/**
 * Copyright (c) Microsoft Corporation.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

import crypto from 'crypto';
import { assert } from './debug';

export function createGuid(): string {
  return crypto.randomBytes(16).toString('hex');
}

export function calculateSha1(buffer: Buffer | string): string {
  const hash = crypto.createHash('sha1');
  hash.update(buffer);
  return hash.digest('hex');
}

// Variable-length quantity encoding aka. base-128 encoding
function encodeBase128(value: number): Buffer {
  const bytes = [];
  do {
    let byte = value & 0x7f;
    value >>>= 7;
    if (bytes.length > 0)
      byte |= 0x80;
    bytes.push(byte);
  } while (value > 0);
  return Buffer.from(bytes.reverse());
}

// ASN1/DER Speficiation:   https://www.itu.int/rec/T-REC-X.680-X.693-202102-I/en
class DER {
  static encodeSequence(data: Buffer[]): Buffer {
    return this._encode(0x30, Buffer.concat(data));
  }
  static encodeInteger(data: number): Buffer {
    assert(data >= -128 && data <= 127);
    return this._encode(0x02, Buffer.from([data]));
  }
  static encodeObjectIdentifier(oid: string): Buffer {
    const parts = oid.split('.').map(v => Number(v));
    // Encode the second part, which could be large, using base-128 encoding if necessary
    const output = [encodeBase128(40 * parts[0] + parts[1])];

    for (let i = 2; i < parts.length; i++)
      output.push(encodeBase128(parts[i]));


    return this._encode(0x06, Buffer.concat(output));
  }
  static encodeNull(): Buffer {
    return Buffer.from([0x05, 0x00]);
  }
  static encodeSet(data: Buffer[]): Buffer {
    assert(data.length === 1, 'Only one item in the set is supported. We\'d need to sort the data to support more.');
    // We expect the data to be already sorted.
    return this._encode(0x31, Buffer.concat(data));
  }
  static encodeExplicitContextDependent(tag: number, data: Buffer): Buffer {
    return this._encode(0xa0 + tag, data);
  }
  static encodePrintableString(data: string): Buffer {
    return this._encode(0x13, Buffer.from(data));
  }
  static encodeBitString(data: Buffer): Buffer {
    // The first byte of the content is the number of unused bits at the end
    const unusedBits = 0; // Assuming all bits are used
    const content = Buffer.concat([Buffer.from([unusedBits]), data]);
    return this._encode(0x03, content);
  }
  static encodeDate(date: Date): Buffer {
    const year = date.getUTCFullYear();
    const isGeneralizedTime = year >= 2050;
    const parts = [
      isGeneralizedTime ? year.toString() : year.toString().slice(-2),
      (date.getUTCMonth() + 1).toString().padStart(2, '0'),
      date.getUTCDate().toString().padStart(2, '0'),
      date.getUTCHours().toString().padStart(2, '0'),
      date.getUTCMinutes().toString().padStart(2, '0'),
      date.getUTCSeconds().toString().padStart(2, '0')
    ];
    const encodedDate = parts.join('') + 'Z';
    const tag = isGeneralizedTime ? 0x18 : 0x17; // 0x18 for GeneralizedTime, 0x17 for UTCTime
    return this._encode(tag, Buffer.from(encodedDate));
  }
  private static _encode(tag: number, data: Buffer): Buffer {
    const lengthBytes = this._encodeLength(data.length);
    return Buffer.concat([Buffer.from([tag]), lengthBytes, data]);
  }
  private static _encodeLength(length: number): Buffer {
    if (length < 128) {
      return Buffer.from([length]);
    } else {
      const lengthBytes = [];
      while (length > 0) {
        lengthBytes.unshift(length & 0xFF);
        length >>= 8;
      }
      return Buffer.from([0x80 | lengthBytes.length, ...lengthBytes]);
    }
  }
}

// X.509 Specification: https://datatracker.ietf.org/doc/html/rfc2459#section-4.1
export function generateSelfSignedCertificate() {
  const { privateKey, publicKey } = crypto.generateKeyPairSync('rsa', { modulusLength: 2048 });
  const publicKeyDer = publicKey.export({ type: 'pkcs1', format: 'der' });

  const oneYearInMilliseconds = 365 * 24 * 60 * 60 * 1_000;
  const notBefore = new Date(new Date().getTime() - oneYearInMilliseconds);
  const notAfter = new Date(new Date().getTime() + oneYearInMilliseconds);

  // List of fields / structure: https://datatracker.ietf.org/doc/html/rfc2459#section-4.1
  const tbsCertificate = DER.encodeSequence([
    DER.encodeExplicitContextDependent(0, DER.encodeInteger(1)), // version
    DER.encodeInteger(1), // serialNumber
    DER.encodeSequence([
      DER.encodeObjectIdentifier('1.2.840.113549.1.1.11'), // sha256WithRSAEncryption PKCS #1
      DER.encodeNull()
    ]), // signature
    DER.encodeSequence([
      DER.encodeSet([
        DER.encodeSequence([
          DER.encodeObjectIdentifier('2.5.4.3'), // commonName X.520 DN component
          DER.encodePrintableString('localhost')
        ]),
      ]),
      DER.encodeSet([
        DER.encodeSequence([
          DER.encodeObjectIdentifier('2.5.4.10'), // organizationName X.520 DN component
          DER.encodePrintableString('Playwright Client Certificate Support')
        ])
      ])
    ]), // issuer
    DER.encodeSequence([
      DER.encodeDate(notBefore), // notBefore
      DER.encodeDate(notAfter), // notAfter
    ]), // validity
    DER.encodeSequence([
      DER.encodeSet([
        DER.encodeSequence([
          DER.encodeObjectIdentifier('2.5.4.3'), // commonName X.520 DN component
          DER.encodePrintableString('localhost')
        ]),
      ]),
      DER.encodeSet([
        DER.encodeSequence([
          DER.encodeObjectIdentifier('2.5.4.10'), // organizationName X.520 DN component
          DER.encodePrintableString('Playwright Client Certificate Support')
        ])
      ])
    ]), // subject
    DER.encodeSequence([
      DER.encodeSequence([
        DER.encodeObjectIdentifier('1.2.840.113549.1.1.1'), // rsaEncryption PKCS #1
        DER.encodeNull()
      ]),
      DER.encodeBitString(publicKeyDer)
    ]), // SubjectPublicKeyInfo
  ]);

  const signature = crypto.sign('sha256', tbsCertificate, privateKey);

  const certificate = DER.encodeSequence([
    tbsCertificate,
    DER.encodeSequence([
      DER.encodeObjectIdentifier('1.2.840.113549.1.1.11'), // sha256WithRSAEncryption PKCS #1
      DER.encodeNull()
    ]),
    DER.encodeBitString(signature)
  ]);

  const certPem = [
    '-----BEGIN CERTIFICATE-----',
    // Split the base64 string into lines of 64 characters
    certificate.toString('base64').match(/.{1,64}/g)!.join('\n'),
    '-----END CERTIFICATE-----'
  ].join('\n');

  return {
    cert: certPem,
    key: privateKey.export({ type: 'pkcs1', format: 'pem' }),
  };
}
