/*
Welcome to the magic behind PassED!
This file is responsible for encrypting passwords in the browser and to only send encrypted passwords to the server.

- https://git.1e99.eu/1e99/passed
- https://discord.gg/NuGxJKtDKS
*/

const ALGORITHM_NAME = "AES-GCM";
const ALGORITHM_LENGTH = 256;
const IV_LENGTH = 16;

const TEXT_ENCODER = new TextEncoder();
const TEXT_DECODER = new TextDecoder();

const ACTIVE_PAGE = "page-active";

/** Coverts an ArrayBuffer into a Base64 encoded string
 * @param {ArrayBuffer} buffer
 * @returns {string}
 */
function bufferToBase64(buffer) {
  let binary = "";
  const bytes = new Uint8Array(buffer);
  const len = bytes.byteLength;
  for (let i = 0; i < len; i++) {
    binary += String.fromCharCode(bytes[i]);
  }

  return btoa(binary);
}

/** Converts a Base64 encoded string into an ArrayBuffer
 * @param {string} base64
 * @returns {ArrayBuffer}
 */
function base64ToBuffer(base64) {
  const binaryString = atob(base64);
  const len = binaryString.length;
  const bytes = new Uint8Array(len);
  for (let i = 0; i < len; i++) {
    bytes[i] = binaryString.charCodeAt(i);
  }

  return bytes.buffer;
}

/** Generates an key and encrypts "password" using it
 * @param {string} password
 */
async function encryptPassword(password) {
  const iv = new Uint8Array(IV_LENGTH);
  window.crypto.getRandomValues(iv);

  const key = await window.crypto.subtle.generateKey(
    {
      name: ALGORITHM_NAME,
      length: ALGORITHM_LENGTH,
    },
    true,
    ["encrypt", "decrypt"],
  );

  const encryptedPassword = await window.crypto.subtle.encrypt(
    {
      name: ALGORITHM_NAME,
      iv: iv,
    },
    key,
    TEXT_ENCODER.encode(password),
  );

  const exportedKey = await window.crypto.subtle.exportKey("raw", key);

  const encodedPassword = bufferToBase64(encryptedPassword);
  const encodedKey = bufferToBase64(exportedKey);
  const encodedIv = bufferToBase64(iv.buffer);

  return {
    password: encodedPassword,
    key: encodedKey,
    iv: encodedIv,
  };
}

/** Decodes to key and iv and decryptes the password
 * @param {string} password
 * @param {string} key
 * @param {string} iv
 */
async function decryptPassword(password, key, iv) {
  const decodedPassword = base64ToBuffer(password);
  const decodedKey = base64ToBuffer(key);
  const decodedIv = base64ToBuffer(iv);

  const cryptoKey = await window.crypto.subtle.importKey(
    "raw",
    decodedKey,
    {
      name: ALGORITHM_NAME,
      length: ALGORITHM_LENGTH,
    },
    true,
    ["encrypt", "decrypt"],
  );

  const decryptedPassword = await window.crypto.subtle.decrypt(
    {
      name: ALGORITHM_NAME,
      iv: decodedIv,
    },
    cryptoKey,
    decodedPassword,
  );

  return TEXT_DECODER.decode(decryptedPassword);
}

function showError(error) {
  const errorDialog = document.querySelector("dialog#error");
  const errorMessage = document.querySelector("textarea#error-message");

  errorMessage.value = error;
  errorDialog.showModal();
}

function init() {
  const passwordForm = document.querySelector("form#password");
  const loadingDialog = document.querySelector("dialog#loading");
  const urlDialog = document.querySelector("dialog#url");
  const urlCopy = document.querySelector("button#url-copy");
  const passwordUrl = document.querySelector("input#password-url");
  const shareAnother = document.querySelector("button#share-another");

  passwordForm.addEventListener("submit", async (ev) => {
    try {
      loadingDialog.showModal();
      ev.preventDefault();
      const data = new FormData(ev.target);

      const encrypted = await encryptPassword(data.get("password"));

      const res = await fetch("/api/password", {
        method: "POST",
        body: JSON.stringify({
          password: encrypted.password,
          "expires-in": data.get("expires-in"),
        }),
      });
      if (!res.ok) {
        const msg = await res.text();
        throw new Error(`Failed to upload password: ${res.status}: ${msg}`);
      }

      const json = await res.json();

      const params = new URLSearchParams();
      params.set("id", json.id);
      params.set("key", encrypted.key);
      params.set("iv", encrypted.iv);

      const url = new URL(window.location);
      url.search = params.toString();
      passwordUrl.value = url.toString();

      urlDialog.showModal();
      passwordUrl.select();
    } catch (error) {
      showError(error);
    } finally {
      loadingDialog.close();
    }
  });

  loadingDialog.addEventListener("close", (ev) => ev.preventDefault());
  shareAnother.addEventListener("click", (ev) => {
    passwordForm.reset();
    passwordUrl.value = "";
    urlDialog.close();
  });
  urlCopy.addEventListener("click", async (ev) => {
    passwordUrl.select();
    passwordUrl.setSelectionRange(0, 99999);
    await navigator.clipboard.writeText(passwordUrl.value);
  });
}

function confirmViewPassword() {
  const confirmDialog = document.querySelector("dialog#confirm-view");
  const confirm = document.querySelector("button#confirm-view");

  confirmDialog.showModal();

  confirm.addEventListener("click", (ev) => {
    confirmDialog.close();
    viewPassword();
  });
}

async function viewPassword() {
  const viewDialog = document.querySelector("dialog#view");
  const password = document.querySelector("textarea#password");
  const loadingDialog = document.querySelector("dialog#loading");
  const params = new URLSearchParams(window.location.search);

  try {
    loadingDialog.showModal();

    const res = await fetch(`/api/password/${params.get("id")}`);
    if (!res.ok) {
      const msg = await res.text();
      throw new Error(`Failed to load password: ${res.status}: ${msg}`);
    }

    const json = await res.json();

    const decrypted = await decryptPassword(
      json.password,
      params.get("key"),
      params.get("iv"),
    );

    password.value = decrypted;
    viewDialog.showModal();
  } catch (error) {
    showError(error);
  } finally {
    loadingDialog.close();
  }
}

window.addEventListener("load", () => {
  const query = window.location.search;
  if (query.trim() != "") {
    confirmViewPassword();
  }

  init();
});