app.py

import gradio as gr
import torch
import torch.nn as nn
import soundfile as sf
import numpy as np
import torchaudio
import os
import gc
import time
from demucs.apply import apply_model
from demucs.pretrained import get_model

print("🚀 Starting SpecTacles...")

# Force CPU for free hosting
device = "cpu"

# ==========================================
# 1. DEFINE BRAIN
# ==========================================
class StemMixer(nn.Module):
    def __init__(self):
        super().__init__()
        self.n_fft, self.hop = 2048, 512
        self.mixer = nn.Sequential(
            nn.Linear(4, 64), nn.BatchNorm1d(64), nn.ReLU(),
            nn.Linear(64, 32), nn.BatchNorm1d(32), nn.ReLU(),
            nn.Linear(32, 16), nn.BatchNorm1d(16), nn.ReLU(),
            nn.Linear(16, 2), nn.Sigmoid()
        )
    def compute_spec(self, x):
        b, s, c, t = x.shape
        x = x.reshape(b * s * c, t)
        return torch.abs(torch.stft(x, self.n_fft, self.hop, window=torch.hann_window(self.n_fft).to(x.device), return_complex=True))
    def forward(self, d, m):
        ds, ms = self.compute_spec(d), self.compute_spec(m)
        b, s, c, t = d.shape
        f, fr = ds.shape[1], ds.shape[2]
        ds, ms = ds.reshape(b, s, c, f, fr), ms.reshape(b, s, c, f, fr)
        inp = torch.cat([ds, ms], dim=2).permute(0, 1, 3, 4, 2).reshape(-1, 4)
        mask = self.mixer(inp).reshape(b, s, f, fr, c).permute(0, 1, 4, 2, 3)
        return mask * ds + (1 - mask) * ms

# ==========================================
# 2. LIGHTWEIGHT STARTUP
# ==========================================
print("Loading Brain...")
mixer = StemMixer().to(device)

if os.path.exists("best_stem_mixer.pth"):
    mixer.load_state_dict(torch.load("best_stem_mixer.pth", map_location=torch.device('cpu')))
else:
    print("⚠️ Model file missing!")
mixer.eval()

# Lazy Loading Variables
model_d = None
model_m = None

def load_heavy_models():
    global model_d, model_m
    if model_d is None:
        print("⏳ Loading Demucs...")
        model_d = get_model('htdemucs').to(device).eval()
    if model_m is None:
        print("⏳ Loading MDX...")
        model_m = get_model('mdx_extra').to(device).eval()

# ==========================================
# 3. PROCESS FUNCTION
# ==========================================
def process(audio):
    if audio is None: return None
    load_heavy_models()
    print(f"Processing...")
    
    wav, sr = torchaudio.load(audio)
    if sr != 44100: wav = torchaudio.transforms.Resample(sr, 44100)(wav)
    if wav.abs().max() > 1.0: wav = wav / wav.abs().max()
    
    chunk = 44100 * 10 
    stems = []
    
    for s in range(0, wav.shape[1], chunk):
        e = min(s + chunk, wav.shape[1])
        c = wav[:, s:e]
        if c.shape[1] < 2048: continue
        
        with torch.no_grad():
            ct = c.unsqueeze(0).to(device)
            d = apply_model(model_d, ct, shifts=0)
            m = apply_model(model_m, ct, shifts=0)
            mix = mixer(d, m)
            
            b,st,ch,t = d.shape
            dc = torch.stft(d.reshape(b*st*ch, t), 2048, 512, window=torch.hann_window(2048).to(device), return_complex=True)
            rec = torch.istft(torch.polar(mix.reshape(b*st*ch, dc.shape[-2], dc.shape[-1]), torch.angle(dc)), 2048, 512, window=torch.hann_window(2048).to(device), length=t)
            stems.append(rec.reshape(st, ch, -1).cpu())

    full = torch.cat(stems, dim=2).numpy()
    paths = []
    ts = int(time.time())
    
    for i, n in enumerate(['Drums', 'Bass', 'Other', 'Vocals']):
        p = f"{n}_{ts}.mp3"
        sf.write(p, np.clip(full[i].T, -0.99, 0.99), 44100)
        paths.append(p)
        
    return paths[3], paths[0], paths[1], paths[2]

# ==========================================
# 4. UI (Nonchalant & Themed)
# ==========================================

# JavaScript to toggle Dark Mode
js_toggle = """
function() {
    document.body.classList.toggle('dark');
}
"""

# CSS for the button and clean look
css = """
.gr-button-primary {
    background: linear-gradient(90deg, #6366f1, #a855f7) !important; 
    color: white !important; 
    border: none !important;
}
h1 {
    font-family: 'Helvetica', sans-serif; 
    font-weight: 700;
}
"""

# Use Soft theme (Looks good in both Light and Dark)
with gr.Blocks(theme=gr.themes.Soft(), css=css) as app:
    
    with gr.Row():
        with gr.Column(scale=10):
            gr.Markdown("# 👓 SpecTacles")
        with gr.Column(scale=1):
            # The Theme Toggle Button
            theme_btn = gr.Button("🌗", variant="secondary")

    with gr.Row():
        inp = gr.Audio(type="filepath", label="Source")
        btn = gr.Button("SEPARATE", variant="primary")
    
    with gr.Row():
        v = gr.Audio(label="Vocals")
        d = gr.Audio(label="Drums")
        b = gr.Audio(label="Bass")
        o = gr.Audio(label="Other")
        
    # Logic
    btn.click(process, inputs=inp, outputs=[v,d,b,o])
    
    # JS Trigger
    theme_btn.click(None, None, None, js=js_toggle)

app.launch()