window.addEventListener("beforeunload", function() {
    let id = getSessionStorageItem("sessionStorageTabId");

    if (getLocalStorageItem('leadTab') === id) {
        electNewLead();
    } else {
        removeTab(id);
    }

    // Chrome requires returnValue to be set
    e.returnValue = '';
});

function initializeTab() {
    if (!getSessionStorageItem('sessionStorageTabId')) {
        setSessionStorageItem('sessionStorageTabId', Math.random().toString())
    }

    return getSessionStorageItem("sessionStorageTabId");
}

function registerTab(currentTabId) {
    console.log("Registering tab with ID:", currentTabId);

    const leadTabID = getLocalStorageItem('leadTab');
    if (leadTabID) {
        if (leadTabID !== currentTabId) {
            console.log("Assigning tab ID: ", currentTabId, "as excess tab.");
            assignAsExcessTab(currentTabId);
            return;
        } else {
            console.log("This tab is already a leader.");
            return;
        }
    }

    console.log("Assigning this (current) tab with ID: ", currentTabId, "as a leader");
    assignAsLeader(currentTabId);
    return;
}

function electNewLead() {
    let existingTabs = JSON.parse(getLocalStorageItem('excessTabs'));

    if (existingTabs && existingTabs[0]) {
        assignAsLeader(existingTabs[0]);
        removeTab(existingTabs[0]);
    }
}

function removeTab(tabId) {
    let existingTabs = JSON.parse(getLocalStorageItem('excessTabs'));

    if (existingTabs) {
        existingTabs = existingTabs.filter(excessTabId => excessTabId !== tabId);
        setLocalStorageItem('excessTabs', JSON.stringify(existingTabs))
    }
}

function assignAsLeader(tabId) {
    setLocalStorageItem('leadTab', tabId);
}

function assignAsExcessTab(tabId) {
    const excessTabs = getLocalStorageItem('excessTabs');
    if(excessTabs) {
        let existingTabs = JSON.parse(excessTabs);

        existingTabs.push(tabId);
        setLocalStorageItem('excessTabs', JSON.stringify(existingTabs));
        console.log("Tab with ID: ", tabId, "was successfully added to the excess tabs list.");
        return;
    } else {
        setLocalStorageItem('excessTabs', JSON.stringify([tabId]));
        console.log("This tab is the first excess tab.");
        return;
    }
}

function getSessionStorageItem(key) {
    return window.sessionStorage.getItem(key);
}

function setSessionStorageItem(key, value) {
    return window.sessionStorage.setItem(key, value);
}

function getLocalStorageItem(key) {
    return window.localStorage.getItem(key);
}

function setLocalStorageItem(key, value) {
    return window.localStorage.setItem(key, value);
}

function removeLocalStorageItem(key) {
    return window.localStorage.removeItem(key);
}

registerTab(initializeTab());