import faiss
import numpy as np
import os
import pickle

class EmbeddingStore:
    def __init__(self, dim: int, index_path="faiss.index", meta_path="faiss_meta.pkl"):
        self.dim = dim
        self.index_path = index_path
        self.meta_path = meta_path

        if os.path.exists(index_path) and os.path.exists(meta_path):
            print("loading FAISS index from disk...")
            self.index = faiss.read_index(index_path)
            with open(meta_path, "rb") as f:
                self.blog_ids = pickle.load(f)
        else:
            print("Creating new FAISS index...")
            self.index = faiss.IndexFlatIP(dim)
            self.blog_ids = []

    def _normalize(self, vector: np.ndarray):
        return vector / np.linalg.norm(vector)

    def add(self, blog_id: int, vector: np.ndarray):
        vector = self._normalize(vector)
        self.index.add(vector.reshape(1, -1))
        self.blog_ids.append(blog_id)
        self.save()

    def search(self, vector: np.ndarray, top_k: int):
        vector = self._normalize(vector)
        scores, indices = self.index.search(vector.reshape(1, -1), top_k)

        results = []
        for score, idx in zip(scores[0], indices[0]):
            if idx == -1:
                continue
            results.append({
                "blogId": self.blog_ids[idx],
                "score": float(score)
            })
        return results

    def save(self):
        faiss.write_index(self.index, self.index_path)
        with open(self.meta_path, "wb") as f:
            pickle.dump(self.blog_ids, f)