const BASE58_ALPHABET = "123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz";

function base58Decode(str: string): Uint8Array {
  let num = 0n;
  for (const char of str) {
    const idx = BASE58_ALPHABET.indexOf(char);
    if (idx === -1) throw new Error("Invalid base58 character");
    num = num * 58n + BigInt(idx);
  }
  const hex = num.toString(16).padStart(2, "0");
  const paddedHex = hex.length % 2 ? "0" + hex : hex;
  const result = new Uint8Array(paddedHex.length / 2);
  for (let i = 0; i < paddedHex.length; i += 2) {
    result[i / 2] = parseInt(paddedHex.slice(i, i + 2), 16);
  }
  return result;
}

function fromBase58Groups(groups: string[]): string {
  return groups.join("");
}

export const PUBLIC_KEY_HEX =
  "c7dc52d2c484696cf8566dbe6cfe69025d114cb47f6cf53c25088ecfd539bdfa";

export interface LicenseInfo {
  valid: boolean;
  plan: "free" | "pro";
  issued?: Date;
}

const LICENSE_PREFIX = "PPK-";

async function importPublicKey(): Promise<CryptoKey> {
  const keyData = hexToBytes(PUBLIC_KEY_HEX);
  return (crypto.subtle as any).importKey(
    "raw",
    keyData,
    { name: "Ed25519" },
    true,
    ["verify"]
  );
}

function hexToBytes(hex: string): Uint8Array {
  const bytes = new Uint8Array(hex.length / 2);
  for (let i = 0; i < hex.length; i += 2) {
    bytes[i / 2] = parseInt(hex.slice(i, i + 2), 16);
  }
  return bytes;
}

export async function validateLicense(keyString: string): Promise<LicenseInfo> {
  if (!keyString || typeof keyString !== "string") {
    return { valid: false, plan: "free" };
  }

  const trimmed = keyString.trim();
  if (!trimmed.startsWith(LICENSE_PREFIX)) {
    return { valid: false, plan: "free" };
  }

  try {
    const withoutPrefix = trimmed.slice(LICENSE_PREFIX.length);
    const groups = withoutPrefix.split("-");
    if (groups.length !== 5) {
      return { valid: false, plan: "free" };
    }

    const base58String = fromBase58Groups(groups);
    const decoded = base58Decode(base58String);

    if (decoded.length !== 76) {
      return { valid: false, plan: "free" };
    }

    const payload = decoded.slice(0, 12);
    const signature = decoded.slice(12, 76);

    if (payload[0] !== 0x01) {
      return { valid: false, plan: "free" };
    }
    if (payload[1] !== 0x01) {
      return { valid: false, plan: "free" };
    }
    if (payload[2] !== 0x01) {
      return { valid: false, plan: "free" };
    }

    const issuedTimestamp = new DataView(payload.buffer, payload.byteOffset + 3, 4).getUint32(0, true);
    const issuedDate = new Date(issuedTimestamp * 86400 * 1000);

    const publicKey = await importPublicKey();
    const isValid = await (crypto.subtle as any).verify(
      "Ed25519",
      publicKey,
      signature,
      payload
    );

    if (!isValid) {
      return { valid: false, plan: "free" };
    }

    return { valid: true, plan: "pro", issued: issuedDate };
  } catch {
    return { valid: false, plan: "free" };
  }
}

export async function getLicenseInfo(): Promise<LicenseInfo> {
  try {
    const result = await chrome.storage.local.get("peach_license") as Record<string, string | undefined>;
    const stored = result["peach_license"];
    if (!stored) {
      return { valid: false, plan: "free" };
    }
    return validateLicense(stored);
  } catch {
    return { valid: false, plan: "free" };
  }
}

const CELEBRATION_KEY = "peach_pro_celebrated";

export async function activateLicense(keyString: string): Promise<LicenseInfo> {
  const validated = await validateLicense(keyString);
  if (validated.valid && validated.plan === "pro") {
    // Reset the celebration flag so every new license activation triggers
    // the full-screen Pro celebration in the popup, even on devices that
    // have celebrated before (e.g., testers who activate repeatedly).
    await chrome.storage.local.set({
      peach_license: keyString.trim(),
      [CELEBRATION_KEY]: false,
    });
    return validated;
  }
  return { valid: false, plan: "free" };
}

export async function isProUser(): Promise<boolean> {
  const info = await getLicenseInfo();
  return info.valid && info.plan === "pro";
}

/** Returns the raw stored license key string, or null if none. */
export async function getLicenseKey(): Promise<string | null> {
  try {
    const result = await chrome.storage.local.get("peach_license") as Record<string, string | undefined>;
    return result["peach_license"] ?? null;
  } catch {
    return null;
  }
}

export async function deactivateLicense(): Promise<void> {
  await chrome.storage.local.remove("peach_license");
}

export async function shouldPlayCelebration(): Promise<boolean> {
  const info = await getLicenseInfo();
  if (!info.valid || info.plan !== "pro") return false;
  const result = await chrome.storage.local.get(CELEBRATION_KEY) as Record<string, boolean | undefined>;
  return !result[CELEBRATION_KEY];
}

export async function markCelebrationPlayed(): Promise<void> {
  await chrome.storage.local.set({ [CELEBRATION_KEY]: true });
}