import { Injectable } from "@nestjs/common";
import { ConfigService } from "@nestjs/config";
import * as svgCaptcha from "svg-captcha";

export interface GeneratedCaptcha {
  text: string;
  image: string;
  expiresAt: number;
}

@Injectable()
export class CaptchaService {
  generate(): GeneratedCaptcha {
    const captcha = svgCaptcha.create({
      size: 5,
      ignoreChars: "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ",
      noise: 1,
      color: false,
      background: "#f8fafc",
      width: 160,
      height: 56,
      fontSize: 52,
    });

    return {
      text: captcha.text,
      image: `data:image/svg+xml;base64,${Buffer.from(captcha.data, "utf8").toString("base64")}`,
      expiresAt: this.buildExpireAt(),
    };
  }

  normalizeAnswer(input: string): string {
    return input.trim().toLowerCase();
  }

  buildExpireAt(): number {
    const raw = Number(
      process.env.EXP_CAPTCHA_TIME ?? process.env.EXP_OTP_TIME ?? "2",
    );
    const minutes = Number.isFinite(raw) && raw > 0 ? raw : 2;
    return Date.now() + minutes * 60 * 1000;
  }
}