/*
 * Copyright 2019 Red Hat, Inc.
 *
 *  All rights reserved. This program and the accompanying materials
 *  are made available under the terms of the Eclipse Public License v1.0
 *  and Apache License v2.0 which accompanies this distribution.
 *
 *  The Eclipse Public License is available at
 *  http://www.eclipse.org/legal/epl-v10.html
 *
 *  The Apache License v2.0 is available at
 *  http://www.opensource.org/licenses/apache2.0.php
 *
 *  You may elect to redistribute this code under either of these licenses.
 */

package io.vertx.ext.auth.impl.cose;

import io.vertx.core.json.JsonObject;
import io.vertx.ext.auth.impl.jose.JWK;

import java.util.Collections;
import java.util.HashMap;
import java.util.Map;

CBOR Object Signing and Encryption (COSE)
Concise Binary Object Representation (CBOR) is a data format designed
for small code size and small message size.  There is a need for the
ability to have basic security services defined for this data format.
This document defines the CBOR Object Signing and Encryption (COSE)
protocol.  This specification describes how to create and process
signatures, message authentication codes, and encryption using CBOR
for serialization.  This specification additionally describes how to
represent cryptographic keys using CBOR.
This class allows converting a COSE KEY to a JOSE KEY for ease of use.
Author:
Paulo Lopes/**
 * CBOR Object Signing and Encryption (COSE)
 *
 * Concise Binary Object Representation (CBOR) is a data format designed
 * for small code size and small message size.  There is a need for the
 * ability to have basic security services defined for this data format.
 * This document defines the CBOR Object Signing and Encryption (COSE)
 * protocol.  This specification describes how to create and process
 * signatures, message authentication codes, and encryption using CBOR
 * for serialization.  This specification additionally describes how to
 * represent cryptographic keys using CBOR.
 *
 * This class allows converting a COSE KEY to a JOSE KEY for ease of use.
 *
 * @author <a href="mailto:plopes@redhat.com">Paulo Lopes</a>
 */
public final class CWK {

  private static class NV {
    private final String name;
    private final Map<String, String> values;

    private NV(String name, String... pairs) {
      this.name = name;
      if (pairs == null || pairs.length == 0) {
        this.values = Collections.emptyMap();
      } else {
        Map<String, String> tmp = new HashMap<>();
        for (int i = 0; i < pairs.length; i += 2) {
          tmp.put(pairs[i], pairs[i + 1]);
        }
        this.values = Collections.unmodifiableMap(tmp);
      }
    }
  }

  // main COSE labels
  // defined here: https://tools.ietf.org/html/rfc8152#section-7.1
  private static final Map<String, NV> COSE_LABELS = Collections.unmodifiableMap(new HashMap<String, NV>() {{
    put("1",
      new NV("kty", "1", "OKP", "2", "EC", "3", "RSA"));
    put("2",
      new NV("kid"));
    put("3",
      new NV("alg", "-7", "ES256", "-8", "EdDSA", "-35", "ES384", "-36", "ES512", "-37", "PS256", "-38", "PS384", "-39", "PS512", "-47", "ES256K", "-257", "RS256", "-258", "RS384", "-259", "RS512", "-65535", "RS1"));
    put("4",
      new NV("key_ops"));
    put("5",
      new NV("base_iv"));
  }});

  // ECDSA key parameters
  // defined here: https://tools.ietf.org/html/rfc8152#section-13.1.1
  private static final Map<String, NV> EC_KEY_PARAMS = Collections.unmodifiableMap(new HashMap<String, NV>() {{
    put("-1",
      new NV("crv", "1", "P-256", "2", "P-384", "3", "P-521", "8", "secp256k1")
    );
    put("-2",
      new NV("x"));
    put("-3",
      new NV("y"));
    put("-4",
      new NV("d"));
  }});

  // EdDSA key parameters
  // defined here: https://tools.ietf.org/html/rfc8152#section-13.1.1
  private static final Map<String, NV> OKP_KEY_PARAMS = Collections.unmodifiableMap(new HashMap<String, NV>() {{
    put("-1",
      new NV("crv", "4", "X25519", "5", "X448", "6", "Ed25519", "7", "Ed448")
    );
    put("-2",
      new NV("x"));
    put("-3",
      new NV("y"));
    put("-4",
      new NV("d"));
  }});

  // RSA key parameters
  // defined here: https://tools.ietf.org/html/rfc8230#section-4
  private static final Map<String, NV> RSA_KEY_PARAMS = Collections.unmodifiableMap(new HashMap<String, NV>() {{
    put("-1",
      new NV("n"));
    put("-2",
      new NV("e"));
    put("-3",
      new NV("d"));
    put("-4",
      new NV("p"));
    put("-5",
      new NV("q"));
    put("-6",
      new NV("dp"));
    put("-7",
      new NV("dq"));
    put("-8",
      new NV("qi"));
    put("-9",
      new NV("other"));
    put("-10",
      new NV("r_i"));
    put("-11",
      new NV("d_i"));
    put("-12",
      new NV("t_i"));
  }});

  private static final Map<String, Map<String, NV>> KEY_PARAMS = Collections.unmodifiableMap(new HashMap<String, Map<String, NV>>() {{
    put("OKP", OKP_KEY_PARAMS);
    put("EC", EC_KEY_PARAMS);
    put("RSA", RSA_KEY_PARAMS);
  }});

  public static JWK toJWK(Iterable<Map.Entry<String, Object>> coseMap) {
    JsonObject retKey = new JsonObject();
    Map<String, String> extraMap = new HashMap<>();

    // parse main COSE labels
    for (Map.Entry<String, Object> kv : coseMap) {
      String key = kv.getKey();
      String value = kv.getValue().toString();

      if (!COSE_LABELS.containsKey(key)) {
        extraMap.put(key, value);
        continue;
      }

      String name = COSE_LABELS.get(key).name;
      if (COSE_LABELS.get(key).values.containsKey(value)) {
        value = COSE_LABELS.get(key).values.get(value);
      }

      retKey.put(name, value);
    }

    Map<String, NV> keyParams = KEY_PARAMS.get(retKey.getString("kty"));

    // parse key-specific parameters
    for (Map.Entry<String, String> kv : extraMap.entrySet()) {
      String key = kv.getKey();
      String value = kv.getValue();

      if (!keyParams.containsKey(key)) {
        throw new RuntimeException("unknown COSE key label: " + retKey.getString("kty") + " " + key);
      }

      String name = keyParams.get(key).name;

      if (keyParams.get(key).values.containsKey(value)) {
        value = keyParams.get(key).values.get(value);
      }

      retKey.put(name, value);
    }

    return new JWK(retKey);
  }
}