from flask import (Flask, render_template, flash, redirect,
                   url_for, request, send_from_directory)
from flask_bootstrap import Bootstrap
from flask_wtf import FlaskForm
from wtforms import DateTimeField, IntegerField, SubmitField
from wtforms.validators import DataRequired, NumberRange

from datetime import datetime, timedelta
import os
import random
import re
import subprocess

from config import Config


app = Flask(__name__)
app.config.from_object(Config)
Bootstrap(app)


class DownloadForm(FlaskForm):
    start_time = DateTimeField('Start time', validators=[DataRequired()],
                               format='%Y-%m-%d %H:%M')
    length = IntegerField('Length', validators=[DataRequired(),
                                                NumberRange(min=1, max=app.config['MAX_LENGTH'])])
    submit = SubmitField('Download')


@app.route('/', methods=['GET', 'POST'])
def download():
    form = DownloadForm()
    if request.method == 'GET':
        form.start_time.data = datetime.now().replace(minute=0, second=0) - timedelta(hours=1)
        form.length.data = 60
    elif form.validate_on_submit():
        try:
            output_filename = prepare_download(form)
            flash('The download should start immediately.', 'success')
            return render_template('download.html', form=form, filename=output_filename)
        except ValueError as e:
            flash('Error preparing download: {}'.format(e), 'warning')
    else:
        flash('Error in form!', 'warning')
    return render_template('download.html', form=form)


@app.route('/download_file/<filename>')
def download_file(filename):
    return send_from_directory(app.config['TMP_DIR'], filename,
                               as_attachment=True)


def prepare_download(form):
    """Prepare a download given the user's request form"""

    def start_time_for_source_fn(fn):
        return datetime.strptime(fn, 'qfhi-%Y%m%d-%H%M.mp3')

    def length_for_source_fn(fn):
        size = os.stat(os.path.join(app.config['DATA_DIR'], fn)).st_size
        length = timedelta(minutes=size / (1000*app.config['KBITS']/8) / 60)
        return length

    # Get a sorted list of all source files with start time and length
    sources = []
    for fn in os.listdir(app.config['DATA_DIR']):
        try:
            start_time = start_time_for_source_fn(fn)
            length = length_for_source_fn(fn)
            sources.append({'fn': fn, 'start_time': start_time, 'length': length})
        except ValueError:
            pass
    sources = sorted(sources, key=lambda s: s['start_time'])

    # Only interested in the source files from the start file
    start_index = None
    for i, source in enumerate(sources):
        if source['start_time'] <= form.start_time.data < source['start_time'] + source['length']:
            start_index = i
    if start_index is None:
        raise ValueError('Could not find start file')
    sources = sources[start_index:]

    # Seek into the first file
    ss = (form.start_time.data - sources[0]['start_time']).total_seconds()

    # Let ffmpeg do the rest of the job
    # XXX Necessary to limit the concat files?
    output_filename = '{}_{}.mp3'.format(form.start_time.data, form.length.data)

    c = ['ffmpeg', '-y']
    c += ['-ss', str(ss)]
    c += ['-i', 'concat:' + '|'.join([os.path.join(app.config['DATA_DIR'],
        source['fn']) for source in sources])]
    c += ['-codec', 'copy']
    c += ['-t', str(form.length.data * 60)]
    c += [os.path.join(app.config['TMP_DIR'], output_filename)]

    app.logger.debug(' '.join(c))
    subprocess.call(c)

    return output_filename


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