User:Remember the dot/Long edit summary.js

Code that you insert on this page could contain malicious content capable of compromising your account. If you import a script from another page with "importScript", "mw.loader.load", "iusc", or "lusc", take note that this causes you to dynamically load a remote script, which could be changed by others. Editors are responsible for all edits and actions they perform, including by scripts. User scripts are not centrally supported and may malfunction or become inoperable due to software changes. A guide to help you find broken scripts is available. If you are unsure whether code you are adding to this page is safe, you can ask at the appropriate village pump.
This code will be executed when previewing this page.

Documentation for this user script can be added at User:Remember the dot/Long edit summary.

Note: After saving, you have to bypass your browser's cache to see the changes. Google Chrome, Firefox, Microsoft Edge and Safari: Hold down the ⇧ Shift key and click the Reload toolbar button. For details and instructions about other browsers, see Wikipedia:Bypass your cache.

// LIMIT EDIT SUMMARIES TO EXACTLY 250 UTF-8 BYTES
// see EditPage::importFormData() in MediaWiki source for the source of the limit
// created by Ilmari Karonen and Remember_the_dot

addOnloadHook(function() {
    var wpSummary = document.getElementById("wpSummary")
    if (wpSummary) {
        var adjustMaxLength = function () {
            // subtract the number of UTF-8 continuation bytes (0x80-0xBF) from the maxlength
            var maxLength = 250 - encodeURI(wpSummary.value).split(/%[89AB]/i).length + 1
            wpSummary.maxLength = maxLength
            
            // the last character or group might've pushed us over; if so, inform the user
            var errorMessage = document.getElementById("editSummaryTooLong")
            if (wpSummary.value.length > maxLength) {
                if (!errorMessage) {
                    wpSummary.style.border = "3px solid red"
                    document.getElementById("wpSave").disabled = true
                    var editSummaryTooLong = document.createElement("div")
                    editSummaryTooLong.id = "editSummaryTooLong"
                    editSummaryTooLong.style.color = "red"
                    editSummaryTooLong.style.fontWeight = "bold"
                    editSummaryTooLong.appendChild(document.createTextNode("Your edit summary is too long."))
                    var wpMinoredit = document.getElementById("wpMinoredit")
                    wpMinoredit.parentNode.insertBefore(editSummaryTooLong, wpMinoredit)
                }
            } else {
                if (errorMessage) {
                    wpSummary.style.border = ""
                    document.getElementById("wpSave").disabled = false
                    errorMessage.parentNode.removeChild(errorMessage)
                }
            }
            oldValue = wpSummary.value
        }
        addHandler(wpSummary, "keyup", adjustMaxLength)
        addHandler(wpSummary, "change", adjustMaxLength)
        adjustMaxLength()
    }
})