import base64
from google.genai.types import Content, ContentListUnion, Part
from browser_use.llm.messages import (
AssistantMessage,
BaseMessage,
SystemMessage,
UserMessage,
)
class GoogleMessageSerializer:
"""Serializer for converting messages to Google Gemini format."""
@staticmethod
def serialize_messages(messages: list[BaseMessage]) -> tuple[ContentListUnion, str | None]:
"""
Convert a list of BaseMessages to Google format, extracting system message.
Google handles system instructions separately from the conversation, so we need to:
1. Extract any system messages and return them separately as a string
2. Convert the remaining messages to Content objects
Args:
messages: List of messages to convert
Returns:
A tuple of (formatted_messages, system_message) where:
- formatted_messages: List of Content objects for the conversation
- system_message: System instruction string or None
"""
messages = [m.model_copy(deep=True) for m in messages]
formatted_messages: ContentListUnion = []
system_message: str | None = None
for message in messages:
role = message.role if hasattr(message, 'role') else None
# Handle system/developer messages
if isinstance(message, SystemMessage) or role in ['system', 'developer']:
# Extract system message content as string
if isinstance(message.content, str):
system_message = message.content
elif message.content is not None:
# Handle Iterable of content parts
parts = []
for part in message.content:
if part.type == 'text':
parts.append(part.text)
system_message = '\n'.join(parts)
continue
# Determine the role for non-system messages
if isinstance(message, UserMessage):
role = 'user'
elif isinstance(message, AssistantMessage):
role = 'model'
else:
# Default to user for any unknown message types
role = 'user'
# Initialize message parts
message_parts: list[Part] = []
# Extract content and create parts
if isinstance(message.content, str):
# Regular text content
message_parts = [Part.from_text(text=message.content)]
elif message.content is not None:
# Handle Iterable of content parts
for part in message.content:
if part.type == 'text':
message_parts.append(Part.from_text(text=part.text))
elif part.type == 'refusal':
message_parts.append(Part.from_text(text=f'[Refusal] {part.refusal}'))
elif part.type == 'image_url':
# Handle images
url = part.image_url.url
# Format: data:image/png;base64,<data>
header, data = url.split(',', 1)
# Decode base64 to bytes
image_bytes = base64.b64decode(data)
# Add image part
image_part = Part.from_bytes(data=image_bytes, mime_type='image/png')
message_parts.append(image_part)
# Create the Content object
if message_parts:
final_message = Content(role=role, parts=message_parts)
# for some reason, the type checker is not able to infer the type of formatted_messages
formatted_messages.append(final_message) # type: ignore
return formatted_messages, system_message
