// Utility: Save and load credentials
function saveCredentials(username, password) {
  localStorage.setItem('username', username);
  localStorage.setItem('password', password);
}
function getCredentials() {
  return {
    username: localStorage.getItem('username'),
    password: localStorage.getItem('password')
  };
}
function clearCredentials() {
  localStorage.removeItem('username');
  localStorage.removeItem('password');
}
function logout() {
  clearCredentials();
  window.location.href = 'login.html';
}

// Registration
if (document.getElementById('registerForm')) {
  document.getElementById('registerForm').onsubmit = async function(e) {
    e.preventDefault();
    const username = document.getElementById('registerUsername').value;
    const password = document.getElementById('registerPassword').value;
    const res = await fetch('http://localhost:8080/users', {
      method: 'POST',
      headers: { 'Content-Type': 'application/json' },
      body: JSON.stringify({ username, password })
    });
    if (res.ok) {
      saveCredentials(username, password);
      window.location.href = 'inbox.html';
    } else {
      const err = await res.text();
      document.getElementById('registerError').innerText = err;
    }
  };
}

// Login
if (document.getElementById('loginForm')) {
  document.getElementById('loginForm').onsubmit = async function(e) {
    e.preventDefault();
    const username = document.getElementById('loginUsername').value;
    const password = document.getElementById('loginPassword').value;
    // Try to fetch mailbox to verify credentials
    const res = await fetch(`http://localhost:8080/mailbox?user=${encodeURIComponent(username)}`, {
      headers: { 'Authorization': 'Basic ' + btoa(username + ':' + password) }
    });
    if (res.ok) {
      saveCredentials(username, password);
      window.location.href = 'inbox.html';
    } else {
      document.getElementById('loginError').innerText = 'Invalid username or password.';
    }
  };
}

// Inbox
if (document.getElementById('email-list')) {
  const { username, password } = getCredentials();
  if (!username || !password) {
    window.location.href = 'login.html';
  } else {
    fetch(`http://localhost:8080/mailbox?user=${encodeURIComponent(username)}`, {
      headers: { 'Authorization': 'Basic ' + btoa(username + ':' + password) }
    })
      .then(res => res.json())
      .then(emails => {
        if (!Array.isArray(emails)) throw new Error('Invalid mailbox response');
        let userDomain = null;
        for (const email of emails) {
          if (email.to === username && email.domain) {
            userDomain = email.domain;
            break;
          }
          if (email.from === username && email.domain) {
            userDomain = email.domain;
            break;
          }
        }
        const userFull = userDomain ? `${username}!${userDomain}` : username;
        const inboxEmails = emails.filter(email => {
          if (!email.to) return false;
          const toFull = email.domain ? `${email.to}!${email.domain}` : email.to;
          return toFull === userFull;
        });
        const sentEmails = emails.filter(email => {
          if (!email.from) return false;
          const fromFull = email.domain ? `${email.from}!${email.domain}` : email.from;
          return fromFull === userFull;
        });
        let currentFolder = 'inbox';
        let selectedEmail = null;
        function renderList() {
          const list = currentFolder === 'inbox' ? inboxEmails : sentEmails;
          let html = `<div class="email-list-section"><div class="email-list-title">${currentFolder === 'inbox' ? 'Inbox' : 'Sent'}</div>`;
          if (list.length === 0) {
            html += '<p>No emails.</p>';
          } else {
            html += list.map((email, idx) => {
              const display = currentFolder === 'inbox'
                ? (email.domain ? `${email.from}!${email.domain}` : email.from)
                : (email.domain ? `${email.to}!${email.domain}` : email.to);
              const fromto = currentFolder === 'inbox' ? `From: ${display}` : `To: ${display}`;
              return `<div class="email-list-item${selectedEmail === idx ? ' selected' : ''}" data-idx="${idx}">
                <div class="subject">${email.subject}</div>
                <div class="fromto">${fromto}</div>
              </div>`;
            }).join('');
          }
          html += '</div>';
          document.getElementById('email-list').innerHTML = html;
          // Add click listeners
          document.querySelectorAll('.email-list-item').forEach(item => {
            item.onclick = function() {
              selectedEmail = parseInt(this.getAttribute('data-idx'));
              renderList();
              renderDetail();
            };
          });
        }
        function renderDetail() {
          const list = currentFolder === 'inbox' ? inboxEmails : sentEmails;
          if (selectedEmail == null || !list[selectedEmail]) {
            document.getElementById('email-detail').innerHTML = '';
            return;
          }
          const email = list[selectedEmail];
          const fromDisplay = email.domain ? `${email.from}!${email.domain}` : email.from;
          const toDisplay = email.domain ? `${email.to}!${email.domain}` : email.to;
          document.getElementById('email-detail').innerHTML = `
            <div class="email-detail-content">
              <div class="email-detail-header">
                <div><strong>From:</strong> ${fromDisplay}</div>
                <div><strong>To:</strong> ${toDisplay}</div>
                <div><strong>Subject:</strong> ${email.subject}</div>
              </div>
              <div class="email-detail-body">${email.body}</div>
            </div>
          `;
        }
        // Sidebar folder switching
        document.getElementById('sidebar-inbox').onclick = function() {
          currentFolder = 'inbox';
          selectedEmail = null;
          document.getElementById('sidebar-inbox').classList.add('active');
          document.getElementById('sidebar-sent').classList.remove('active');
          renderList();
          renderDetail();
        };
        document.getElementById('sidebar-sent').onclick = function() {
          currentFolder = 'sent';
          selectedEmail = null;
          document.getElementById('sidebar-inbox').classList.remove('active');
          document.getElementById('sidebar-sent').classList.add('active');
          renderList();
          renderDetail();
        };
        renderList();
        renderDetail();
      })
      .catch(err => {
        document.getElementById('inboxError').innerText = 'Failed to load inbox.';
      });
  }
}

// Send Email
if (document.getElementById('sendForm')) {
  document.getElementById('sendForm').onsubmit = async function(e) {
    e.preventDefault();
    const { username, password } = getCredentials();
    if (!username || !password) {
      window.location.href = 'login.html';
      return;
    }
    const toField = document.getElementById('to').value.trim();
    // Require <username>!<domain> format
    if (!/^\w+!.+/.test(toField)) {
      document.getElementById('sendError').innerText = 'Recipient must be in the format username!domain';
      return;
    }
    let to = toField;
    let domain = '';
    if (toField.includes('!')) {
      [to, domain] = toField.split('!');
    }
    const subject = document.getElementById('subject').value;
    const body = document.getElementById('body').value;
    const email = domain ? { from: username, to, domain, subject, body } : { from: username, to, subject, body };
    const res = await fetch('http://localhost:8080/email', {
      method: 'POST',
      headers: {
        'Content-Type': 'application/json',
        'Authorization': 'Basic ' + btoa(username + ':' + password)
      },
      body: JSON.stringify(email)
    });
    if (res.ok) {
      window.location.href = 'inbox.html';
    } else {
      const err = await res.text();
      document.getElementById('sendError').innerText = err;
    }
  };
}

// Compose Overlay logic
if (document.getElementById('openComposeBtn')) {
  const overlay = document.getElementById('composeOverlay');
  const openBtn = document.getElementById('openComposeBtn');
  const closeBtn = document.getElementById('closeComposeBtn');
  const form = document.getElementById('composeForm');
  const errorP = document.getElementById('composeError');
  openBtn.onclick = function() {
    overlay.style.display = 'flex';
    form.reset();
    errorP.innerText = '';
  };
  closeBtn.onclick = function() {
    overlay.style.display = 'none';
  };
  form.onsubmit = async function(e) {
    e.preventDefault();
    const { username, password } = getCredentials();
    if (!username || !password) {
      window.location.href = 'login.html';
      return;
    }
    const toField = document.getElementById('composeTo').value.trim();
    if (!/^\w+!.+/.test(toField)) {
      errorP.innerText = 'Recipient must be in the format username!domain';
      return;
    }
    let to = toField;
    let domain = '';
    if (toField.includes('!')) {
      [to, domain] = toField.split('!');
    }
    const subject = document.getElementById('composeSubject').value;
    const body = document.getElementById('composeBody').value;
    const email = domain ? { from: username, to, domain, subject, body } : { from: username, to, subject, body };
    const res = await fetch('http://localhost:8080/email', {
      method: 'POST',
      headers: {
        'Content-Type': 'application/json',
        'Authorization': 'Basic ' + btoa(username + ':' + password)
      },
      body: JSON.stringify(email)
    });
    if (res.ok) {
      overlay.style.display = 'none';
      location.reload();
    } else {
      const err = await res.text();
      errorP.innerText = err;
    }
  };
}