function parsePage() {
    let entry = {
        url: window.location.href,
        title: "",
        publishedDate: ""
    };

    // fix the URL's of certain websites
    if (entry.url.startsWith('https://freedium.cfd/')) {    // extract original article link from freedium url
        entry.url = entry.url.replace('https://freedium.cfd/', '');
    }

    // if schema.org JSON-LD is present, read that data
    const jsonLDElem = document.querySelector('script[type="application/ld+json"]');
    if (jsonLDElem) {
        const jsonLDObj = JSON.parse(jsonLDElem.textContent);
        if (jsonLDObj['@type'] == 'NewsArticle') {
            entry.publishedDate = jsonLDObj.datePublished?.slice(0, 19) ?? "";
            entry.author = jsonLDObj.author?.name ?? ""
            entry.title = jsonLDObj.headline ?? ""
        }
    }

    return entry;
}

// thanks stack overflow: https://stackoverflow.com/questions/12413243/javascript-date-format-like-iso-but-local
function dateToISOLikeButLocal(date) {
    const offsetMs = date.getTimezoneOffset() * 60 * 1000;
    const msLocal =  date.getTime() - offsetMs;
    const dateLocal = new Date(msLocal);
    const iso = dateLocal.toISOString();
    const isoLocal = iso.slice(0, 19);
    return isoLocal;
}

function fillForm(entry) {
    const curDate = new Date();
    
    document.getElementById('url').value = entry.url;
    document.getElementById('title').value = entry.title ?? "";
    document.getElementById('author').value = entry.author ?? "";
    document.getElementById('publishedDate').value = entry.publishedDate ?? "";
    document.getElementById('accessedDate').value = dateToISOLikeButLocal(curDate);
}

function runContentScript(tabId) {
    chrome.scripting.executeScript({
    target: { tabId: tabId},
        func: parsePage,
    }).then((injectionResults) => {
        fillForm(injectionResults[0].result);
    });
}

function generateJSON(event) {
    event.preventDefault();

    const urlField = document.getElementById('url');
    const titleField = document.getElementById('title');
    const authorField = document.getElementById('author');
    const publishedDateField = document.getElementById('publishedDate');
    const accessedDateField = document.getElementById('accessedDate');
    const noteField = document.getElementById('note');

    const errorElem = document.getElementById('error');
    const JSONElem = document.getElementById('generated');

    // first, make sure all of our required fields are in place
    if ((urlField.value == null || urlField.value == "") ||
        (titleField.value == null || titleField.value == "") ||
        (accessedDateField.value == null || accessedDateField.value == "") ||
        (noteField.value == null || noteField.value == "")) {
            errorElem.textContent = "ERROR: Missing required field."
            return;
        }
    
    errorElem.textContent = ""
    JSONElem.value = `{
        "url": "${urlField.value}",
        "title": "${titleField.value}",
        "author": "${authorField.value}",
        "publishedDate": "${publishedDateField.value.replace('T', ' ')}",
        "accessedDate": "${accessedDateField.value.replace('T', ' ')}",
        "note": "${noteField.value}",\n},`
}

window.addEventListener('DOMContentLoaded', () => {
    chrome.tabs.query({
        active: true,
        currentWindow: true
    }, tabs => {
        runContentScript(tabs[0].id);
    });
    
    const form = document.getElementById('sharefeed')
    form.addEventListener('submit', generateJSON);
});