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Event Encoder

The Agent User Interaction Protocol uses a streaming approach to send events from agents to clients. The EventEncoder class provides the functionality to encode events into a format that can be sent over HTTP.

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EventEncoder

from ag_ui.encoder import EventEncoder The EventEncoder class is responsible for encoding BaseEvent objects into string representations that can be transmitted to clients. 
from ag_ui.core import BaseEvent
from ag_ui.encoder import EventEncoder

# Initialize the encoder
encoder = EventEncoder()

# Encode an event
encoded_event = encoder.encode(event)

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Usage

The EventEncoder is typically used in HTTP handlers to convert event objects into a stream of data. The current implementation encodes events as Server-Sent Events (SSE), which can be consumed by clients using the EventSource API.

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Methods

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__init__(accept: str = None)

Creates a new encoder instance.
ParameterTypeDescription
acceptstr (optional)Content type accepted by the client

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encode(event: BaseEvent) -> str

Encodes an event into a string representation.
ParameterTypeDescription
eventBaseEventThe event to encode
Returns: A string representation of the event in SSE format.

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Example

from ag_ui.core import TextMessageContentEvent, EventType
from ag_ui.encoder import EventEncoder

# Create an event
event = TextMessageContentEvent(
    type=EventType.TEXT_MESSAGE_CONTENT,
    message_id="msg_123",
    delta="Hello, world!"
)

# Initialize the encoder
encoder = EventEncoder()

# Encode the event
encoded_event = encoder.encode(event)
print(encoded_event)
# Output: data: {"type":"TEXT_MESSAGE_CONTENT","messageId":"msg_123","delta":"Hello, world!"}\n\n

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Implementation Details

Internally, the encoder converts events to JSON and formats them as Server-Sent Events with the following structure: 
data: {json-serialized event}\n\n
This format allows clients to receive a continuous stream of events and process them as they arrive.