from bs4 import BeautifulSoup
from datetime import datetime, timezone
import pytz
import hashlib
import os
from flask import Flask, request, send_file, render_template, Response
import requests
from requests_ntlm import HttpNtlmAuth
import urllib

# ------------------------------------------------------------
# Config
# ------------------------------------------------------------

LOCAL_TZ = pytz.timezone("Europe/London")
URL = "https://webapp.coventry.ac.uk/Timetable-main/Timetable/Current"

print(URL.format(urllib.parse.quote_plus("hello/world")))

app = Flask(__name__)


def parse_events(events_data):
    events_data = events_data.replace("new Date", "")
    cleaned_data = ""

    for line in events_data.split("\n"):
        comment_pos = line.find("//")
        if comment_pos != -1:
            line = line[:comment_pos]

        if ":" in line:
            key, val = line.split(":", 1)
            line = f"'{key}': {val}"

        cleaned_data += line + "\n"

    parsed_data = eval(cleaned_data)

    for event in parsed_data:
        if "start" in event:
            s = list(event["start"])
            s[1] += 1
            s.append(0)
            event["start"] = LOCAL_TZ.localize(datetime(*s))

        if "end" in event:
            e = list(event["end"])
            e[1] += 1
            e.append(0)
            event["end"] = LOCAL_TZ.localize(datetime(*e))

    return parsed_data


def get_events_data(page_data):
    soup = BeautifulSoup(page_data, features="html.parser")

    for script in soup.head.find_all("script", {"type": "text/javascript"}):
        if not script.has_attr("src"):
            source = script.text
            break
    else:
        raise RuntimeError("Could not find inline timetable script")

    return source.split("events:")[1].split("]")[0] + "]"


def ics_time(dt):
    return dt.astimezone(timezone.utc).strftime("%Y%m%dT%H%M%SZ")


def make_uid(event):
    key = f"{event['moduleDesc']}|{event['title']}|{event['start'].isoformat()}"
    return hashlib.sha1(key.encode()).hexdigest() + "@timetable"


def create_ics_event(event):
    return {
        "uid": make_uid(event),
        "summary": f"{event['moduleDesc']} - {event['title']}",
        "description": f"{event['lecturer']} - {event['room']}",
        "start": event["start"],
        "end": event["end"],
    }


def load_existing_uids(path):
    uids = set()
    return uids
    if not os.path.exists(path):
        return uids

    with open(path, "r", encoding="utf-8") as f:
        current_uid = None
        cancelled = False

        for line in f:
            line = line.strip()

            if line == "BEGIN:VEVENT":
                current_uid = None
                cancelled = False
            elif line.startswith("UID:"):
                current_uid = line[4:]
            elif line == "STATUS:CANCELLED":
                cancelled = True
            elif line == "END:VEVENT" and current_uid and not cancelled:
                uids.add(current_uid)

    return uids


def fetch_timetable(username, password):
    session = requests.Session()
    session.auth = HttpNtlmAuth(username, password)

    r = session.get(URL)
    r.raise_for_status()

    session.close()
    return r.text


def build_calendar(page_data):
    events_js = get_events_data(page_data)
    parsed_events = parse_events(events_js)

    new_events = [create_ics_event(e) for e in parsed_events if e]

    old_uids = set()
    new_uids = {e["uid"] for e in new_events}

    now = ics_time(datetime.now(timezone.utc))

    lines = [
        "BEGIN:VCALENDAR",
        "VERSION:2.0",
        "PRODID:-//Timetable Sync//EN",
        "CALSCALE:GREGORIAN",
    ]

    for ev in new_events:
        lines.extend(
            [
                "BEGIN:VEVENT",
                f"UID:{ev['uid']}",
                f"DTSTAMP:{now}",
                f"DTSTART:{ics_time(ev['start'])}",
                f"DTEND:{ics_time(ev['end'])}",
                f"SUMMARY:{ev['summary']}",
                f"DESCRIPTION:{ev['description']}",
                "END:VEVENT",
            ]
        )

    for uid in old_uids - new_uids:
        lines.extend(
            [
                "BEGIN:VEVENT",
                f"UID:{uid}",
                f"DTSTAMP:{now}",
                "STATUS:CANCELLED",
                "END:VEVENT",
            ]
        )

    lines.append("END:VCALENDAR")

    return "\n".join(lines)


# ------------------------------------------------------------
# Flask
# ------------------------------------------------------------
@app.route("/")
def index():
    return render_template("login.jinja")


@app.route("/login-and-download", methods=["POST"])
def login_and_download():
    data = request.form
    username = data["username"]
    password = data["password"]
    try:
        data = build_calendar(fetch_timetable(f"COVENTRY\\{username}", password))
        return Response(
            data,
            mimetype="text/calendar",
            headers={"Content-Disposition": f'attachment; filename="{username}-timetable.ics"'},
        )
    except Exception as e:
        return render_template("login.jinja", error=str(e)), 401


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