// Submitting the moment a reader meant, rather than the words they typed.
//
// A `datetime-local` box asks for a time the way a person says one -- "the 14th
// at half past two" -- and that names a different moment in Denver than it does
// in Berlin. A route storing an instant needs the moment, and nothing in HTML
// converts one to the other: the box submits the characters. So somebody
// converts, and in this renderer that is here.
//
// It is here rather than above the renderer because the browser is the only
// party that knows what "your computer's time zone" means. A description cannot
// answer it; a server can only guess; a terminal and an egui host would each
// answer it their own way. `makeover_layout::Field::as_instant` is the
// description saying it wants the conversion and declining to say how, and this
// file is the how for one host.
//
// It reads one attribute the form renderer writes, `data-instant`, and it is
// the whole of the per-app publish-at plumbing this stack exists to delete. The
// MNW server carried its own copy under a private `data-config` vocabulary.
(() => {
    "use strict";

    // The mark makeover-webview puts on a datetime input whose description
    // asked for an instant. Only that kind is marked: a date and a time are
    // each half a moment and cannot name one on their own.
    const MARK = "data-instant";

    /**
     * The absolute instant a local wall-clock string names, as RFC 3339.
     *
     * `new Date(v)` reads a bare `YYYY-MM-DDTHH:mm` in the browser's own zone,
     * which is exactly the reading wanted. A value the browser cannot parse is
     * left alone rather than replaced with `Invalid Date`: an unparseable value
     * is a validation failure the route should see and answer, and rewriting it
     * here would turn a legible error into an unreadable one.
     */
    const instant = (local) => {
        const at = new Date(local);
        return Number.isNaN(at.getTime()) ? null : at.toISOString();
    };

    // Rewrite on the way out, on the request htmx is about to make, so nothing
    // the reader can see changes: the box keeps showing the time they typed and
    // the wire carries the moment it names.
    //
    // The walk is over the submitting element's own marked inputs rather than
    // over the document, so a page with two forms on it converts the one being
    // submitted. `htmx:config:request` is htmx 4's name; 2.x spelled it
    // `htmx:configRequest`.
    document.body.addEventListener("htmx:config:request", (event) => {
        const source = event.detail?.ctx?.sourceElement;
        const body = event.detail?.ctx?.request?.body;
        if (!source?.querySelectorAll || !body) return;

        const marked =
            source.matches?.(`[${MARK}]`) === true
                ? [source]
                : source.querySelectorAll(`[${MARK}]`);
        for (const input of marked) {
            const name = input.getAttribute("name");
            if (!name) continue;
            const local = body.get(name);
            if (typeof local !== "string" || !local) continue;
            const moment = instant(local);
            if (moment !== null) body.set(name, moment);
        }
    });
})();