rag-ultimate

const STOPWORDS = new Set([
  "about", "after", "again", "also", "another", "answer", "because", "before",
  "between", "could", "detail", "details", "discuss", "explain", "from", "have",
  "how", "into", "more", "other", "please", "question", "should", "show", "some",
  "that", "their", "there", "these", "this", "those", "what", "when", "where",
  "which", "with", "would", "your",
]);

export interface MemoryEntry {
  topic: string;
  summary: string;
  timestamp: number;
}

const MAX_TOPIC_CACHE = 256;
const MAX_ENTRIES_PER_TOPIC = 20;
const MAX_RETRIEVE_ENTRIES = 5;
const TOPIC_CACHE_PRUNE_THRESHOLD = 1000;

export class MemoryService {
  private static memory = new Map<string, MemoryEntry[]>();
  private static topicCache = new Map<string, string>();
  private static cacheOps = 0;

  public static save(topic: string, summary: string): void {
    const cleanedTopic = this.normalizeTopic(topic);
    if (!cleanedTopic) return;

    let entries = this.memory.get(cleanedTopic);
    if (!entries) {
      entries = [];
      this.memory.set(cleanedTopic, entries);
    }
    entries.push({ topic: cleanedTopic, summary, timestamp: Date.now() });
    if (entries.length > MAX_ENTRIES_PER_TOPIC) {
      this.memory.set(cleanedTopic, entries.slice(-MAX_ENTRIES_PER_TOPIC));
    }
  }

  public static retrieve(topic: string): string {
    const cleanedTopic = this.normalizeTopic(topic);
    const entries = this.memory.get(cleanedTopic);
    if (!entries?.length) return "";

    const last = entries.slice(-MAX_RETRIEVE_ENTRIES);
    let result = "";
    for (let i = 0; i < last.length; i++) {
      if (i > 0) result += "\n";
      result += `- ${last[i].summary}`;
    }
    return result;
  }

  public static extractTopic(prompt: string): string {
    const cached = this.topicCache.get(prompt);
    if (cached !== undefined) return cached;

    let word = "";
    let start = 0;
    const words: string[] = [];
    while (start < prompt.length) {
      const match = /\W/.exec(prompt[start]);
      if (match) {
        word = prompt.substring(start, start + match.index).toLowerCase();
        if (word.length > 3 && !STOPWORDS.has(word)) {
          words.push(word);
        }
        start += match.index + 1;
      } else {
        word = prompt.substring(start).toLowerCase();
        if (word.length > 3 && !STOPWORDS.has(word)) {
          words.push(word);
        }
        break;
      }
    }

    const topic = words.slice(0, 6).join(" ");

    this.topicCache.set(prompt, topic);
    this.cacheOps++;

    if (this.cacheOps > TOPIC_CACHE_PRUNE_THRESHOLD && this.topicCache.size > MAX_TOPIC_CACHE) {
      const toRemove = this.topicCache.size - MAX_TOPIC_CACHE;
      let removed = 0;
      for (const key of this.topicCache.keys()) {
        if (removed++ >= toRemove) break;
        this.topicCache.delete(key);
      }
      this.cacheOps = 0;
    }

    return topic;
  }

  private static normalizeTopic(topic: string): string {
    return topic.toLowerCase().replace(/\s+/g, " ").trim().slice(0, 80);
  }
}