2chen overlay rotator

// ==UserScript==
// @name         2chen overlay rotator
// @namespace    https://2chen.moe/
// @version      1.1
// @description  Rotate mouse-over'd images and videos
// @author       Anonymous (You)
// @match        https://2chen.moe/*
// @grant        none
// ==/UserScript==

let rotateCW = ["ControlLeft", "AltLeft"]
let rotateCCW = ["AltLeft", "ControlLeft"]

var idxCW = 0
var idxCCW = 0

function getOverlayElement() {
    let overlay = document.getElementById("hover-overlay")
    let img = overlay.getElementsByTagName("img")[0]
    let vid = overlay.getElementsByTagName("video")[0]
    if (vid != null) return vid
    else if(img != null) return img
    else return null
}

function currentRotation(transform) {
    let rot = transform.match(/rotateZ\((-?\d+)deg\)/)
    if (rot != null) return parseInt(rot[1])
    else return 0
}

function rotate(deg) {
    console.log("ROT "+deg)
    let elem = getOverlayElement()
    if (elem != null) {
        let tf = elem.style.transform
        let tfNoRot = tf.replace(/ ?rotateZ\(-?\d+deg\)/, "")
        let rot = (currentRotation(tf) + deg) % 360
        elem.style.transform = tfNoRot + " rotateZ(" + rot + "deg)"
        if (rot % 180 == 0) {
            elem.style.width = "100vw"
            elem.style.height = "100vh"
        } else {
            elem.style.width = "100vh"
            elem.style.height = "100vw"
        }
    }
}

document.addEventListener("keydown", (event) => {
    if(event.code == rotateCW[idxCW]) {
        idxCW++
        if(idxCW == rotateCW.length) {
            rotate(90)
        }
    }
    if(event.code == rotateCCW[idxCCW]) {
        idxCCW++
        if(idxCCW == rotateCCW.length) {
            rotate(-90)
        }
    }
});

// keyup should reset shortcut input, but also allow repeated presses of the last key in the shortcut to trigger the rotation again
document.addEventListener("keyup", (event) => {
    if (event.code == rotateCW[rotateCW.length - 1]) idxCW--
    else idxCW = 0
    if (event.code == rotateCCW[rotateCCW.length - 1]) idxCCW--
    else idxCCW = 0
});