import os
import io
import wave
import struct
from flask import Flask, render_template, request, send_file, jsonify
from werkzeug.utils import secure_filename

app = Flask(__name__)

UPLOAD_FOLDER = '/tmp'
ALLOWED_EXTENSIONS = {'mp3', 'wav'}

app.config['UPLOAD_FOLDER'] = UPLOAD_FOLDER

def allowed_file(filename):
    return '.' in filename and filename.rsplit('.', 1)[1].lower() in ALLOWED_EXTENSIONS

@app.route('/')
def index():
    return render_template('index.html')

@app.route('/process', methods=['POST'])
def process_file():
    if 'file' not in request.files:
        return jsonify({'error': 'No file part'}), 400
    file = request.files['file']
    if file.filename == '':
        return jsonify({'error': 'No selected file'}), 400
    if file and allowed_file(file.filename):
        filename = secure_filename(file.filename)
        filepath = os.path.join(app.config['UPLOAD_FOLDER'], filename)
        file.save(filepath)

        factor = int(request.form['factor'])
        is_decrypting = filename.lower().endswith('.mp3')

        try:
            if is_decrypting:
                output = deconvert_file(filepath, factor)
                output_filename = 'deconverted_file.wav'
                mimetype = 'audio/wav'
            else:
                output = convert_file(filepath, factor)
                output_filename = 'converted_file.mp3'
                mimetype = 'audio/mpeg'

            os.remove(filepath)

            return send_file(
                io.BytesIO(output),
                mimetype=mimetype,
                as_attachment=True,
                download_name=output_filename
            )
        except Exception as e:
            os.remove(filepath)
            return jsonify({'error': str(e)}), 500

    return jsonify({'error': 'Invalid file type'}), 400

def convert_file(filepath, factor):
    with wave.open(filepath, 'rb') as wav_file:
        params = wav_file.getparams()
        frames = wav_file.readframes(wav_file.getnframes())
    
    audio_data = struct.unpack(f'{len(frames)//params.sampwidth}h', frames)
    modified_data = [int(sample * factor / 100) for sample in audio_data]
    
    output = io.BytesIO()
    with wave.open(output, 'wb') as wav_output:
        wav_output.setparams(params)
        wav_output.writeframes(struct.pack(f'{len(modified_data)}h', *modified_data))
    
    return output.getvalue()

def deconvert_file(filepath, factor):
    with wave.open(filepath, 'rb') as wav_file:
        params = wav_file.getparams()
        frames = wav_file.readframes(wav_file.getnframes())
    
    audio_data = struct.unpack(f'{len(frames)//params.sampwidth}h', frames)
    modified_data = [int(sample * 100 / factor) for sample in audio_data]
    
    output = io.BytesIO()
    with wave.open(output, 'wb') as wav_output:
        wav_output.setparams(params)
        wav_output.writeframes(struct.pack(f'{len(modified_data)}h', *modified_data))
    
    return output.getvalue()

if __name__ == '__main__':
    app.run(debug=True)