const fetch = require('node-fetch');

export const getiCalFile = async (user: string, file: string, showBlockers: boolean, electiveModule: string, profileModule: string): Promise<string> => {
    try {
        let iCalFileContents = '';

        let baseUrl = 'https://rapla.dhbw-karlsruhe.de/rapla?page=ical';
        baseUrl += '&user=' + user;
        baseUrl += '&file=' + file;

        const response = await fetch(baseUrl);

        let body = await response.text();

        // Parse the ical file
        let iCalFile = parseIcal(body);

        // Now remove unwanted shit from the iCal file
        if (!showBlockers) {
            iCalFile = removeBlockers(iCalFile);
        }

        if (electiveModule !== '') {
            iCalFile = removeElective(iCalFile, electiveModule);
        }

        if (profileModule !== '') {
            iCalFile = removeProfile(iCalFile, profileModule);
        }

        // Turn into one file again
        let resultingFile = serializeIcal(iCalFile);

        return resultingFile;
    } catch (err) {
        throw err;
    }
};

export const parseIcal = function (icalContents: string): iCalFile {
    const fileHeaderRegex: RegExp = /^BEGIN:VCALENDAR.*?BEGIN:VEVENT$/ms;
    const eventRegex: RegExp = /^BEGIN:VEVENT.*?END:VEVENT$/msg;

    let headerMatch = fileHeaderRegex.exec(icalContents);
    let header = '';

    if (headerMatch) {
        header = headerMatch[0];
    }

    header = header.substr(0, header.lastIndexOf('\n') + 1);

    let events: iCalEvent[] = [];
    let match: any;
    while (match = eventRegex.exec(icalContents)) {
        if (match) {
            events.push({
                content: match[0],
                duration: getDuration(match[0])
            });
        }
    }

    return {
        head: header,
        body: events
    };
};

export const getDuration = function (event: string): number {
    let startRegex: RegExp = /DTSTART.*?(\d{4})(\d{2})(\d{2})T(\d{2})(\d{2})(\d{2})Z?\r/gm;
    let endRegex: RegExp = /DTEND.*?(\d{4})(\d{2})(\d{2})T(\d{2})(\d{2})(\d{2})Z?\r/gm;

    let startMatch = startRegex.exec(event);

    let startDtYear = 0;
    let startDtMonth = 0;
    let startDtDay = 0;
    let startDtHour = 0;
    let startDtMinute = 0;
    if (startMatch) {
        startDtYear = parseInt(startMatch[1]);
        startDtMonth = parseInt(startMatch[2]);
        startDtDay = parseInt(startMatch[3]);
        startDtHour = parseInt(startMatch[4]);
        startDtMinute = parseInt(startMatch[5]);
    }

    let endMatch = endRegex.exec(event);
    let endDtYear = 0;
    let endDtMonth = 0;
    let endDtDay = 0;
    let endDtHour = 0;
    let endDtMinute = 0;
    if (endMatch) {
        endDtYear = parseInt(endMatch[1]);
        endDtMonth = parseInt(endMatch[2]);
        endDtDay = parseInt(endMatch[3]);
        endDtHour = parseInt(endMatch[4]);
        endDtMinute = parseInt(endMatch[5]);
    }

    let startDt = new Date(startDtYear, startDtMonth - 1, startDtDay, startDtHour, startDtMinute);
    let endDt = new Date(endDtYear, endDtMonth - 1, endDtDay, endDtHour, endDtMinute);

    let hourDifference = endDt.getHours() - startDt.getHours();
    let minuteDifference = 0;

    if (hourDifference === 0) {
        minuteDifference = endDt.getMinutes() - startDt.getMinutes();
    }

    return hourDifference + (minuteDifference / 60);
};

export const serializeIcal = function (ical: iCalFile): string {
    let resString = ical.head;
    ical.body.forEach((event) => {
        resString += event.content + '\n';
    });
    resString += 'END:VCALENDAR\n';

    return resString;
};

export const removeBlockers = function (ical: iCalFile): iCalFile {
    let remainingEvents: iCalEvent[] = [];

    ical.body.forEach((event) => {
        if (
            !event.content.includes('SUMMARY:Beginn Theorie')
            && !event.content.includes('SUMMARY:Präsenz')
            && event.duration < 10
            && event.duration > 0.25
        ) {
            remainingEvents.push(event);
        }
    });

    ical.body = remainingEvents;

    return ical;
};

export const removeElective = function (ical: iCalFile, chosenElective: string): iCalFile {
    let remainingEvents: iCalEvent[] = [];

    let electiveToRemove = [
        {name: 'ERP-Systeme'},
        {name: 'Ethik für Informatiker'},
        {name: 'Evolutionäre Algorithmen'},
        {name: 'Forensik'},
        {name: 'Kryptographische Verfahren'},
        {name: 'Robotik'},
        {name: 'Web-Services'},
        {name: 'High Performance Computing'}
    ];
    electiveToRemove.splice(parseInt(chosenElective), 1);

    ical.body.forEach((event) => {
        let addEvent = true;
        electiveToRemove.forEach((module) => {
            if (event.content.includes(module.name)) {
                addEvent = false;
            }
        });

        if (addEvent) {
            remainingEvents.push(event);
        }
    });

    ical.body = remainingEvents;

    return ical;
};

export const removeProfile = function (ical: iCalFile, chosenProfile: string): iCalFile {
    let remainingEvents: iCalEvent[] = [];

    let profileToRemove = [
        {names: ['.Grundlagen der KI (KI und BV)', 'Bildverarbeitung (KI und BV)']},
        {names: ['Bildverarbeitung', 'Computergraphik']},
        {names: ['Interaktive Systeme', 'Grundlagen der KI']},
        {names: ['e Business', 'angewandtes Projektmanagement']},
        {names: ['Kommunikations und Netztechnik II']}
    ];
    profileToRemove.splice(parseInt(chosenProfile), 1);

    ical.body.forEach((event) => {
        let addEvent = true;
        profileToRemove.forEach((module) => {
            module.names.forEach((name) => {
                if (event.content.includes(name)) {
                    addEvent = false;
                }
            });
        });

        if (addEvent) {
            remainingEvents.push(event);
        }
    });

    ical.body = remainingEvents;

    return ical;
};

export interface iCalFile {
    head: string;
    body: iCalEvent[];
}

export interface iCalEvent {
    content: string;
    duration: number; // Duration in hours
}