import pandas as pd
from gensim.models import Word2Vec
import numpy as np
from sklearn.metrics.pairwise import cosine_similarity
from nltk.tokenize import word_tokenize
from keras.preprocessing.text import Tokenizer
from keras.preprocessing.sequence import pad_sequences

def recommend_papers(positive_csv_path, unlabelled_csv_path, n):
    # Load positive labelled data and unlabelled labelled data
    positive_labelled_info = pd.read_csv(positive_csv_path)
    unlabelled_labelled = pd.read_csv(unlabelled_csv_path)

    # Combine title and abstract for positive labelled data and unlabelled labelled data
    positive_labelled_info['text'] = positive_labelled_info['title'] + ' ' + positive_labelled_info['abstract']
    unlabelled_labelled['text'] = unlabelled_labelled['title'] + ' ' + unlabelled_labelled['abstract']

    # Preprocess text and tokenize
    positive_labelled_info['tokenized_text'] = positive_labelled_info['text'].apply(word_tokenize)
    unlabelled_labelled['tokenized_text'] = unlabelled_labelled['text'].apply(word_tokenize)

    # Train Word2Vec model on the tokenized text of positive labelled data
    word2vec_model = Word2Vec(sentences=positive_labelled_info['tokenized_text'], vector_size=100, window=5, min_count=1, workers=4)

    # Initialize tokenizer
    tokenizer = Tokenizer()
    tokenizer.fit_on_texts(positive_labelled_info['text'])

    # Convert text to sequences of integer indices
    positive_sequences = tokenizer.texts_to_sequences(positive_labelled_info['text'])
    unlabelled_sequences = tokenizer.texts_to_sequences(unlabelled_labelled['text'])

    # Pad or truncate sequences to a fixed length
    max_length = 50  # Adjust as needed
    padded_positive_sequences = pad_sequences(positive_sequences, maxlen=max_length, padding='post', truncating='post')
    padded_unlabelled_sequences = pad_sequences(unlabelled_sequences, maxlen=max_length, padding='post', truncating='post')

    # Compute centroid of positive examples' word embeddings
    centroid = np.mean([word2vec_model.wv[token] for token in tokenizer.index_word.values() if token in word2vec_model.wv], axis=0)

    # Compute similarity scores for each document in the unlabelled labelled data
    similarity_scores = []
    for sequence in padded_unlabelled_sequences:
        embeddings = [word2vec_model.wv[token] for token in sequence if token in word2vec_model.wv]
        if len(embeddings) > 0:
            similarity_score = cosine_similarity([centroid], [np.mean(embeddings, axis=0)])[0][0]
        else:
            similarity_score = 0  # Default similarity score for empty embeddings
        similarity_scores.append(similarity_score)

    # Add similarity scores to unlabelled labelled data
    unlabelled_labelled['similarity_score'] = similarity_scores

    # Sort unlabelled labelled data by similarity score in descending order
    recommended_documents = unlabelled_labelled.sort_values(by='similarity_score', ascending=False)

    # Return top n recommended documents
    return recommended_documents[['id', 'title', 'similarity_score']].head(n)