"""HTTP SSE 编码；事件字段的唯一来源为 runtime.events。"""
from __future__ import annotations

import json
from runtime.events import *  # noqa: F401,F403
from runtime.events import EventBuilder, ExecutionEvent


def serialize_event(event: ExecutionEvent) -> str:
    return f"data: {json.dumps(event, ensure_ascii=False, default=str)}\n\n"


class EventWriter(EventBuilder[str]):
    """兼容既有调用方；把中立事件编码成 SSE 帧。"""
    def __init__(self, session_id: str, trace_id: str = ""):
        super().__init__(session_id, trace_id, encode=serialize_event)

    def frame(self, event_type: str, **fields) -> str:
        return self.event(event_type, **fields)

    def comment(self, text: str) -> str:
        return f": {text}\n\n"