/*
 * Copyright 2013-2020 Software Radio Systems Limited
 *
 * This file is part of srsLTE.
 *
 * srsLTE is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License as
 * published by the Free Software Foundation, either version 3 of
 * the License, or (at your option) any later version.
 *
 * srsLTE 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 Affero General Public License for more details.
 *
 * A copy of the GNU Affero General Public License can be found in
 * the LICENSE file in the top-level directory of this distribution
 * and at http://www.gnu.org/licenses/.
 *
 */

#ifndef SRSENB_RRC_MOBILITY_H
#define SRSENB_RRC_MOBILITY_H

#include "rrc.h"
#include "rrc_ue.h"
#include "srslte/common/fsm.h"
#include "srslte/common/logmap.h"
#include <map>

namespace srsenb {

enum class ho_interface_t { S1, X2, intra_enb };

class rrc::ue::rrc_mobility : public srslte::fsm_t<rrc::ue::rrc_mobility>
{
public:
  // public events
  struct user_crnti_upd_ev {
    uint16_t crnti;
    uint16_t temp_crnti;
  };
  struct ho_cancel_ev {};

  explicit rrc_mobility(srsenb::rrc::ue* outer_ue);

  bool fill_conn_recfg_no_ho_cmd(asn1::rrc::rrc_conn_recfg_r8_ies_s* conn_recfg);
  void handle_ue_meas_report(const asn1::rrc::meas_report_s& msg);
  void handle_ho_preparation_complete(bool is_success, srslte::unique_byte_buffer_t container);
  bool is_ho_running() const { return not is_in_state<idle_st>(); }

  // S1-Handover
  bool start_s1_tenb_ho(const asn1::s1ap::ho_request_s&                                   msg,
                        const asn1::s1ap::sourceenb_to_targetenb_transparent_container_s& container);

  static uint16_t
  start_ho_ue_resource_alloc(const asn1::s1ap::ho_request_s&                                   msg,
                             const asn1::s1ap::sourceenb_to_targetenb_transparent_container_s& container);

private:
  // helper methods
  bool update_ue_var_meas_cfg(uint32_t                src_earfcn,
                              const cell_info_common& target_pcell,
                              asn1::rrc::meas_cfg_s*  diff_meas_cfg);

  // Handover from source cell
  bool start_ho_preparation(uint32_t target_eci, uint8_t measobj_id, bool fwd_direct_path_available);
  bool start_enb_status_transfer();

  // Handover to target cell
  void fill_mobility_reconf_common(asn1::rrc::dl_dcch_msg_s& msg,
                                   const cell_info_common&   target_cell,
                                   uint32_t                  src_dl_earfcn,
                                   uint32_t                  src_pci);
  bool apply_ho_prep_cfg(const asn1::rrc::ho_prep_info_r8_ies_s& ho_prep, const asn1::s1ap::ho_request_s& ho_req_msg);

  rrc::ue*                  rrc_ue  = nullptr;
  rrc*                      rrc_enb = nullptr;
  srslte::byte_buffer_pool* pool    = nullptr;
  srslte::log_ref           rrc_log;

  // vars
  asn1::rrc::meas_cfg_s                current_meas_cfg;
  asn1::rrc::rrc_conn_recfg_complete_s pending_recfg_complete;

  // events
  struct ho_meas_report_ev {
    uint32_t                                target_eci = 0;
    const asn1::rrc::meas_obj_to_add_mod_s* meas_obj   = nullptr;
  };
  struct ho_req_rx_ev {
    const asn1::s1ap::ho_request_s*                                   ho_req_msg;
    const asn1::s1ap::sourceenb_to_targetenb_transparent_container_s* transparent_container;
  };
  using unsuccessful_outcome_ev = std::false_type;
  using recfg_complete_ev       = asn1::rrc::rrc_conn_recfg_complete_s;
  using status_transfer_ev      = asn1::s1ap::bearers_subject_to_status_transfer_list_l;

  // states
  struct idle_st {};
  struct intraenb_ho_st {
    const cell_info_common* target_cell     = nullptr;
    const cell_info_common* source_cell     = nullptr;
    uint16_t                last_temp_crnti = SRSLTE_INVALID_RNTI;

    void enter(rrc_mobility* f, const ho_meas_report_ev& meas_report);
  };
  struct s1_target_ho_st {};
  struct wait_recfg_comp {};
  struct s1_source_ho_st : public subfsm_t<s1_source_ho_st> {
    ho_meas_report_ev report;
    using ho_cmd_msg = asn1::rrc::ho_cmd_r8_ies_s;

    struct wait_ho_req_ack_st {
      void enter(s1_source_ho_st* f, const ho_meas_report_ev& ev);
    };
    struct status_transfer_st {
      void enter(s1_source_ho_st* f);
    };

    explicit s1_source_ho_st(rrc_mobility* parent_) : base_t(parent_) {}

  private:
    void send_ho_cmd(wait_ho_req_ack_st& s, const ho_cmd_msg& ho_cmd);
    void handle_ho_cancel(const ho_cancel_ev& ev);

  protected:
    using fsm = s1_source_ho_st;
    state_list<wait_ho_req_ack_st, status_transfer_st> states{this};
    // clang-format off
    using transitions = transition_table<
    //           Start                 Target                   Event       Action                 Guard
    //      +-------------------+------------------+---------------------+-----------------------+---------------------+
    to_state<                     idle_st,            srslte::failure_ev                                               >,
    to_state<                     idle_st,            ho_cancel_ev,        &fsm::handle_ho_cancel                      >,
         row< wait_ho_req_ack_st, status_transfer_st, ho_cmd_msg,          &fsm::send_ho_cmd                           >
    //      +-------------------+------------------+---------------------+-----------------------+---------------------+
    >;
    // clang-format on
  };

  // FSM guards
  bool needs_s1_ho(idle_st& s, const ho_meas_report_ev& meas_report);
  bool needs_intraenb_ho(idle_st& s, const ho_meas_report_ev& meas_report);

  // FSM transition handlers
  void handle_crnti_ce(intraenb_ho_st& s, const user_crnti_upd_ev& ev);
  void handle_recfg_complete(intraenb_ho_st& s, const recfg_complete_ev& ev);
  void handle_ho_req(idle_st& s, const ho_req_rx_ev& ho_req);
  void handle_status_transfer(s1_target_ho_st& s, const status_transfer_ev& ev);
  void defer_recfg_complete(s1_target_ho_st& s, const recfg_complete_ev& ev);
  void handle_recfg_complete(wait_recfg_comp& s, const recfg_complete_ev& ev);

protected:
  // states
  state_list<idle_st, intraenb_ho_st, s1_target_ho_st, wait_recfg_comp, s1_source_ho_st> states{this,
                                                                                                idle_st{},
                                                                                                intraenb_ho_st{},
                                                                                                s1_target_ho_st{},
                                                                                                wait_recfg_comp{},
                                                                                                s1_source_ho_st{this}};

  // transitions
  using fsm = rrc_mobility;
  // clang-format off
  using transitions = transition_table<
  //      Start         Target              Event                Action                      Guard
  // +----------------+-------------------+---------------------+----------------------------+-------------------------+
  row< idle_st,         s1_source_ho_st,   ho_meas_report_ev,   nullptr,                      &fsm::needs_s1_ho        >,
  row< idle_st,         intraenb_ho_st,    ho_meas_report_ev,   nullptr,                      &fsm::needs_intraenb_ho  >,
  row< idle_st,         s1_target_ho_st,   ho_req_rx_ev,        &fsm::handle_ho_req                                    >,
  // +----------------+-------------------+---------------------+----------------------------+-------------------------+
  upd< intraenb_ho_st,                     user_crnti_upd_ev,   &fsm::handle_crnti_ce                                  >,
  row< intraenb_ho_st,  idle_st,           recfg_complete_ev,   &fsm::handle_recfg_complete                            >,
  // +----------------+-------------------+---------------------+----------------------------+-------------------------+
  row< s1_target_ho_st, wait_recfg_comp,   status_transfer_ev,  &fsm::handle_status_transfer                           >,
  upd< s1_target_ho_st,                    recfg_complete_ev,   &fsm::defer_recfg_complete                             >,
  row< wait_recfg_comp, idle_st,           recfg_complete_ev,   &fsm::handle_recfg_complete                            >
  // +----------------+-------------------+---------------------+----------------------------+-------------------------+
  >;
  // clang-format on
};

} // namespace srsenb
#endif // SRSENB_RRC_MOBILITY_H