/* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
/*
 * Copyright (c) 2013-2025 Regents of the University of California.
 *
 * This file is part of ndn-cxx library (NDN C++ library with eXperimental eXtensions).
 *
 * ndn-cxx library is free software: you can redistribute it and/or modify it under the
 * terms of the GNU Lesser General Public License as published by the Free Software
 * Foundation, either version 3 of the License, or (at your option) any later version.
 *
 * ndn-cxx library is distributed in the hope that it will be useful, but WITHOUT ANY
 * WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A
 * PARTICULAR PURPOSE.  See the GNU Lesser General Public License for more details.
 *
 * You should have received copies of the GNU General Public License and GNU Lesser
 * General Public License along with ndn-cxx, e.g., in COPYING.md file.  If not, see
 * <http://www.gnu.org/licenses/>.
 *
 * See AUTHORS.md for complete list of ndn-cxx authors and contributors.
 */

#ifndef NDN_CXX_MGMT_DISPATCHER_HPP
#define NDN_CXX_MGMT_DISPATCHER_HPP

#include "ndn-cxx/face.hpp"
#include "ndn-cxx/ims/in-memory-storage-fifo.hpp"
#include "ndn-cxx/mgmt/control-parameters-base.hpp"
#include "ndn-cxx/mgmt/control-response.hpp"
#include "ndn-cxx/mgmt/status-dataset-context.hpp"
#include "ndn-cxx/security/key-chain.hpp"

#include <unordered_map>

namespace ndn::mgmt {

// ---- AUTHORIZATION ----

/** \brief A function to be called if authorization is successful.
 *  \param requester a string that indicates the requester, whose semantics is determined by
 *                   the Authorization function; this value is intended for logging only,
 *                   and should not affect how the request is processed
 */
using AcceptContinuation = std::function<void(const std::string& requester)>;

/**
 * \brief Indicates how to reply in case authorization is rejected.
 */
enum class RejectReply {
  /**
   * \brief Do not reply.
   */
  SILENT,
  /**
   * \brief Reply with a ControlResponse where StatusCode is 403.
   */
  STATUS403
};

/**
 * \brief A function to be called if authorization is rejected.
 */
using RejectContinuation = std::function<void(RejectReply)>;

/** \brief A function that performs authorization.
 *  \param prefix top-level prefix, e.g., `/localhost/nfd`;
 *                This argument can be inspected to allow Interests only under a subset of
 *                top-level prefixes (e.g., allow "/localhost/nfd" only),
 *                or to use different trust model regarding to the prefix.
 *  \param interest incoming Interest
 *  \param params parsed ControlParameters for ControlCommand, otherwise nullptr;
 *                This is guaranteed to be not-null and have correct type for the command,
 *                but may not be valid (e.g., can have missing fields).
 *
 *  Either \p accept or \p reject must be called after authorization completes.
 */
using Authorization = std::function<void(const Name& prefix, const Interest& interest,
                                         const ControlParametersBase* params,
                                         const AcceptContinuation& accept,
                                         const RejectContinuation& reject)>;

/**
 * \brief Return an Authorization that accepts all Interests, with empty string as requester.
 */
Authorization
makeAcceptAllAuthorization();

// ---- CONTROL COMMAND ----

/**
 * \brief A function to validate and normalize the incoming request parameters.
 * \param params The parsed ControlParameters; guaranteed to be of the correct (sub-)type
 *               for the command.
 */
using ValidateParameters = std::function<bool(ControlParametersBase& params)>;

/**
 * \brief A function to be called after a ControlCommandHandler completes.
 * \param resp The response that should be sent back to the requester.
 */
using CommandContinuation = std::function<void(const ControlResponse& resp)>;

/**
 * \brief A function to handle an authorized ControlCommand.
 * \param prefix Top-level prefix, e.g., `/localhost/nfd`.
 * \param interest Incoming Interest carrying the request.
 * \param params The parsed ControlParameters; guaranteed to be of the correct (sub-)type
 *               and to be valid for the command (e.g., has all the required fields).
 * \param done Function that must be called after command processing is complete.
 */
using ControlCommandHandler = std::function<void(const Name& prefix, const Interest& interest,
                                                 const ControlParametersBase& params,
                                                 const CommandContinuation& done)>;

// ---- STATUS DATASET ----

/** \brief A function to handle a StatusDataset request.
 *  \param prefix top-level prefix, e.g., "/localhost/nfd";
 *  \param interest incoming Interest; its Name doesn't contain version and segment components
 *
 *  This function can generate zero or more blocks and pass them to \p append,
 *  and must call \p end upon completion.
 */
using StatusDatasetHandler = std::function<void(const Name& prefix, const Interest& interest,
                                                StatusDatasetContext& context)>;

//---- NOTIFICATION STREAM ----

/**
 * \brief A function to post a notification.
 */
using PostNotification = std::function<void(const Block& notification)>;

// ---- DISPATCHER ----

/**
 * \brief Implements a request dispatcher on server side of NFD Management protocol.
 */
class Dispatcher : noncopyable
{
public:
  /** \brief Constructor.
   *  \param face the Face on which the dispatcher operates
   *  \param keyChain a KeyChain to sign Data
   *  \param signingInfo signing parameters to sign Data with \p keyChain
   *  \param imsCapacity capacity of the internal InMemoryStorage used by dispatcher
   */
  Dispatcher(Face& face, KeyChain& keyChain,
             const security::SigningInfo& signingInfo = security::SigningInfo(),
             size_t imsCapacity = 256);

  /** \brief Add a top-level prefix.
   *  \param prefix a top-level prefix, e.g., "/localhost/nfd"
   *  \param wantRegister whether prefix registration should be performed through the Face
   *  \param signingInfo signing parameters to sign the prefix registration command
   *  \throw std::out_of_range \p prefix overlaps with an existing top-level prefix
   *
   *  Procedure for adding a top-level prefix:
   *  1. if the new top-level prefix overlaps with an existing top-level prefix
   *     (one top-level prefix is a prefix of another top-level prefix), throw std::domain_error.
   *  2. if \p wantRegister is true, invoke Face::registerPrefix for the top-level prefix;
   *     the returned RegisteredPrefixHandle shall be recorded internally, indexed by the top-level
   *     prefix.
   *  3. for each `relPrefix` from ControlCommands and StatusDatasets,
   *     join the top-level prefix with `relPrefix` to obtain the full prefix,
   *     and invoke non-registering overload of Face::setInterestFilter,
   *     with the InterestHandler set to an appropriate private method to handle incoming Interests
   *     for the ControlCommand or StatusDataset; the returned InterestFilterHandle shall be
   *     recorded internally, indexed by the top-level prefix.
   */
  void
  addTopPrefix(const Name& prefix, bool wantRegister = true,
               const security::SigningInfo& signingInfo = security::SigningInfo());

  /** \brief Remove a top-level prefix.
   *  \param prefix a top-level prefix, e.g., "/localhost/nfd"
   *
   *  Procedure for removing a top-level prefix:
   *  1. if the top-level prefix has not been added, abort these steps.
   *  2. if the top-level prefix has been added with `wantRegister`, unregister the prefix.
   *  3. clear all Interest filters set during addTopPrefix().
   */
  void
  removeTopPrefix(const Name& prefix);

public: // ControlCommand
  /**
   * \brief Register a ControlCommand (old style).
   * \tparam ParametersType Concrete subclass of ControlParameters used by this command.
   * \param relPrefix The name prefix for this command relative to the top-level prefix,
   *                  e.g., "faces/create". The prefixes across all ControlCommands,
   *                  StatusDatasets, and NotificationStreams must not overlap (no relPrefix
   *                  is a prefix of another relPrefix).
   * \param authorize Callback to authorize the incoming commands
   * \param validate Callback to validate parameters of the incoming commands
   * \param handle Callback to handle the commands
   * \pre No top-level prefix has been added.
   * \throw std::out_of_range \p relPrefix overlaps with an existing relPrefix.
   * \throw std::domain_error One or more top-level prefixes have been added.
   *
   * Procedure for processing a ControlCommand registered through this function:
   *  1. Extract the NameComponent containing ControlParameters (the component after relPrefix),
   *     and parse ControlParameters into ParametersType; if parsing fails, abort these steps.
   *  2. Perform authorization; if the authorization is rejected, perform the RejectReply action
   *     and abort these steps.
   *  3. Validate the ControlParameters; if validation fails, create a ControlResponse with
   *     StatusCode 400 and go to step 5.
   *  4. Invoke the command handler, wait until CommandContinuation is called.
   *  5. Encode the ControlResponse into one Data packet.
   *  6. Sign the Data packet.
   *  7. If the Data packet is too large, log an error and abort these steps.
   *  8. Send the signed Data packet.
   */
  template<typename ParametersType,
           std::enable_if_t<std::is_convertible_v<ParametersType*, ControlParametersBase*>, int> = 0>
  void
  addControlCommand(const PartialName& relPrefix,
                    Authorization authorize,
                    ValidateParameters validate,
                    ControlCommandHandler handle)
  {
    checkPrefix(relPrefix);

    auto relPrefixLen = relPrefix.size();
    ParametersParser parse = [relPrefixLen] (const Name& prefix,
                                             const auto& interest) -> ControlParametersPtr {
      const name::Component& comp = interest.getName().get(prefix.size() + relPrefixLen);
      return make_shared<ParametersType>(comp.blockFromValue());
    };

    m_handlers[relPrefix] = [this,
                             parser = std::move(parse),
                             authorizer = std::move(authorize),
                             validator = std::move(validate),
                             handler = std::move(handle)] (const auto& prefix, const auto& interest) {
      processCommand(prefix, interest, parser, authorizer, std::move(validator), std::move(handler));
    };
  }

  /**
   * \brief Register a ControlCommand (new style).
   * \tparam Command The type of ControlCommand to register.
   * \param authorize Callback to authorize the incoming commands.
   * \param handle Callback to handle the commands.
   * \pre No top-level prefix has been added.
   * \throw std::out_of_range \p relPrefix overlaps with an existing relPrefix.
   * \throw std::domain_error One or more top-level prefixes have been added.
   *
   * Procedure for processing a ControlCommand registered through this function:
   *  1. Extract the parameters from the request by invoking `Command::parseRequest` on the
   *     incoming Interest; if parsing fails, abort these steps.
   *  2. Perform authorization; if the authorization is rejected, perform the RejectReply action
   *     and abort these steps.
   *  3. Validate the parameters with `Command::validateRequest`.
   *  4. Normalize the parameters with `Command::applyDefaultsToRequest`.
   *  5. If either step 3 or 4 fails, create a ControlResponse with StatusCode 400 and go to step 7.
   *  6. Invoke the command handler, wait until CommandContinuation is called.
   *  7. Encode the ControlResponse into one Data packet.
   *  8. Sign the Data packet.
   *  9. If the Data packet is too large, log an error and abort these steps.
   * 10. Send the signed Data packet.
   */
  template<typename Command>
  void
  addControlCommand(Authorization authorize, ControlCommandHandler handle)
  {
    auto relPrefix = Command::getName();
    checkPrefix(relPrefix);

    ParametersParser parse = [] (const Name& prefix, const auto& interest) {
      return Command::parseRequest(interest, prefix.size());
    };
    ValidateParameters validate = [] (auto& params) {
      auto& reqParams = static_cast<typename Command::RequestParameters&>(params);
      Command::validateRequest(reqParams);
      Command::applyDefaultsToRequest(reqParams);
      // for compatibility with ValidateParameters signature; consider refactoring in the future
      return true;
    };

    m_handlers[relPrefix] = [this,
                             parser = std::move(parse),
                             authorizer = std::move(authorize),
                             validator = std::move(validate),
                             handler = std::move(handle)] (const auto& prefix, const auto& interest) {
      processCommand(prefix, interest, parser, authorizer, std::move(validator), std::move(handler));
    };
  }

public: // StatusDataset
  /**
   * \brief Register a StatusDataset or a prefix under which StatusDatasets can be requested.
   * \param relPrefix The name prefix for this dataset relative to the top-level prefix,
   *                  e.g., "faces/list". The prefixes across all ControlCommands,
   *                  StatusDatasets, and NotificationStreams must not overlap (no relPrefix
   *                  is a prefix of another relPrefix).
   * \param authorize should set identity to Name() if the dataset is public
   * \param handle Callback to process the incoming dataset requests
   * \pre No top-level prefix has been added.
   * \throw std::out_of_range \p relPrefix overlaps with an existing relPrefix.
   * \throw std::domain_error One or more top-level prefixes have been added.
   *
   * The payload of the returned status dataset data packet is at most half of the maximum
   * data packet size.
   *
   * Procedure for processing a StatusDataset request:
   *  1. If the request Interest contains version or segment components, abort these steps
   *     (note: the request may contain more components after relPrefix, e.g., a query condition).
   *  2. Perform authorization; if the authorization is rejected, perform the RejectReply action
   *     and abort these steps.
   *  3. Invoke the handler, store blocks passed to StatusDatasetAppend calls in a buffer,
   *     wait until StatusDatasetEnd is called.
   *  4. Allocate a version.
   *  5. Segment the buffer into one or more segments under the allocated version,
   *     such that the Data packets will not become too large after signing.
   *  6. Set FinalBlockId on at least the last segment.
   *  7. Sign the Data packets.
   *  8. Send the signed Data packets.
   *
   * As an optimization, a Data packet may be sent as soon as enough octets have been collected
   * through StatusDatasetAppend calls.
   */
  void
  addStatusDataset(const PartialName& relPrefix,
                   Authorization authorize,
                   StatusDatasetHandler handle);

public: // NotificationStream
  /**
   * \brief Register a NotificationStream.
   * \param relPrefix The name prefix for this notification stream relative to the top-level prefix,
   *                  e.g., "faces/events". The prefixes across all ControlCommands,
   *                  StatusDatasets, and NotificationStreams must not overlap (no relPrefix
   *                  is a prefix of another relPrefix).
   * \return A function into which notifications can be posted.
   * \pre No top-level prefix has been added.
   * \throw std::out_of_range \p relPrefix overlaps with an existing relPrefix.
   * \throw std::domain_error One or more top-level prefixes have been added.
   *
   * Procedure for posting a notification:
   *  1. If no top-level prefix has been added, or more than one top-level prefixes have been
   *     added, abort these steps and log an error.
   *  2. Assign the next sequence number to the notification.
   *  3. Place the notification block into one Data packet under the sole top-level prefix.
   *  4. Sign the Data packet.
   *  5. If the Data packet is too large, abort these steps and log an error.
   *  6. Send the signed Data packet.
   */
  PostNotification
  addNotificationStream(const PartialName& relPrefix);

private:
  using ControlParametersPtr = shared_ptr<ControlParametersBase>;
  using InterestHandler = std::function<void(const Name& prefix, const Interest&)>;

  /**
   * @brief The parser for extracting the parameters from a command request.
   * @return A shared pointer to the extracted ControlParameters.
   * @throw tlv::Error The request parameters cannot be parsed.
   */
  using ParametersParser = std::function<ControlParametersPtr(const Name& prefix, const Interest&)>;

  void
  checkPrefix(const PartialName& relPrefix) const;

  /**
   * @brief Process unauthorized request.
   * @param act action to reply
   * @param interest the incoming Interest
   */
  void
  afterAuthorizationRejected(RejectReply act, const Interest& interest);

  /**
   * @brief Query Data in the in-memory storage for a given Interest.
   *
   * If the query fails, invoke @p missContinuation to process @p interest.
   *
   * @param prefix the top-level prefix
   * @param interest the request
   * @param missContinuation the handler of request when the query fails
   */
  void
  queryStorage(const Name& prefix, const Interest& interest, const InterestHandler& missContinuation);

  enum class SendDestination {
    NONE = 0,
    FACE = 1,
    IMS  = 2,
    FACE_AND_IMS = 3,
  };

  /**
   * @brief Send data to the face and/or in-memory storage.
   *
   * Create a Data packet with the given @p dataName, @p content, and @p metaInfo,
   * set its FreshnessPeriod to 1 second, and then send it out through the face
   * and/or insert it into the in-memory storage as specified by @p destination.
   *
   * If it's toward the in-memory storage, set its CachePolicy to NO_CACHE and limit
   * its FreshnessPeriod in the storage to 1 second.
   *
   * @param dataName the name of this piece of data
   * @param content the content of this piece of data
   * @param metaInfo some meta information of this piece of data
   * @param destination where to send this piece of data
   */
  void
  sendData(const Name& dataName, const Block& content, const MetaInfo& metaInfo,
           SendDestination destination);

  /**
   * @brief Send out a Data packet through the face.
   */
  void
  sendOnFace(const Data& data);

  /**
   * @brief Process an incoming control command Interest before authorization.
   *
   * @param prefix the top-level prefix
   * @param interest the incoming Interest
   * @param parse function to extract the control parameters from the command
   * @param authorize function to determine whether the command is authorized
   * @param validate function to validate the command parameters
   * @param handler function to execute the command after it is authorized and validated
   */
  void
  processCommand(const Name& prefix,
                 const Interest& interest,
                 const ParametersParser& parse,
                 const Authorization& authorize,
                 ValidateParameters validate,
                 ControlCommandHandler handler);

  /**
   * @brief Process an authorized control command.
   *
   * @param prefix the top-level prefix
   * @param interest the incoming Interest
   * @param parameters control parameters of this command
   * @param validate function to validate the command parameters
   * @param handler function to execute the command after its parameters are validated
   */
  void
  processAuthorizedCommand(const Name& prefix,
                           const Interest& interest,
                           const ControlParametersPtr& parameters,
                           const ValidateParameters& validate,
                           const ControlCommandHandler& handler);

  void
  sendControlResponse(const ControlResponse& resp, const Interest& interest, bool isNack = false);

  /**
   * @brief Process a StatusDataset Interest before authorization.
   *
   * @param prefix the top-level prefix
   * @param interest the incoming Interest
   * @param authorize function to determine whether the request is authorized
   * @param handler function to continue processing the request after it is authorized
   */
  void
  processStatusDatasetInterest(const Name& prefix,
                               const Interest& interest,
                               const Authorization& authorize,
                               StatusDatasetHandler handler);

  /**
   * @brief Process an authorized StatusDataset request.
   *
   * @param prefix the top-level prefix
   * @param interest the incoming Interest
   * @param handler function to process the dataset request
   */
  void
  processAuthorizedStatusDatasetInterest(const Name& prefix,
                                         const Interest& interest,
                                         const StatusDatasetHandler& handler);

  /**
   * @brief Send a segment of StatusDataset.
   *
   * @param dataName the name of this piece of data
   * @param content the content of this piece of data
   * @param isFinalBlock indicates whether this piece of data is the final block
   */
  void
  sendStatusDatasetSegment(const Name& dataName, const Block& content, bool isFinalBlock);

  void
  postNotification(const Block& notification, const PartialName& relPrefix);

private:
  Face& m_face;
  KeyChain& m_keyChain;
  security::SigningInfo m_signingInfo;

  struct TopPrefixEntry
  {
    ScopedRegisteredPrefixHandle registeredPrefix;
    std::vector<ScopedInterestFilterHandle> interestFilters;
  };
  std::unordered_map<Name, TopPrefixEntry> m_topLevelPrefixes;

  std::unordered_map<PartialName, InterestHandler> m_handlers;

  // NotificationStream name => next sequence number
  std::unordered_map<Name, uint64_t> m_streams;

NDN_CXX_PUBLIC_WITH_TESTS_ELSE_PRIVATE:
  InMemoryStorageFifo m_storage;
};

} // namespace ndn::mgmt

#endif // NDN_CXX_MGMT_DISPATCHER_HPP