app.py

from flask import Flask, request, send_file, jsonify
from pydub import AudioSegment, effects
import numpy as np
import requests
import io
import os

app = Flask(__name__)

@app.route("/result")
def process_song():
    url = request.args.get("song")
    if not url:
        return jsonify({"error": "Please provide a song link with ?song=<url>"})
    
    try:
        # --- Download audio ---
        headers = {"User-Agent": "Mozilla/5.0"}
        resp = requests.get(
            url,
            stream=True,
            headers=headers,
            allow_redirects=True,
            timeout=30
        )
        resp.raise_for_status()

        # Buffer to BytesIO
        data = io.BytesIO()
        for chunk in resp.iter_content(chunk_size=1024 * 1024):
            if chunk:
                data.write(chunk)
        data.seek(0)

        # --- Detect format from URL extension ---
        ext = os.path.splitext(url.split("?")[0])[-1].lstrip(".").lower()
        fmt = ext if ext in ["mp3", "wav", "flac", "ogg", "m4a"] else None

        # --- Load with auto-detect ---
        try:
            sound = AudioSegment.from_file(data, format=fmt)
        except Exception:
            data.seek(0)  # retry without forcing format
            sound = AudioSegment.from_file(data)

        # --- Normalize ---
        sound = effects.normalize(sound)

        # --- Split channels ---
        left, right = sound.split_to_mono()
        output = AudioSegment.silent(duration=len(sound), frame_rate=sound.frame_rate)

        # --- Pan & effect settings ---
        chunk_ms = 10
        pan_period = 6.0
        base_depth = 0.7
        depth_variation = 0.2
        reverb_delay = 80

        steps = len(sound) // chunk_ms
        for i in range(steps):
            t = (i * chunk_ms) / 1000.0
            ratio = (np.sin(2 * np.pi * t / pan_period) + 1) / 2
            depth = base_depth + depth_variation * np.sin(2 * np.pi * t / (pan_period * 2))

            left_gain = (1 - depth * ratio) * -3
            right_gain = (depth * ratio) * -3

            left_chunk = left[i * chunk_ms:(i + 1) * chunk_ms] + left_gain
            right_chunk = right[i * chunk_ms:(i + 1) * chunk_ms] + right_gain

            stereo_chunk = AudioSegment.from_mono_audiosegments(left_chunk, right_chunk)
            output += stereo_chunk

        # --- Stereo widening ---
        widened = output.overlay(output.pan(-0.5), gain_during_overlay=-6)
        widened = widened.overlay(output.pan(0.5), gain_during_overlay=-6)

        # --- Subtle reverb ---
        reverb = widened.overlay(widened - 8, delay=reverb_delay)
        reverb = reverb.overlay(widened - 14, delay=reverb_delay * 2)

        # --- Final mastering ---
        final = effects.normalize(reverb)

        # --- Export to memory ---
        buf = io.BytesIO()
        final.export(buf, format="mp3")
        buf.seek(0)

        return send_file(
            buf,
            mimetype="audio/mpeg",
            as_attachment=True,
            download_name="panned_heavenly.mp3"
        )

    except Exception as e:
        return jsonify({"error": str(e)}), 500


if __name__ == "__main__":
    app.run(host="0.0.0.0", port=7860)