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

    // 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') {  // medium, etc.
            entry.publishedDate = jsonLDObj.datePublished.slice(0, 19);
            entry.author = jsonLDObj.author.name ?? jsonLDObj.author[0].name;
            entry.title = jsonLDObj.headline;
        }
        if (jsonLDObj['@type'] == 'VideoObject') {  // youtube, etc.
            entry.url = jsonLDObj['@id'];   // url fix
            entry.publishedDate = jsonLDObj.uploadDate.slice(0, 19);
            entry.author = jsonLDObj.author;
            entry.title = jsonLDObj.name;
        }
    }

    // youtube specific data section
    const youtubeMetaElem = document.getElementById('watch7-content');
    if (youtubeMetaElem) {
        // url fix
        entry.url = document.querySelector('link[itemprop="url"]').getAttribute('href');
        entry.title = document.querySelector('meta[itemprop="name"]').getAttribute('content');
        entry.author = document.querySelector('span[itemprop="author"] link[itemprop="name"]').getAttribute('content');
        entry.publishedDate = document.querySelector('meta[itemprop="datePublished"]').getAttribute('content').slice(0, 19);
    }

    // github scraping
    const githubIdentElem = document.getElementById('repository-container-header');
    if (githubIdentElem) {
        githubRepoName = document.querySelector('strong[itemprop="name"] a').textContent;
        githubRepoDesc = document.querySelector('div#responsive-meta-container div p').textContent;

        entry.title = githubRepoName + ' - ' + githubRepoDesc.slice(9, -6);
        entry.author = document.querySelector('a[rel="author"]').textContent.slice(9);
    }

    // forgejo meta elements
    const forgejoIdentElem = document.querySelector('meta[name="keywords"]');
    if (forgejoIdentElem && forgejoIdentElem.content.includes('forgejo')) {
        entry.title = document.querySelector('meta[name="description"]').content;
        entry.author = document.querySelector('meta[name="author"]').content;
    }

    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');

    const fixedNote = noteField.value.replace('"', '\\"');

    // 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": "${accessedDateField.value.replace('T', ' ')}",
        "note": "${fixedNote}"\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);
});