import streamlit as st
import pandas as pd
import numpy as np
from sklearn.metrics.pairwise import cosine_similarity
import joblib

@st.cache_data
def load_weights():
    try:
        weights_path = 'weights'
        content_tfidf_matrix = joblib.load(f'{weights_path}/content_tfidf_matrix.joblib')
        title_to_index = joblib.load(f'{weights_path}/content_title_to_index.joblib')
        content_vectorizer = joblib.load(f'{weights_path}/content_vectorizer.joblib')
        movies = joblib.load(f'{weights_path}/movies_data.joblib')
        user_profiles = joblib.load(f'{weights_path}/user_profiles.joblib')
        user_tfidf_matrix = joblib.load(f'{weights_path}/user_tfidf_matrix.joblib')
        movie_id_to_idx = joblib.load(f'{weights_path}/user_movie_id_to_idx.joblib')
        train_ratings = joblib.load(f'{weights_path}/train_ratings.joblib')
        return {
            "movies": movies,
            "content_tfidf_matrix": content_tfidf_matrix,
            "title_to_index": title_to_index,
            "content_vectorizer": content_vectorizer,
            "user_profiles": user_profiles,
            "user_tfidf_matrix": user_tfidf_matrix,
            "movie_id_to_idx": movie_id_to_idx,
            "train_ratings": train_ratings
        }
    except FileNotFoundError as e:
        st.error(f"Missing file: {e.filename}")
        st.stop()
    except Exception as e:
        st.error(f"Error loading weights: {str(e)}")
        st.stop()

# Content-based recommendation (real-time cosine similarity)
def get_similar_movies(title, tfidf_matrix, title_to_index, movies, N=5):
    try:
        index = title_to_index[title]
        target_vector = tfidf_matrix[index]
        similarity_scores = cosine_similarity(target_vector, tfidf_matrix).flatten()
        similar_indices = similarity_scores.argsort()[::-1][1:N+1]
        similar_movies = movies.iloc[similar_indices][['title', 'genres']]
        similar_scores = similarity_scores[similar_indices]
        return list(zip(similar_movies['title'], similar_scores))
    except KeyError:
        return None

# User profile-based recommendation
def get_top_n_recommendations(user_id, user_profiles, tfidf_matrix, movie_id_to_idx, movies, train_ratings, n=5):
    if user_id not in user_profiles:
        return None
    user_profile = user_profiles[user_id]
    similarities = cosine_similarity(user_profile.reshape(1, -1), tfidf_matrix).flatten()
    movie_indices = np.argsort(similarities)[::-1]
    rated_movies = set(train_ratings[train_ratings['userId'] == user_id]['movieId'].values)
    top_n_indices = [idx for idx in movie_indices if movies['id'].iloc[idx] not in rated_movies][:n]
    return [(movies['title'].iloc[idx], 1 + 4 * similarities[idx]) for idx in top_n_indices]

# Streamlit App
st.set_page_config(page_title="Movie Recommender", page_icon="🎬")
st.title("🎬 Movie Recommender System")

st.markdown("""
This app supports:
- **Content-Based Recommendations**: Find similar movies based on genre.
- **User Profile-Based Recommendations**: Personalized picks based on your ratings.
""")

# Load all weights
weights = load_weights()

# Recommendation type selector
recommendation_type = st.sidebar.radio("Choose Recommendation Type", ["Content-Based", "User Profile-Based"])

if recommendation_type == "Content-Based":
    st.header("📽️ Content-Based Recommendations")
    movie_title = st.selectbox("Choose a Movie Title", [""] + sorted(weights["movies"]['title'].dropna().unique()))
    
    if movie_title:
        recommendations = get_similar_movies(
            title=movie_title,
            tfidf_matrix=weights["content_tfidf_matrix"],
            title_to_index=weights["title_to_index"],
            movies=weights["movies"],
            N=5
        )
        if recommendations:
            st.subheader(f"If you liked **{movie_title}**, you might enjoy:")
            for i, (movie, score) in enumerate(recommendations, 1):
                st.write(f"{i}. {movie} (Similarity Score: {score:.2f})")
        else:
            st.warning(f"No similar movies found for '{movie_title}'.")

else:
    st.header("👤 User Profile-Based Recommendations")
    user_id = st.number_input("Enter your User ID", min_value=1, step=1, value=1)
    
    if st.button("Get Recommendations"):
        recommendations = get_top_n_recommendations(
            user_id=user_id,
            user_profiles=weights["user_profiles"],
            tfidf_matrix=weights["user_tfidf_matrix"],
            movie_id_to_idx=weights["movie_id_to_idx"],
            movies=weights["movies"],
            train_ratings=weights["train_ratings"],
            n=5
        )
        if recommendations:
            st.subheader(f"Top 5 picks for User ID {user_id}:")
            for i, (movie, pred_rating) in enumerate(recommendations, 1):
                st.write(f"{i}. {movie} (Predicted Rating: {pred_rating:.2f})")
        else:
            st.warning(f"User ID {user_id} not found or not enough ratings.")