import type { NextApiRequest, NextApiResponse } from "next";
import prisma from "@lib/prisma";
import { EventType, User } from "@prisma/client";
import { CalendarEvent, getBusyCalendarTimes } from "@lib/calendarClient";
import { v5 as uuidv5 } from "uuid";
import short from "short-uuid";
import { getBusyVideoTimes } from "@lib/videoClient";
import EventAttendeeMail from "../../../lib/emails/EventAttendeeMail";
import { getEventName } from "@lib/event";
import dayjs from "dayjs";
import logger from "../../../lib/logger";
import EventManager, { CreateUpdateResult, EventResult } from "@lib/events/EventManager";

import utc from "dayjs/plugin/utc";
import timezone from "dayjs/plugin/timezone";
import isBetween from "dayjs/plugin/isBetween";
import dayjsBusinessDays from "dayjs-business-days";
import { Exception } from "handlebars";
import EventOrganizerRequestMail from "@lib/emails/EventOrganizerRequestMail";

dayjs.extend(dayjsBusinessDays);
dayjs.extend(utc);
dayjs.extend(isBetween);
dayjs.extend(timezone);

const translator = short();
const log = logger.getChildLogger({ prefix: ["[api] book:user"] });

function isAvailable(busyTimes, time, length) {
  // Check for conflicts
  let t = true;

  if (Array.isArray(busyTimes) && busyTimes.length > 0) {
    busyTimes.forEach((busyTime) => {
      const startTime = dayjs(busyTime.start);
      const endTime = dayjs(busyTime.end);

      // Check if time is between start and end times
      if (dayjs(time).isBetween(startTime, endTime, null, "[)")) {
        t = false;
      }

      // Check if slot end time is between start and end time
      if (dayjs(time).add(length, "minutes").isBetween(startTime, endTime)) {
        t = false;
      }

      // Check if startTime is between slot
      if (startTime.isBetween(dayjs(time), dayjs(time).add(length, "minutes"))) {
        t = false;
      }
    });
  }

  return t;
}

function isOutOfBounds(
  time: dayjs.ConfigType,
  { periodType, periodDays, periodCountCalendarDays, periodStartDate, periodEndDate, timeZone }
): boolean {
  const date = dayjs(time);

  switch (periodType) {
    case "rolling": {
      const periodRollingEndDay = periodCountCalendarDays
        ? dayjs().tz(timeZone).add(periodDays, "days").endOf("day")
        : dayjs().tz(timeZone).businessDaysAdd(periodDays, "days").endOf("day");
      return date.endOf("day").isAfter(periodRollingEndDay);
    }

    case "range": {
      const periodRangeStartDay = dayjs(periodStartDate).tz(timeZone).endOf("day");
      const periodRangeEndDay = dayjs(periodEndDate).tz(timeZone).endOf("day");
      return date.endOf("day").isBefore(periodRangeStartDay) || date.endOf("day").isAfter(periodRangeEndDay);
    }

    case "unlimited":
    default:
      return false;
  }
}

export async function handleLegacyConfirmationMail(
  results: Array<EventResult>,
  eventType: EventType,
  evt: CalendarEvent,
  hashUID: string
): Promise<{ error: Exception; message: string | null }> {
  if (results.length === 0 && !eventType.requiresConfirmation) {
    // Legacy as well, as soon as we have a separate email integration class. Just used
    // to send an email even if there is no integration at all.
    try {
      const mail = new EventAttendeeMail(evt, hashUID);
      await mail.sendEmail();
    } catch (e) {
      return { error: e, message: "Booking failed" };
    }
  }
  return null;
}

export default async function handler(req: NextApiRequest, res: NextApiResponse): Promise<void> {
  const { user } = req.query;
  log.debug(`Booking ${user} started`);

  try {
    const isTimeInPast = (time) => {
      return dayjs(time).isBefore(new Date(), "day");
    };

    if (isTimeInPast(req.body.start)) {
      const error = {
        errorCode: "BookingDateInPast",
        message: "Attempting to create a meeting in the past.",
      };

      log.error(`Booking ${user} failed`, error);
      return res.status(400).json(error);
    }

    let currentUser: User = await prisma.user.findFirst({
      where: {
        username: user,
      },
      select: {
        id: true,
        credentials: true,
        timeZone: true,
        email: true,
        name: true,
      },
    });

    const selectedCalendars = await prisma.selectedCalendar.findMany({
      where: {
        userId: currentUser.id,
      },
    });

    const hasCalendarIntegrations =
      currentUser.credentials.filter((cred) => cred.type.endsWith("_calendar")).length > 0;
    const hasVideoIntegrations =
      currentUser.credentials.filter((cred) => cred.type.endsWith("_video")).length > 0;

    const calendarAvailability = await getBusyCalendarTimes(
      currentUser.credentials,
      dayjs(req.body.start).startOf("day").utc().format("YYYY-MM-DDTHH:mm:ss[Z]"),
      dayjs(req.body.end).endOf("day").utc().format("YYYY-MM-DDTHH:mm:ss[Z]"),
      selectedCalendars
    );
    const videoAvailability = await getBusyVideoTimes(currentUser.credentials);
    let commonAvailability = [];

    if (hasCalendarIntegrations && hasVideoIntegrations) {
      commonAvailability = calendarAvailability.filter((availability) =>
        videoAvailability.includes(availability)
      );
    } else if (hasVideoIntegrations) {
      commonAvailability = videoAvailability;
    } else if (hasCalendarIntegrations) {
      commonAvailability = calendarAvailability;
    }

    // Now, get the newly stored credentials (new refresh token for example).
    currentUser = await prisma.user.findFirst({
      where: {
        username: user,
      },
      select: {
        id: true,
        credentials: true,
        timeZone: true,
        email: true,
        name: true,
      },
    });

    // Initialize EventManager with credentials
    const eventManager = new EventManager(currentUser.credentials);
    const rescheduleUid = req.body.rescheduleUid;

    const eventType: EventType = await prisma.eventType.findFirst({
      where: {
        userId: currentUser.id,
        id: req.body.eventTypeId,
      },
      select: {
        id: true,
        eventName: true,
        title: true,
        length: true,
        periodType: true,
        periodDays: true,
        periodStartDate: true,
        periodEndDate: true,
        periodCountCalendarDays: true,
        requiresConfirmation: true,
      },
    });

    const invitee = [{ email: req.body.email, name: req.body.name, timeZone: req.body.timeZone }];
    const guests = req.body.guests.map((guest) => {
      const g = {
        email: guest,
        name: "",
        timeZone: req.body.timeZone,
      };
      return g;
    });
    const attendeesList = [...invitee, ...guests];

    const evt: CalendarEvent = {
      type: eventType.title,
      title: getEventName(req.body.name, eventType.title, eventType.eventName),
      description: req.body.notes,
      startTime: req.body.start,
      endTime: req.body.end,
      organizer: { email: currentUser.email, name: currentUser.name, timeZone: currentUser.timeZone },
      attendees: attendeesList,
      location: req.body.location, // Will be processed by the EventManager later.
    };

    let isAvailableToBeBooked = true;

    try {
      isAvailableToBeBooked = isAvailable(commonAvailability, req.body.start, eventType.length);
    } catch {
      log.debug({
        message: "Unable set isAvailableToBeBooked. Using true. ",
      });
    }

    if (!isAvailableToBeBooked) {
      const error = {
        errorCode: "BookingUserUnAvailable",
        message: `${currentUser.name} is unavailable at this time.`,
      };

      log.debug(`Booking ${user} failed`, error);
      return res.status(400).json(error);
    }

    let timeOutOfBounds = false;

    try {
      timeOutOfBounds = isOutOfBounds(req.body.start, {
        periodType: eventType.periodType,
        periodDays: eventType.periodDays,
        periodEndDate: eventType.periodEndDate,
        periodStartDate: eventType.periodStartDate,
        periodCountCalendarDays: eventType.periodCountCalendarDays,
        timeZone: currentUser.timeZone,
      });
    } catch {
      log.debug({
        message: "Unable set timeOutOfBounds. Using false. ",
      });
    }

    if (timeOutOfBounds) {
      const error = {
        errorCode: "BookingUserUnAvailable",
        message: `${currentUser.name} is unavailable at this time.`,
      };

      log.debug(`Booking ${user} failed`, error);
      return res.status(400).json(error);
    }

    let results: Array<EventResult> = [];
    let referencesToCreate = [];

    if (rescheduleUid) {
      // Use EventManager to conditionally use all needed integrations.
      const updateResults: CreateUpdateResult = await eventManager.update(evt, rescheduleUid);

      if (results.length > 0 && results.every((res) => !res.success)) {
        const error = {
          errorCode: "BookingReschedulingMeetingFailed",
          message: "Booking Rescheduling failed",
        };

        log.error(`Booking ${user} failed`, error, results);
        return res.status(500).json(error);
      }

      // Forward results
      results = updateResults.results;
      referencesToCreate = updateResults.referencesToCreate;
    } else if (!eventType.requiresConfirmation) {
      // Use EventManager to conditionally use all needed integrations.
      const createResults: CreateUpdateResult = await eventManager.create(evt);

      if (results.length > 0 && results.every((res) => !res.success)) {
        const error = {
          errorCode: "BookingCreatingMeetingFailed",
          message: "Booking failed",
        };

        log.error(`Booking ${user} failed`, error, results);
        return res.status(500).json(error);
      }

      // Forward results
      results = createResults.results;
      referencesToCreate = createResults.referencesToCreate;
    }

    const hashUID =
      results.length > 0 ? results[0].uid : translator.fromUUID(uuidv5(JSON.stringify(evt), uuidv5.URL));
    // TODO Should just be set to the true case as soon as we have a "bare email" integration class.
    // UID generation should happen in the integration itself, not here.
    const legacyMailError = await handleLegacyConfirmationMail(results, eventType, evt, hashUID);
    if (legacyMailError) {
      log.error("Sending legacy event mail failed", legacyMailError.error);
      log.error(`Booking ${user} failed`);
      res.status(500).json({ message: legacyMailError.message });
      return;
    }

    try {
      await prisma.booking.create({
        data: {
          uid: hashUID,
          userId: currentUser.id,
          references: {
            create: referencesToCreate,
          },
          eventTypeId: eventType.id,
          title: evt.title,
          description: evt.description,
          startTime: evt.startTime,
          endTime: evt.endTime,
          attendees: {
            create: evt.attendees,
          },
          confirmed: !eventType.requiresConfirmation,
          location: evt.location,
        },
      });
    } catch (e) {
      log.error(`Booking ${user} failed`, "Error when saving booking to db", e);
      res.status(500).json({ message: "Booking already exists" });
      return;
    }

    if (eventType.requiresConfirmation) {
      await new EventOrganizerRequestMail(evt, hashUID).sendEmail();
    }

    log.debug(`Booking ${user} completed`);
    return res.status(204).json({ message: "Booking completed" });
  } catch (reason) {
    log.error(`Booking ${user} failed`, reason);
    return res.status(500).json({ message: "Booking failed for some unknown reason" });
  }
}