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// 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
//
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package org.openqa.selenium.remote.http;

import com.google.common.base.Preconditions;
import com.google.common.collect.ImmutableMap;
import org.openqa.selenium.json.Json;

import java.util.LinkedList;
import java.util.List;
import java.util.Map;
import java.util.Objects;
import java.util.function.Function;
import java.util.function.Predicate;
import java.util.function.Supplier;
import java.util.stream.Stream;
import java.util.stream.StreamSupport;

import static com.google.common.base.Preconditions.checkArgument;
import static com.google.common.collect.ImmutableList.toImmutableList;
import static java.net.HttpURLConnection.HTTP_INTERNAL_ERROR;
import static java.net.HttpURLConnection.HTTP_NOT_FOUND;
import static org.openqa.selenium.remote.http.Contents.utf8String;
import static org.openqa.selenium.remote.http.HttpMethod.DELETE;
import static org.openqa.selenium.remote.http.HttpMethod.GET;
import static org.openqa.selenium.remote.http.HttpMethod.POST;
import static org.openqa.selenium.remote.http.UrlPath.ROUTE_PREFIX_KEY;

public abstract class Route implements HttpHandler, Routable {

  private static final Json JSON = new Json();

  public HttpHandler fallbackTo(Supplier handler) {
    Objects.requireNonNull(handler, "Handler to use must be set.");
    return req -> {
      if (matches(req)) {
        return Route.this.execute(req);
      }
      return Objects.requireNonNull(handler.get(), "Handler to use must be set.").execute(req);
    };
  }

  @Override
  public final HttpResponse execute(HttpRequest req) {
    if (!matches(req)) {
      return new HttpResponse()
        .setStatus(HTTP_NOT_FOUND)
        .setContent(utf8String(JSON.toJson(ImmutableMap.of(
          "value", ImmutableMap.of(
            "error", "unknown command",
            "message", "Unable to find handler for " + req,
            "stacktrace", "")))));
    }

    HttpResponse res = handle(req);

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

    return new HttpResponse()
      .setStatus(HTTP_INTERNAL_ERROR)
      .addHeader("WebDriver-Error", "unsupported operation")
      .addHeader("Selenium-Route", "NULL_RES")
      .setContent(utf8String(JSON.toJson(ImmutableMap.of(
        "value", ImmutableMap.of(
          "error", "unsupported operation",
          "message", String.format("Found handler for %s, but nothing was returned", req),
          "stacktrace", "")))));
  }

  protected abstract HttpResponse handle(HttpRequest req);

  public static PredicatedConfig matching(Predicate predicate) {
    Objects.requireNonNull(predicate, "Predicate to use must be set.");
    return new PredicatedConfig(predicate);
  }

  public static TemplatizedRouteConfig delete(String template) {
    Objects.requireNonNull(template, "URL template to use must be set.");
    UrlTemplate urlTemplate = new UrlTemplate(template);

    return new TemplatizedRouteConfig(
        new MatchesHttpMethod(DELETE).and(new MatchesTemplate(urlTemplate)),
        urlTemplate);
  }

  public static TemplatizedRouteConfig get(String template) {
    Objects.requireNonNull(template, "URL template to use must be set.");
    UrlTemplate urlTemplate = new UrlTemplate(template);

    return new TemplatizedRouteConfig(
        new MatchesHttpMethod(GET).and(new MatchesTemplate(urlTemplate)),
        urlTemplate);
  }

  public static TemplatizedRouteConfig post(String template) {
    Objects.requireNonNull(template, "URL template to use must be set.");
    UrlTemplate urlTemplate = new UrlTemplate(template);

    return new TemplatizedRouteConfig(
        new MatchesHttpMethod(POST).and(new MatchesTemplate(urlTemplate)),
        urlTemplate);
  }

  public static NestedRouteConfig prefix(String prefix) {
    Objects.requireNonNull(prefix, "Prefix to use must be set.");
    checkArgument(!prefix.isEmpty(), "Prefix to use must not be of 0 length");
    return new NestedRouteConfig(prefix);
  }

  public static Route combine(Routable first, Routable... others) {
    Objects.requireNonNull(first, "At least one route must be set.");
    return new CombinedRoute(Stream.concat(Stream.of(first), Stream.of(others)));
  }

  public static Route combine(Iterable routes) {
    Objects.requireNonNull(routes, "At least one route must be set.");

    return new CombinedRoute(StreamSupport.stream(routes.spliterator(), false));
  }

  public static class TemplatizedRouteConfig {

    private final Predicate predicate;
    private final UrlTemplate template;

    private TemplatizedRouteConfig(Predicate predicate, UrlTemplate template) {
      this.predicate = Objects.requireNonNull(predicate);
      this.template = Objects.requireNonNull(template);
    }

    public Route to(Supplier handler) {
      Objects.requireNonNull(handler, "Handler supplier must be set.");
      return to(params -> handler.get());
    }

    public Route to(Function, HttpHandler> handlerFunc) {
      Objects.requireNonNull(handlerFunc, "Handler creator must be set.");
      return new TemplatizedRoute(template, predicate, handlerFunc);
    }
  }

  private static class TemplatizedRoute extends Route {

    private final UrlTemplate template;
    private final Predicate predicate;
    private final Function, HttpHandler> handlerFunction;

    private TemplatizedRoute(
        UrlTemplate template,
        Predicate predicate,
        Function, HttpHandler> handlerFunction) {
      this.template = Objects.requireNonNull(template);
      this.predicate = Objects.requireNonNull(predicate);
      this.handlerFunction = Objects.requireNonNull(handlerFunction);
    }

    @Override
    public boolean matches(HttpRequest request) {
      return predicate.test(request);
    }

    @Override
    protected HttpResponse handle(HttpRequest req) {
      UrlTemplate.Match match = template.match(req.getUri());
      HttpHandler handler = handlerFunction.apply(
          match == null ? ImmutableMap.of() : match.getParameters());

      if (handler == null) {
        return new HttpResponse()
            .setStatus(HTTP_INTERNAL_ERROR)
            .setContent(utf8String("Unable to find handler for " + req));
      }

      return handler.execute(req);
    }
  }

  private static class MatchesHttpMethod implements Predicate {

    private final HttpMethod method;

    private MatchesHttpMethod(HttpMethod method) {
      this.method = Objects.requireNonNull(method, "HTTP method to test must be set.");
    }

    @Override
    public boolean test(HttpRequest request) {
      return method == request.getMethod();
    }
  }

  private static class MatchesTemplate implements Predicate {

    private final UrlTemplate template;

    private MatchesTemplate(UrlTemplate template) {
      this.template = Objects.requireNonNull(template, "URL template to test must be set.");
    }

    @Override
    public boolean test(HttpRequest request) {
      return template.match(request.getUri()) != null;
    }
  }

  public static class NestedRouteConfig {

    private final String prefix;

    private NestedRouteConfig(String prefix) {
      this.prefix = Objects.requireNonNull(prefix, "Prefix must be set.");
    }

    public Route to(Route route) {
      Objects.requireNonNull(route, "Target for requests must be set.");
      return new NestedRoute(prefix, route);
    }
  }

  private static class NestedRoute extends Route {

    private final String[] prefixPaths;
    private final String prefix;
    private final Route route;

    private NestedRoute(String prefix, Route route) {
      this.prefixPaths = Objects.requireNonNull(prefix, "Prefix must be set.").split("/");
      this.prefix = prefix;
      this.route = Objects.requireNonNull(route, "Target for requests must be set.");
    }

    @Override
    public boolean matches(HttpRequest request) {
      return hasPrefix(request) && route.matches(transform(request));
    }

    private boolean hasPrefix(HttpRequest request) {
      String[] parts = request.getUri().split("/");
      if (parts.length < prefixPaths.length) {
        return false;
      }
      for (int i = 0; i < prefixPaths.length; i++) {
        if (!prefixPaths[i].equals(parts[i])) {
          return false;
        }
      }
      return true;
    }

    @Override
    protected HttpResponse handle(HttpRequest req) {
      return route.execute(transform(req));
    }

    private HttpRequest transform(HttpRequest request) {
      // Strip the prefix from the existing request and forward it.
      String unprefixed = hasPrefix(request) ?
                          request.getUri().substring(prefix.length()) :
                          request.getUri();

      HttpRequest toForward = new HttpRequest(request.getMethod(), unprefixed);

      request.getHeaderNames().forEach(name -> {
        if (name == null) {
          return;
        }
        request.getHeaders(name).forEach(value -> toForward.addHeader(name, value));
      });

      request.getAttributeNames().forEach(
          attr -> toForward.setAttribute(attr, request.getAttribute(attr)));

      // Don't forget to register our prefix
      Object rawPrefixes = request.getAttribute(ROUTE_PREFIX_KEY);
      if (!(rawPrefixes instanceof List)) {
        rawPrefixes = new LinkedList<>();
      }
      List prefixes = Stream.concat(((List) rawPrefixes).stream(), Stream.of(prefix))
        .map(String::valueOf)
        .collect(toImmutableList());
      toForward.setAttribute(ROUTE_PREFIX_KEY, prefixes);

      request.getQueryParameterNames().forEach(name -> {
        request.getQueryParameters(name).forEach(value -> toForward.addQueryParameter(name, value));
      });

      toForward.setContent(request.getContent());

      return toForward;
    }
  }

  private static class CombinedRoute extends Route {

    private final List allRoutes;

    private CombinedRoute(Stream routes) {
      // We want later routes to have a greater chance of being called so that we can override
      // routes as necessary.
      allRoutes = routes.collect(toImmutableList()).reverse();
      Preconditions.checkArgument(!allRoutes.isEmpty(), "At least one route must be specified.");
    }

    @Override
    public boolean matches(HttpRequest request) {
      return allRoutes.stream().anyMatch(route -> route.matches(request));
    }

    @Override
    protected HttpResponse handle(HttpRequest req) {
      return allRoutes.stream()
          .filter(route -> route.matches(req))
          .findFirst()
          .map(route -> (HttpHandler) route)
          .orElse(request -> new HttpResponse()
              .setStatus(HTTP_NOT_FOUND)
              .setContent(utf8String("No handler found for " + request)))
          .execute(req);
    }
  }

  public static class PredicatedConfig {
    private final Predicate predicate;

    private PredicatedConfig(Predicate predicate) {
        this.predicate = Objects.requireNonNull(predicate);
    }

    public Route to(Supplier handler) {
      Objects.requireNonNull(handler, "Handler supplier must be set.");
      return new PredicatedRoute(predicate, handler);
    }
  }

  private static class PredicatedRoute extends Route {

    private final Predicate predicate;
    private final Supplier supplier;

    private PredicatedRoute(Predicate predicate, Supplier supplier) {
      this.predicate = Objects.requireNonNull(predicate);
      this.supplier = Objects.requireNonNull(supplier);
    }

    @Override
    public boolean matches(HttpRequest httpRequest) {
      return predicate.test(httpRequest);
    }

    @Override
    protected HttpResponse handle(HttpRequest req) {
      HttpHandler handler = supplier.get();
      if (handler == null) {
        throw new IllegalStateException("No handler available.");
      }
      return handler.execute(req);
    }
  }
}