/* Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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.
 */

// This code is based on AOSP /libcore/luni/src/main/java/java/net/ProxySelectorImpl.java

package org.mozilla.gecko.util;

import android.text.TextUtils;
import androidx.annotation.Nullable;
import java.io.IOException;
import java.net.InetSocketAddress;
import java.net.Proxy;
import java.net.URI;
import java.net.URLConnection;
import java.util.List;

public class ProxySelector {
  public static URLConnection openConnectionWithProxy(final URI uri) throws IOException {
    final java.net.ProxySelector ps = java.net.ProxySelector.getDefault();
    Proxy proxy = Proxy.NO_PROXY;
    if (ps != null) {
      final List<Proxy> proxies = ps.select(uri);
      if (proxies != null && !proxies.isEmpty()) {
        proxy = proxies.get(0);
      }
    }

    return uri.toURL().openConnection(proxy);
  }

  public ProxySelector() {}

  public Proxy select(final String scheme, final String host) {
    int port = -1;
    Proxy proxy = null;
    String nonProxyHostsKey = null;
    boolean httpProxyOkay = true;
    if ("http".equalsIgnoreCase(scheme)) {
      port = 80;
      nonProxyHostsKey = "http.nonProxyHosts";
      proxy = lookupProxy("http.proxyHost", "http.proxyPort", Proxy.Type.HTTP, port);
    } else if ("https".equalsIgnoreCase(scheme)) {
      port = 443;
      nonProxyHostsKey = "https.nonProxyHosts"; // RI doesn't support this
      proxy = lookupProxy("https.proxyHost", "https.proxyPort", Proxy.Type.HTTP, port);
    } else if ("ftp".equalsIgnoreCase(scheme)) {
      port = 80; // not 21 as you might guess
      nonProxyHostsKey = "ftp.nonProxyHosts";
      proxy = lookupProxy("ftp.proxyHost", "ftp.proxyPort", Proxy.Type.HTTP, port);
    } else if ("socket".equalsIgnoreCase(scheme)) {
      httpProxyOkay = false;
    } else {
      return Proxy.NO_PROXY;
    }

    if (nonProxyHostsKey != null && isNonProxyHost(host, System.getProperty(nonProxyHostsKey))) {
      return Proxy.NO_PROXY;
    }

    if (proxy != null) {
      return proxy;
    }

    if (httpProxyOkay) {
      proxy = lookupProxy("proxyHost", "proxyPort", Proxy.Type.HTTP, port);
      if (proxy != null) {
        return proxy;
      }
    }

    proxy = lookupProxy("socksProxyHost", "socksProxyPort", Proxy.Type.SOCKS, 1080);
    if (proxy != null) {
      return proxy;
    }

    return Proxy.NO_PROXY;
  }

  /** Returns the proxy identified by the {@code hostKey} system property, or null. */
  @Nullable
  private Proxy lookupProxy(
      final String hostKey, final String portKey, final Proxy.Type type, final int defaultPort) {
    final String host = System.getProperty(hostKey);
    if (TextUtils.isEmpty(host)) {
      return null;
    }

    final int port = getSystemPropertyInt(portKey, defaultPort);
    if (port == -1) {
      // Port can be -1. See bug 1270529.
      return null;
    }

    return new Proxy(type, InetSocketAddress.createUnresolved(host, port));
  }

  private int getSystemPropertyInt(final String key, final int defaultValue) {
    final String string = System.getProperty(key);
    if (string != null) {
      try {
        return Integer.parseInt(string);
      } catch (final NumberFormatException ignored) {
      }
    }
    return defaultValue;
  }

  /**
   * Returns true if the {@code nonProxyHosts} system property pattern exists and matches {@code
   * host}.
   */
  private boolean isNonProxyHost(final String host, final String nonProxyHosts) {
    if (host == null || nonProxyHosts == null) {
      return false;
    }

    // construct pattern
    final StringBuilder patternBuilder = new StringBuilder();
    for (int i = 0; i < nonProxyHosts.length(); i++) {
      final char c = nonProxyHosts.charAt(i);
      switch (c) {
        case '.':
          patternBuilder.append("\\.");
          break;
        case '*':
          patternBuilder.append(".*");
          break;
        default:
          patternBuilder.append(c);
      }
    }
    // check whether the host is the nonProxyHosts.
    final String pattern = patternBuilder.toString();
    return host.matches(pattern);
  }
}