Example Photoshop code.

#target photoshop

// Ensure a document is open
if (app.documents.length === 0) {
    alert("No document is open. Please open a document and try again.");
    throw new Error("No document open");
}

var doc = app.activeDocument;

// Step 1: Create a new layer
var newLayer = doc.artLayers.add();
newLayer.name = "Example";

// Step 2: Get current dimensions in pixels
var originalWidth = doc.width.as('px');
var originalHeight = doc.height.as('px');

// Function to resize the document
function resizeDocument() {
    var newWidth, newHeight;

    if (originalWidth > 1024 || originalHeight > 1024) {
        if (originalWidth === originalHeight) {
            // Square image
            newWidth = 1024;
            newHeight = 1024;
        } else {
            // Non-square image
            if (originalWidth > originalHeight) {
                newWidth = 1024;
                newHeight = Math.round((originalHeight / originalWidth) * 1024);
            } else {
                newHeight = 1024;
                newWidth = Math.round((originalWidth / originalHeight) * 1024);
            }
        }

        // Resize the image
        doc.resizeImage(UnitValue(newWidth, "px"), UnitValue(newHeight, "px"), null, ResampleMethod.BICUBIC);
    } else {
        // Image is already within the desired size
        return false;
    }
    return true;
}

// Step 3: Resize if necessary
var resized = resizeDocument();

// Step 4: Save the document
function saveDocument() {
    var saveFile;
    var newName;

    if (doc.saved) {
        // The document has been saved before
        try {
            var originalPath = doc.path;
            var originalName = doc.name;

            // Extract name and extension
            var dotIndex = originalName.lastIndexOf(".");
            if (dotIndex === -1) {
                alert("The document does not have an extension. Cannot determine file type.");
                throw new Error("No file extension");
            }

            var nameWithoutExt = originalName.substring(0, dotIndex);
            var extension = originalName.substring(dotIndex);

            // Create new filename with "_edit" appended
            newName = nameWithoutExt + "_edit" + extension;
            saveFile = File(originalPath + "/" + newName);
        } catch (e) {
            alert("Error accessing the document's path. Please choose a save location manually.\n\nError: " + e.message);
            saveFile = File.saveDialog("Choose a location to save the edited image", "All Files:*.*");
            if (saveFile === null) {
                alert("Save operation cancelled.");
                throw new Error("Save cancelled");
            }

            // Append "_edit" to the filename
            var selectedName = saveFile.name;
            var dotIndex = selectedName.lastIndexOf(".");
            if (dotIndex === -1) {
                // No extension; append "_edit"
                newName = selectedName + "_edit";
                saveFile = new File(saveFile.path + "/" + newName);
            } else {
                var nameWithoutExt = selectedName.substring(0, dotIndex);
                var extension = selectedName.substring(dotIndex);
                newName = nameWithoutExt + "_edit" + extension;
                saveFile = new File(saveFile.path + "/" + newName);
            }
        }
    } else {
        // The document has not been saved before; prompt user to choose save location
        saveFile = File.saveDialog("Choose a location to save the edited image", "All Files:*.*");
        if (saveFile === null) {
            alert("Save operation cancelled.");
            throw new Error("Save cancelled");
        }

        // Append "_edit" to the filename
        var selectedName = saveFile.name;
        var dotIndex = selectedName.lastIndexOf(".");
        if (dotIndex === -1) {
            // No extension; append "_edit"
            newName = selectedName + "_edit";
            saveFile = new File(saveFile.path + "/" + newName);
        } else {
            var nameWithoutExt = selectedName.substring(0, dotIndex);
            var extension = selectedName.substring(dotIndex);
            newName = nameWithoutExt + "_edit" + extension;
            saveFile = new File(saveFile.path + "/" + newName);
        }
    }

    // Determine the save format based on extension
    var extension = newName.split('.').pop().toLowerCase();
    var saveOptions;

    switch (extension) {
        case 'jpg':
        case 'jpeg':
            saveOptions = new JPEGSaveOptions();
            saveOptions.quality = 12;
            break;
        case 'png':
            saveOptions = new PNGSaveOptions();
            break;
        case 'tif':
        case 'tiff':
            saveOptions = new TiffSaveOptions();
            break;
        case 'psd':
            saveOptions = new PhotoshopSaveOptions();
            break;
        default:
            alert("Unsupported file format. Saving as PNG.");
            saveOptions = new PNGSaveOptions();
            // Ensure the file has a .png extension
            if (!newName.toLowerCase().endsWith('.png')) {
                saveFile = new File(saveFile.path + "/" + newName + ".png");
            }
    }

    // Save the document
    try {
        doc.saveAs(saveFile, saveOptions, true, Extension.LOWERCASE);
        alert("Image saved successfully as:\n" + saveFile.fsName);
    } catch (e) {
        alert("Failed to save the image. Error: " + e.message);
    }
}

saveDocument();

alert("Script completed successfully.");