#!/usr/bin/python3
import mailbox
import jinja2
import email.header
import email.utils
import yaml
import datetime
import sys, os
import pypandoc
import argparse
import quopri
from pprint import pprint

CONFIG_FILE = "generator.conf"

WEEKDAYS = { 0: "Montag",
             1: "Dienstag",
             2: "Mittwoch",
             3: "Donnerstag",
             4: "Freitag",
             5: "Samstag",
             6: "Sonntag" }

def decode_header(header):
    return "".join([ x[0].decode(x[1] or "ascii") if isinstance(x[0], bytes) else x[0]  for x in email.header.decode_header(header) ])

class Top:
    def __init__(self, title=None, sender=None, body=None, protostub=None, message=None):
        if message:
            self.title = decode_header(message["Subject"])[6:]
            real_name, address = email.utils.parseaddr(message["From"])
            self.sender = real_name or address
            payload = message.get_payload()
            if message["Content-Transfer-Encoding"] == "quoted-printable":
                payload = quopri.decodestring(payload.encode("ascii")).decode("utf8")
            self.body = payload.rpartition("\n--")[0] if "\n--" in payload else payload
        elif title:
            self.title = title
            self.sender = sender
            self.body = body
            self.protostub = protostub
        else:
            raise ValueError("One of title or message is needed")

    def __repr__(self):
        return "<TOP "+self.title+">"

# from https://stackoverflow.com/questions/6558535/find-the-date-for-the-first-monday-after-a-given-a-date
def next_weekday(d, weekday):
    days_ahead = weekday - d.weekday()
    if days_ahead < 0: # Target day already happened this week
        days_ahead += 7
    return d + datetime.timedelta(days_ahead)

def last_weekday(d, weekday):
    days_ahead = weekday - d.weekday()
    if days_ahead >= 0: # Target day already happened this week
        days_ahead -= 7
    return d + datetime.timedelta(days_ahead)

def wiki2latex(intext):
    intext = intext.replace(":\n", ":\n\n")
    return pypandoc.convert_text(intext, 'latex', format='md')

def j2replace(intext):
    return j2env.from_string(intext).render(context)

def date(indate):
    return indate.strftime("%d.%m.%Y")

def time(intime):
    return intime.strftime("%H:%M")

def weekday(indate):
    return WEEKDAYS[indate.weekday()]

def conf2top(top):
    sender = None
    body = None
    protostub = None
    try:
        sender = top["sender"]
    except KeyError:
        pass
    try:
        body = top["body"]
    except KeyError:
        pass
    try:
        protostub = top["protostub"]
    except KeyError:
        pass

    if "file" in top:
        try:
            body = open(top["file"]).read()
        except OSError as e:
            print("Warning: Error opening", top["file"], file=sys.stderr)

    return Top(top["title"], sender, body, protostub)

if __name__ == "__main__":
    parser = argparse.ArgumentParser()
    parser.add_argument("--config", default=CONFIG_FILE)
    mode = parser.add_mutually_exclusive_group(required=True)
    mode.add_argument("--invite", action="store_true")
    mode.add_argument("--presentation", action="store_true")
    mode.add_argument("--protocol", action="store_true")
    parser.add_argument("--debug", action="store_true", help=argparse.SUPPRESS)
    parser.add_argument("--write-mbox", action="store_true")
    args = parser.parse_args()

    config = yaml.full_load(open(args.config))

    if args.invite:
        template_file = config["invite_template_file"]
    elif args.presentation:
        template_file = config["presentation_template_file"]
    elif args.protocol:
        template_file = config["protocol_template_file"]
    else:
        raise Exception("Should never happen")

    j2env = jinja2.Environment()
    j2env.filters["wiki2latex"] = wiki2latex
    j2env.filters["j2replace"] = j2replace
    j2env.filters["date"] = date
    j2env.filters["time"] = time
    j2env.filters["weekday"] = weekday
    template = j2env.from_string(open(template_file).read())

    mbox = mailbox.mbox(config["top_mbox_file"])

    current_date = next_weekday(datetime.date.today(), config["default_weekday"])
    next_date = current_date + datetime.timedelta(days=7)
    last_date = last_weekday(current_date, config["default_weekday"])

    time = datetime.time.fromisoformat(config["default_time"])

    pre_tops = []
    post_tops = []

    for top in config["pre_tops"]:
        pre_tops.append(conf2top(top))

    for top in config["post_tops"]:
        post_tops.append(conf2top(top))

    email_tops = []

    for message in mbox:
        if args.debug:
            print(message.get_payload())
        top = Top(message=message)
        email_tops.append(top)

    to = pre_tops + email_tops + post_tops

    context = {"to": to,
               "redeleitung": config["redeleitung"],
               "protokoll": config["protokoll"],
               "date": current_date,
               "time": time,
               "place": config["place"],
               "next_date": next_date,
               "last_date": last_date,
               "meeting_link": config["meeting_link"],
               "email_tops": email_tops,
               "WEEKDAYS": WEEKDAYS}

    if args.debug:
        for top in to:  
            pprint(top.__dict__)
        pprint(context)
    elif args.write_mbox:
        msg = email.message.EmailMessage()
        msg.set_content(template.render(context))
        msg["Subject"] = j2env.from_string(config["invite_subject"]).render(context)
        msg["From"] = email.utils.formataddr((config["redeleitung"]["name"], config["redeleitung"]["email"]))
        msg["To"] = config["invite_mail"]
        mbox = mailbox.mbox(config["mbox_out"])
        mbox.add(msg)
        mbox.close()
        print(mbox)
    else:
        print(template.render(context))