Useful algorithms for Photopea plugin development

addImageAndWait.js

// uses Photopea.js
var addImageAndWait = async function(contentWindow, imgURI) {
    return new Promise(async function(resolve) {
        var layerCountOld = "done";
        while (layerCountOld == "done") layerCountOld = (await Photopea.runScript(contentWindow, `app.echoToOE(app.activeDocument.layers.length)`))[0];
        var layerCountNew = layerCountOld;
        await Photopea.runScript(contentWindow, `app.open("${imgURI}", null, true);`);
        var layerCheckInterval = async function () {
            layerCountNew = (await Photopea.runScript(contentWindow, `app.echoToOE(app.activeDocument.layers.length)`))[0];
            if (layerCountNew == layerCountOld + 1) {
                resolve();
                return;
            }
            else setTimeout(layerCheckInterval, 50);
        };
        layerCheckInterval();
    });
};

getDocumentAsImage.js

// uses Photopea.js
var getDocumentAsImage = async function(contentWindow) {
    // returns Image object containing image data from Photopea document
    return new Promise(async function(resolve) {
        Photopea.runScript(contentWindow, "app.activeDocument.saveToOE('png')").then(function(data) {
            var buffer = data[0];
            var fR = new FileReader();
            fR.addEventListener("load", function(e) {
                let img = new Image();
                img.src = e.target.result;
                resolve(img);
            });
            fR.readAsDataURL(new Blob([buffer], { type: "image/png" }));
        });
    });
};