const {google} = require('googleapis');
import createNewEventEmail from "./emails/new-event";

const googleAuth = () => {
    const {client_secret, client_id, redirect_uris} = JSON.parse(process.env.GOOGLE_API_CREDENTIALS).web;
    return new google.auth.OAuth2(client_id, client_secret, redirect_uris[0]);
};

function handleErrorsJson(response) {
    if (!response.ok) {
        response.json().then(console.log);
        throw Error(response.statusText);
    }
    return response.json();
}

function handleErrorsRaw(response) {
    if (!response.ok) {
        response.text().then(console.log);
        throw Error(response.statusText);
    }
    return response.text();
}

const o365Auth = (credential) => {

    const isExpired = (expiryDate) => expiryDate < +(new Date());

    const refreshAccessToken = (refreshToken) => fetch('https://login.microsoftonline.com/common/oauth2/v2.0/token', {
        method: 'POST',
        headers: {'Content-Type': 'application/x-www-form-urlencoded'},
        body: new URLSearchParams({
            'scope': 'User.Read Calendars.Read Calendars.ReadWrite',
            'client_id': process.env.MS_GRAPH_CLIENT_ID,
            'refresh_token': refreshToken,
            'grant_type': 'refresh_token',
            'client_secret': process.env.MS_GRAPH_CLIENT_SECRET,
        })
    })
        .then(handleErrorsJson)
        .then((responseBody) => {
            credential.key.access_token = responseBody.access_token;
            credential.key.expiry_date = Math.round((+(new Date()) / 1000) + responseBody.expires_in);
            return credential.key.access_token;
        })

    return {
        getToken: () => !isExpired(credential.key.expiry_date) ? Promise.resolve(credential.key.access_token) : refreshAccessToken(credential.key.refresh_token)
    };
};

interface Person {
    name?: string,
    email: string,
    timeZone: string
}

interface CalendarEvent {
    type: string;
    title: string;
    startTime: string;
    endTime: string;
    description?: string;
    location?: string;
    organizer: Person;
    attendees: Person[];
};

interface CalendarApiAdapter {
    createEvent(event: CalendarEvent): Promise<any>;

    updateEvent(uid: String, event: CalendarEvent);

    deleteEvent(uid: String);

    getAvailability(dateFrom, dateTo): Promise<any>;
}

const MicrosoftOffice365Calendar = (credential): CalendarApiAdapter => {

    const auth = o365Auth(credential);

    const translateEvent = (event: CalendarEvent) => {

        let optional = {};
        if (event.location) {
            optional.location = {displayName: event.location};
        }

        return {
            subject: event.title,
            body: {
                contentType: 'HTML',
                content: event.description,
            },
            start: {
                dateTime: event.startTime,
                timeZone: event.organizer.timeZone,
            },
            end: {
                dateTime: event.endTime,
                timeZone: event.organizer.timeZone,
            },
            attendees: event.attendees.map(attendee => ({
                emailAddress: {
                    address: attendee.email,
                    name: attendee.name
                },
                type: "required"
            })),
            ...optional
        }
    };

    return {
        getAvailability: (dateFrom, dateTo) => {
            const payload = {
                schedules: [credential.key.email],
                startTime: {
                    dateTime: dateFrom,
                    timeZone: 'UTC',
                },
                endTime: {
                    dateTime: dateTo,
                    timeZone: 'UTC',
                },
                availabilityViewInterval: 60
            };

            return auth.getToken().then(
                (accessToken) => fetch('https://graph.microsoft.com/v1.0/me/calendar/getSchedule', {
                    method: 'post',
                    headers: {
                        'Authorization': 'Bearer ' + accessToken,
                        'Content-Type': 'application/json'
                    },
                    body: JSON.stringify(payload)
                })
                    .then(handleErrorsJson)
                    .then(responseBody => {
                        return responseBody.value[0].scheduleItems.map((evt) => ({
                            start: evt.start.dateTime + 'Z',
                            end: evt.end.dateTime + 'Z'
                        }))
                    })
            ).catch((err) => {
                console.log(err);
            });
        },
        createEvent: (event: CalendarEvent) => auth.getToken().then(accessToken => fetch('https://graph.microsoft.com/v1.0/me/calendar/events', {
            method: 'POST',
            headers: {
                'Authorization': 'Bearer ' + accessToken,
                'Content-Type': 'application/json',
            },
            body: JSON.stringify(translateEvent(event))
        }).then(handleErrorsJson).then((responseBody) => ({
            ...responseBody,
            disableConfirmationEmail: true,
        }))),
        deleteEvent: (uid: String) => auth.getToken().then(accessToken => fetch('https://graph.microsoft.com/v1.0/me/calendar/events/' + uid, {
            method: 'DELETE',
            headers: {
                'Authorization': 'Bearer ' + accessToken
            }
        }).then(handleErrorsRaw)),
        updateEvent: (uid: String, event: CalendarEvent) => auth.getToken().then(accessToken => fetch('https://graph.microsoft.com/v1.0/me/calendar/events/' + uid, {
            method: 'PATCH',
            headers: {
                'Authorization': 'Bearer ' + accessToken,
                'Content-Type': 'application/json'
            },
            body: JSON.stringify(translateEvent(event))
        }).then(handleErrorsRaw)),
    }
};

const GoogleCalendar = (credential): CalendarApiAdapter => {
    const myGoogleAuth = googleAuth();
    myGoogleAuth.setCredentials(credential.key);
    return {
        getAvailability: (dateFrom, dateTo) => new Promise((resolve, reject) => {
            const calendar = google.calendar({version: 'v3', auth: myGoogleAuth});
            calendar.calendarList
                .list()
                .then(cals => {
                    calendar.freebusy.query({
                        requestBody: {
                            timeMin: dateFrom,
                            timeMax: dateTo,
                            items: cals.data.items
                        }
                    }, (err, apires) => {
                        if (err) {
                            reject(err);
                        }
                        resolve(
                            Object.values(apires.data.calendars).flatMap(
                                (item) => item["busy"]
                            )
                        )
                    });
                })
                .catch((err) => {
                    reject(err);
                });

        }),
        createEvent: (event: CalendarEvent) => new Promise((resolve, reject) => {
            const payload = {
                summary: event.title,
                description: event.description,
                start: {
                    dateTime: event.startTime,
                    timeZone: event.organizer.timeZone,
                },
                end: {
                    dateTime: event.endTime,
                    timeZone: event.organizer.timeZone,
                },
                attendees: event.attendees,
                reminders: {
                    useDefault: false,
                    overrides: [
                        {'method': 'email', 'minutes': 60}
                    ],
                },
            };

            if (event.location) {
                payload['location'] = event.location;
            }

            const calendar = google.calendar({version: 'v3', auth: myGoogleAuth});
            calendar.events.insert({
                auth: myGoogleAuth,
                calendarId: 'primary',
                resource: payload,
            }, function (err, event) {
                if (err) {
                    console.log('There was an error contacting the Calendar service: ' + err);
                    return reject(err);
                }
                return resolve(event.data);
            });
        }),
        updateEvent: (uid: String, event: CalendarEvent) => new Promise((resolve, reject) => {
            const payload = {
                summary: event.title,
                description: event.description,
                start: {
                    dateTime: event.startTime,
                    timeZone: event.organizer.timeZone,
                },
                end: {
                    dateTime: event.endTime,
                    timeZone: event.organizer.timeZone,
                },
                attendees: event.attendees,
                reminders: {
                    useDefault: false,
                    overrides: [
                        {'method': 'email', 'minutes': 60}
                    ],
                },
            };

            if (event.location) {
                payload['location'] = event.location;
            }

            const calendar = google.calendar({version: 'v3', auth: myGoogleAuth});
            calendar.events.update({
                auth: myGoogleAuth,
                calendarId: 'primary',
                eventId: uid,
                sendNotifications: true,
                sendUpdates: 'all',
                resource: payload
            }, function (err, event) {
                if (err) {
                    console.log('There was an error contacting the Calendar service: ' + err);
                    return reject(err);
                }
                return resolve(event.data);
            });
        }),
        deleteEvent: (uid: String) => new Promise( (resolve, reject) => {
            const calendar = google.calendar({version: 'v3', auth: myGoogleAuth});
            calendar.events.delete({
                auth: myGoogleAuth,
                calendarId: 'primary',
                eventId: uid,
                sendNotifications: true,
                sendUpdates: 'all',
            }, function (err, event) {
                if (err) {
                    console.log('There was an error contacting the Calendar service: ' + err);
                    return reject(err);
                }
                return resolve(event.data);
            });
        })
    };
};

// factory
const calendars = (withCredentials): CalendarApiAdapter[] => withCredentials.map((cred) => {
    switch (cred.type) {
        case 'google_calendar':
            return GoogleCalendar(cred);
        case 'office365_calendar':
            return MicrosoftOffice365Calendar(cred);
        default:
            return; // unknown credential, could be legacy? In any case, ignore
    }
}).filter(Boolean);


const getBusyTimes = (withCredentials, dateFrom, dateTo) => Promise.all(
    calendars(withCredentials).map(c => c.getAvailability(dateFrom, dateTo))
).then(
    (results) => results.reduce((acc, availability) => acc.concat(availability), [])
);

const createEvent = (credential, calEvent: CalendarEvent): Promise<any> => {

    createNewEventEmail(
        calEvent,
    );

    if (credential) {
        return calendars([credential])[0].createEvent(calEvent);
    }

    return Promise.resolve({});
};

const updateEvent = (credential, uid: String, calEvent: CalendarEvent): Promise<any> => {
    if (credential) {
        return calendars([credential])[0].updateEvent(uid, calEvent);
    }

    return Promise.resolve({});
};

const deleteEvent = (credential, uid: String): Promise<any> => {
    if (credential) {
        return calendars([credential])[0].deleteEvent(uid);
    }

    return Promise.resolve({});
};

export {getBusyTimes, createEvent, updateEvent, deleteEvent, CalendarEvent};