app/audio/processor.py

import os
import tempfile
import subprocess
import numpy as np
import librosa
from fastapi import UploadFile, HTTPException
from typing import Tuple
import logging
from app.config import settings

logger = logging.getLogger(__name__)

class AudioProcessor:
    """Production-grade audio preprocessing"""
    
    @staticmethod
    async def validate_file(file: UploadFile) -> Tuple[bytes, str]:
        """Validate file size and format"""
        
        # Check file size
        contents = await file.read()
        size_mb = len(contents) / (1024 * 1024)
        
        if size_mb > settings.MAX_FILE_SIZE_MB:
            raise HTTPException(
                status_code=413,
                detail=f"File too large. Max {settings.MAX_FILE_SIZE_MB}MB"
            )
        
        # Check format
        ext = file.filename.split('.')[-1].lower()
        if ext not in settings.SUPPORTED_FORMATS:
            raise HTTPException(
                status_code=415,
                detail=f"Unsupported format. Supported: {settings.SUPPORTED_FORMATS}"
            )
        
        return contents, ext
    
    @staticmethod
    async def convert_to_wav(input_bytes: bytes, input_ext: str) -> bytes:
        """Convert audio to WAV format (16kHz, mono)"""
        
        with tempfile.NamedTemporaryFile(delete=False, suffix=f".{input_ext}") as f_in:
            f_in.write(input_bytes)
            input_path = f_in.name
        
        with tempfile.NamedTemporaryFile(delete=False, suffix=".wav") as f_out:
            output_path = f_out.name
        
        try:
            # FFmpeg conversion
            cmd = [
                "ffmpeg",
                "-i", input_path,
                "-ar", str(settings.TARGET_SAMPLE_RATE),
                "-ac", "1",
                "-acodec", "pcm_s16le",
                "-y",  # Overwrite output
                output_path
            ]
            
            result = subprocess.run(
                cmd, 
                capture_output=True, 
                text=True,
                timeout=30
            )
            
            if result.returncode != 0:
                logger.error(f"FFmpeg error: {result.stderr}")
                raise HTTPException(
                    status_code=422,
                    detail="Audio conversion failed"
                )
            
            # Read converted file
            with open(output_path, "rb") as f:
                return f.read()
                
        except subprocess.TimeoutExpired:
            raise HTTPException(
                status_code=408,
                detail="Audio conversion timeout"
            )
        finally:
            # Cleanup
            for path in [input_path, output_path]:
                if os.path.exists(path):
                    os.unlink(path)
    
    @staticmethod
    def get_audio_info(audio_bytes: bytes) -> dict:
        """Get audio metadata"""
        with tempfile.NamedTemporaryFile(delete=False, suffix=".wav") as tmp:
            tmp.write(audio_bytes)
            path = tmp.name
        
        try:
            y, sr = librosa.load(path, sr=None)
            duration = len(y) / sr
            
            return {
                "duration_seconds": round(duration, 2),
                "sample_rate": sr,
                "channels": 1 if len(y.shape) == 1 else y.shape[1],
                "samples": len(y)
            }
        finally:
            os.unlink(path)

audio_processor = AudioProcessor()