export async function deriveKeyFromPassword(password: string): Promise<string> {
  const encoder = new TextEncoder();
  const keyMaterial = await crypto.subtle.importKey(
    "raw",
    encoder.encode(password),
    "PBKDF2",
    false,
    ["deriveBits", "deriveKey"]
  );
  const key = await crypto.subtle.deriveKey(
    {
      name: "PBKDF2",
      salt: encoder.encode("dead-man-switch-salt"),
      iterations: 100000,
      hash: "SHA-256",
    },
    keyMaterial,
    { name: "AES-GCM", length: 256 },
    true,
    ["encrypt", "decrypt"]
  );
  const exported = await crypto.subtle.exportKey("raw", key);
  return btoa(String.fromCharCode(...new Uint8Array(exported)));
}

export async function generateKey(): Promise<string> {
  const key = await crypto.subtle.generateKey(
    { name: "AES-GCM", length: 256 },
    true,
    ["encrypt", "decrypt"]
  );
  const exported = await crypto.subtle.exportKey("raw", key);
  return btoa(String.fromCharCode(...new Uint8Array(exported)));
}

export async function importKey(keyString: string): Promise<CryptoKey> {
  const keyData = Uint8Array.from(atob(keyString), (c) => c.charCodeAt(0));
  return crypto.subtle.importKey(
    "raw",
    keyData,
    { name: "AES-GCM", length: 256 },
    false,
    ["encrypt", "decrypt"]
  );
}

export async function encrypt(data: string, keyString: string): Promise<string> {
  const key = await importKey(keyString);
  const iv = crypto.getRandomValues(new Uint8Array(12));
  const encoded = new TextEncoder().encode(data);
  const encrypted = await crypto.subtle.encrypt(
    { name: "AES-GCM", iv },
    key,
    encoded
  );
  const combined = new Uint8Array(iv.length + encrypted.byteLength);
  combined.set(iv);
  combined.set(new Uint8Array(encrypted), iv.length);
  return btoa(String.fromCharCode(...combined));
}

export async function decrypt(encryptedData: string, keyString: string): Promise<string> {
  const key = await importKey(keyString);
  const combined = Uint8Array.from(atob(encryptedData), (c) => c.charCodeAt(0));
  const iv = combined.slice(0, 12);
  const data = combined.slice(12);
  const decrypted = await crypto.subtle.decrypt(
    { name: "AES-GCM", iv },
    key,
    data
  );
  return new TextDecoder().decode(decrypted);
}

export async function encryptFile(file: File, keyString: string): Promise<Blob> {
  const key = await importKey(keyString);
  const iv = crypto.getRandomValues(new Uint8Array(12));
  const arrayBuffer = await file.arrayBuffer();
  const encrypted = await crypto.subtle.encrypt(
    { name: "AES-GCM", iv },
    key,
    arrayBuffer
  );
  const combined = new Uint8Array(iv.length + encrypted.byteLength);
  combined.set(iv);
  combined.set(new Uint8Array(encrypted), iv.length);
  return new Blob([combined], { type: "application/octet-stream" });
}

export async function decryptFile(encryptedBlob: Blob, keyString: string): Promise<ArrayBuffer> {
  const key = await importKey(keyString);
  const combined = new Uint8Array(await encryptedBlob.arrayBuffer());
  const iv = combined.slice(0, 12);
  const data = combined.slice(12);
  return crypto.subtle.decrypt({ name: "AES-GCM", iv }, key, data);
}