import type { Course } from '@shared/types/Course';
import type { Distribution, LetterGrade } from '@shared/types/Distribution';
import { extendedColors } from '@shared/types/ThemeColors';
import Link from '@views/components/common/Link';
import Text from '@views/components/common/Text/Text';
import {
    NoDataError,
    queryAggregateDistribution,
    querySemesterDistribution,
} from '@views/lib/database/queryDistribution';
import Highcharts from 'highcharts';
import HighchartsReact from 'highcharts-react-official';
import type { ChangeEvent } from 'react';
import React, { useEffect, useMemo, useRef, useState } from 'react';
import Skeleton from 'react-loading-skeleton';

const UT_GRADE_DISTRIBUTION_URL = 'https://reports.utexas.edu/spotlight-data/ut-course-grade-distributions';

interface GradeDistributionProps {
    course: Course;
}

const DataStatus = {
    LOADING: 'LOADING',
    FOUND: 'FOUND',
    NOT_FOUND: 'NOT_FOUND',
    ERROR: 'ERROR',
} as const satisfies Record<string, string>;

type DataStatusType = (typeof DataStatus)[keyof typeof DataStatus];

const GRADE_COLORS = {
    A: extendedColors.gradeDistribution.a,
    'A-': extendedColors.gradeDistribution.aminus,
    'B+': extendedColors.gradeDistribution.bplus,
    B: extendedColors.gradeDistribution.b,
    'B-': extendedColors.gradeDistribution.bminus,
    'C+': extendedColors.gradeDistribution.cplus,
    C: extendedColors.gradeDistribution.c,
    'C-': extendedColors.gradeDistribution.cminus,
    'D+': extendedColors.gradeDistribution.dplus,
    D: extendedColors.gradeDistribution.d,
    'D-': extendedColors.gradeDistribution.dminus,
    F: extendedColors.gradeDistribution.f,
    Other: extendedColors.gradeDistribution.other,
} as const satisfies Record<LetterGrade, string>;

/**
 * Renders the grade distribution chart for a specific course.
 *
 * @param course - The course for which to display the grade distribution.
 * @returns The grade distribution chart component.
 */
export default function GradeDistribution({ course }: GradeDistributionProps): JSX.Element {
    const [semester, setSemester] = useState('Aggregate');
    type Distributions = Record<string, { data: Distribution; instructorIncluded: boolean }>;
    const [distributions, setDistributions] = useState<Distributions>({});
    const [status, setStatus] = useState<DataStatusType>(DataStatus.LOADING);
    const ref = useRef<HighchartsReact.RefObject>(null);

    const chartData = useMemo(() => {
        if (status === DataStatus.FOUND && distributions[semester]) {
            return Object.entries(distributions[semester]!.data).map(([grade, count]) => ({
                y: count,
                color: GRADE_COLORS[grade as LetterGrade],
            }));
        }
        return Array(13).fill(0);
    }, [distributions, semester, status]);

    useEffect(() => {
        const fetchInitialData = async () => {
            try {
                const [aggregateDist, semesters, instructorIncludedAggregate] =
                    await queryAggregateDistribution(course);
                const initialDistributions: Distributions = {
                    Aggregate: { data: aggregateDist, instructorIncluded: instructorIncludedAggregate },
                };
                const semesterPromises = semesters.map(semester => querySemesterDistribution(course, semester));
                const semesterDistributions = await Promise.allSettled(semesterPromises);
                semesters.forEach((semester, i) => {
                    const distributionResult = semesterDistributions[i];

                    if (!distributionResult) {
                        throw new Error('Distribution result is undefined');
                    }

                    if (distributionResult.status === 'fulfilled') {
                        const [distribution, instructorIncluded] = distributionResult.value;
                        initialDistributions[`${semester.season} ${semester.year}`] = {
                            data: distribution,
                            instructorIncluded,
                        };
                    }
                });
                setDistributions(initialDistributions);
                setStatus(DataStatus.FOUND);
            } catch (e) {
                console.error(e);
                if (e instanceof NoDataError) {
                    setStatus(DataStatus.NOT_FOUND);
                } else {
                    setStatus(DataStatus.ERROR);
                }
            }
        };

        fetchInitialData();
    }, [course]);

    const handleSelectSemester = (event: ChangeEvent<HTMLSelectElement>) => {
        setSemester(event.target.value);
    };

    const chartOptions: Highcharts.Options = {
        title: { text: undefined },
        subtitle: { text: undefined },
        legend: { enabled: false },
        xAxis: {
            labels: {
                y: 20,
                style: {
                    fontSize: '0.6875rem',
                    fontWeight: '500',
                    letterSpacing: '0',
                    lineHeight: 'normal',
                    fontStyle: 'normal',
                },
            },
            title: {
                text: 'Grades',
                style: {
                    color: '#333F48',
                    fontSize: '0.80rem',
                    fontWeight: '400',
                },
            },
            categories: ['A', 'A-', 'B+', 'B', 'B-', 'C+', 'C', 'C-', 'D+', 'D', 'D-', 'F', 'Other'],
            tickInterval: 1,
            tickWidth: 1,
            tickLength: 10,
            tickColor: '#9CADB7',
            crosshair: { color: `${extendedColors.theme.offwhite}50` },
            lineColor: '#9CADB7',
        },
        yAxis: {
            labels: {
                style: {
                    fontSize: '0.80rem',
                    fontWeight: '400',
                    color: '#333F48',
                    lineHeight: '100%',
                    fontStyle: 'normal',
                },
            },
            min: 0,
            title: {
                text: 'Students',
                style: {
                    color: '#333F48',
                    fontSize: '0.80rem',
                    fontWeight: '400',
                },
            },
        },
        chart: {
            style: { fontFamily: 'Roboto Flex, Roboto Flex Local', fontWeight: '600' },
            spacingBottom: 25,
            spacingTop: 25,
            spacingLeft: 1.5,
            height: 250,
        },
        credits: { enabled: false },
        accessibility: { enabled: true },
        tooltip: {
            headerFormat: '<span style="display:block; font-weight:700;">{point.key}</span>',
            pointFormat: '<span style="display:block; font-weight:500;">{point.y:.0f} Students</span>',
            shared: true,
            useHTML: true,
            style: {
                color: 'var(--Other-Colors-UTRP-Black, #1A2024)',
                textAlign: 'center',
                fontFamily: 'Roboto Flex, Roboto Flex Local',
                fontSize: '0.88875rem',
                lineHeight: 'normal',
            },
            backgroundColor: 'white',
            borderRadius: 4,
            shadow: {
                offsetX: 0,
                offsetY: 1,
                color: 'rgba(51, 63, 72, 0.30)',
            },
        },
        plotOptions: {
            bar: { pointPadding: 0.2, borderWidth: 0 },
            series: { animation: { duration: 700 } },
        },
        series: [
            {
                type: 'column',
                name: 'Grades',
                data: chartData,
            },
        ],
    };

    return (
        <div className='pt-3'>
            {status === DataStatus.LOADING && <Skeleton height={300} />}
            {status === DataStatus.NOT_FOUND && (
                <HighchartsReact
                    ref={ref}
                    highcharts={Highcharts}
                    options={{
                        ...chartOptions,
                        title: {
                            text: `There is currently no grade distribution data for ${course.department} ${course.getNumberWithoutTerm()}`,
                        },
                        tooltip: { enabled: false },
                    }}
                />
            )}
            {status === DataStatus.ERROR && <Text variant='p'>Error fetching grade distribution data</Text>}
            {status === DataStatus.FOUND && (
                <>
                    <div className='flex flex-wrap content-center items-center self-stretch justify-center gap-3'>
                        <Text variant='small' className='text-ut-black'>
                            Grade Distribution for{' '}
                            <Text variant='small' className='font-extrabold!' as='strong'>
                                {course.department} {course.getNumberWithoutTerm()}
                            </Text>
                        </Text>
                        <select
                            className='border border rounded border-solid px-3 py-2'
                            onChange={handleSelectSemester}
                        >
                            {Object.keys(distributions)
                                .sort((k1, k2) => {
                                    if (k1 === 'Aggregate') {
                                        return -1;
                                    }
                                    if (k2 === 'Aggregate') {
                                        return 1;
                                    }

                                    const [season1, year1] = k1.split(' ');
                                    const [, year2] = k2.split(' ');

                                    if (year1 !== year2) {
                                        return parseInt(year2 as string, 10) - parseInt(year1 as string, 10);
                                    }

                                    return season1 === 'Fall' ? -1 : 1;
                                })
                                .map(semester => (
                                    <option key={semester} value={semester}>
                                        {semester}
                                    </option>
                                ))}
                        </select>
                        <Link variant='small' href={UT_GRADE_DISTRIBUTION_URL} className='link'>
                            Data Source
                        </Link>
                    </div>
                    {distributions[semester] && !distributions[semester]!.instructorIncluded && (
                        <div className='mt-3 flex flex-wrap content-center items-center self-stretch justify-center gap-3 text-center'>
                            <Text variant='small' className='text-theme-red'>
                                We couldn&apos;t find {semester !== 'Aggregate' && ` ${semester}`} grades for this
                                instructor, so here are the grades for all {course.department}{' '}
                                {course.getNumberWithoutTerm()} sections.
                            </Text>
                        </div>
                    )}
                    <HighchartsReact ref={ref} highcharts={Highcharts} options={chartOptions} />
                </>
            )}
        </div>
    );
}