import pandas as pd
from bs4 import BeautifulSoup
from pathlib import Path
from langchain.text_splitter import RecursiveCharacterTextSplitter
from sentence_transformers import SentenceTransformer
import numpy as np
import faiss
import tiktoken

CHUNK_SIZE = 300
CHUNK_OVERLAP = 50
EMBEDDING_MODEL = "all-MiniLM-L6-v2"
TOP_K = 5

def tiktoken_len(text):
    return len(tiktoken.encoding_for_model("gpt-4").encode(text))

def load_html_docs(csv_path, html_dir=None):
    df = pd.read_csv(csv_path)
    base_path = Path(csv_path).parent if html_dir is None else Path(html_dir)
    documents = []
    for _, row in df.iterrows():
        html_path = base_path / row['File']
        if not html_path.exists():
            print(f"[ADVERTENCIA] Archivo no encontrado: {html_path}")
            continue
        with open(html_path, 'r', encoding='utf-8') as f:
            soup = BeautifulSoup(f.read(), 'html.parser')
            text = soup.get_text(separator="\n")
            print(f"[INFO] Cargando HTML: {html_path.name}")
            documents.append({
                "title": row.get("Title", "Sin título"),
                "author_id": row.get("Author ID", "Desconocido"),
                "filename": html_path.name,
                "content": text
            })
    return documents

def process_documents(documents, chunk_size=CHUNK_SIZE, chunk_overlap=CHUNK_OVERLAP):
    splitter = RecursiveCharacterTextSplitter(
        chunk_size=chunk_size,
        chunk_overlap=chunk_overlap,
        length_function=tiktoken_len
    )
    all_chunks = []
    for doc in documents:
        chunks = splitter.create_documents([doc["content"]])
        for chunk in chunks:
            chunk.metadata = doc
        all_chunks.extend(chunks)
    texts = [chunk.page_content for chunk in all_chunks]
    embedder = SentenceTransformer(EMBEDDING_MODEL)
    vectors = embedder.encode(texts)
    return vectors, all_chunks, embedder

def build_faiss_index(vectors, chunks):
    if len(vectors) == 0:
        raise ValueError("No se generaron vectores. Verifica si los HTML contienen texto útil y fueron encontrados.")
    dim = vectors[0].shape[0]
    index = faiss.IndexFlatL2(dim)
    index.add(np.array(vectors))
    chunk_lookup = {i: chunks[i] for i in range(len(chunks))}
    return index, chunk_lookup

def get_context(query, embedder, index, chunk_lookup, top_k=5):
    q_vector = embedder.encode([query])
    scores, indices = index.search(np.array(q_vector), top_k)
    selected = [chunk_lookup[i] for i in indices[0]]
    return "\n\n".join([doc.page_content for doc in selected])