services/beat_tracker.py

import librosa
import numpy as np

class BeatTracker:
    def __init__(self):
        pass

    def track(self, audio_path: str):
        """
        Track beats and tempo from audio file.
        Returns: {
            "bpm": float,
            "beats": list[float]  # timestamps
        }
        """
        try:
            print(f"Tracking beats for {audio_path}...")
            y, sr = librosa.load(audio_path)
            
            # Estimate tempo and beats
            tempo, beat_frames = librosa.beat.beat_track(y=y, sr=sr)
            
            # Log output to be sure
            # tempo is usually a scalar, but sometimes an array in older versions
            if isinstance(tempo, np.ndarray):
                tempo = tempo[0]
            
            beat_times = librosa.frames_to_time(beat_frames, sr=sr)
            
            return {
                "bpm": round(float(tempo), 2),
                "beats": [round(float(t), 2) for t in beat_times]
            }
            
        except Exception as e:
            print(f"Error tracking beats: {e}")
            return {"bpm": 0, "beats": []}