73 lines
1.8 KiB
Python
73 lines
1.8 KiB
Python
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"""Backend-neutral chat contract."""
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from collections.abc import AsyncIterator
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from dataclasses import dataclass, field
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from typing import Any, Protocol
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@dataclass(frozen=True)
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class ChatInput:
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"""Input shared by all chat backend implementations."""
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session_id: str
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text: str
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need_form_update: bool = False
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@dataclass(frozen=True)
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class TextDelta:
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"""A piece of raw model text.
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The text may contain a partial ``<state>...</state>`` prefix. Parsing that
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public protocol remains the responsibility of the FastAPI layer.
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"""
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text: str
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@dataclass(frozen=True)
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class FormUpdate:
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"""A structured form update produced alongside model text."""
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data: Any
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ChatStreamEvent = TextDelta | FormUpdate
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@dataclass(frozen=True)
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class ChatResult:
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"""Backend-neutral result for a non-streaming chat request."""
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content: str
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status_code: str | None = None
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form_update: Any = field(default_factory=dict)
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class ChatBackend(Protocol):
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"""Contract implemented by FastGPT today and LangGraph later."""
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def stream(self, chat_input: ChatInput) -> AsyncIterator[ChatStreamEvent]:
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"""Stream raw text and structured side-channel events."""
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...
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async def complete(self, chat_input: ChatInput) -> ChatResult:
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"""Return one complete backend-neutral chat result."""
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...
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class ChatBackendError(Exception):
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"""Base error raised by a chat backend adapter."""
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class ChatBackendAuthenticationError(ChatBackendError):
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"""The backend rejected its configured credentials."""
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class ChatBackendRateLimitError(ChatBackendError):
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"""The backend rejected the request because of rate limiting."""
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class ChatBackendAPIError(ChatBackendError):
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"""The backend API failed or returned an invalid response."""
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