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

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

from config import Config


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

attachment_filenames = {}


class DownloadForm(FlaskForm):
    start_time = DateTimeField('Startzeit',
                               validators=[InputRequired()],
                               format='%Y-%m-%d %H:%M')
    length = IntegerField('Länge',
                          validators=[
                              InputRequired(),
                              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, attachment_filename = prepare_download(form)
            attachment_filenames[output_filename] = attachment_filename
            flash('Der Download sollte sofort starten.', 'success')
            return render_template('download.html', form=form, filename=output_filename)
        except ValueError as e:
            flash('Fehler beim Erstellen des Downloads: {}'.format(e), 'warning')
    else:
        flash('Fehler im Formular!', 'warning')
    return render_template('download.html', form=form)


@app.route('/download_file/<filename>')
def download_file(filename):
    """Download an output file"""

    if filename not in attachment_filenames:
        abort(404)
    attachment_filename = attachment_filenames.pop(filename)

    fh = open(os.path.join(app.config['TMP_DIR'], filename), 'rb')
    os.remove(os.path.join(app.config['TMP_DIR'], filename))

    # XXX How to close fh?
    return send_file(fh, as_attachment=True,
                     attachment_filename=attachment_filename)


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('Konnte Startdatei nicht finden!')
    sources = sources[start_index:]

    # Super lazy: Limit to 5 source files input
    sources = sources[:5]

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

    # Let ffmpeg do the rest of the job
    _, output_filename = mkstemp(suffix='.mp3', dir=app.config['TMP_DIR'])
    output_filename = os.path.basename(output_filename)
    attachment_filename = '{}_{}.mp3'.format(form.start_time.data, form.length.data)

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

    return output_filename, attachment_filename


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