from datetime import datetime, timedelta
from typing import Iterable

import click
import pyperclip
import requests

# typing
RawEvent = dict[str : tuple[str | datetime, str]]
Event = dict[str:str]
TableMetaData = dict[str:int]

ICAL_URL = "https://bwsyncandshare.kit.edu/remote.php/dav/public-calendars/69o9HEM9aeZnER8S/?export"

ICS_DATE_FORMAT = "%Y%m%dT%H%M%S"
GERMAN_DATE_FORMAT = "%d.%m.%Y %H:%M"

EARLIEST = datetime.now() - timedelta(days=30 * 3)
LATEST = datetime.now() + timedelta(days=30 * 6)

TABLE_COLUMN_ORDER = ("date", "location", "presenter")

# for mail sending
MAIL_RECIPIENTS = ",".join(
    [
        "cpistaff@imtek.de",
        "andrealayedra@hotmail.com",
        "jaro.homburger@biologie.uni-freiburg.de",
        "kubilay.acar@continental.com",
        "Mario.diehlmann@basf.com",
        "paul.fernandez@fmf.uni-freiburg.de",
        "sunil.shetty@uniklinik-freiburg.de",
        "sofia.genoves94@gmail.com",
        "sofia.genoves@yahoo.com.ar",
    ]
)
MAIL_SUBJECT = "Updated Group Meeting Schedule"
MAIL_START = """
Dear All,

There is an updated group-seminar schedule available: 
"""
MAIL_END = """
If (and only if) you can't make it in person, you can join the presentations via zoom: https://uni-freiburg.zoom-x.de/j/62063730956?pwd=6poraREYWvuHkStuYDRvYhO4vhmTbt.1

Meeting-ID: 620 6373 0956
Code: Lm5xaDXPH 

You can have a look in our group meeting calendar at: https://bwsyncandshare.kit.edu/apps/calendar/p/69o9HEM9aeZnER8S

Or on our wiki: https://wiki.cpi.imtek.uni-freiburg.de/SeminarSchedule

If you want to add the schedule to your calendar app of choice, please use this subscribe link: https://bwsyncandshare.kit.edu/remote.php/dav/public-calendars/69o9HEM9aeZnER8S/?export

Best,
Holgi
"""

# parsers


def _parse_text(ics_text: str) -> str:
    text = ics_text.strip()
    return text.replace("\\,", ",")


def _parse_presenter(ics_text: str) -> str:
    text = _parse_text(ics_text)
    first, sep, last = text.partition(":")
    return first if not sep else last.strip()


def _parse_datetime(ics_text: str) -> str:
    return datetime.strptime(ics_text.strip(), ICS_DATE_FORMAT)


def _format_datetime(date: datetime) -> str:
    return datetime.strftime(date, GERMAN_DATE_FORMAT)


class Transformer:
    def __init__(self, name, parser, formater):
        self.name = name
        self.parser = parser
        self.formater = formater


vevent_transformer = {
    "DTSTART": Transformer(
        "date", parser=_parse_datetime, formater=_format_datetime
    ),
    "LOCATION": Transformer("location", parser=_parse_text, formater=str),
    "SUMMARY": Transformer("presenter", parser=_parse_presenter, formater=str),
}


def get_ics(url: str) -> str:
    try:
        response = requests.get(url)
    except IndexError:
        msg = f"Could not load calender from url"
        raise IOError(msg)
    return response.text


def extract_event_info(response: str) -> Iterable[Event]:
    events = (
        event
        for event in _extract_event_info(response)
        if EARLIEST < event["date"][0] < LATEST
    )
    for event in sorted(events, key=lambda d: d["date"]):
        yield {key: values[1] for key, values in event.items()}


def _extract_event_info(response: str) -> Iterable[RawEvent]:
    handle = (line for line in response.splitlines())
    for line in handle:
        if line.upper().startswith("BEGIN:VEVENT"):
            yield extract_vevent(handle)


def extract_vevent(handle: Iterable[str]) -> RawEvent:
    event = {}
    for line in handle:
        if line.upper().startswith("END:VEVENT"):
            break
        raw_key, _, raw_value = line.partition(":")
        key, _, _ = raw_key.partition(";")
        if t := vevent_transformer.get(key):
            value = t.parser(raw_value)
            text = t.formater(value)
            event[t.name] = (value, text)
    return event


def create_wiki_table(events: Iterable[Event]) -> str:
    table_meta_data = _get_table_meta_data(events)
    headers = {key: f"'''{key.capitalize()}'''" for key in TABLE_COLUMN_ORDER}
    lines = [
        _create_table_line(headers, table_meta_data, sep="||", bracket=True),
    ]
    lines.extend(
        _create_table_body(events, table_meta_data, sep="||", bracket=True)
    )
    return "\n".join(lines)


def create_email_table(events: Iterable[Event]) -> str:
    table_meta_data = _get_table_meta_data(events)
    lines = _create_table_body(events, table_meta_data, sep="|", bracket=False)
    return "\n".join(lines)


def _create_table_body(
    events: Iterable[Event], meta: TableMetaData, sep: str, *, bracket: bool
) -> list[str]:
    return [_create_table_line(event, meta, sep=sep, bracket=bracket) for event in events]


def _create_table_line(
    event: Event, meta: TableMetaData, sep: str, *, bracket: bool
) -> str:
    columns = [event[key].ljust(meta[key]) for key in TABLE_COLUMN_ORDER]
    inner = f" {sep} ".join(columns)
    return f"{sep} {inner} {sep}" if bracket else inner


def _get_table_meta_data(events: Iterable[Event]) -> TableMetaData:
    meta = {}
    for event in events:
        for key, value in event.items():
            meta[key] = max(meta.get(key, 0), len(value))
    return meta


@click.command()
def group_schedule():
    ics_file = get_ics(ICAL_URL)
    events = list(extract_event_info(ics_file))

    wiki_table = create_wiki_table(events)
    email_table = create_email_table(events)

    components = [
        wiki_table,
        "",
        "",
        "",
        MAIL_RECIPIENTS,
        "",
        MAIL_SUBJECT,
        MAIL_START,
        email_table,
        MAIL_END,
    ]
    text = "\n".join(components)
    print(text)
    pyperclip.copy(text)