import { randomBytes, createHash } from "node:crypto";

function randomInt(min: number, max: number): number {
  const range = max - min + 1;
  const maxRand = 256 - (256 % range);
  let rand: number;
  do {
    rand = randomBytes(1)[0];
  } while (rand >= maxRand);
  return min + (rand % range);
}

function randomChar(charset: string): string {
  return charset[randomInt(0, charset.length - 1)];
}

export function generateCaptchaCode(length: number = 4): string {
  const charset = "ABCDEFGHJKLMNPQRSTUVWXYZ23456789";
  let code = "";
  for (let i = 0; i < length; i++) {
    code += randomChar(charset);
  }
  return code;
}

export function generateCaptchaToken(): string {
  return randomBytes(32).toString("hex");
}

export function generateCaptchaSvg(code: string): string {
  const width = 120;
  const height = 44;
  const charWidth = width / code.length;
  const colors = ["#0066cc", "#1d1d1f", "#0071e3", "#333333"];

  let paths = "";
  let texts = "";

  for (let i = 0; i < 3; i++) {
    const x1 = randomInt(0, width);
    const y1 = randomInt(0, height);
    const x2 = randomInt(0, width);
    const y2 = randomInt(0, height);
    paths += `<line x1="${x1}" y1="${y1}" x2="${x2}" y2="${y2}" stroke="#e0e0e0" stroke-width="1" />`;
  }

  for (let i = 0; i < code.length; i++) {
    const x = charWidth * i + randomInt(4, charWidth - 20);
    const y = randomInt(26, 34);
    const rotate = randomInt(-20, 20);
    const color = colors[randomInt(0, colors.length - 1)];
    const fontSize = randomInt(22, 28);
    texts += `<text x="${x}" y="${y}" font-size="${fontSize}" fill="${color}" transform="rotate(${rotate}, ${x}, ${y})" font-family="Arial, sans-serif" font-weight="bold">${code[i]}</text>`;
  }

  return `<svg xmlns="http://www.w3.org/2000/svg" width="${width}" height="${height}" viewBox="0 0 ${width} ${height}">
    <rect width="${width}" height="${height}" fill="#fafafc" rx="8" />
    ${paths}
    ${texts}
  </svg>`;
}

export function captchaSvgToDataUri(svg: string): string {
  const base64 = Buffer.from(svg).toString("base64");
  return `data:image/svg+xml;base64,${base64}`;
}