import os
import logging
import numpy as np
import matplotlib.pyplot as plt
from sklearn.metrics import roc_curve, auc

logger = logging.getLogger(__name__)

def evaluate_predictions(scores, true_labels, diagnosis, output_dir="results"):
    """Calculates AUC and generates ROC plot."""
    
    if not os.path.exists(output_dir):
        os.makedirs(output_dir)
        
    fpr, tpr, thresholds = roc_curve(true_labels, scores)
    roc_auc = auc(fpr, tpr)
    
    logger.info(f"Diagnosis: {diagnosis}")
    logger.info(f"AUC: {roc_auc:.4f}")
    
    # Plot ROC curve
    plt.figure()
    lw = 2
    plt.plot(
        fpr,
        tpr,
        color="darkorange",
        lw=lw,
        label="ROC curve (area = %0.2f)" % roc_auc,
    )
    plt.plot([0, 1], [0, 1], color="navy", lw=lw, linestyle="--")
    plt.xlim([0.0, 1.0])
    plt.ylim([0.0, 1.05])
    plt.xlabel("False Positive Rate")
    plt.ylabel("True Positive Rate")
    plt.title(f"ROC for {diagnosis}")
    plt.legend(loc="lower right")
    
    plot_path = os.path.join(output_dir, f"roc_{diagnosis}.png")
    plt.savefig(plot_path)
    logger.info(f"ROC plot saved to {plot_path}")
    
    return roc_auc