inject<TodoStore>();
    private ComponentFactory factory = inject<ComponentFactory>();
    private HttpContext http_context = inject<HttpContext>();
}
```

### Creating Components

Use `ComponentFactory.create<T>()` (not `inject<T>()` which only works in field initializers):

```vala
var child = factory.create<ChildComponent>();
child.item_id = item.id;
items.add(child);
```

## Common Patterns

### List with Items Pattern

```vala
// Parent component
class ListComponent : Component {
    public void set_items(Enumerable<Renderable> items) {
        set_outlet_children("items", items);
    }
    
    public override string markup { get {
        return """
        <div id="my-list" sid="my-list">
            <spry-outlet sid="items"/>
        </div>
        """;
    }}
}

// Item component with prepare()
class ItemComponent : Component {
    private TodoStore store = inject<TodoStore>();
    private HttpContext http_context = inject<HttpContext>();
    private HeaderComponent header = inject<HeaderComponent>();
    
    private int _item_id;
    public int item_id { set { _item_id = value; } }
    
    public override string markup { get {
        return """
        <div class="item" sid="item">
            <span sid="title"></span>
            <button sid="toggle-btn" spry-action=":Toggle" spry-target="item" hx-swap="outerHTML"></button>
        </div>
        """;
    }}
    
    public override void prepare() throws Error {
        var item = store.get_by_id(_item_id);
        this["title"].text_content = item.title;
        // hx-vals on parent is inherited by children
        this["item"].set_attribute("hx-vals", @"{\"id\":$_item_id}");
    }
    
    public async override void handle_action(string action) throws Error {
        var id = int.parse(http_context.request.query_params.get_any_or_default("id"));
        _item_id = id;
        
        if (action == "Toggle") {
            store.toggle(id);
            // Add header globals for OOB swap (header's prepare() fetches stats)
            add_globals_from(header);
        }
    }
}

// Creating the list
var items = new Series<Renderable>();
store.all().iterate((item) => {
    var component = factory.create<ItemComponent>();
    component.item_id = item.id; // Only set ID, prepare() handles rest
    items.add(component);
});
list.set_items(items);
```

### Cross-Component Action Pattern

```vala
// Form in one component triggers action on another
<form spry-action="ListComponent:Add" hx-target="#my-list" hx-swap="outerHTML">
    <input name="title"/>
    <button type="submit">Add</button>
</form>

// ListComponent handles the Add action
class ListComponent : Component {
    public async override void handle_action(string action) throws Error {
        if (action == "Add") {
            var title = http_context.request.query_params.get_any_or_default("title");
            store.add(title);
        }
        // Rebuild list...
    }
}
```

## HTML Escaping

`<pre>` and `<code>` tags do NOT escape their contents. Manually escape:

```vala
// Wrong
<pre><button spry-action=":Toggle">Click</button></pre>

// Correct
<pre>&lt;button spry-action=":Toggle"&gt;Click&lt;/button&gt;</pre>
```

## SpryModule

Automatically registers `ComponentEndpoint` at `/_spry/{component-id}/{action}`:

```vala
application.add_module<SpryModule>();
```

This enables the declarative `spry-action` attributes to work without manual endpoint registration.

## Declarative Child Components with `<spry-component>`

### When to Use `<spry-component>` vs `<spry-outlet>`

- **`<spry-component name="ComponentName" sid="..."/>`** - For single, known child components
- **`<spry-outlet sid="..."/>`** - For dynamic lists (multiple items from data)

### Declaring Child Components

Use `<spry-component>` in markup for declarative composition:

```vala
class TodoPage : PageComponent {
    public override string markup { get {
        return """
        <!DOCTYPE html>
        <html>
        <body>
            <spry-component name="HeaderComponent" sid="header"/>
            <spry-component name="TodoListComponent" sid="todo-list"/>
            <spry-component name="AddFormComponent" sid="add-form"/>
            <spry-component name="FooterComponent" sid="footer"/>
        </body>
        </html>
        """;
    }}
}
```

### Accessing Child Components with `get_component_child<T>()`

Use `get_component_child<T>(sid)` in `prepare()` to access and configure child components:

```vala
class TodoPage : PageComponent {
    private TodoStore todo_store = inject<TodoStore>();
    private ComponentFactory factory = inject<ComponentFactory>();
    
    public override async void prepare() throws Error {
        // Get child component and configure it
        var todo_list = get_component_child<TodoListComponent>("todo-list");
        
        // Populate the list (which still uses spry-outlet for dynamic items)
        var items = new Series<Renderable>();
        todo_store.all().iterate((item) => {
            var component = factory.create<TodoItemComponent>();
            component.item_id = item.id;
            items.add(component);
        });
        todo_list.set_items(items);
    }
}
```

## PageComponent - Combining Component and Endpoint

`PageComponent` is a base class that acts as both a `Component` AND an `Endpoint`. This eliminates the need for separate endpoint classes:

```vala
// Before: Separate endpoint class
class HomePageEndpoint : Object, Endpoint {
    private ComponentFactory factory = inject<ComponentFactory>();
    
    public async HttpResult handle_request(HttpContext context, RouteContext route) throws Error {
        var page = factory.create<PageLayoutComponent>();
        return yield page.to_result();
    }
}

// After: PageComponent handles both roles
class TodoPage : PageComponent {
    public override string markup { get { return "..."; } }
    public override async void prepare() throws Error { /* ... */ }
}
```

## SpryConfigurator - Component and Page Registration

Use `SpryConfigurator` to register components and pages in a structured way:

```vala
// Get the configurator
var spry_cfg = application.configure_with<SpryConfigurator>();

// Register child components (transient lifecycle)
spry_cfg.add_component<HeaderComponent>();
spry_cfg.add_component<TodoListComponent>();
spry_cfg.add_component<TodoItemComponent>();
spry_cfg.add_component<AddFormComponent>();
spry_cfg.add_component<FooterComponent>();

// Register pages (scoped lifecycle, acts as Endpoint)
spry_cfg.add_page<TodoPage>(new EndpointRoute("/"));

// Other endpoints still use add_endpoint
application.add_endpoint<TodoJsonEndpoint>(new EndpointRoute("/api/todos"));
```

### Registration Methods

| Method | Lifecycle | Use Case |
|--------|-----------|----------|
| `add_component<T>()` | Transient | Child components created via factory |
| `add_page<T>(route)` | Scoped | Page components that act as endpoints |
| `add_template<T>(prefix)` | Transient | Page templates for layout wrapping |