import type { ContentBlock, HistoryMessage } from "$lib/api/types";

const MAX_BYTES = 250_000;
const TAIL = 200;

function slim(message: HistoryMessage): HistoryMessage {
  if (typeof message.content === "string") {
    return message;
  }
  const content: ContentBlock[] = message.content.map((block) =>
    block.type === "tool_result" ? { ...block, content: "" } : block
  );
  return { ...message, content };
}

// The tail of a thread as it is worth keeping between opens: tool results
// dropped (hidden by default, and the bulk of the bytes), then trimmed from
// the head until it fits a slice of localStorage.
export function cacheableHistory(messages: HistoryMessage[]): HistoryMessage[] {
  let tail = messages.slice(-TAIL).map(slim);
  while (tail.length > 1 && JSON.stringify(tail).length > MAX_BYTES) {
    tail = tail.slice(Math.ceil(tail.length / 4));
  }
  return tail;
}

export const historyKey = (id: string) => `history:${id}`;
export const infoKey = (id: string) => `info:${id}`;