Script to integrate local LLM for proofreading

Slowly getting there... my script does send highlighted text over the api now, and processes the corrected text. I have two issues left, any help would be greatly appreciated:

1. the returned text always replaces the whole paragraph instead of the highlighted text, and 

2. Sometimes I get a weird error from this snippet:

alert("Failed to parse JSON response: " + e.toString()); 

The error message is "reference error: ) has no value". Is that maybe related to the charset, i.e. is my llm returning unsupported characters?

Here's my updated code, I'll truncate/delete my post from above, as it's not relevant anymore:

var doc, postData, postRequest, conn, response, bodyStart, body, jsonResponse, correctedText;

// Make variables for the active document and the current text selection.
doc = app.ActiveDoc;

if (doc.ObjectValid() == true) {
    var textRange = doc.TextSelection; // TextRange object
    var highlightedText = getText(textRange, doc); // Use the getText function to get the highlighted text

    if (highlightedText !== "") {
        // Prepare your JSON payload using the highlighted text
        postData = JSON.stringify({
            "messages": [
                {
                    "role": "user",
                    "content": "You are a precise and accurate proof reader. You only ever give the corrected text, but no further explanation! Correct the following text: " + highlightedText
                }
            ]
        });

        // Create the POST request
        postRequest = "POST /v1/chat/completions HTTP/1.1\r\n" +
            "Host: localhost:1234\r\n" +
            "Content-Type: application/json; charset=utf-8\r\n" + // Specify UTF-8 charset
            "Content-Length: " + postData.length + "\r\n" +
            "\r\n" +
            postData;

        conn = new Socket;
        // Attempt to open our socket connection
        if (conn.open("localhost:1234", "binary")) {
            conn.write(postRequest);

            // Response reading
            response = conn.read(999999); // Adjust as necessary
            conn.close();

            // Parsing
            bodyStart = response.indexOf("\r\n\r\n") + 4;
            body = response.substring(bodyStart);

            // Assuming JSON response
            try {
                jsonResponse = JSON.parse(decodeURIComponent(escape(body))); // Decode the response body
                correctedText = jsonResponse.choices[0].message.content; // Adjust based on actual JSON field
                alert("Corrected Text:\n\n" + correctedText);

                // Start replacing the text as per the example provided
                // First, select the text to be replaced
                textRange.beg.obj = textRange.end.obj = textRange.beg.obj; // Assuming the text range is within a single paragraph/object
                textRange.beg.offset = 0;
                textRange.end.offset = Constants.FV_OBJ_END_OFFSET;
                doc.TextSelection = textRange;
                textRange = doc.TextSelection;
                textRange.end.offset--;
                doc.TextSelection = textRange;

                // Clear the selected text
                doc.Clear(0);

                // Insert the corrected text
                doc.AddText(textRange.beg, correctedText);

            } catch (e) {
                alert("Failed to parse JSON response: " + e.toString());
            }
        } else {
            alert("Failed to open a connection to the API.");
        }
    } else {
        alert("No text is highlighted or selected. Please highlight the text you want to correct.");
    }
} else {
    alert("No active document found. Cannot continue.");
}

alert("Script complete!");