cjm-fasthtml-sse 0.0.4

Real-time Server-Sent Events (SSE) and HTMX integration library for FastHTML with cross-tab synchronization support.

cjm-fasthtml-sse

Install

pip install cjm_fasthtml_sse

Project Structure

nbs/
├── components/ (2)
│   ├── builders.ipynb  # Generic builders for creating SSE-enabled elements with HTMX
│   └── monitors.ipynb  # Client-side SSE connection monitoring and management utilities
├── core/ (3)
│   ├── broadcast.ipynb   # SSE broadcast infrastructure for managing connections and broadcasting updates to multiple clients
│   ├── decorators.ipynb  # Route decorators and utilities for FastHTML SSE endpoints
│   └── streaming.ipynb   # SSE streaming utilities for creating and managing Server-Sent Events streams
└── integrations/ (1)
    └── fasthtml.ipynb  # High-level FastHTML integration for SSE with HTMX

Total: 6 notebooks across 3 directories

Module Dependencies

graph LR
    components_builders[components.builders<br/>builders]
    components_monitors[components.monitors<br/>monitors]
    core_broadcast[core.broadcast<br/>broadcast]
    core_decorators[core.decorators<br/>decorators]
    core_streaming[core.streaming<br/>streaming]
    integrations_fasthtml[integrations.fasthtml<br/>fasthtml]

    core_decorators --> core_streaming
    core_decorators --> core_broadcast
    core_streaming --> core_broadcast
    integrations_fasthtml --> components_builders
    integrations_fasthtml --> core_streaming
    integrations_fasthtml --> core_decorators
    integrations_fasthtml --> core_broadcast
    integrations_fasthtml --> components_monitors

8 cross-module dependencies detected

CLI Reference

No CLI commands found in this project.

Module Overview

Detailed documentation for each module in the project:

broadcast (broadcast.ipynb)

SSE broadcast infrastructure for managing connections and broadcasting updates to multiple clients

Import

from cjm_fasthtml_sse.core.broadcast import (
    BroadcastEventType,
    BroadcastMessage,
    SSEBroadcastManager,
    SSEConnection
)

Classes

class BroadcastEventType(Enum):
    "Standard broadcast event types"

@dataclass
class BroadcastMessage:
    "Structured broadcast message"
    
    type: str
    data: Dict[str, Any]
    timestamp: str = field(...)
    target_ids: Optional[List[str]]  # Specific element IDs to update
    metadata: Optional[Dict[str, Any]]
    
    def to_dict(
            self
        ) -> Dict[str, Any]:  # Dictionary representation of the message
        "Convert to dictionary for JSON serialization"
    
    def to_json(
            self
        ) -> str:  # JSON string representation of the message
        "Convert to JSON string"

class SSEBroadcastManager:
    def __init__(self,
    "Manages SSE connections and broadcasting across multiple clients. This class provides a centralized way to manage Server-Sent Events connections and broadcast messages to all connected clients, enabling real-time updates and cross-tab synchronization."
    
    def __init__(self,
        "Initialize the SSE Broadcast Manager."
    
    async def register_connection(self, 
                                      queue: Optional[asyncio.Queue] = None,  # Optional pre-existing queue (creates new if None)
                                      metadata: Optional[Dict[str, Any]] = None # Optional metadata for this connection
                                     ) -> asyncio.Queue: # The queue for this connection
        "Register a new client connection."
    
    async def unregister_connection(
            self,
            queue: asyncio.Queue  # The queue to unregister
        )
        "Remove a client connection."
    
    async def broadcast(self, 
                            event_type: str,   # Type of event to broadcast
                            data: Dict[str, Any], # Data to broadcast
                            target_ids: Optional[List[str]] = None,  # Optional list of element IDs to target for updates
                            metadata: Optional[Dict[str, Any]] = None # Optional metadata for the message
                           ) -> int: # Number of clients successfully notified
        "Broadcast a message to all connected clients."
    
    async def run_message_handlers(
            self,
            message: BroadcastMessage  # Message to process
        ) -> BroadcastMessage:  # Potentially modified message
        "Run message through registered handlers."
    
    async def broadcast_message(
            self,
            message: BroadcastMessage  # Message to broadcast
        ) -> int:  # Number of clients successfully notified
        "Broadcast a pre-constructed message to all connected clients."
    
    def add_message_handler(self,
                                handler: Callable[[BroadcastMessage], Awaitable[Optional[BroadcastMessage]]] # Async function that takes and optionally returns a BroadcastMessage
                               )
        "Add a message handler that can transform messages before broadcasting. Handlers are called in the order they are added and can modify messages or return None to pass through unchanged."
    
    def get_connection_count(
            self
        ) -> int:  # Current number of active connections
        "Get the current number of active connections"
    
    def get_history(
            self,
            limit: Optional[int] = None  # Maximum number of messages to return (None for all)
        ) -> List[BroadcastMessage]:  # List of historical messages
        "Get message history."
    
    async def clear_history(self):
            """Clear the message history"""
            self.history.clear()
            self._log("Message history cleared")
        
        async def close_all_connections(self)
        "Clear the message history"
    
    async def close_all_connections(self):
            """
            Close all active connections. Useful for cleanup during shutdown.
            """
            async with self.lock
        "Close all active connections. Useful for cleanup during shutdown."

class SSEConnection:
    def __init__(self, 
                 manager: SSEBroadcastManager,  # The SSEBroadcastManager to register with
                 metadata: Optional[Dict[str, Any]] = None # Optional metadata for this connection
                )
    "Context manager for SSE connections. Automatically registers/unregisters connections with the broadcast manager."
    
    def __init__(self,
                     manager: SSEBroadcastManager,  # The SSEBroadcastManager to register with
                     metadata: Optional[Dict[str, Any]] = None # Optional metadata for this connection
                    )
        "Initialize SSE connection context."

builders (builders.ipynb)

Generic builders for creating SSE-enabled elements with HTMX

Import

from cjm_fasthtml_sse.components.builders import (
    add_sse_attrs,
    add_oob_swap,
    SSEConfig,
    OOBUpdate,
    MultiUpdateBuilder,
    generate_sse_cleanup_script,
    get_htmx_sse_extension_url,
    create_sse_attrs,
    create_oob_attrs
)

Functions

def add_sse_attrs(
    element: Any,  # Any element with an attrs dictionary
    endpoint: str,  # SSE endpoint URL
    event_name: str = "message",  # SSE event to listen for
    swap_mode: Optional[str] = None,  # Optional HTMX swap mode **extra_attrs: Additional attributes to add
    **extra_attrs
) -> Any:  # The modified element
    "Add SSE attributes to any element. This function modifies an element in-place by adding the necessary HTMX SSE attributes. It's framework-agnostic and works with any element that has an attrs dictionary."

def add_oob_swap(
    "Add out-of-band swap attributes to any element."

def generate_sse_cleanup_script(
) -> str:  # JavaScript code as a string
    "Generate JavaScript for proper SSE connection cleanup."

def get_htmx_sse_extension_url(
    version: str = "2.2.3"  # Version of the extension
) -> str:  # CDN URL as a string
    "Get the CDN URL for the HTMX SSE extension."

def create_sse_attrs(
    endpoint: str,  # SSE endpoint
    event: str = "message",  # Event name to listen for
    swap: Optional[str] = None,  # Optional swap mode **kwargs: Additional attributes
    **kwargs
) -> Dict[str, str]:  # Dictionary of attributes
    "Create a dictionary of SSE attributes. This is a convenience function for creating SSE attributes that can be spread into element constructors."

def create_oob_attrs(
    element_id: str,  # ID of target element
    swap_type: str = "innerHTML"  # Type of swap
) -> Dict[str, str]:  # Dictionary of attributes
    "Create a dictionary of OOB swap attributes."

Classes

@dataclass
class SSEConfig:
    """
    Configuration for SSE-enabled elements.
    
    This dataclass provides a clean way to configure SSE attributes
    that can be applied to any element.
    """
    
    endpoint: str
    event_name: str = 'message'
    swap_mode: Optional[str]
    reconnect_time: Optional[int]
    extra_attrs: Dict[str, Any] = field(...)
    
    def apply_to(
            self,
            element: Any  # Element to configure
        ) -> Any:  # The configured element
        "Apply this SSE configuration to an element."
    
    def to_attrs(
            self
        ) -> Dict[str, str]:  # Dictionary of HTMX SSE attributes
        "Convert configuration to attribute dictionary."

@dataclass
class OOBUpdate:
    """
    Represents an out-of-band update.
    
    This is a generic container for OOB updates that doesn't
    depend on specific element types.
    """
    
    element: Any
    swap_type: str = 'innerHTML'
    target_id: Optional[str]
    
    def prepare(
            self
        ) -> Any:  # Element with OOB swap attributes
        "Prepare element with OOB attributes."

class MultiUpdateBuilder:
    def __init__(
        self,
        container_factory: Optional[Callable] = None  # Optional factory function for creating containers.  Should accept *children as arguments.
    )
    """
    Builder for creating multiple OOB updates.
    
    This builder is framework-agnostic and works with any elements.
    """
    
    def __init__(
            self,
            container_factory: Optional[Callable] = None  # Optional factory function for creating containers.  Should accept *children as arguments.
        )
        "Initialize the builder."
    
    def add(
            self,
            element: Any,  # Element to add
            swap_type: str = "innerHTML",  # Type of swap
            target_id: Optional[str] = None  # Optional target ID
        ) -> 'MultiUpdateBuilder':  # Self for chaining
        "Add an update to the builder."
    
    def add_many(
            self,
            updates: List[Union[OOBUpdate, tuple, Any]] # List of updates (OOBUpdate objects, tuples, or elements)
        ) -> 'MultiUpdateBuilder':  # Self for chaining
        "Add multiple updates at once."
    
    def build(
            self
        ) -> Any:  # Container with all prepared OOB updates
        "Build the final multi-update container."
    
    def clear(
            self
        ) -> 'MultiUpdateBuilder':  # Self for chaining
        "Clear all pending updates."

decorators (decorators.ipynb)

Route decorators and utilities for FastHTML SSE endpoints

Import

from cjm_fasthtml_sse.core.decorators import (
    sse_endpoint,
    broadcast_action,
    sse_generator_endpoint
)

Functions

def sse_endpoint(
    broadcast_manager: Optional[SSEBroadcastManager] = None,  # Optional SSEBroadcastManager for automatic broadcasting
    config: Optional[SSEStreamConfig] = None,  # Optional SSEStreamConfig for stream configuration
    message_filter: Optional[Callable[[BroadcastMessage], bool]] = None,
    client_metadata_fn: Optional[Callable[..., Dict[str, Any]]] = None
)
    "Decorator for creating SSE endpoints with optional broadcast integration. This decorator can work in two modes: 1. With broadcast_manager: Automatically connects to broadcast stream 2. Without broadcast_manager: Wraps custom async generator functions"

def broadcast_action(
    manager: SSEBroadcastManager,  # SSEBroadcastManager to broadcast through
    event_type: Optional[str] = None,  # Event type to broadcast (defaults to function name)
    extract_data: Optional[Callable[..., Dict[str, Any]]] = None,
    broadcast_before: bool = False,  # Broadcast before executing function
    broadcast_after: bool = True,  # Broadcast after executing function
    include_result: bool = True  # Include function result in broadcast data
)
    "Decorator that broadcasts events when actions occur. This decorator automatically broadcasts SSE messages when the decorated function is called, useful for notifying clients of state changes."

def sse_generator_endpoint(
    interval: float = 1.0,  # Seconds between data checks
    event_type: Optional[str] = None,  # Optional event type for messages
    heartbeat: Optional[float] = 30.0  # Heartbeat interval in seconds
)
    "Decorator for creating simple SSE endpoints from data functions. This decorator converts a function that returns data into an SSE streaming endpoint."

fasthtml (fasthtml.ipynb)

High-level FastHTML integration for SSE with HTMX

Import

from cjm_fasthtml_sse.integrations.fasthtml import (
    FastHTMLSSEConfig,
    FastHTMLSSE,
    setup_sse,
    create_sse_page_template
)

Functions

def setup_sse(
    app: Any,  # FastHTML application
    prefix: str = "/sse",  # URL prefix for SSE routes
    **kwargs  # Additional configuration options
) -> FastHTMLSSE:  # Configured FastHTMLSSE instance
    "Quick setup function for SSE in FastHTML apps."

def create_sse_page_template(
    sse: FastHTMLSSE,  # FastHTMLSSE instance
    title: str = "SSE Demo",  # Page title
    content: Any = None  # Page content
)
    "Create a basic page template with SSE setup."

Classes

@dataclass
class FastHTMLSSEConfig:
    """
    Configuration for FastHTML SSE integration.
    
    Attributes:
        app: FastHTML application instance
        prefix: URL prefix for SSE endpoints
        enable_monitor: Add connection monitoring scripts
        enable_cleanup: Add cleanup script for proper SSE closure
        enable_htmx_extension: Add HTMX SSE extension script
        monitor_debug: Enable debug logging in monitor
        broadcast_history: Number of messages to keep in history
        default_stream_config: Default configuration for SSE streams
    """
    
    app: Any  # FastHTML app
    prefix: str = '/sse'
    enable_monitor: bool = True
    enable_cleanup: bool = True
    enable_htmx_extension: bool = True
    monitor_debug: bool = False
    broadcast_history: int = 50
    default_stream_config: Optional[SSEStreamConfig]

class FastHTMLSSE:
    def __init__(
        self,
        config: FastHTMLSSEConfig  # Configuration for the SSE integration
    )
    """
    Main integration class for SSE with FastHTML.
    
    This class provides a high-level API for adding SSE capabilities
    to FastHTML applications with minimal configuration.
    """
    
    def __init__(
            self,
            config: FastHTMLSSEConfig  # Configuration for the SSE integration
        )
        "Initialize FastHTML SSE integration.

Args:
    config: Configuration for the integration"
    
    async def broadcast(
            self,
            event_type: str,  # Type of event to broadcast
            data: Dict[str, Any],  # Data payload to broadcast
            target_ids: Optional[List[str]] = None  # Optional list of element IDs to update
        ) -> int:  # Number of clients successfully notified
        "Broadcast a message to all connected clients.

Args:
    event_type: Type of event
    data: Data to broadcast
    target_ids: Optional list of element IDs to update
    
Returns:
    Number of clients notified"
    
    def create_sse_element(
            self,
            element_id: str,  # ID for the HTML element
            endpoint: Optional[str] = None,  # SSE endpoint URL
            content: Any = None,  # Initial content for the element
            hidden: bool = False,  # Whether to hide the element
            **kwargs
        )
        "Create an SSE-enabled element.

Args:
    element_id: ID for the element
    endpoint: SSE endpoint (defaults to global)
    content: Initial content
    hidden: Whether to hide the element
    **kwargs: Additional attributes
    
Returns:
    Configured element"
    
    def create_monitor(
            self,
            sse_element_id: str = "global-sse",  # ID for the SSE connection element
            status_element_id: str = "connection-status"  # ID for the status display element
        )
        "Create connection monitor elements.

Args:
    sse_element_id: ID for SSE connection element
    status_element_id: ID for status display element
    
Returns:
    Tuple of (sse_element, status_element, monitor_script)"
    
    def create_oob_update(
            self,
            updates: List[tuple]  # List of (element_id, content, swap_type) tuples
        ) -> str:  # Formatted SSE message with OOB updates
        "Create an OOB update message.

Args:
    updates: List of (element_id, content, swap_type) tuples
    
Returns:
    Formatted SSE message with OOB updates"
    
    def sse_route(
            self,
            path: str,  # Route path for the SSE endpoint
            message_filter: Optional[Callable] = None  # Optional filter function for messages
        )
        "Decorator for creating SSE routes.

Args:
    path: Route path
    message_filter: Optional filter function
    
Returns:
    Route decorator"
    
    def action_route(
            self,
            path: str,  # Route path for the action endpoint
            event_type: Optional[str] = None,  # Event type to broadcast after action
            method: str = "post"  # HTTP method for the route
        )
        "Decorator for creating action routes that broadcast.

Args:
    path: Route path
    event_type: Event type to broadcast
    method: HTTP method
    
Returns:
    Route decorator"

monitors (monitors.ipynb)

Client-side SSE connection monitoring and management utilities

Import

from cjm_fasthtml_sse.components.monitors import (
    ConnectionState,
    MonitorConfig,
    generate_monitor_script,
    generate_simple_monitor,
    generate_connection_counter
)

Functions

def generate_monitor_script(
    config: MonitorConfig,  # Monitor configuration
    status_indicators: Optional[Dict[ConnectionState, str]] = None
) -> str:  # JavaScript code as a string
    "Generate JavaScript for monitoring SSE connections."

def generate_simple_monitor(
    sse_element_id: str,  # ID of SSE element to monitor
    status_element_id: Optional[str] = None,  # Optional status display element
    debug: bool = False  # Enable console logging
) -> str:  # JavaScript code for basic monitoring
    "Generate a simple SSE connection monitor."

def generate_connection_counter(
) -> str:  # JavaScript code that tracks connection count
    "Generate JavaScript for counting active SSE connections."

Classes

class ConnectionState(Enum):
    "SSE connection states"

@dataclass
class MonitorConfig:
    """
    Configuration for SSE connection monitoring.
    
    Attributes:
        sse_element_id: ID of the SSE connection element to monitor
        status_element_id: ID of element to update with connection status
        auto_reconnect: Whether to automatically reconnect on failures
        reconnect_delay: Delay in ms before reconnection attempts
        max_reconnect_attempts: Maximum number of reconnection attempts (None = infinite)
        visibility_reconnect: Reconnect when tab becomes visible
        heartbeat_timeout: Timeout in ms to consider connection dead (None = no timeout)
        debug: Enable console logging
        callbacks: JavaScript callbacks for state changes
    """
    
    sse_element_id: str
    status_element_id: Optional[str]
    auto_reconnect: bool = True
    reconnect_delay: int = 3000
    max_reconnect_attempts: Optional[int]
    visibility_reconnect: bool = True
    heartbeat_timeout: Optional[int]
    debug: bool = False
    callbacks: Dict[str, str] = field(...)
    
    def to_js_config(
            self
        ) -> str:  # JSON string of the JavaScript configuration object
        "Convert to JavaScript configuration object"

streaming (streaming.ipynb)

SSE streaming utilities for creating and managing Server-Sent Events streams

Import

from cjm_fasthtml_sse.core.streaming import (
    format_sse_message,
    format_sse_comment,
    SSEStreamConfig,
    sse_broadcast_stream,
    sse_generator,
    OOBUpdate,
    format_oob_updates,
    create_oob_message
)

Functions

def format_sse_message(
    data: Union[str, Dict[str, Any], Any],
    event: Optional[str] = None,  # Optional event type
    id: Optional[str] = None,  # Optional event ID
    retry: Optional[int] = None  # Optional retry interval in milliseconds
) -> str:  # Formatted SSE message string
    "Format data as a Server-Sent Event message."

def format_sse_comment(
    comment: str  # Comment text
) -> str:  # Formatted SSE comment
    "Format a comment for SSE (typically used for heartbeats)."

async def sse_broadcast_stream(
    manager: SSEBroadcastManager,  # The SSEBroadcastManager to connect to
    client_metadata: Optional[Dict[str, Any]] = None,
    config: Optional[SSEStreamConfig] = None,  # Optional stream configuration
    message_filter: Optional[Callable[[BroadcastMessage], bool]] = None
) -> AsyncIterator[str]:  # Async iterator yielding formatted SSE messages
    "Create an SSE stream that receives messages from a broadcast manager. This is the main function for creating SSE endpoints that receive broadcast messages and format them for SSE delivery."

async def sse_generator(
    data_source: Union[AsyncIterator, Callable],
    interval: float = 1.0,  # Seconds between data checks (if using callable)
    event_type: Optional[str] = None,  # Optional event type for all messages
    heartbeat: Optional[float] = 30.0  # Heartbeat interval in seconds (None to disable)
) -> AsyncIterator[str]:  # Async iterator yielding formatted SSE messages
    "Create an SSE stream from a data source. This is useful for creating SSE streams from custom data sources without using the broadcast manager."

def format_oob_updates(
    updates: List[OOBUpdate]  # List of OOB updates to format
) -> str:  # Combined HTML string with all OOB updates
    "Format multiple OOB updates into a single HTML string."

def create_oob_message(
    updates: List[OOBUpdate],  # List of OOB updates
    event: str = "message"  # SSE event type
) -> str:  # Formatted SSE message with OOB HTML
    "Create an SSE message containing OOB updates for HTMX."

Classes

@dataclass
class SSEStreamConfig:
    "Configuration for SSE streams."
    
    heartbeat_interval: Optional[float] = 30.0  # Seconds between heartbeat messages (None to disable)
    reconnect_time: Optional[int] = 3000  # Suggested reconnect time for clients in milliseconds
    timeout: Optional[float]  # Maximum time to wait for messages before closing stream
    initial_event: Optional[Dict[str, Any]]  # Event to send when stream starts
    closing_event: Optional[Dict[str, Any]]  # Event to send when stream closes
    debug: bool = False  # Enable debug logging

@dataclass
class OOBUpdate:
    "Represents an out-of-band update for HTMX."
    
    target_id: str  # The ID of the element to update
    content: str  # The HTML content to swap in
    swap_type: str = 'innerHTML'  # The type of swap (innerHTML, outerHTML, etc.)
    
    def to_html(
            self
        ) -> str:  # HTML string with hx-swap-oob attribute for HTMX
        "Convert to HTML with hx-swap-oob attribute"