// Copyright (C) 2026 Whiterun LLC,
// This software is licensed under the GNU Lesser General Public License (LGPL), version 3.0 or later.
// A copy of the license can be found in the LICENSE file or at https://www.gnu.org/licenses/lgpl-3.0.html

import {
  generatePrivateKey,
  binToHex,
  hexToBin,
  binToBech32Padded,
  bech32PaddedToBin,
} from "@bitauth/libauth";
import { deriveNostrPublicKey } from "./utilnostr.js";

export const DEFAULT_RELAY_HOSTNAME = "relay.riften.net";
export const DEFAULT_RELAY_PORT = 443;
export const DEFAULT_RELAY_PROTOCOL: "wss" = "wss";

/** All default relay URLs, primary first. */
export const DEFAULT_RELAY_URLS: readonly string[] = [
  "wss://relay.riften.net:443",
  "wss://relay.cauldron.quest:443",
];

export interface KeyExchangeCredentials {
  privateKey: string;
  publicKey: string;
  secret: string;
}

export function generateKeyExchangeCredentials(): KeyExchangeCredentials {
  const privateKey = generatePrivateKey();
  const privateKeyHex = binToHex(privateKey);
  const publicKeyHex = deriveNostrPublicKey(privateKey);

  const secretBytes = generatePrivateKey();
  const secretShort = secretBytes.slice(0, 8);
  const secret = binToHex(secretShort);

  return {
    privateKey: privateKeyHex,
    publicKey: publicKeyHex,
    secret: secret,
  };
}

export interface DecodedKeyExchangeURI {
  publicKey: string;
  secret: string;
  hostname: string;
  port: number;
  protocol: "ws" | "wss";
}

export interface KeyExchangeURIOptions {
  hostname?: string;
  port?: number;
  protocol?: "ws" | "wss";
}

export interface KeyExchangeURIResult {
  /** Standard URI for copy-paste and display: wiz://?p=...&s=... */
  uri: string;
  /** Fully QR-alphanumeric-safe URI for QR code generation: WIZ://%3FP%3D... */
  qrUri: string;
}

export function encodeKeyExchangeURI(
  publicKey: string,
  secret: string,
  options: KeyExchangeURIOptions = {},
): KeyExchangeURIResult {
  const publicKeyBin = hexToBin(publicKey);
  const secretBin = hexToBin(secret);

  if (publicKeyBin.length !== 32) {
    throw new Error(
      `Invalid public key length: expected 32 bytes, got ${publicKeyBin.length}`,
    );
  }
  if (secretBin.length !== 8) {
    throw new Error(
      `Invalid secret length: expected 8 bytes, got ${secretBin.length}`,
    );
  }

  const publicKeyBech32 = binToBech32Padded(publicKeyBin).toLowerCase();
  const secretBech32 = binToBech32Padded(secretBin).toLowerCase();

  const hostname = options.hostname || DEFAULT_RELAY_HOSTNAME;
  const port = options.port ?? DEFAULT_RELAY_PORT;
  const protocol = options.protocol || DEFAULT_RELAY_PROTOCOL;

  const isDefaultHostname = hostname === DEFAULT_RELAY_HOSTNAME;
  const defaultPort = protocol === "wss" ? 443 : 80;
  const isDefaultPort = port === defaultPort;
  const isDefaultProtocol = protocol === DEFAULT_RELAY_PROTOCOL;

  let uri: string;
  if (isDefaultHostname && isDefaultPort && isDefaultProtocol) {
    uri = `wiz://?p=${publicKeyBech32}&s=${secretBech32}`;
  } else {
    const portPart = isDefaultPort ? "" : `:${port}`;
    const authority = `${hostname}${portPart}`;

    uri = `wiz://${authority}?p=${publicKeyBech32}&s=${secretBech32}`;

    if (!isDefaultProtocol) {
      uri += `&pr=${protocol}`;
    }
  }

  const qrUri = uri
    .toUpperCase()
    .replace("?", "%3F")
    .replace(/=/g, "%3D")
    .replace(/&/g, "%26");

  return { uri, qrUri };
}

export function decodeKeyExchangeURI(uri: string): DecodedKeyExchangeURI {
  let url: URL;
  try {
    const lower = uri.toLowerCase();
    const isQr = lower.includes("%3f") && !lower.includes("?");
    const toParse = isQr
      ? lower.replace("%3f", "?").replace(/%3d/g, "=").replace(/%26/g, "&")
      : lower;
    url = new URL(toParse);
  } catch (error) {
    throw new Error(
      `Invalid URI format: ${error instanceof Error ? error.message : "unknown error"}`,
      { cause: error },
    );
  }

  if (url.protocol !== "wiz:") {
    throw new Error("Invalid URI scheme. Expected: wiz://");
  }

  let hostname = url.hostname || DEFAULT_RELAY_HOSTNAME;
  let port: number;
  if (url.port) {
    const parsedPort = parseInt(url.port, 10);
    if (isNaN(parsedPort) || parsedPort < 1 || parsedPort > 65535) {
      throw new Error(`Invalid port number: ${url.port}`);
    }
    port = parsedPort;
  } else {
    port = DEFAULT_RELAY_PORT;
  }

  const publicKeyBech32 = url.searchParams.get("p");
  const secretBech32 = url.searchParams.get("s");

  if (!publicKeyBech32 || !secretBech32) {
    throw new Error(
      "Invalid URI format. Missing required parameters: p (public key) or s (secret)",
    );
  }

  const protocol = url.searchParams.get("pr") as "ws" | "wss" | null;

  const publicKeyBech32Normalized = publicKeyBech32.toLowerCase();
  const secretBech32Normalized = secretBech32.toLowerCase();

  let publicKeyBin: Uint8Array;
  let secretBin: Uint8Array;

  try {
    const pubkeyResult = bech32PaddedToBin(publicKeyBech32Normalized);
    const secretResult = bech32PaddedToBin(secretBech32Normalized);

    if (
      pubkeyResult instanceof Uint8Array &&
      secretResult instanceof Uint8Array
    ) {
      publicKeyBin = pubkeyResult;
      secretBin = secretResult;
    } else {
      const pubkeyError =
        typeof pubkeyResult === "string" ? pubkeyResult : "Unknown error";
      const secretError =
        typeof secretResult === "string" ? secretResult : "Unknown error";
      throw new Error(
        `Bech32 decoding failed: pubkey=${pubkeyError}, secret=${secretError}`,
      );
    }
  } catch (error) {
    throw new Error(
      `Invalid bech32 encoding: ${error instanceof Error ? error.message : "unknown error"}`,
      { cause: error },
    );
  }

  if (publicKeyBin.length !== 32) {
    throw new Error(
      `Invalid public key length: expected 32 bytes, got ${publicKeyBin.length}`,
    );
  }
  if (secretBin.length !== 8) {
    throw new Error(
      `Invalid secret length: expected 8 bytes, got ${secretBin.length}`,
    );
  }

  if (protocol && protocol !== "ws" && protocol !== "wss") {
    throw new Error(`Invalid protocol: ${protocol}. Must be 'ws' or 'wss'`);
  }

  if (!url.port && protocol === "ws") {
    port = 80;
  }

  return {
    publicKey: binToHex(publicKeyBin),
    secret: binToHex(secretBin),
    hostname: hostname,
    port: port,
    protocol: protocol || DEFAULT_RELAY_PROTOCOL,
  };
}