app.py

import gradio as gr
import spaces
import torch
import torchaudio
import io
import base64
import uuid
import os
import time
import re
import threading
import gc
import random
import numpy as np
from einops import rearrange
from huggingface_hub import login
from stable_audio_tools import get_pretrained_model
from stable_audio_tools.inference.generation import generate_diffusion_cond
from gradio_client import Client
from contextlib import contextmanager

# Global model storage
model_cache = {}
model_lock = threading.Lock()

@contextmanager
def resource_cleanup():
    """Context manager to ensure proper cleanup of GPU resources."""
    try:
        yield
    finally:
        if torch.cuda.is_available():
            torch.cuda.synchronize()
            torch.cuda.empty_cache()
        gc.collect()

def load_stable_audio_model():
    """Load stable-audio-open-small model if not already loaded."""
    with model_lock:
        if 'stable_audio_model' not in model_cache:
            print("🔄 Loading stable-audio-open-small model...")
            
            # Authenticate with HF
            hf_token = os.getenv('HF_TOKEN')
            if hf_token:
                login(token=hf_token)
                print(f"✅ HF authenticated")
            
            # Load model
            model, config = get_pretrained_model("stabilityai/stable-audio-open-small")
            device = "cuda" if torch.cuda.is_available() else "cpu"
            model = model.to(device)
            if device == "cuda":
                model = model.half()
            
            model_cache['stable_audio_model'] = model
            model_cache['stable_audio_config'] = config
            model_cache['stable_audio_device'] = device
            print(f"✅ Stable Audio model loaded on {device}")
        
        return (model_cache['stable_audio_model'], 
                model_cache['stable_audio_config'], 
                model_cache['stable_audio_device'])

@spaces.GPU
def generate_stable_audio_loop(prompt, loop_type, bpm, bars, seed=-1):
    """Generate a BPM-aware loop using stable-audio-open-small"""
    try:
        model, config, device = load_stable_audio_model()
        
        # Calculate loop duration based on BPM and bars
        seconds_per_beat = 60.0 / bpm
        seconds_per_bar = seconds_per_beat * 4  # 4/4 time
        target_loop_duration = seconds_per_bar * bars
        
        # Enhance prompt based on loop type and BPM
        if loop_type == "drums":
            enhanced_prompt = f"{prompt} drum loop {bpm}bpm"
            negative_prompt = "melody, harmony, pitched instruments, vocals, singing"
        else:  # instruments
            enhanced_prompt = f"{prompt} instrumental loop {bpm}bpm"
            negative_prompt = "drums, percussion, kick, snare, hi-hat"
        
        # Set seed
        if seed == -1:
            seed = random.randint(0, 2**32 - 1)
        
        torch.manual_seed(seed)
        if device == "cuda":
            torch.cuda.manual_seed(seed)
        
        print(f"🎵 Generating {loop_type} loop:")
        print(f"   Enhanced prompt: {enhanced_prompt}")
        print(f"   Target duration: {target_loop_duration:.2f}s ({bars} bars at {bpm}bpm)")
        print(f"   Seed: {seed}")
        
        # Prepare conditioning
        conditioning = [{
            "prompt": enhanced_prompt,
            "seconds_total": 12  # Model generates 12s max
        }]
        
        negative_conditioning = [{
            "prompt": negative_prompt,
            "seconds_total": 12
        }]
        
        start_time = time.time()
        
        with resource_cleanup():
            if device == "cuda":
                torch.cuda.empty_cache()
            
            with torch.cuda.amp.autocast(enabled=(device == "cuda")):
                output = generate_diffusion_cond(
                    model,
                    steps=8,  # Fast generation
                    cfg_scale=1.0,  # Good balance for loops
                    conditioning=conditioning,
                    negative_conditioning=negative_conditioning,
                    sample_size=config["sample_size"],
                    sampler_type="pingpong",
                    device=device,
                    seed=seed
                )
            
            generation_time = time.time() - start_time
            
            # Post-process audio
            output = rearrange(output, "b d n -> d (b n)")  # (2, N) stereo
            output = output.to(torch.float32).div(torch.max(torch.abs(output))).clamp(-1, 1)
            
            # Extract the loop portion
            sample_rate = config["sample_rate"]
            loop_samples = int(target_loop_duration * sample_rate)
            available_samples = output.shape[1]
            
            if loop_samples > available_samples:
                loop_samples = available_samples
                actual_duration = available_samples / sample_rate
                print(f"⚠️ Requested {target_loop_duration:.2f}s, got {actual_duration:.2f}s")
            
            # Extract loop from beginning (cleanest beat alignment)
            loop_output = output[:, :loop_samples]
            loop_output_int16 = loop_output.mul(32767).to(torch.int16).cpu()
            
            # Save to temporary file
            loop_filename = f"loop_{loop_type}_{bpm}bpm_{bars}bars_{seed}.wav"
            torchaudio.save(loop_filename, loop_output_int16, sample_rate)
            
            actual_duration = loop_samples / sample_rate
            print(f"✅ {loop_type.title()} loop generated: {actual_duration:.2f}s in {generation_time:.2f}s")
            
            return loop_filename, f"Generated {actual_duration:.2f}s {loop_type} loop at {bpm}bpm ({bars} bars)"
    
    except Exception as e:
        print(f"❌ Generation error: {str(e)}")
        return None, f"Error: {str(e)}"

def combine_loops(drums_audio, instruments_audio, bpm, bars, num_repeats):
    """Combine drum and instrument loops with specified repetitions"""
    try:
        if not drums_audio and not instruments_audio:
            return None, "No audio files to combine"
        
        # Calculate timing
        seconds_per_beat = 60.0 / bpm
        seconds_per_bar = seconds_per_beat * 4
        loop_duration = seconds_per_bar * bars
        total_duration = loop_duration * num_repeats
        
        print(f"🎛️ Combining loops:")
        print(f"   Loop duration: {loop_duration:.2f}s ({bars} bars)")
        print(f"   Repeats: {num_repeats}")
        print(f"   Total duration: {total_duration:.2f}s")
        
        combined_audio = None
        sample_rate = None
        
        # Process each audio file
        for audio_path, audio_type in [(drums_audio, "drums"), (instruments_audio, "instruments")]:
            if audio_path:
                # Load audio
                waveform, sr = torchaudio.load(audio_path)
                if sample_rate is None:
                    sample_rate = sr
                
                # Ensure we have the exact loop duration
                target_samples = int(loop_duration * sr)
                if waveform.shape[1] > target_samples:
                    waveform = waveform[:, :target_samples]
                elif waveform.shape[1] < target_samples:
                    # Pad if necessary
                    padding = target_samples - waveform.shape[1]
                    waveform = torch.cat([waveform, torch.zeros(waveform.shape[0], padding)], dim=1)
                
                # Repeat the loop
                repeated_waveform = waveform.repeat(1, num_repeats)
                
                print(f"   {audio_type}: {waveform.shape[1]/sr:.2f}s repeated {num_repeats}x = {repeated_waveform.shape[1]/sr:.2f}s")
                
                # Add to combined audio
                if combined_audio is None:
                    combined_audio = repeated_waveform
                else:
                    combined_audio = combined_audio + repeated_waveform
        
        if combined_audio is None:
            return None, "No valid audio to combine"
        
        # Normalize to prevent clipping
        combined_audio = combined_audio / torch.max(torch.abs(combined_audio))
        combined_audio = combined_audio.clamp(-1, 1)
        
        # Convert to int16 and save
        combined_audio_int16 = combined_audio.mul(32767).to(torch.int16)
        combined_filename = f"combined_{bpm}bpm_{bars}bars_{num_repeats}loops_{random.randint(1000, 9999)}.wav"
        torchaudio.save(combined_filename, combined_audio_int16, sample_rate)
        
        actual_duration = combined_audio.shape[1] / sample_rate
        status = f"Combined into {actual_duration:.2f}s audio ({num_repeats} × {bars} bars at {bpm}bpm)"
        
        print(f"✅ {status}")
        return combined_filename, status
    
    except Exception as e:
        print(f"❌ Combine error: {str(e)}")
        return None, f"Combine error: {str(e)}"

def transform_with_melodyflow_api(audio_path, prompt, solver="euler", flowstep=0.12):
    """Transform audio using Facebook/MelodyFlow space API"""
    if audio_path is None:
        return None, "❌ No audio file provided"
    
    try:
        # Initialize client for Facebook MelodyFlow space
        client = Client("facebook/MelodyFlow")
        
        # Set steps based on solver
        if solver == "midpoint":
            base_steps = 128
            effective_steps = base_steps // 2  # 64 effective steps
        else:  # euler
            base_steps = 125  
            effective_steps = base_steps // 5  # 25 effective steps
        
        print(f"🎛️ MelodyFlow transformation:")
        print(f"   Prompt: {prompt}")
        print(f"   Solver: {solver} ({effective_steps} effective steps)")
        print(f"   Flowstep: {flowstep}")
        
        # Call the MelodyFlow API - pass file path directly
        result = client.predict(
            model="facebook/melodyflow-t24-30secs",
            text=prompt,
            solver=solver,
            steps=base_steps,
            target_flowstep=flowstep,
            regularize=solver == "euler",
            regularization_strength=0.2,
            duration=30,
            melody=audio_path,  # Pass file path directly instead of handle_file(audio_path)
            api_name="/predict"
        )
        
        if result and len(result) > 0 and result[0]:
            # Save the result locally
            output_filename = f"melodyflow_transformed_{random.randint(1000, 9999)}.wav"
            import shutil
            shutil.copy2(result[0], output_filename)
            
            status_msg = f"✅ Transformed with prompt: '{prompt}' (flowstep: {flowstep}, {effective_steps} steps)"
            return output_filename, status_msg
        else:
            return None, "❌ MelodyFlow API returned no results"
            
    except Exception as e:
        return None, f"❌ MelodyFlow API error: {str(e)}"

def calculate_optimal_bars(bpm):
    """Calculate optimal bar count for given BPM to fit in ~10s"""
    seconds_per_beat = 60.0 / bpm
    seconds_per_bar = seconds_per_beat * 4
    max_duration = 10.0
    
    for bars in [8, 4, 2, 1]:
        if seconds_per_bar * bars <= max_duration:
            return bars
    return 1

# ========== GRADIO INTERFACE ==========

with gr.Blocks(title="🎵 Stable Audio Loop Generator") as iface:
    gr.Markdown("# 🎵 Stable Audio Loop Generator")
    gr.Markdown("**Generate synchronized drum and instrument loops with stable-audio-open-small, then transform with MelodyFlow!**")
    
    with gr.Accordion("How This Works", open=False):
        gr.Markdown("""
        **Workflow:**
        1. **Set global BPM and bars** - affects both drum and instrument generation
        2. **Generate drum loop** - creates BPM-aware percussion
        3. **Generate instrument loop** - creates melodic/harmonic content  
        4. **Combine loops** - layer them together with repetitions (up to 30s)
        5. **Transform** - use MelodyFlow to stylistically transform the combined result
        
        **Features:**
        - BPM-aware generation ensures perfect sync between loops
        - Negative prompting separates drums from instruments cleanly
        - Smart bar calculation optimizes loop length for the BPM
        - MelodyFlow integration for advanced style transfer
        """)
    
    # ========== GLOBAL CONTROLS ==========
    gr.Markdown("## 🎛️ Global Settings")
    
    with gr.Row():
        global_bpm = gr.Dropdown(
            label="Global BPM",
            choices=[90, 100, 110, 120, 130, 140, 150],
            value=120,
            info="BPM applied to both drum and instrument generation"
        )
        
        global_bars = gr.Dropdown(
            label="Loop Length (Bars)",
            choices=[1, 2, 4, 8],
            value=4,
            info="Number of bars for each loop"
        )
        
        base_prompt = gr.Textbox(
            label="Base Prompt",
            value="techno",
            placeholder="e.g., 'techno', 'jazz', 'ambient', 'hip-hop'",
            info="Style applied to both loops"
        )
    
    # Auto-suggest optimal bars based on BPM
    def update_suggested_bars(bpm):
        optimal = calculate_optimal_bars(bpm)
        return gr.update(info=f"Suggested: {optimal} bars for {bpm}bpm (≤10s)")
    
    global_bpm.change(update_suggested_bars, inputs=[global_bpm], outputs=[global_bars])
    
    # ========== LOOP GENERATION ==========
    gr.Markdown("## 🥁 Step 1: Generate Individual Loops")
    
    with gr.Row():
        with gr.Column():
            gr.Markdown("### 🥁 Drum Loop")
            generate_drums_btn = gr.Button("Generate Drums", variant="primary", size="lg")
            drums_audio = gr.Audio(label="Drum Loop", type="filepath")
            drums_status = gr.Textbox(label="Drums Status", value="Ready to generate")
            
        with gr.Column():
            gr.Markdown("### 🎹 Instrument Loop")
            generate_instruments_btn = gr.Button("Generate Instruments", variant="secondary", size="lg")
            instruments_audio = gr.Audio(label="Instrument Loop", type="filepath")
            instruments_status = gr.Textbox(label="Instruments Status", value="Ready to generate")
    
    # Seed controls
    with gr.Row():
        drums_seed = gr.Number(label="Drums Seed", value=-1, info="-1 for random")
        instruments_seed = gr.Number(label="Instruments Seed", value=-1, info="-1 for random")
    
    # ========== COMBINATION ==========
    gr.Markdown("## 🎛️ Step 2: Combine Loops")
    
    with gr.Row():
        num_repeats = gr.Slider(
            label="Number of Repetitions",
            minimum=1,
            maximum=5,
            step=1,
            value=2,
            info="How many times to repeat each loop (creates longer audio)"
        )
        combine_btn = gr.Button("🎛️ Combine Loops", variant="primary", size="lg")
    
    combined_audio = gr.Audio(label="Combined Loops", type="filepath")
    combine_status = gr.Textbox(label="Combine Status", value="Generate loops first")
    
    # ========== MELODYFLOW TRANSFORMATION ==========
    gr.Markdown("## 🎨 Step 3: Transform with MelodyFlow")
    
    with gr.Row():
        with gr.Column():
            transform_prompt = gr.Textbox(
                label="Transformation Prompt",
                value="aggressive industrial techno with distorted sounds",
                placeholder="Describe the style transformation",
                lines=2
            )
            
        with gr.Column():
            transform_solver = gr.Dropdown(
                label="Solver",
                choices=["euler", "midpoint"],
                value="euler",
                info="EULER: faster (25 steps), MIDPOINT: slower (64 steps)"
            )
            transform_flowstep = gr.Slider(
                label="Transform Intensity",
                minimum=0.0,
                maximum=0.15,
                step=0.01,
                value=0.12,
                info="Lower = more dramatic transformation"
            )
    
    transform_btn = gr.Button("🎨 Transform Audio", variant="secondary", size="lg")
    transformed_audio = gr.Audio(label="Transformed Audio", type="filepath")
    transform_status = gr.Textbox(label="Transform Status", value="Combine audio first")
    
    # ========== EVENT HANDLERS ==========
    
    # Generate drums
    generate_drums_btn.click(
        generate_stable_audio_loop,
        inputs=[base_prompt, gr.State("drums"), global_bpm, global_bars, drums_seed],
        outputs=[drums_audio, drums_status]
    )
    
    # Generate instruments  
    generate_instruments_btn.click(
        generate_stable_audio_loop,
        inputs=[base_prompt, gr.State("instruments"), global_bpm, global_bars, instruments_seed],
        outputs=[instruments_audio, instruments_status]
    )
    
    # Combine loops
    combine_btn.click(
        combine_loops,
        inputs=[drums_audio, instruments_audio, global_bpm, global_bars, num_repeats],
        outputs=[combined_audio, combine_status]
    )
    
    # Transform with MelodyFlow
    transform_btn.click(
        transform_with_melodyflow_api,
        inputs=[combined_audio, transform_prompt, transform_solver, transform_flowstep],
        outputs=[transformed_audio, transform_status]
    )
    
    # ========== EXAMPLES ==========
    gr.Markdown("## 🎯 Example Workflows")
    
    examples = gr.Examples(
        examples=[
            ["techno", 128, 4, "aggressive industrial techno"],
            ["jazz", 110, 2, "smooth lo-fi jazz with vinyl crackle"],
            ["ambient", 90, 8, "ethereal ambient soundscape"],
            ["hip-hop", 100, 4, "classic boom bap hip-hop"],
            ["drum and bass", 140, 4, "liquid drum and bass"],
        ],
        inputs=[base_prompt, global_bpm, global_bars, transform_prompt],
    )

if __name__ == "__main__":
    iface.launch()