from __future__ import annotations

import json
from collections.abc import AsyncIterator
from typing import Any

import httpx


class SseChunk:
    __slots__ = ("event", "data")

    def __init__(self, event: str, data: dict[str, Any]) -> None:
        self.event = event
        self.data = data


def _parse_sse_part(part: str) -> SseChunk | None:
    if not part.strip():
        return None
    event = "message"
    data = ""
    for line in part.split("\n"):
        if line.startswith("event: "):
            event = line[7:]
        elif line.startswith("data: "):
            data = line[6:]
    if not data:
        return None
    return SseChunk(event=event, data=json.loads(data))


async def iter_sse(response: httpx.Response) -> AsyncIterator[SseChunk]:
    if response.status_code >= 400:
        detail = (await response.aread()).decode("utf-8", errors="replace")
        raise RuntimeError(detail or f"HTTP {response.status_code}")

    buffer = ""
    async for chunk in response.aiter_text():
        buffer += chunk
        parts = buffer.split("\n\n")
        buffer = parts.pop() if parts else ""
        for part in parts:
            parsed = _parse_sse_part(part)
            if parsed:
                yield parsed

    if buffer.strip():
        parsed = _parse_sse_part(buffer)
        if parsed:
            yield parsed