function startApp(){
    $('#linkLogout').hide();
    const baseUsersUrl = "https://baas.kinvey.com/user/kid_B1gXZK3DZ";
    const baseAppDataUrl = "https://baas.kinvey.com/appdata/kid_B1gXZK3DZ";
    setGreeting();
    const app_key = 'kid_B1gXZK3DZ';
    const app_secret = '39a1afe1eba3447aba5349547c3e8532';
    let btnRegister = $('#viewRegister input[value="Register"]');
    let btnLogin = $('#viewLogin input[value="Login"]');
    let btnCreateBook = $('#viewCreateBook input[value="Create"]');
    let btnEditBook = $('#viewEditBook input[value="Edit"]');
    btnRegister.on('click', register);
    btnLogin.on('click', logIn);
    btnCreateBook.on('click', createBook);
    btnEditBook('click', editBook);
    $('#linkListBooks').on('click', ()=>{
        hideSections();
        $('#viewBooks').show();
    });
    addEventClick('Home');
    addEventClick('Login');
    addEventClick('Register');
    addEventClick('CreateBook');
    $('#linkLogout').on('click',logOut);
    function logIn(e){
        e.preventDefault();
        let password = $('#viewLogin input[name="passwd"]');
        let username = $('#viewLogin input[name="username"]');
        let obj = {
            url:baseUsersUrl+"/login",
            method:"POST",
            headers:{
                "Authorization":`Basic ${btoa(app_key +":" +app_secret)}:`,
                "Content-Type":'application/json',
            },
            data:JSON.stringify({
                username:username.val(),
                password:password.val(),
            }),
            success:function(res){
                setUsernameAndAuth(res);
                infoBoxShow('Successfully logged in');
                showView("Books");
                $('#linkLogout').show('slow');
                $('#linkLogin').hide()
                $('#linkRegister').hide();
            },
            error:function(err){
                errorBoxShow(err.statusText)
            }
        };

        $.ajax(obj);
        password.val('');
        username.val('');
    }
    function register(e){
        e.preventDefault();
        let password = $('#viewRegister input[name="passwd"]');
        let passRep = $('#viewRegister input[name="passwdRep"]');
        let username = $('#viewRegister input[name="username"]');
        if(password.val()!==passRep.val()){
            errorBoxShow("Passwords do not match");
        }
        else {
            let obj = {
                url:baseUsersUrl,
                method:"POST",
                headers:{
                    "Authorization":`Basic ${btoa(app_key +":" +app_secret)}:`,
                    "Content-Type":'application/json',
                },
                data:JSON.stringify({
                    username:username.val(),
                    password:password.val(),
                    books:""
                }),
                success:function(res){
                    setUsernameAndAuth(res);
                    infoBoxShow('Success')
                },
                error:function(err){
                    errorBoxShow(err.statusText)
                }
            }
            $.ajax(obj)
        }
        password.val('');
        passRep.val('');
        username.val('');
    }
    function logOut(){
        let obj = {
            url:baseUsersUrl+"/_logout",
            method:"POST",
            headers:{
                "Authorization":`Kinvey ${sessionStorage.getItem("authtoken")}`,
                "X-Kinvey-Api-Version":'1',
            },
            success:function(){
                hideSections();
                $('#loggedInUser').text("");
                sessionStorage.clear();
                $('#linkLogout').hide();
                $('#linkLogin').show('slow');
                $('#linkRegister').show();
                showView('Home');
                setGreeting();
                infoBoxShow('Successfully logged out')
            },
            error:function(err){
                errorBoxShow(err.statusText)
            }
        }
        $.ajax(obj)
    }
    function addEventClick(btn){
        $('#link'+btn).on('click', ()=>{
            hideSections();
            showView(btn);
        });
    }
    function showView(btn){
        hideSections();
        $('#view'+btn).show();
    }
    function hideSections(){
        $('section').hide();
    }
    function loadingBoxShow(msg){
        let loadingBox = $('#loadingBox');
        loadingBox.text(msg);
        loadingBox.show('slow');
        setTimeout(()=>{loadingBox.hide()}, 3000)
    }
    function infoBoxShow(msg){
        let infoBox = $('#infoBox');
        infoBox.text(msg);
        infoBox.show('slow');
        setTimeout(()=>{infoBox.hide()}, 3000)
    }
    function errorBoxShow(msg){
        let errorBox = $('#errorBox');
        errorBox.text(msg);
        errorBox.show('slow');
        setTimeout(()=>{errorBox.fadeOut()}, 3000)
    }
    function setUsernameAndAuth(res){
        console.log(res)
        sessionStorage
            .setItem('authtoken', res._kmd.authtoken);
        sessionStorage
            .setItem('username', res.username);
        sessionStorage
            .setItem('id', res._id);
        setGreeting();
    }
    function setGreeting(){
        if(sessionStorage.getItem("username")){
            $('#viewBooks tr').has("td").remove();
            console.log($('#viewBooks table'));
            listBooks();
            $('#loggedInUser').text("Greetings, " + sessionStorage.getItem("username"));
            $('#linkLogout').show();
            $('#linkLogin').hide();
            $('#linkListBooks').show();
            $('#linkCreateBook').show();
        }
        else{
            let firstChild = $('#viewBooks tr:has(td)').first();
            console.log(firstChild);
            $('#linkListBooks').hide();
            $('#linkCreateBook').hide();
        }
    }
    function listBooks(){
        console.log(sessionStorage.getItem("authtoken"));
            let obj = {
                url:baseAppDataUrl+ "/books",
                method:"GET",
                headers:{
                    "Authorization":`Kinvey ${sessionStorage.getItem("authtoken")}`,
                },
                success:loadBooks,
                error:(err)=>{
                    errorBoxShow(err.statusText)
                }
            };
            $.ajax(obj);
        function loadBooks(data){
            console.log(data)
            for (let obj of data) {
                let lastTd = $('<td>');
                if(sessionStorage.getItem('id') == obj._acl.creator){
                    let aEdit = $('<a href="#">[Edit]</a>');
                    let aDelete = $('<a href="#">[Delete]</a>');
                    aDelete.on('click',null, obj, deletePost);
                    aEdit.on('click',null, obj, editPost);
                    lastTd.append(aEdit)
                        .append(aDelete)
                }

                $('#books table')
                    .append($("<tr>")
                        .append($(`<td>${obj.name}</td>>`))
                        .append($(`<td>${obj.author}</td>>`))
                        .append($(`<td>${obj.description}</td>>`))
                        .append(lastTd))
            }
        }
    }

    function deletePost(e){
        let postId = e.data._id;
        let anchor = $(this);
        let obj = {
            url:`https://baas.kinvey.com/appdata/kid_B1gXZK3DZ/books/${postId}`,
            method:"DELETE",
            headers:{
                "Authorization":`Kinvey ${sessionStorage.getItem("authtoken")}`
            },
            success: function(){
                console.log(anchor.parent().parent());
                anchor.parent().parent().remove();
                infoBoxShow('Deleted successfully')
            },
            error:function(err){
                errorBoxShow(err.statusText);
            }
        };
        $.ajax(obj);
    }
    function editPost(e){
        let postId = e.data._id;
        let anchor = $(this);
        hideSections();

    }
    function createBook(e){
        e.preventDefault();
        let title = $('#viewCreateBook input[name="title"]');
        let author = $('#viewCreateBook input[name="author"]');
        let description = $('#viewCreateBook textarea[name="description"]');
        let obj = {
            url:baseAppDataUrl+ "/books",
            method:"POST",
            headers:{
                "Authorization":`Kinvey ${sessionStorage.getItem("authtoken")}`,
                "Content-Type":"application/json"
            },
            data:JSON.stringify({
                name:title.val(),
                author:author.val(),
                description:description.val()
            }),
            success:(data) => {
                console.log(title.val());
                $('#books table')
                    .append($("<tr>")
                        .append($(`<td>${title.val()}</td>>`))
                        .append($(`<td>${author.val()}</td>>`))
                        .append($(`<td>${description.val()}</td>>`))
                        .append($('<td>')
                            .append($('<a href="#">[Edit]</a>'))
                            .append($('<a href="#">[Delete]</a>'))));
                infoBoxShow("You; successfully uploaded the book")
            },
            error:(err)=>{
                errorBoxShow(err.statusText)
            }
        };
        $.ajax(obj);
        title.val('');
        author.val('');
        description.val('');
    }
}