import React, { useEffect, useRef, useState } from "react";
import { Box } from "@chakra-ui/react";
import { useRouter } from "next/router";
import {
  endOfMonth,
  getDate,
  getDay,
  getMonth,
  getYear,
  isAfter,
  isBefore,
  isSameMonth
} from "date-fns";
import findValidDateRange from "../../lib/findValidDateRange";
import ErrorPage from "next/error";
import Calender from "../../components/calender";
import { CalenderContextProvider } from "../../contexts/CalenderContext";
import { StickersContextProvider } from "../../contexts/StickerContext";

const DateRoute: React.FC<unknown> = () => {
  const router = useRouter();
  const { date: slug } = router.query;

  const [date, setDate] = useState<UpdateCalendarProps | null>(null);

  const [error, setError] = useState<boolean>(false);

  const dateRange = useRef(findValidDateRange());
  const validDateRange = Object.assign({}, dateRange.current);

  const validateDateInput = (dateArr: number[]): UpdateCalendarProps => {
    if (!(dateArr.length >= 2) && !(dateArr.length <= 3)) {
      return {
        year: 0,
        month: 0,
        day: 0
      };
    }

    const date = {
      year: 0,
      month: 0,
      day: 0
    };

    if (/^(19|20)\d{2}$/.test(`${dateArr[0]}`)) {
      date.year = dateArr[0];
    }

    if (dateArr[1] > 0 && dateArr[1] <= 12) {
      date.month = dateArr[1];
    }

    if (date.month && date.year) {
      const lastDay = getDay(
        endOfMonth(new Date(date.year, date.month - 1, 1))
      );
      if (dateArr[2] && dateArr[2] > 0 && dateArr[2] <= lastDay) {
        date.day = dateArr[2];
      } else if (!dateArr[2]) {
        date.day = 1;
      }
    } else {
      return date;
    }

    return date;
  };

  /**
   * ! This function does not work as is. It is causing infinite loops whe used within the useEffect.
   */
  const validateDateRange = (
    slugDate: Date
  ): [Date, "after" | "before" | "valid"] => {
    const { start: validStart, end: validEnd } = validDateRange;

    // Check if the slug date is beyond the valid end date.
    if (isAfter(slugDate, validEnd)) {
      // router.push("/calender/now");
      console.warn(
        "Slug date is after the valid date range for this calendar!!!"
      );
      return [validEnd, "after"];
      // Check if the slug is before the valid start date.
    } else if (isBefore(slugDate, validStart)) {
      console.warn(
        "Slug date is before the valid date range for this calendar!!!"
      );
      return [validStart, "before"];
      // router.push(`/${getYear(validStart)}/${getMonth(validStart) + 1}`);
    } else {
      console.info(
        "Slug date is within the valid date range for this calendar."
      );
      return [slugDate, "valid"];
    }
  };

  useEffect(() => {
    // Checking if the slug exists and is an array.
    if (slug && Array.isArray(slug)) {
      // Grabbing the slug length
      const length = slug.length;

      // Parsing the slug to convert it from strings to numbers.
      const parsedSlug = slug.map((e) => {
        return parseInt(e);
      });

      // Checking if the slug is not "now" when the length is 1.
      // ! Update this to include a check for "today".
      if (length === 1 && slug[0] !== "now") {
        setError(true);
        return console.warn("improper date input:", slug);
      }

      // Checking if the slug has 2 to 3 numbers within the array. year/month/day.
      if (length >= 2 && slug.length <= 3) {
        // Validate that the date is valid.
        const newDate = validateDateInput(parsedSlug);

        // If anything is invalid the year/day/month would be set to 0. This checks for the invalid condition.
        if (newDate.year === 0 || newDate.month === 0 || newDate.day === 0) {
          setError(true);
          // Set the date to the valid date.
        } else {
          // TODO: Make sure the date is within the valid range using the validateDateRange function.
          const validDate = new Date(
            newDate.year,
            newDate.month - 1,
            newDate.day
          );

          const validDateWithinRange = validateDateRange(validDate)[0];

          setDate({
            ...{
              year: getYear(validDateWithinRange),
              month: getMonth(validDateWithinRange) + 1,
              day: getDate(validDateWithinRange)
            }
          });
        }
      }
    }
  }, [slug]);

  useEffect(() => {
    // Check is slug and date are valid.
    if (slug && date && date !== null) {
      // Check if the slug is an array and has a length of 2.
      if (Array.isArray(slug) && slug.length === 2) {
        const dateState = new Date(date.year, date.month - 1, date.day);

        const parsedSlug = slug.map((e) => {
          return parseInt(e);
        });
        const slugDate = new Date(parsedSlug[0], parsedSlug[1] - 1, 1);

        if (!isSameMonth(dateState, slugDate)) {
          const validDateWithinRange = validateDateRange(dateState);

          if (validDateRange[1] === "after") {
            router.push("/now");
          } else {
            router.push(
              `/${getYear(validDateWithinRange[0])}/${getMonth(
                validDateWithinRange[0]
              )}`
            );
          }
        }
      }
    }
  }, [date]);

  if (router.isFallback) {
    return <ErrorPage statusCode={404} />;
  }

  /**
   * TODO: Update to disallow navigation in the future and too far in the past.
   * Update so that a date given in the future take the user to /now to today's date.
   * Update so that a date given beyond the last valid date will bring the user to the
   * last month that has stickers within it (When filter is enabled) or to the creation date of the chart..
   */

  return error ? (
    <ErrorPage statusCode={404} />
  ) : (
    <Box textAlign="center" w="100%" h="auto" pt="50px" pb="10vh">
      <CalenderContextProvider>
        <StickersContextProvider>
          <Calender {...date} />
        </StickersContextProvider>
      </CalenderContextProvider>
    </Box>
  );
};

export default DateRoute;
