/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

const { fromBER } = asn1js.asn1js;
const { Certificate } = pkijs.pkijs;
import {
  b64urltodec,
  b64urltohex,
  getObjPath,
  hash,
  hashify,
} from "./utils.js";
import { strings } from "./strings.js";
import { ctLogNames } from "./ctlognames.js";

const getTimeZone = () => {
  let timeZone = new Date().toString().match(/\(([A-Za-z\s].*)\)/);
  if (timeZone === null) {
    // America/Chicago
    timeZone = Intl.DateTimeFormat().resolvedOptions().timeZone;
  } else if (timeZone.length > 1) {
    timeZone = timeZone[1]; // Central Daylight Time
  } else {
    timeZone = "Local Time"; // not sure if this is right, but let's go with it for now
  }
  return timeZone;
};

const getPublicKeyInfo = x509 => {
  let spki = Object.assign(
    {
      crv: undefined,
      e: undefined,
      kty: undefined,
      n: undefined,
      keysize: undefined,
      x: undefined,
      xy: undefined,
      y: undefined,
    },
    x509.subjectPublicKeyInfo
  );

  if (spki.kty === "RSA") {
    spki.e = b64urltodec(spki.e); // exponent
    spki.keysize = b64urltohex(spki.n).length * 8; // key size in bits
    spki.n = hashify(b64urltohex(spki.n)); // modulus
  } else if (spki.kty === "EC") {
    spki.kty = "Elliptic Curve";
    spki.keysize = parseInt(spki.crv.split("-")[1]); // this is a bit hacky
    spki.x = hashify(b64urltohex(spki.x)); // x coordinate
    spki.y = hashify(b64urltohex(spki.y)); // y coordinate
    spki.xy = `04:${spki.x}:${spki.y}`; // 04 (uncompressed) public key
  }
  return spki;
};

const getX509Ext = (extensions, v) => {
  for (var extension in extensions) {
    if (extensions[extension].extnID === v) {
      return extensions[extension];
    }
  }
  return {
    extnValue: undefined,
    parsedValue: undefined,
  };
};

const getKeyUsages = (x509, criticalExtensions) => {
  let keyUsages = {
    critical: criticalExtensions.includes("2.5.29.15"),
    purposes: [],
  };

  let keyUsagesBS = getX509Ext(x509.extensions, "2.5.29.15").parsedValue;
  if (keyUsagesBS !== undefined) {
    // parse the bit string, shifting as necessary
    let unusedBits = keyUsagesBS.valueBlock.unusedBits;
    keyUsagesBS = parseInt(keyUsagesBS.valueBlock.valueHex, 16) >> unusedBits;

    // iterate through the bit string
    strings.keyUsages.slice(unusedBits - 1).forEach(usage => {
      if (keyUsagesBS & 1) {
        keyUsages.purposes.push(usage);
      }

      keyUsagesBS = keyUsagesBS >> 1;
    });

    // reverse the order for legibility
    keyUsages.purposes.reverse();
  }

  return keyUsages;
};

const parseSubsidiary = distinguishedNames => {
  const subsidiary = {
    cn: "",
    dn: [],
    entries: [],
  };

  distinguishedNames.forEach(dn => {
    const name = strings.names[dn.type];
    const value = dn.value.valueBlock.value;

    if (name === undefined) {
      subsidiary.dn.push(`OID.${dn.type}=${value}`);
      subsidiary.entries.push([`OID.${dn.type}`, value]);
    } else if (name.short === undefined) {
      subsidiary.dn.push(`OID.${dn.type}=${value}`);
      subsidiary.entries.push([name.long, value]);
    } else {
      subsidiary.dn.push(`${name.short}=${value}`);
      subsidiary.entries.push([name.long, value]);

      // add the common name for tab display
      if (name.short === "cn") {
        subsidiary.cn = value;
      }
    }
  });

  // turn path into a string
  subsidiary.dn = subsidiary.dn.join(", ");

  return subsidiary;
};

const getSubjectAltNames = (x509, criticalExtensions) => {
  let san = getX509Ext(x509.extensions, "2.5.29.17").parsedValue;
  if (san && san.hasOwnProperty("altNames")) {
    san = Object.keys(san.altNames).map(x => {
      const type = san.altNames[x].type;

      switch (type) {
        case 4: // directory
          return [
            strings.san[type],
            parseSubsidiary(san.altNames[x].value.typesAndValues).dn,
          ];
        case 7: // ip address
          let address = san.altNames[x].value.valueBlock.valueHex;

          if (address.length === 8) {
            // ipv4
            return [
              strings.san[type],
              address
                .match(/.{1,2}/g)
                .map(x => parseInt(x, 16))
                .join("."),
            ];
          } else if (address.length === 32) {
            // ipv6
            return [
              strings.san[type],
              address
                .toLowerCase()
                .match(/.{1,4}/g)
                .join(":")
                .replace(/\b:?(?:0+:?){2,}/, "::"),
            ];
          }
          return [strings.san[type], "Unknown IP address"];

        default:
          return [strings.san[type], san.altNames[x].value];
      }
    });
  } else {
    san = [];
  }
  san = {
    altNames: san,
    critical: criticalExtensions.includes("2.5.29.17"),
  };
  return san;
};

const getBasicConstraints = (x509, criticalExtensions) => {
  let basicConstraints;
  const basicConstraintsExt = getX509Ext(x509.extensions, "2.5.29.19");
  if (basicConstraintsExt && basicConstraintsExt.parsedValue) {
    basicConstraints = {
      cA:
        basicConstraintsExt.parsedValue.cA !== undefined &&
        basicConstraintsExt.parsedValue.cA,
      critical: criticalExtensions.includes("2.5.29.19"),
    };
  }
  return basicConstraints;
};

const getEKeyUsages = (x509, criticalExtensions) => {
  let eKeyUsages = getX509Ext(x509.extensions, "2.5.29.37").parsedValue;
  if (eKeyUsages) {
    eKeyUsages = {
      critical: criticalExtensions.includes("2.5.29.37"),
      purposes: eKeyUsages.keyPurposes.map(x => strings.eKU[x] || x),
    };
  }
  return eKeyUsages;
};

const getSubjectKeyID = (x509, criticalExtensions) => {
  let sKID = getX509Ext(x509.extensions, "2.5.29.14").parsedValue;
  if (sKID) {
    sKID = {
      critical: criticalExtensions.includes("2.5.29.14"),
      id: hashify(sKID.valueBlock.valueHex),
    };
  }
  return sKID;
};

const getAuthorityKeyID = (x509, criticalExtensions) => {
  let aKID = getX509Ext(x509.extensions, "2.5.29.35").parsedValue;
  if (!aKID || !aKID.keyIdentifier) {
    return null;
  }
  aKID = {
    critical: criticalExtensions.includes("2.5.29.35"),
    id: hashify(aKID.keyIdentifier.valueBlock.valueHex),
  };
  return aKID;
};

const getCRLPoints = (x509, criticalExtensions) => {
  let crlPoints = getX509Ext(x509.extensions, "2.5.29.31").parsedValue;
  if (crlPoints) {
    crlPoints = {
      critical: criticalExtensions.includes("2.5.29.31"),
      points: crlPoints.distributionPoints.map(
        x => x.distributionPoint[0].value
      ),
    };
  }
  return crlPoints;
};

const getOcspStaple = (x509, criticalExtensions) => {
  let ocspStaple = getX509Ext(x509.extensions, "1.3.6.1.5.5.7.1.24").extnValue;
  if (ocspStaple && ocspStaple.valueBlock.valueHex === "3003020105") {
    ocspStaple = {
      critical: criticalExtensions.includes("1.3.6.1.5.5.7.1.24"),
      required: true,
    };
  } else {
    ocspStaple = {
      critical: criticalExtensions.includes("1.3.6.1.5.5.7.1.24"),
      required: false,
    };
  }
  return ocspStaple;
};

const getAuthorityInfoAccess = (x509, criticalExtensions) => {
  let aia = getX509Ext(x509.extensions, "1.3.6.1.5.5.7.1.1").parsedValue;
  if (aia) {
    aia = aia.accessDescriptions.map(x => {
      return {
        location: x.accessLocation.value,
        method: strings.aia[x.accessMethod],
      };
    });
  }

  aia = {
    descriptions: aia,
    critical: criticalExtensions.includes("1.3.6.1.5.5.7.1.1"),
  };
  return aia;
};

const getSCTs = (x509, criticalExtensions) => {
  let scts = getX509Ext(x509.extensions, "1.3.6.1.4.1.11129.2.4.2").parsedValue;
  if (scts) {
    scts = Object.keys(scts.timestamps).map(x => {
      let logId = scts.timestamps[x].logID.toLowerCase();
      let sctsTimestamp = scts.timestamps[x].timestamp;
      return {
        logId: hashify(logId),
        name: ctLogNames.hasOwnProperty(logId) ? ctLogNames[logId] : undefined,
        signatureAlgorithm: `${scts.timestamps[x].hashAlgorithm.replace(
          "sha",
          "SHA-"
        )} ${scts.timestamps[x].signatureAlgorithm.toUpperCase()}`,
        timestamp: `${sctsTimestamp.toLocaleString()} (${getTimeZone()})`,
        timestampUTC: sctsTimestamp.toUTCString(),
        version: scts.timestamps[x].version + 1,
      };
    });
  } else {
    scts = [];
  }

  scts = {
    critical: criticalExtensions.includes("1.3.6.1.4.1.11129.2.4.2"),
    timestamps: scts,
  };
  return scts;
};

const getCertificatePolicies = (x509, criticalExtensions) => {
  let cp = getX509Ext(x509.extensions, "2.5.29.32").parsedValue;
  if (cp && cp.hasOwnProperty("certificatePolicies")) {
    cp = cp.certificatePolicies.map(x => {
      let id = x.policyIdentifier;
      let name = strings.cps.hasOwnProperty(id)
        ? strings.cps[id].name
        : undefined;
      let qualifiers = undefined;
      let value = strings.cps.hasOwnProperty(id)
        ? strings.cps[id].value
        : undefined;

      // ansi organization identifiers
      if (id.startsWith("2.16.840.")) {
        value = id;
        id = "2.16.840";
        name = strings.cps["2.16.840"].name;
      }

      // statement identifiers
      if (id.startsWith("1.3.6.1.4.1")) {
        value = id;
        id = "1.3.6.1.4.1";
        name = strings.cps["1.3.6.1.4.1"].name;
      }

      if (x.hasOwnProperty("policyQualifiers")) {
        qualifiers = x.policyQualifiers.map(qualifier => {
          let id = qualifier.policyQualifierId;
          let name = strings.cps.hasOwnProperty(id)
            ? strings.cps[id].name
            : undefined;
          let value = qualifier.qualifier.valueBlock.value;

          // sometimes they are multiple qualifier subblocks, and for now we'll
          // only return the first one because it's getting really messy at this point
          if (Array.isArray(value) && value.length === 1) {
            value = value[0].valueBlock.value;
          } else if (Array.isArray(value) && value.length > 1) {
            value = "(currently unsupported)";
          }

          return {
            id,
            name,
            value,
          };
        });
      }

      return {
        id,
        name,
        qualifiers,
        value,
      };
    });
  }

  cp = {
    critical: criticalExtensions.includes("2.5.29.32"),
    policies: cp,
  };
  return cp;
};

const getMicrosoftCryptographicExtensions = (x509, criticalExtensions) => {
  // now let's parse the Microsoft cryptographic extensions
  let msCrypto = {
    caVersion: getX509Ext(x509.extensions, "1.3.6.1.4.1.311.21.1").parsedValue,
    certificatePolicies: getX509Ext(x509.extensions, "1.3.6.1.4.1.311.21.10")
      .parsedValue,
    certificateTemplate: getX509Ext(x509.extensions, "1.3.6.1.4.1.311.21.7")
      .parsedValue,
    certificateType: getX509Ext(x509.extensions, "1.3.6.1.4.1.311.20.2")
      .parsedValue,
    previousHash: getX509Ext(x509.extensions, "1.3.6.1.4.1.311.21.2")
      .parsedValue,
  };

  if (
    msCrypto.caVersion &&
    Number.isInteger(msCrypto.caVersion.keyIndex) &&
    Number.isInteger(msCrypto.caVersion.certificateIndex)
  ) {
    msCrypto.caVersion = {
      critical: criticalExtensions.includes("1.3.6.1.4.1.311.21.1"),
      caRenewals: msCrypto.caVersion.certificateIndex,
      keyReuses:
        msCrypto.caVersion.certificateIndex - msCrypto.caVersion.keyIndex,
    };
  }

  if (msCrypto.certificatePolicies) {
    msCrypto.certificatePolicies = {
      critical: criticalExtensions.includes("1.3.6.1.4.1.311.21.10"),
      purposes: msCrypto.certificatePolicies.certificatePolicies.map(
        x => strings.eKU[x.policyIdentifier] || x.policyIdentifier
      ),
    };
  }

  if (msCrypto.certificateTemplate) {
    msCrypto.certificateTemplate = {
      critical: criticalExtensions.includes("1.3.6.1.4.1.311.21.7"),
      id: msCrypto.certificateTemplate.extnID,
      major: msCrypto.certificateTemplate.templateMajorVersion,
      minor: msCrypto.certificateTemplate.templateMinorVersion,
    };
  }

  if (msCrypto.certificateType) {
    msCrypto.certificateType = {
      critical: criticalExtensions.includes("1.3.6.1.4.1.311.20.2"),
      type:
        strings.microsoftCertificateTypes[
          msCrypto.certificateType.valueBlock.value
        ] || "Unknown",
    };
  }

  if (msCrypto.previousHash) {
    msCrypto.previousHash = {
      critical: criticalExtensions.includes("1.3.6.1.4.1.311.21.2"),
      previousHash: hashify(msCrypto.previousHash.valueBlock.valueHex),
    };
  }

  msCrypto.exists = !!(
    msCrypto.caVersion ||
    msCrypto.certificatePolicies ||
    msCrypto.certificateTemplate ||
    msCrypto.certificateType ||
    msCrypto.previousHash
  );

  return msCrypto;
};

export const parse = async certificate => {
  // certificate could be an array of BER or an array of buffers
  const supportedExtensions = [
    "1.3.6.1.4.1.311.20.2", // microsoft certificate type
    "1.3.6.1.4.1.311.21.2", // microsoft certificate previous hash
    "1.3.6.1.4.1.311.21.7", // microsoft certificate template
    "1.3.6.1.4.1.311.21.1", // microsoft certification authority renewal
    "1.3.6.1.4.1.311.21.10", // microsoft certificate policies
    "1.3.6.1.4.1.11129.2.4.2", // embedded scts
    "1.3.6.1.5.5.7.1.1", // authority info access
    "1.3.6.1.5.5.7.1.24", // ocsp stapling
    "1.3.101.77", // ct redaction - deprecated and not displayed
    "2.5.29.14", // subject key identifier
    "2.5.29.15", // key usages
    "2.5.29.17", // subject alt names
    "2.5.29.19", // basic constraints
    "2.5.29.31", // crl points
    "2.5.29.32", // certificate policies
    "2.5.29.35", // authority key identifier
    "2.5.29.37", // extended key usage
  ];

  let timeZone = getTimeZone();

  // parse the certificate
  const asn1 = fromBER(certificate);

  let x509 = new Certificate({ schema: asn1.result });
  x509 = x509.toJSON();

  // convert the cert to PEM
  const certBTOA = window
    .btoa(String.fromCharCode.apply(null, new Uint8Array(certificate)))
    .match(/.{1,64}/g)
    .join("\r\n");

  // get which extensions are critical
  const criticalExtensions = [];
  if (x509.extensions) {
    x509.extensions.forEach(ext => {
      if (ext.hasOwnProperty("critical") && ext.critical === true) {
        criticalExtensions.push(ext.extnID);
      }
    });
  }
  const spki = getPublicKeyInfo(x509);
  const keyUsages = getKeyUsages(x509, criticalExtensions);
  const san = getSubjectAltNames(x509, criticalExtensions);
  const basicConstraints = getBasicConstraints(x509, criticalExtensions);
  const eKeyUsages = getEKeyUsages(x509, criticalExtensions);
  const sKID = getSubjectKeyID(x509, criticalExtensions);
  const aKID = getAuthorityKeyID(x509, criticalExtensions);
  const crlPoints = getCRLPoints(x509, criticalExtensions);
  const ocspStaple = getOcspStaple(x509, criticalExtensions);
  const aia = getAuthorityInfoAccess(x509, criticalExtensions);
  const scts = getSCTs(x509, criticalExtensions);
  const cp = getCertificatePolicies(x509, criticalExtensions);
  const msCrypto = getMicrosoftCryptographicExtensions(
    x509,
    criticalExtensions
  );

  // determine which extensions weren't supported
  let unsupportedExtensions = [];
  if (x509.extensions) {
    x509.extensions.forEach(ext => {
      if (!supportedExtensions.includes(ext.extnID)) {
        unsupportedExtensions.push(ext.extnID);
      }
    });
  }

  // the output shell
  return {
    ext: {
      aia,
      aKID,
      basicConstraints,
      crlPoints,
      cp,
      eKeyUsages,
      keyUsages,
      msCrypto,
      ocspStaple,
      scts,
      sKID,
      san,
    },
    files: {
      der: undefined, // TODO: implement!
      pem: encodeURI(
        `-----BEGIN CERTIFICATE-----\r\n${certBTOA}\r\n-----END CERTIFICATE-----\r\n`
      ),
    },
    fingerprint: {
      sha1: await hash("SHA-1", certificate),
      sha256: await hash("SHA-256", certificate),
    },
    issuer: parseSubsidiary(x509.issuer.typesAndValues),
    notBefore: `${x509.notBefore.value.toLocaleString()} (${timeZone})`,
    notBeforeUTC: x509.notBefore.value.toUTCString(),
    notAfter: `${x509.notAfter.value.toLocaleString()} (${timeZone})`,
    notAfterUTC: x509.notAfter.value.toUTCString(),
    subject: parseSubsidiary(x509.subject.typesAndValues),
    serialNumber: hashify(getObjPath(x509, "serialNumber.valueBlock.valueHex")),
    signature: {
      name: strings.signature[getObjPath(x509, "signature.algorithmId")],
      type: getObjPath(x509, "signature.algorithmId"),
    },
    subjectPublicKeyInfo: spki,
    unsupportedExtensions,
    version: (x509.version + 1).toString(),
  };
};