studio-umzu/themes/duckquill/static/search-elasticlunr.js

// Based on https://github.com/getzola/zola/blob/1ac1231de1e342bbaf4d7a51a8a9a40ea152e246/docs/static/search.js
function debounce(func, wait) {
	var timeout;

	return function () {
		var context = this;
		var args = arguments;
		clearTimeout(timeout);

		timeout = setTimeout(function () {
			timeout = null;
			func.apply(context, args);
		}, wait);
	};
}

// Taken from mdbook
// The strategy is as follows:
// First, assign a value to each word in the document:
//  Words that correspond to search terms (stemmer aware): 40
//  Normal words: 2
//  First word in a sentence: 8
// Then use a sliding window with a constant number of words and count the
// sum of the values of the words within the window. Then use the window that got the
// maximum sum. If there are multiple maximas, then get the last one.
// Enclose the terms in <b>.
function makeTeaser(body, terms) {
	var TERM_WEIGHT = 40;
	var NORMAL_WORD_WEIGHT = 2;
	var FIRST_WORD_WEIGHT = 8;
	var TEASER_MAX_WORDS = 30;

	var stemmedTerms = terms.map(function (w) {
		return elasticlunr.stemmer(w.toLowerCase());
	});
	var termFound = false;
	var index = 0;
	var weighted = []; // contains elements of ["word", weight, index_in_document]

	// split in sentences, then words
	var sentences = body.toLowerCase().split(". ");

	for (var i in sentences) {
		var words = sentences[i].split(" ");
		var value = FIRST_WORD_WEIGHT;

		for (var j in words) {
			var word = words[j];

			if (word.length > 0) {
				for (var k in stemmedTerms) {
					if (elasticlunr.stemmer(word).startsWith(stemmedTerms[k])) {
						value = TERM_WEIGHT;
						termFound = true;
					}
				}
				weighted.push([word, value, index]);
				value = NORMAL_WORD_WEIGHT;
			}

			index += word.length;
			index += 1;  // ' ' or '.' if last word in sentence
		}

		index += 1;  // because we split at a two-char boundary '. '
	}

	if (weighted.length === 0) {
		return body;
	}

	var windowWeights = [];
	var windowSize = Math.min(weighted.length, TEASER_MAX_WORDS);
	// We add a window with all the weights first
	var curSum = 0;
	for (var i = 0; i < windowSize; i++) {
		curSum += weighted[i][1];
	}
	windowWeights.push(curSum);

	for (var i = 0; i < weighted.length - windowSize; i++) {
		curSum -= weighted[i][1];
		curSum += weighted[i + windowSize][1];
		windowWeights.push(curSum);
	}

	// If we didn't find the term, just pick the first window
	var maxSumIndex = 0;
	if (termFound) {
		var maxFound = 0;
		// backwards
		for (var i = windowWeights.length - 1; i >= 0; i--) {
			if (windowWeights[i] > maxFound) {
				maxFound = windowWeights[i];
				maxSumIndex = i;
			}
		}
	}

	var teaser = [];
	var startIndex = weighted[maxSumIndex][2];
	for (var i = maxSumIndex; i < maxSumIndex + windowSize; i++) {
		var word = weighted[i];
		if (startIndex < word[2]) {
			// missing text from index to start of `word`
			teaser.push(body.substring(startIndex, word[2]));
			startIndex = word[2];
		}

		// add <strong> around search terms
		if (word[1] === TERM_WEIGHT) {
			teaser.push("<strong>");
		}
		startIndex = word[2] + word[0].length;
		teaser.push(body.substring(word[2], startIndex));

		if (word[1] === TERM_WEIGHT) {
			teaser.push("</strong>");
		}
	}
	teaser.push("…");
	return teaser.join("");
}

function formatSearchResultItem(item, terms) {
	return '<div class="item">'
		+ `<a href="${item.ref}">${item.doc.title}</a>`
		+ `<span>${makeTeaser(item.doc.body, terms)}</span>`
		+ '</div>';
}

function initSearch() {
	var searchBar = document.getElementById("search-bar");
	var searchContainer = document.getElementById("search-container");
	var searchResults = document.getElementById("search-results");
	var MAX_ITEMS = 10;

	var options = {
		bool: "AND",
		fields: {
			title: { boost: 2 },
			body: { boost: 1 },
		}
	};
	var currentTerm = "";
	var index;

	var initIndex = async function () {
		if (index === undefined) {
			let searchIndex = document.getElementById("search-index").textContent;
			index = fetch(searchIndex)
				.then(
					async function (response) {
						return await elasticlunr.Index.load(await response.json());
					}
				);
		}
		let res = await index;
		return res;
	}

	searchBar.addEventListener("keyup", debounce(async function () {
		var term = searchBar.value.trim();
		if (term === currentTerm) {
			return;
		}
		searchResults.style.display = term === "" ? "none" : "flex";
		searchResults.innerHTML = "";
		currentTerm = term;
		if (term === "") {
			return;
		}

		var results = (await initIndex()).search(term, options);
		if (results.length === 0) {
			searchResults.style.display = "none";
			return;
		}

		for (var i = 0; i < Math.min(results.length, MAX_ITEMS); i++) {
			searchResults.innerHTML += formatSearchResultItem(results[i], term.split(" "));
		}
	}, 150));

	document.addEventListener("keydown", function (event) {
		if (event.key === "/") {
			event.preventDefault();
			toggleSearch();
		}
	});

	document.getElementById("search-toggle").addEventListener("click", toggleSearch);
}

function toggleSearch() {
	var searchContainer = document.getElementById("search-container");
	var searchBar = document.getElementById("search-bar");
	searchContainer.classList.toggle("active");
	searchBar.toggleAttribute("disabled");
	searchBar.focus();
}

if (document.readyState === "complete" ||
	(document.readyState !== "loading" && !document.documentElement.doScroll)
) {
	initSearch();
} else {
	document.addEventListener("DOMContentLoaded", initSearch);
}