var user = 0;
var selectedMessage = 0;
var selectedItem = null;
var coreUrl = "https://cmsc106.net/mail/";
var activeMessage = 0;
var activeRecipients = [];

function receiveUser(data) {
    user = data.userid;
    loadHandles();
    document.getElementById('login_div').style.display='none';
    document.getElementById('main_div').style.display='';
}

function doLogin() {
    var url = coreUrl + "user?user="+document.getElementById('user_field').value+"&password="+document.getElementById('password_field').value;
    document.getElementById('login_error').textContent = '';
    fetch(url).then(function(response) {
        if (!response.ok) {
            throw new Error("HTTP error: " + response.status);
        }
        return response.json();
    }).then(receiveUser)
      .catch(function(error) {
          document.getElementById('login_error').textContent =
              'Login failed. Please check your user name and password.';
      });
}

function doCreateAccount() {
    var url = coreUrl + "user";
    var account = {name: document.getElementById('user_field').value,
                   password: document.getElementById('password_field').value};
    var toSend = JSON.stringify(account);
    document.getElementById('login_error').textContent = '';
    fetch(url, {
      method: 'POST',
      body: toSend,
      headers: {'Content-Type':'application/json'}
    }).then(function(response) {
        if (!response.ok) {
            throw new Error("HTTP error: " + response.status);
        }
        return response.json();
    }).then(receiveUser)
      .catch(function(error) {
          document.getElementById('login_error').textContent =
              'Could not create account. Please try again.';
      });
}

function setSelection() {    
    if(selectedItem)
        selectedItem.classList.remove('active');
    selectedItem = this;
    this.classList.add('active');
    selectedMessage = this.getAttribute('data-message');
}

function receiveHandles(data) {
    var handlesList = document.getElementById('handles');
    handlesList.replaceChildren();
    var handle;
    for(handle of data) {
        var newEntry = document.createElement('li');
        newEntry.setAttribute('class','list-group-item');
        newEntry.textContent = handle.sender + ":" + handle.subject;
        newEntry.setAttribute('data-message',handle.messageId);
        newEntry.addEventListener('click', setSelection);
        handlesList.appendChild(newEntry);
    }
}

function loadHandles() {
    var url = coreUrl + "handles?receiver="+user;
    fetch(url).then(function(response){return response.json();}).then(receiveHandles);
}

function formatSentDate(timestamp) {
    var datePart = timestamp.split(/[T ]/)[0];
    var parts = datePart.split('-');
    var months = ['January','February','March','April','May','June',
                  'July','August','September','October','November','December'];
    return months[parseInt(parts[1],10) - 1] + " " +
           parseInt(parts[2],10) + ", " + parts[0];
}

function receiveMessage(data) {
    document.getElementById('main_div').style.display='none';
    document.getElementById('sender_area').textContent = data.sender;
    document.getElementById('sent_area').textContent = formatSentDate(data.sent);
    document.getElementById('body_area').value = data.body;
    document.getElementById('read_div').style.display='';
}

function doRead() {
    var url = coreUrl + "message/"+selectedMessage;
    fetch(url).then(function(response){return response.json();}).then(receiveMessage);
}

function doCompose() {
    document.getElementById('main_div').style.display='none';
    document.getElementById('content_area').value = '';
    document.getElementById('subject_field').value = '';
    document.getElementById('recipients_field').value = '';
    document.getElementById('compose_div').style.display='';
}

function closeRead() {
    document.getElementById('read_div').style.display='none';
    loadHandles();
    document.getElementById('main_div').style.display='';
}

function deleteMessage() {
    var url = coreUrl + "recipient/"+user+"/message/" + selectedMessage;
    fetch(url, {method:'DELETE'}).then(closeRead);
}

function sendOneRecipient(data) {
    if(activeRecipients.length > 0) {
        var recipient = activeRecipients[0];
        activeRecipients.splice(0,1);
        var url = coreUrl + "recipient";
        var recipientObj = {message:activeMessage,
                       recipient:recipient};
        var toSend = JSON.stringify(recipientObj);
        fetch(url, {
          method: 'POST',
          body: toSend,
          headers: {'Content-Type':'application/json'}
        }).then(sendOneRecipient);
    } else
        closeCompose();
}

function sendRecipients(data) {
    activeMessage = data.messageId;
    activeRecipients = document.getElementById('recipients_field').value.split(',');
    sendOneRecipient();
}

function sendMessage() {
    var url = coreUrl + "message";
    var message = {subject:document.getElementById('subject_field').value,
                   body:document.getElementById('content_area').value,
                   sender:user};
    var toSend = JSON.stringify(message);
    fetch(url, {
      method: 'POST',
      body: toSend,
      headers: {'Content-Type':'application/json'}
    }).then(function(response){return response.json();}).then(sendRecipients);
}

function closeCompose() {
    document.getElementById('compose_div').style.display='none';
    loadHandles();
    document.getElementById('main_div').style.display='';
}

function setup() {
    document.getElementById('main_div').style.display='none';
    document.getElementById('read_div').style.display='none';
    document.getElementById('compose_div').style.display='none';

    document.getElementById('login_button').addEventListener('click',doLogin);
    document.getElementById('new_account_button').addEventListener('click',doCreateAccount);
    document.getElementById('read_button').addEventListener('click',doRead);
    document.getElementById('compose_button').addEventListener('click',doCompose);
    document.getElementById('close_button').addEventListener('click',closeRead);
    document.getElementById('delete_button').addEventListener('click',deleteMessage);
    document.getElementById('send_button').addEventListener('click',sendMessage);
    document.getElementById('cancel_button').addEventListener('click',closeCompose);
}

window.addEventListener('load',setup,false)