// Create needed constants
const list = document.querySelector('ul');
const titleInput = document.querySelector('#title');
const dateInput = document.querySelector('#date');
const contentInput = document.querySelector('#content');
const form = document.querySelector('form');
const newBtn = document.querySelector('#newBtn');
// Create an instance of a db object for us to store the open database in
let db;
// Open our database; it is created if it doesn't already exist
// (see the upgradeneeded handler below)
const openRequest = window.indexedDB.open("notes_db", 1);
// error handler signifies that the database didn't open successfully
openRequest.addEventListener("error", () => console.error("Database failed to open"));
// Create a submit event handler so that when the form is submitted the addData() function is run
form.addEventListener("submit", addData);
// success handler signifies that the database opened successfully
openRequest.addEventListener("success", () => {
    console.log("Database opened successfully");
    // Store the opened database object in the db variable. 
    // This is used a lot below.
    db = openRequest.result;
    // Run the displayData() function to display the notes already in the IDB
    displayData();
});
// Finally for this section, we'll add probably the most important event 
// handler for setting up the database: upgradeneeded. This handler runs if the 
// database has not already been set up, or if the database is opened with a 
// bigger version number than the existing stored database (when performing an 
// upgrade). Add the following code, below your previous handler: 
// Set up the database tables if this has not already been done.
// Here we first grab a reference to the existing database from the result 
// property of the event's target (e.target.result), which is the request 
// object. This is equivalent to the line db = openRequest.result; inside the 
// success event handler, but we need to do this separately here because the 
// upgradeneeded event handler (if needed) will run before the success event 
// handler, meaning that the db value wouldn't be available if we didn't do 
// this.
openRequest.addEventListener("upgradeneeded", (e) => {
    // Grab a reference to the opened database
    db = e.target.result;
    // Create an objectStore in our database to store notes and an 
    // auto-incrementing key
    // An objectStore is similar to a 'table' in a relational database
    const objectStore = db.createObjectStore("notes_os", {
        keyPath: "id",
        autoIncrement: true,
    });
    // Define what data items the objectStore will contain
    objectStore.createIndex("title", "title", { unique: false });
    objectStore.createIndex("content", "content", { unique: false });
    objectStore.createIndex("date", "date", { unique: false });
    // Print the outcome of the setup
    console.log("Database setup completed.");
});
// Define the addData() function
function addData(e) {
    // prevent default - we don't want the form to submit in the conventional way
    e.preventDefault();
    // grab the values entered into the form fields and store them in an object ready for being inserted into the DB
    const newItem = {
        title: titleInput.value,
        content: contentInput.value,
        date: dateInput.value
    };
    // open a read/write db transaction, ready for adding the data,
    // name of the db: notes_os
    // IDBDatabase.transaction()
    const transaction = db.transaction(["notes_os"], "readwrite");
    // call an object store that's already been added to the database
    // IDBTransaction.objectStore()
    const objectStore = transaction.objectStore("notes_os");
    // Make a request to add our newItem object to the object store
    //  IDBObjectStore.add()
    const addRequest = objectStore.add(newItem);
    // If the transaction is successful
    addRequest.addEventListener("success", () => {
        // Clear the form, ready for adding the next entry
        titleInput.value = "";
        contentInput.value = "";
        dateInput.value = "";
    });
    // Report on the success of the transaction completing, when everything is done
    transaction.addEventListener("complete", () => {
        console.log("Transaction completed: database modification finished.");
        // update the display of data to show the newly added item, by running displayData() again.
        displayData();
    });
    // If there is error in the transaction
    transaction.addEventListener("error", () => console.log("Transaction not opened due to error"));
}
// Define the displayData() function
function displayData() {
    // Here we empty the contents of the list element each time the display is updated
    // If you didn't do this, you'd get duplicates listed each time a new note is added
    while (list.firstChild) {
        list.removeChild(list.firstChild);
    }
    // Open our object store and then get a cursor - which iterates through all the
    // different data items in the store
    const transaction = db.transaction("notes_os");
    const objectStore = transaction.objectStore("notes_os");
    // IDBObjectStore: openCursor(). Returns an IDBRequest object, and, in a 
    // separate thread, returns a new IDBCursorWithValue object. Used for 
    // iterating through an object store with a cursor. 
    objectStore.openCursor().addEventListener("success", (e) => {
        // Get a reference to the cursor
        const cursor = e.target.result;
        // If there is still another data item to iterate through, keep running this code,
        // In short:
        // if (cursor) {
        //     cursor.value contains the current record being iterated through
        //     this is where you'd do something with the result
        //     cursor.continue();
        //} 
        // else {
        //     no more results
        //}
        if (cursor) {
            // Create a list item, h3, and p to put each data item inside when displaying it
            // structure the HTML fragment, and append it inside the list
            const listItem = document.createElement("li");
            const h3 = document.createElement("h3");
            const para = document.createElement("p");
            listItem.appendChild(h3);
            listItem.appendChild(para);
            list.appendChild(listItem);
            // Put the data from the cursor inside the h3 and para
            h3.textContent = cursor.value.title;
            para.textContent = `${cursor.value.date}: ${cursor.value.content}`;
            // Store the ID of the data item inside an attribute on the listItem, so we know
            // which item it corresponds to. This will be useful later when we want to delete items
            listItem.setAttribute("data-note-id", cursor.value.id);
            // Create a button and place it inside each listItem
            const deleteBtn = document.createElement("button");
            listItem.appendChild(deleteBtn);
            deleteBtn.textContent = "Delete";
            // Set an event handler so that when the button is clicked, the deleteItem()
            // function is run
            deleteBtn.addEventListener("click", deleteItem);
            // Iterate to the next item in the cursor
            cursor.continue();
        }
        else {
            // Again, if list item is empty, display a 'No notes stored' message
            if (!list.firstChild) {
                const listItem = document.createElement("li");
                listItem.textContent = "No notes stored.";
                list.appendChild(listItem);
            }
            // if there are no more cursor items to iterate through, say so
            console.log("Notes all displayed");
        }
    });
}
// Define the deleteItem() function
function deleteItem(e) {
    // retrieve the name of the task we want to delete. We need
    // to convert it to a number before trying to use it with IDB; IDB key
    // values are type-sensitive.
    const ulNode = e.target.parentNode;
    // const noteId = Number(e.target.parentNode.getAttribute("data-note-id"));
    // We do however need to pass the attribute through the global built-in 
    // Number() object as it is of datatype string, and therefore wouldn't be 
    // recognized by the database, which expects a number.
    const noteId = Number(ulNode.getAttribute("data-note-id"));
    // open a database transaction and delete the task, finding it using the id we retrieved above
    const transaction = db.transaction(["notes_os"], "readwrite");
    const objectStore = transaction.objectStore("notes_os");
    const deleteRequest = objectStore.delete(noteId);
    // report that the data item has been deleted
    transaction.addEventListener("complete", () => {
        // delete the parent of the button
        // which is the list item, so it is no longer displayed
        //e.target.parentNode.parentNode.removeChild(e.target.parentNode);
        ulNode.parentNode.removeChild(ulNode);
        console.log(`Note ${noteId} deleted.`);
        // Again, if list item is empty, display a 'No notes stored' message
        if (!list.firstChild) {
            const listItem = document.createElement("li");
            listItem.textContent = "No notes stored.";
            list.appendChild(listItem);
        }
    });
}