// ==UserScript==
// @name        Canvas Grade Calculator
// @description Calculate grade totals for Canvas courses that have it disabled.
// @namespace   https://github.com/uncenter/canvas-grade-calculator
// @match       https://*.instructure.com/courses/*/grades
// @grant       none
// @homepageURL https://github.com/uncenter/canvas-grade-calculator
// @version     0.2.2
// @author      uncenter
// @license     MIT
// @downloadURL none
// ==/UserScript==

function calculate() {
	if (!document.querySelector('.ic-app-main-content')) {
		console.error('Not on Canvas!');
		return;
	}

	if (!document.querySelector('#grade-summary-content')) {
		console.error('Not on grades page!');
		return;
	}

	const weights = {};

	for (const element of document.querySelectorAll(
		'[aria-label="Assignment Weights"] > table tbody > tr'
	)) {
		const group = element.querySelector('th').textContent;
		if (group === 'Total') continue;
		const weight =
			Number.parseFloat(element.querySelector('td').textContent.slice(0, 2)) /
			100;
		weights[group] = weight;
	}

	const assignments = [];

	for (const element of document.querySelectorAll(
		'#grades_summary tr.assignment_graded.student_assignment'
	)) {
		let earned, available, title, group;

		const a = element.querySelector('th.title');
		title = a.querySelector('a').textContent;
		group = a.querySelector('div.context').textContent;
		const grades = element.querySelector(
			'td.assignment_score > div > span.tooltip > span.grade'
		);

		earned = Number.parseFloat(
			[...grades.childNodes]
				.find(
					(node) =>
						node.nodeType === Node.TEXT_NODE && node.textContent.trim() !== ''
				)
				?.textContent.trim()
		);
		if (typeof earned !== 'number' || Number.isNaN(earned)) continue;

		available = Number.parseFloat(
			grades.nextElementSibling.textContent.replace('/', '').trim()
		);

		assignments.push({ earned, available, title, group });
	}

	if (assignments.length === 0) {
		console.warn('No graded assignments found!');
		return;
	}

	/* eslint-disable unicorn/prevent-abbreviations, unicorn/no-array-reduce */
	const totalsPerGroup = assignments.reduce(
		(acc, { group, earned, available }) => {
			acc[group] = acc[group] || { totalEarned: 0, totalAvailable: 0 };
			acc[group].totalEarned += earned;
			acc[group].totalAvailable += available;
			return acc;
		},
		{}
	);
	/* eslint-enable */

	const weightedPerGroup = {};
	for (const category in totalsPerGroup) {
		const { totalEarned, totalAvailable } = totalsPerGroup[category];
		weightedPerGroup[category] =
			(totalEarned / totalAvailable) * 100 || undefined;
	}

	let grade = 0;
	if (Object.entries(weights).length === 0) {
		console.log('Categories are not weighted.');
		const scores = Object.values(weightedPerGroup).filter(
			(x) => x !== undefined
		);
		grade = scores.reduce((total, score) => total + score, 0) / scores.length;
	} else {
		for (const category in weightedPerGroup) {
			grade += weightedPerGroup[category] * weights[category];
		}
	}

	console.log(
		`${grade.toFixed(2)}% across ${assignments.length} graded assignments.`
	);

	(
		document.querySelector('#student-grades-final') ||
		document.querySelector('.student_assignment.final_grade')
	).outerHTML = `<div class="student_assignment final_grade">Total: <span class="grade">${grade.toFixed(
		2
	)}%</span></div>`;
}

if (document.querySelector('#student-grades-final')) {
	const observer = new MutationObserver(calculate);

	observer.observe(document.querySelector('#grades_summary'), {
		childList: true,
		subtree: true,
	});

	calculate();
}