/**
 * Encoding utilities for WHMCS helpers (domain-internal)
 *
 * Avoid hard Node `Buffer` dependency. Use it when available; otherwise fall back
 * to pure JS UTF-8 + base64.
 */

const BASE64_ALPHABET = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";

function encodeUtf8Fallback(value: string): Uint8Array {
  const bytes: number[] = [];
  for (let i = 0; i < value.length; i++) {
    let codePoint = value.charCodeAt(i);

    // Handle surrogate pairs
    if (codePoint >= 0xd800 && codePoint <= 0xdbff && i + 1 < value.length) {
      const next = value.charCodeAt(i + 1);
      if (next >= 0xdc00 && next <= 0xdfff) {
        codePoint = ((codePoint - 0xd800) << 10) + (next - 0xdc00) + 0x10000;
        i++;
      }
    }

    if (codePoint <= 0x7f) {
      bytes.push(codePoint);
    } else if (codePoint <= 0x7ff) {
      bytes.push(0xc0 | (codePoint >> 6));
      bytes.push(0x80 | (codePoint & 0x3f));
    } else if (codePoint <= 0xffff) {
      bytes.push(0xe0 | (codePoint >> 12));
      bytes.push(0x80 | ((codePoint >> 6) & 0x3f));
      bytes.push(0x80 | (codePoint & 0x3f));
    } else {
      bytes.push(0xf0 | (codePoint >> 18));
      bytes.push(0x80 | ((codePoint >> 12) & 0x3f));
      bytes.push(0x80 | ((codePoint >> 6) & 0x3f));
      bytes.push(0x80 | (codePoint & 0x3f));
    }
  }
  return new Uint8Array(bytes);
}

function encodeUtf8(value: string): Uint8Array {
  if (typeof TextEncoder !== "undefined") {
    return new TextEncoder().encode(value);
  }
  return encodeUtf8Fallback(value);
}

export function byteLengthUtf8(value: string): number {
  if (typeof Buffer !== "undefined") {
    return Buffer.byteLength(value, "utf8");
  }
  return encodeUtf8(value).length;
}

function base64EncodeBytes(bytes: Uint8Array): string {
  let out = "";
  for (let i = 0; i < bytes.length; i += 3) {
    const b1 = bytes[i] ?? 0;
    const b2 = bytes[i + 1] ?? 0;
    const b3 = bytes[i + 2] ?? 0;

    const triplet = (b1 << 16) | (b2 << 8) | b3;

    out += BASE64_ALPHABET[(triplet >> 18) & 0x3f];
    out += BASE64_ALPHABET[(triplet >> 12) & 0x3f];
    out += i + 1 < bytes.length ? BASE64_ALPHABET[(triplet >> 6) & 0x3f] : "=";
    out += i + 2 < bytes.length ? BASE64_ALPHABET[triplet & 0x3f] : "=";
  }
  return out;
}

export function utf8ToBase64(value: string): string {
  if (typeof Buffer !== "undefined") {
    return Buffer.from(value, "utf8").toString("base64");
  }
  return base64EncodeBytes(encodeUtf8(value));
}