export type SseEvent = {
  event: string;
  data: string;
};

export type TencentReplyEvent = {
  type?: "reply";
  payload?: {
    content?: string;
    is_evil?: boolean;
    is_final?: boolean;
    is_from_self?: boolean;
    is_llm_generated?: boolean;
  };
};

export type TencentErrorEvent = {
  type?: "error";
  error?: {
    code?: number;
    message?: string;
  };
  message?: string;
  status?: number;
};

export function parseJsonSafely<T>(value: string): T | null {
  try {
    return JSON.parse(value) as T;
  } catch {
    return null;
  }
}

export function splitSseEvents(buffer: string): {
  events: SseEvent[];
  rest: string;
} {
  const blocks = buffer.split(/\r?\n\r?\n/);
  const rest = blocks.pop() ?? "";
  const events = blocks
    .map(parseSseEventBlock)
    .filter((event): event is SseEvent => event !== null);

  return { events, rest };
}

function parseSseEventBlock(block: string): SseEvent | null {
  const lines = block.split(/\r?\n/);
  let eventName = "message";
  const dataLines: string[] = [];

  for (const rawLine of lines) {
    const line = rawLine.trimEnd();
    if (!line || line.startsWith(":")) {
      continue;
    }

    if (line.startsWith("event:")) {
      eventName = line.slice(6).trim();
      continue;
    }

    if (line.startsWith("data:")) {
      dataLines.push(line.slice(5).trimStart());
    }
  }

  if (dataLines.length === 0) {
    return null;
  }

  return {
    event: eventName,
    data: dataLines.join("\n"),
  };
}