(function () {
    "use strict";

    /**
     * Suggest a completion as a user types
     *
     * Use `data-autocomplete="<completions set identifier>"`on the input field.
     * specifying the trie to be used for autocomplete
     *
     * @example
     * <input
     *     type="input"
     *     data-autocomplete="mimetype"
     * >
     * @param  {Event} event
     * @return {undefined}
     */
    function autocomplete(event) {
        const input = event.target;

        // Get suggestions
        let suggestions = getSuggestions(input.value, mimetypeTrie);

        const boxId = input.getAttribute("list");

        // Create suggestion box, if needed
        let suggestionsBox = document.getElementById(boxId);

        // Clear existing suggestions
        suggestionsBox.innerHTML = "";

        // Populate suggestions box
        suggestions.forEach((suggestion) => {
            const suggestionItem = document.createElement("option");

            suggestionItem.textContent = suggestion;
            suggestionsBox.appendChild(suggestionItem);
        });
    }

    function getSuggestions(input, trie) {
        // Follow the trie through the provided input
        input.split("").forEach((letter) => {
            trie = trie[letter];

            if (!trie) {
                return;
            }
        });

        if (!trie) {
            return [];
        }

        return searchTrie(trie);
    }

    function searchTrie(trie) {
        const options = Object.values(trie);

        if (typeof trie == "string") {
            return [trie];
        }

        return options
            .map((option) => {
                const newTrie = option;

                if (typeof newTrie == "string") {
                    return [newTrie];
                }

                return searchTrie(newTrie);
            })
            .reduce((prev, next) => prev.concat(next));
    }

    document.querySelectorAll("[data-autocomplete]").forEach((input) => {
        input.addEventListener("input", autocomplete);
    });
})();

const mimetypeTrie = {
    a: {
        a: {
            c: "AAC",
        },
        z: {
            w: "AZW",
        },
    },
    d: "Daisy",
    e: "ePub",
    f: "FLAC",
    h: "HTML",
    m: {
        4: {
            a: "M4A",
            b: "M4B",
        },
        o: "MOBI",
        p: "MP3",
    },
    o: "OGG",
    p: {
        d: {
            f: "PDF",
        },
        l: "Plaintext",
    },
};