from __future__ import annotations

import json
import re
from typing import Any

from ag_ui.core.events import BaseEvent
from ag_ui.encoder.encoder import EventEncoder

_EVENT_TYPE_RE = re.compile(r"^[A-Z0-9_]+$")
_ENCODER = EventEncoder()


def to_sse_event(stream_id: str, event: dict[str, Any]) -> str:
    safe_stream_id = str(stream_id).replace("\r", "").replace("\n", "")
    try:
        event_model = BaseEvent.model_validate(event)
        event_type = event_model.type.value
        encoded_data = _ENCODER.encode(event_model)
        return f"id: {safe_stream_id}\nevent: {event_type}\n{encoded_data}"
    except Exception:  # noqa: BLE001
        raw_event_type = (
            str(event.get("type", "MESSAGE")).replace("\r", "").replace("\n", "")
        )
        event_type = (
            raw_event_type if _EVENT_TYPE_RE.fullmatch(raw_event_type) else "MESSAGE"
        )
        payload = json.dumps(event, ensure_ascii=True, separators=(",", ":"))
        return f"id: {safe_stream_id}\nevent: {event_type}\ndata: {payload}\n\n"