#!/usr/bin/env python3
#
#   SPDX-License-Identifier: ISC
#
#   Copyright © 2019 Free Software Foundation of India.
#

import html
import datetime
import os
import os.path
import re
import subprocess as subp
import sys


URL = 'https://fsfi.ricketyspace.net'
SECTIONS = ['news']

F_PH = {
    'name': '<!-- Feed Name -->',
    'link': '<!-- Feed Link -->',
    'updated': '<!-- Feed Updated -->',
    'entries': '<!-- Entries -->'
}

E_PH = {
    'id': '<!-- Entry Id -->',
    'title': '<!-- Entry Title -->',
    'link': '<!-- Entry Link -->',
    'updated': '<!-- Entry Updated -->',
    'content': '<!-- Entry Content -->'
}


def err(s):
    print('Error: {}'.format(s))
    sys.exit(1)


def fok(f):
    p = os.path.basename(f.path)

    if re.search(r'(^[\.\#])|(~$)', p):
        return False

    return True


def files(sec):
    files = os.scandir('md' + '/' + sec)

    fs = []
    for f in files:
        if not fok(f):
            print('Ignoring {}'.format(f.path))
        else:
            fs.append(f)

    return fs


def read(f):
    with open(f) as f:
        c = f.read()
    return c


def write(p, c):
    d = os.path.dirname(p)

    if not os.path.exists(d):
        os.makedirs(d)

    with open(p, 'w') as f:
        f.write(c)


def slug(p):
    m = re.search(r'([a-zA-Z\-]+)\.md', p)

    if not m:
        err('Unable to get slug')

    return m.group(1)


def template(type):
    return read('templates/atom/{}.atom'.format(type))


def title(c):
    m = re.search(r'^\# (.+)$', c, re.M)

    if not m:
        err('Title not found')

    return m.group(1)


def elink(sec, s):
    return '/'.join([URL, sec, s])


def flink(sec):
    return '/'.join([URL, sec, 'feed.atom'])


def time(c):
    m = re.search(r'pubdate: ([0-9]{8})', c)

    if not m:
        err('Publication date not found')

    d = m.group(1)
    d = datetime.datetime.strptime(d,'%Y%m%d').strftime('%Y-%m-%d')

    return d + 'T00:00:00Z'


def markdown(c):
    try:
        r = subp.run(['bin/markdown'],
                     input=c,
                     stdout=subp.PIPE,
                     check=True,
                     universal_newlines=True)
    except Exception as e:
        p('Markdown failed for {}'.format(c))

    return r.stdout


def massage(c):
    c = html.escape(c)
    c = c.replace('\n', '&#xA;')
    c = re.sub(r' +', ' ', c)

    return c


def content(c):
    m = re.search(r'^\# (.+)$', c, re.M)

    if not m:
        err('Unable to slurp content')

    c = c[m.end():]
    c = markdown(c)

    return massage(c)


def now():
    n = datetime.datetime.today()

    return n.strftime('%Y-%m-%dT%H:%M:%SZ')


def entry(sec, f):
    c = read(f.path)
    s = slug(f.path)

    e = template('entry')
    e = e.replace(E_PH['id'], s, 1)
    e = e.replace(E_PH['title'], title(c), 1)
    e = e.replace(E_PH['link'], elink(sec, s), 1)
    e = e.replace(E_PH['updated'], time(c), 1)
    e = e.replace(E_PH['content'], content(c), 1)

    return e


def feed(sec, es):
    f = template('feed')
    f = f.replace(F_PH['name'], sec, 2)
    f = f.replace(F_PH['link'], flink(sec), 1)
    f = f.replace(F_PH['updated'], now(), 1)
    f = f.replace(F_PH['entries'], es, 1)

    return f


def process(sec):
    es = ''
    for f in files(sec):
        es += entry(sec, f)

    write('/'.join(['_build', sec, 'feed.atom']), feed(sec, es))


def run():
    for sec in SECTIONS:
        process(sec)


if __name__ == '__main__':
    run()