import { CryptoFunctionService } from "../abstractions/cryptoFunction.service";
import { LogService } from "../abstractions/log.service";
import { TotpService as TotpServiceAbstraction } from "../abstractions/totp.service";
import { Utils } from "../misc/utils";

const B32Chars = "ABCDEFGHIJKLMNOPQRSTUVWXYZ234567";
const SteamChars = "23456789BCDFGHJKMNPQRTVWXY";

export class TotpService implements TotpServiceAbstraction {
  constructor(
    private cryptoFunctionService: CryptoFunctionService,
    private logService: LogService
  ) {}

  async getCode(key: string): Promise<string> {
    if (key == null) {
      return null;
    }
    let period = 30;
    let alg: "sha1" | "sha256" | "sha512" = "sha1";
    let digits = 6;
    let keyB32 = key;
    const isOtpAuth = key.toLowerCase().indexOf("otpauth://") === 0;
    const isSteamAuth = !isOtpAuth && key.toLowerCase().indexOf("steam://") === 0;
    if (isOtpAuth) {
      const params = Utils.getQueryParams(key);
      if (params.has("digits") && params.get("digits") != null) {
        try {
          const digitParams = parseInt(params.get("digits").trim(), null);
          if (digitParams > 10) {
            digits = 10;
          } else if (digitParams > 0) {
            digits = digitParams;
          }
        } catch {
          this.logService.error("Invalid digits param.");
        }
      }
      if (params.has("period") && params.get("period") != null) {
        try {
          const periodParam = parseInt(params.get("period").trim(), null);
          if (periodParam > 0) {
            period = periodParam;
          }
        } catch {
          this.logService.error("Invalid period param.");
        }
      }
      if (params.has("secret") && params.get("secret") != null) {
        keyB32 = params.get("secret");
      }
      if (params.has("algorithm") && params.get("algorithm") != null) {
        const algParam = params.get("algorithm").toLowerCase();
        if (algParam === "sha1" || algParam === "sha256" || algParam === "sha512") {
          alg = algParam;
        }
      }
    } else if (isSteamAuth) {
      keyB32 = key.substr("steam://".length);
      digits = 5;
    }

    const epoch = Math.round(new Date().getTime() / 1000.0);
    const timeHex = this.leftPad(this.decToHex(Math.floor(epoch / period)), 16, "0");
    const timeBytes = Utils.fromHexToArray(timeHex);
    const keyBytes = this.b32ToBytes(keyB32);

    if (!keyBytes.length || !timeBytes.length) {
      return null;
    }

    const hash = await this.sign(keyBytes, timeBytes, alg);
    if (hash.length === 0) {
      return null;
    }

    const offset = hash[hash.length - 1] & 0xf;
    const binary =
      ((hash[offset] & 0x7f) << 24) |
      ((hash[offset + 1] & 0xff) << 16) |
      ((hash[offset + 2] & 0xff) << 8) |
      (hash[offset + 3] & 0xff);

    let otp = "";
    if (isSteamAuth) {
      let fullCode = binary & 0x7fffffff;
      for (let i = 0; i < digits; i++) {
        otp += SteamChars[fullCode % SteamChars.length];
        fullCode = Math.trunc(fullCode / SteamChars.length);
      }
    } else {
      otp = (binary % Math.pow(10, digits)).toString();
      otp = this.leftPad(otp, digits, "0");
    }

    return otp;
  }

  getTimeInterval(key: string): number {
    let period = 30;
    if (key != null && key.toLowerCase().indexOf("otpauth://") === 0) {
      const params = Utils.getQueryParams(key);
      if (params.has("period") && params.get("period") != null) {
        try {
          period = parseInt(params.get("period").trim(), null);
        } catch {
          this.logService.error("Invalid period param.");
        }
      }
    }
    return period;
  }

  // Helpers

  private leftPad(s: string, l: number, p: string): string {
    if (l + 1 >= s.length) {
      s = Array(l + 1 - s.length).join(p) + s;
    }
    return s;
  }

  private decToHex(d: number): string {
    return (d < 15.5 ? "0" : "") + Math.round(d).toString(16);
  }

  private b32ToHex(s: string): string {
    s = s.toUpperCase();
    let cleanedInput = "";

    for (let i = 0; i < s.length; i++) {
      if (B32Chars.indexOf(s[i]) < 0) {
        continue;
      }

      cleanedInput += s[i];
    }
    s = cleanedInput;

    let bits = "";
    let hex = "";
    for (let i = 0; i < s.length; i++) {
      const byteIndex = B32Chars.indexOf(s.charAt(i));
      if (byteIndex < 0) {
        continue;
      }
      bits += this.leftPad(byteIndex.toString(2), 5, "0");
    }
    for (let i = 0; i + 4 <= bits.length; i += 4) {
      const chunk = bits.substr(i, 4);
      hex = hex + parseInt(chunk, 2).toString(16);
    }
    return hex;
  }

  private b32ToBytes(s: string): Uint8Array {
    return Utils.fromHexToArray(this.b32ToHex(s));
  }

  private async sign(
    keyBytes: Uint8Array,
    timeBytes: Uint8Array,
    alg: "sha1" | "sha256" | "sha512"
  ) {
    const signature = await this.cryptoFunctionService.hmac(timeBytes.buffer, keyBytes.buffer, alg);
    return new Uint8Array(signature);
  }
}