import pandas as pd
import numpy as np
from sklearn.preprocessing import LabelEncoder
from sklearn.feature_extraction.text import TfidfVectorizer
from sklearn.model_selection import train_test_split
from sklearn.ensemble import RandomForestRegressor
from sklearn.linear_model import LinearRegression
from sklearn.svm import SVR
from sklearn.metrics import mean_squared_error, r2_score, mean_absolute_error, explained_variance_score
from sklearn.metrics.pairwise import cosine_similarity

def preprocess_data(df):
    df = df.dropna(subset=['rating', 'plot']).copy()

    df['votes'] = df['votes'].astype(str).str.replace(',', '', regex=True)
    df['votes'] = pd.to_numeric(df['votes'], errors='coerce').fillna(0)

    df['year'] = pd.to_numeric(df['year'], errors='coerce').fillna(df['year'].median())

    df['certificate'] = df['certificate'].fillna('Unknown')
    le = LabelEncoder()
    df['certificate'] = le.fit_transform(df['certificate'])

    tfidf = TfidfVectorizer(stop_words='english', max_features=200)
    tfidf_matrix = tfidf.fit_transform(df['plot'])

    tfidf_feature_names = [f'tfidf_{name}' for name in tfidf.get_feature_names_out()]
    tfidf_df = pd.DataFrame(tfidf_matrix.toarray(), columns=tfidf_feature_names, index=df.index)

    genre_cols = ['Action', 'Adventure', 'Comedy', 'Crime', 'Family', 'Fantasy', 'Mystery', 'Sci-Fi', 'Thriller']
    genre_df = df[genre_cols].astype(int)

    features_df = pd.concat([df[['votes', 'certificate', 'year']], genre_df, tfidf_df], axis=1)

    return features_df, df['rating'], tfidf, le, df

def train_models(X, y):
    X_train, X_test, y_train, y_test = train_test_split(X, y, test_size=0.2, random_state=42)

    models = {
        'RandomForest': RandomForestRegressor(random_state=42),
        'LinearRegression': LinearRegression(),
        'SVR': SVR()
    }

    trained_models = {}
    metrics = {}

    for name, model in models.items():
        model.fit(X_train, y_train)
        y_pred = model.predict(X_test)

        mse = mean_squared_error(y_test, y_pred)
        rmse = np.sqrt(mse)
        r2 = r2_score(y_test, y_pred)
        mae = mean_absolute_error(y_test, y_pred)
        evs = explained_variance_score(y_test, y_pred)

        metrics[name] = {
            'RMSE': rmse,
            'R2': r2,
            'MAE': mae,
            'Explained Variance': evs
        }
        trained_models[name] = model

    return trained_models, metrics

def recommend_similar(df, tfidf, user_plot, user_genres, top_n=50):
    user_vec = tfidf.transform([user_plot])

    genre_cols = ['Action', 'Adventure', 'Comedy', 'Crime', 'Family', 'Fantasy', 'Mystery', 'Sci-Fi', 'Thriller']
    user_genre_vec = np.array([1 if genre in user_genres else 0 for genre in genre_cols]).reshape(1, -1)

    plot_sim = cosine_similarity(user_vec, tfidf.transform(df['plot']))[0]
    genre_sim = cosine_similarity(user_genre_vec, df[genre_cols])[0]

    combined_sim = 0.7 * plot_sim + 0.3 * genre_sim

    top_indices = combined_sim.argsort()[::-1][:top_n]

    return df.iloc[top_indices][['name', 'year', 'rating', 'votes', 'certificate']]