const loginLink = document.querySelector("#login-link");
const logoutButton = document.querySelector("#logout-button");
const userChip = document.querySelector("#user-chip");
const loggedOutPanel = document.querySelector("#logged-out-panel");
const appPanel = document.querySelector("#app-panel");
const linksSection = document.querySelector("#links-section");
const form = document.querySelector("#shorten-form");
const input = document.querySelector("#url");
const button = document.querySelector("#submit-button");
const alertBox = document.querySelector("#alert");
const result = document.querySelector("#result");
const shortUrl = document.querySelector("#short-url");
const longUrl = document.querySelector("#long-url");
const copyButton = document.querySelector("#copy-button");
const refreshButton = document.querySelector("#refresh-button");
const linksList = document.querySelector("#links-list");
const emptyState = document.querySelector("#empty-state");
const template = document.querySelector("#link-template");

let currentUser = null;

async function api(path, options = {}) {
  const response = await fetch(path, {
    ...options,
    headers: {
      "Content-Type": "application/json",
      ...(options.headers || {}),
    },
  });

  if (response.status === 204) {
    return null;
  }

  const payload = await response.json().catch(() => ({}));

  if (!response.ok) {
    throw new Error(payload.error || "Die Anfrage ist fehlgeschlagen.");
  }

  return payload;
}

function showError(message) {
  alertBox.textContent = message;
  alertBox.hidden = false;
}

function clearError() {
  alertBox.textContent = "";
  alertBox.hidden = true;
}

function setLoading(isLoading) {
  button.disabled = isLoading;
  button.textContent = isLoading ? "Kürze..." : "Kürzen";
}

function setAuthenticated(user) {
  currentUser = user.authenticated ? user : null;

  if (currentUser) {
    userChip.textContent = currentUser.email
      ? `${currentUser.username} · ${currentUser.email}`
      : currentUser.username;
    userChip.hidden = false;
    logoutButton.hidden = false;
    loginLink.hidden = true;
    loggedOutPanel.hidden = true;
    appPanel.hidden = false;
    linksSection.hidden = false;
    loadLinks();
  } else {
    userChip.hidden = true;
    logoutButton.hidden = true;
    loginLink.hidden = false;
    loggedOutPanel.hidden = false;
    appPanel.hidden = true;
    linksSection.hidden = true;
  }
}

async function loadMe() {
  const user = await api("/api/me");
  setAuthenticated(user);
}

async function loadLinks() {
  if (!currentUser) return;

  linksList.innerHTML = "";
  emptyState.hidden = true;

  try {
    const links = await api("/api/links");
    emptyState.hidden = links.length !== 0;
    links.forEach(renderLink);
  } catch (error) {
    showError(error.message);
  }
}

function renderLink(link) {
  const node = template.content.cloneNode(true);
  const card = node.querySelector(".link-card");
  const short = node.querySelector(".link-short");
  const long = node.querySelector(".link-long");
  const form = node.querySelector(".edit-form");
  const editInput = node.querySelector(".edit-input");
  const saveButton = node.querySelector(".save-button");
  const copyButton = node.querySelector(".copy-link-button");
  const deleteButton = node.querySelector(".delete-button");

  short.href = link.short_url;
  short.textContent = link.short_url;
  long.textContent = link.long_url;
  editInput.value = link.long_url;

  form.addEventListener("submit", async (event) => {
    event.preventDefault();
    clearError();
    saveButton.disabled = true;
    saveButton.textContent = "Speichere...";

    try {
      const updated = await api(`/api/links/${encodeURIComponent(link.code)}`, {
        method: "PUT",
        body: JSON.stringify({ url: editInput.value.trim() }),
      });

      long.textContent = updated.long_url;
      editInput.value = updated.long_url;
      saveButton.textContent = "Gespeichert";
      setTimeout(() => {
        saveButton.textContent = "Speichern";
      }, 1200);
    } catch (error) {
      showError(error.message);
      saveButton.textContent = "Speichern";
    } finally {
      saveButton.disabled = false;
    }
  });

  copyButton.addEventListener("click", async () => {
    await copyToClipboard(link.short_url, copyButton);
  });

  deleteButton.addEventListener("click", async () => {
    const ok = confirm("Diesen Kurzlink wirklich löschen?");
    if (!ok) return;

    clearError();
    try {
      await api(`/api/links/${encodeURIComponent(link.code)}`, { method: "DELETE" });
      card.remove();
      if (!linksList.children.length) emptyState.hidden = false;
    } catch (error) {
      showError(error.message);
    }
  });

  linksList.appendChild(node);
}

async function copyToClipboard(value, targetButton) {
  try {
    await navigator.clipboard.writeText(value);
    const old = targetButton.textContent;
    targetButton.textContent = "Kopiert!";
    setTimeout(() => {
      targetButton.textContent = old;
    }, 1500);
  } catch {
    showError("Kopieren ist fehlgeschlagen. Bitte kopiere den Link manuell.");
  }
}

form.addEventListener("submit", async (event) => {
  event.preventDefault();
  clearError();
  result.hidden = true;
  setLoading(true);

  try {
    const payload = await api("/api/shorten", {
      method: "POST",
      body: JSON.stringify({ url: input.value.trim() }),
    });

    shortUrl.textContent = payload.short_url;
    shortUrl.href = payload.short_url;
    longUrl.textContent = payload.long_url;
    result.hidden = false;
    copyButton.textContent = "Kopieren";
    input.value = "";
    await loadLinks();
  } catch (error) {
    showError(error.message);
  } finally {
    setLoading(false);
  }
});

copyButton.addEventListener("click", async () => {
  await copyToClipboard(shortUrl.href, copyButton);
});

refreshButton.addEventListener("click", loadLinks);

logoutButton.addEventListener("click", async () => {
  await fetch("/auth/logout", { method: "POST" });
  window.location.href = "/";
});

loadMe().catch((error) => {
  console.error(error);
});