#pragma once

#include <string>

#include "envoy/buffer/buffer.h"

#include "envoy/common/pure.h"

#include "envoy/http/header_map.h"

#include "envoy/server/admin.h"

#include "absl/strings/string_view.h"

namespace Envoy {

namespace Server {

class AdminHtmlUtil {

public:

  // Overridable mechanism to provide resources for constructing HTML resources.

  // The default implementation uses files that were imported into C++ constants

  // via the build system in target //source/server/admin/html:generate_admin_html.

  // The override can be used to facilitate interactive debugging by dynamically

  // reading resource contents from the file system.

  //

  // Note: rather than creating a new interface here, we could have re-used

  // Filesystem::Instance, however the current implementation of MemFileSystem

  // is intended for tests, and it's simpler to create a much leaner new API

  // rather than make a production-ready version of the full memory-based

  // filesystem.

  class ResourceProvider {

  public:

    virtual ~ResourceProvider() = default;

    /**

     * @param buf a buffer that may be used by the implementation to prepare the return value.

     * @return resource contents

     */

    virtual absl::string_view getResource(absl::string_view resource_name, std::string& buf) PURE;

  };

  /**

   * @param buf a buffer that may be used by the implementation to prepare the return value.

   * @return resource contents

   */

  static absl::string_view getResource(absl::string_view resource_name, std::string& buf);

  /**

   * Renders the beginning of the help-table into the response buffer provided

   * in the constructor.

   */

  static void renderTableBegin(Buffer::Instance&);

  /**

   * Renders the end of the help-table into the response buffer provided in the

   * constructor.

   */

  static void renderTableEnd(Buffer::Instance&);

  /**

   * Renders the head of an admin HTML page. This provides shared styling

   * between the admin home page and endpoints with HTML support. This

   * must be matched with a call to finalize().

   */

  static void renderHead(Http::ResponseHeaderMap& response_headers, Buffer::Instance& response);

  /**

   * Renders the end of a web page that has had renderHead called on it.

   */

  static void finalize(Buffer::Instance& response);

  /**

   * Renders a table row for a URL endpoint, including the name of the endpoint,

   * entries for each parameter, and help text.

   *

   * This must be called after renderTableBegin and before renderTableEnd. Any

   * number of URL Handlers can be rendered.

   *

   * @param response buffer to write the HTML for the handler

   * @param handler the URL handler.

   * @param query query params

   * @param index url handler's index.

   * @param submit_on_change by default, editing parameters does not cause a

   *        form-submit -- you have to click on the link or button first. This

   *        is useful for the admin home page which lays out all the parameters

   *        so users can tweak them before submitting. Setting to true, the form

   *        auto-submits when any parameters change, and does not have its own

   *        explicit submit button. This is used to enable the user to adjust

   *        query-parameters while visiting an html-rendered endpoint.

   * @param active indicates

   */

  static void renderEndpointTableRow(Buffer::Instance& response, const Admin::UrlHandler& handler,

                                     OptRef<const Http::Utility::QueryParams> query, int index,

                                     bool submit_on_change, bool active);

  /**

   * By default, JS, HTML, and CSS files are compiled into the binary. To make it

   * faster to iterate while debugging, You can override the resource provider to

   * load these assets from the file-system every time they are rendered.

   *

   * This function is thread hostile; it must be called before threads are

   * started up, e.g. while parsing arguments in main().

   *

   * The previous resource provider is provided to make unit-testing easier.

   *

   * @return the previous resource provider

   */

  static std::unique_ptr<ResourceProvider>

  setResourceProvider(std::unique_ptr<ResourceProvider> resource_provider);

private:

  static void renderHandlerParam(Buffer::Instance& response, absl::string_view id,

                                 absl::string_view name, absl::string_view path,

                                 Admin::ParamDescriptor::Type type,

                                 OptRef<const Http::Utility::QueryParams> query,

                                 const std::vector<absl::string_view>& enum_choices,

                                 bool submit_on_change);

};

} // namespace Server

} // namespace Envoy