backend/runner.py

import os
import subprocess
import uuid
import shutil
import glob
from pathlib import Path

# Get the directory of the current script (backend/)
BASE_DIR = os.path.dirname(os.path.abspath(__file__))
MEDIA_DIR = os.path.join(BASE_DIR, "media")

def cleanup_old_files():
    """Clean up old scene files and media to free memory"""
    try:
        # Remove old scene files (keep only last 2)
        scene_files = sorted(glob.glob(os.path.join(BASE_DIR, "scene_*.py")), key=os.path.getmtime)
        for old_file in scene_files[:-2]:
            try:
                os.remove(old_file)
                print(f"🗑️ Cleaned up old scene file: {old_file}")
            except Exception as e:
                print(f"⚠️ Could not remove {old_file}: {e}")
        
        # Remove old video folders (keep only last 3)
        videos_dir = os.path.join(MEDIA_DIR, "videos")
        if os.path.exists(videos_dir):
            video_folders = sorted(
                [f for f in Path(videos_dir).iterdir() if f.is_dir()],
                key=os.path.getmtime
            )
            for old_folder in video_folders[:-3]:
                try:
                    shutil.rmtree(old_folder)
                    print(f"🗑️ Cleaned up old video folder: {old_folder}")
                except Exception as e:
                    print(f"⚠️ Could not remove {old_folder}: {e}")
        
        # Remove old step audio files (keep only last 5)
        audio_files = sorted(glob.glob(os.path.join(BASE_DIR, "step_*_narration.mp3")), key=os.path.getmtime)
        for old_audio in audio_files[:-5]:
            try:
                os.remove(old_audio)
                print(f"🗑️ Cleaned up old audio file: {old_audio}")
            except Exception as e:
                print(f"⚠️ Could not remove {old_audio}: {e}")
        
        # Remove old combined audio files (keep only last 2)
        combined_files = sorted(glob.glob(os.path.join(BASE_DIR, "combined_narration*.mp3")), key=os.path.getmtime)
        for old_combined in combined_files[:-2]:
            try:
                os.remove(old_combined)
                print(f"🗑️ Cleaned up old combined audio: {old_combined}")
            except Exception as e:
                print(f"⚠️ Could not remove {old_combined}: {e}")
                
    except Exception as e:
        print(f"⚠️ Cleanup error: {e}")

async def render_scene(code: str):
    # Clean up old files before rendering
    cleanup_old_files()
    
    # Create a unique ID for this run
    run_id = str(uuid.uuid4())
    filename = f"scene_{run_id}.py"
    
    # Save code to file in the backend directory
    filepath = os.path.join(BASE_DIR, filename)
    with open(filepath, "w", encoding='utf-8') as f:
        f.write(code)
        
    # Run Manim with LOW quality (-ql) for better memory usage
    # -ql = 480p15, much lighter than -qm (720p30)
    
    cmd = ["manim", "-ql", "--media_dir", MEDIA_DIR, filepath, "GenScene"]
    
    try:
        result = subprocess.run(cmd, capture_output=True, text=True, check=True)
        print("✓ Manim render completed")
    except subprocess.CalledProcessError as e:
        print("❌ Manim Error:", e.stderr)
        # Clean up failed scene file
        try:
            os.remove(filepath)
        except:
            pass
        raise Exception(f"Manim failed: {e.stderr}")
        
    # Construct expected output path
    # Low quality: {MEDIA_DIR}/videos/{filename_without_extension}/480p15/GenScene.mp4
    
    video_folder = filename.replace(".py", "")
    video_path = os.path.join(MEDIA_DIR, "videos", video_folder, "480p15", "GenScene.mp4")
    
    if not os.path.exists(video_path):
        # Clean up scene file
        try:
            os.remove(filepath)
        except:
            pass
        raise Exception(f"Video file not found at {video_path}")
    
    print(f"✓ Video created: {video_path}")
    
    # Clean up the scene file immediately after successful render
    try:
        os.remove(filepath)
        print(f"🗑️ Cleaned up scene file: {filepath}")
    except Exception as e:
        print(f"⚠️ Could not remove scene file: {e}")
        
    return video_path