// This file is taken from Node.js project.
// Full implementation can be found from https://github.com/nodejs/node/blob/main/lib/internal/querystring.js

const hexTable = Array.from(
  { length: 256 },
  (_, i) => "%" + ((i < 16 ? "0" : "") + i.toString(16)).toUpperCase(),
);

// These characters do not need escaping when generating query strings:
// ! - . _ ~
// ' ( ) *
// digits
// alpha (uppercase)
// alpha (lowercase)
// rome-ignore format: the array should not be formatted
const noEscape = new Int8Array([
  0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, // 0 - 15
  0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, // 16 - 31
  0, 1, 0, 0, 0, 0, 0, 1, 1, 1, 1, 0, 0, 1, 1, 0, // 32 - 47
  1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, // 48 - 63
  0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, // 64 - 79
  1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, 1, // 80 - 95
  0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, // 96 - 111
  1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 1, 0,  // 112 - 127
]);

/**
 * @param {string} str
 * @returns {string}
 */
function encodeString(str) {
  const len = str.length;
  if (len === 0) return "";

  let out = "";
  let lastPos = 0;
  let i = 0;

  outer: for (; i < len; i++) {
    let c = str.charCodeAt(i);

    // ASCII
    while (c < 0x80) {
      if (noEscape[c] !== 1) {
        if (lastPos < i) out += str.slice(lastPos, i);
        lastPos = i + 1;
        out += hexTable[c];
      }

      if (++i === len) break outer;

      c = str.charCodeAt(i);
    }

    if (lastPos < i) out += str.slice(lastPos, i);

    // Multi-byte characters ...
    if (c < 0x800) {
      lastPos = i + 1;
      out += hexTable[0xC0 | (c >> 6)] + hexTable[0x80 | (c & 0x3F)];
      continue;
    }
    if (c < 0xD800 || c >= 0xE000) {
      lastPos = i + 1;
      out +=
        hexTable[0xE0 | (c >> 12)] +
        hexTable[0x80 | ((c >> 6) & 0x3F)] +
        hexTable[0x80 | (c & 0x3F)];
      continue;
    }
    // Surrogate pair
    ++i;

    // This branch should never happen because all URLSearchParams entries
    // should already be converted to USVString. But, included for
    // completion's sake anyway.
    if (i >= len) {
      throw new Error("URI malformed");
    }

    const c2 = str.charCodeAt(i) & 0x3FF;

    lastPos = i + 1;
    c = 0x10000 + (((c & 0x3FF) << 10) | c2);
    out +=
      hexTable[0xF0 | (c >> 18)] +
      hexTable[0x80 | ((c >> 12) & 0x3F)] +
      hexTable[0x80 | ((c >> 6) & 0x3F)] +
      hexTable[0x80 | (c & 0x3F)];
  }
  if (lastPos === 0) return str;
  if (lastPos < len) return out + str.slice(lastPos);
  return out;
}

module.exports = { encodeString };