/**
 *
 * \section COPYRIGHT
 *
 * Copyright 2013-2021 Software Radio Systems Limited
 *
 * By using this file, you agree to the terms and conditions set
 * forth in the LICENSE file which can be found at the top level of
 * the distribution.
 *
 */

#ifndef SRSRAN_SCHED_NR_PDCCH_H
#define SRSRAN_SCHED_NR_PDCCH_H

#include "srsgnb/hdr/stack/mac/sched_nr_cfg.h"
#include "srsran/adt/bounded_bitset.h"
#include "srsran/adt/bounded_vector.h"
#include "srsran/phy/common/phy_common_nr.h"
#include "srsran/phy/phch/dci.h"

namespace srsenb {

namespace sched_nr_impl {

using coreset_bitmap = srsran::bounded_bitset<SRSRAN_CORESET_FREQ_DOMAIN_RES_SIZE * SRSRAN_CORESET_DURATION_MAX, true>;

class coreset_region
{
public:
  coreset_region(const bwp_params_t& bwp_cfg_,
                 uint32_t            coreset_id_,
                 uint32_t            slot_idx,
                 pdcch_dl_list_t&    pdcch_dl_list,
                 pdcch_ul_list_t&    pdcch_ul_list);
  void reset();

  pdcch_dl_t* alloc_dl_pdcch(srsran_rnti_type_t         rnti_type,
                             uint32_t                   aggr_idx,
                             uint32_t                   search_space_id,
                             const ue_carrier_params_t* user = nullptr);

  pdcch_ul_t* alloc_ul_pdcch(uint32_t aggr_idx, uint32_t search_space_id, const ue_carrier_params_t* user);

  void rem_last_pdcch();

  uint32_t get_td_symbols() const { return coreset_cfg->duration; }
  uint32_t get_freq_resources() const { return nof_freq_res; }
  uint32_t nof_cces() const { return nof_freq_res * get_td_symbols(); }
  size_t   nof_allocs() const { return dfs_tree.size(); }

private:
  bool alloc_pdcch_common(srsran_rnti_type_t         rnti_type,
                          bool                       is_dl,
                          uint32_t                   aggr_idx,
                          uint32_t                   search_space_id,
                          const ue_carrier_params_t* user = nullptr);

  const srsran_coreset_t* coreset_cfg;
  uint32_t                coreset_id;
  uint32_t                slot_idx;
  uint32_t                nof_freq_res = 0;

  const bwp_cce_pos_list&                          rar_cce_list;
  const srsran::optional_vector<bwp_cce_pos_list>& common_cce_list;

  // List of PDCCH grants
  struct alloc_record {
    uint32_t                   aggr_idx;
    uint32_t                   ss_id;
    uint32_t                   idx;
    srsran_rnti_type_t         rnti_type;
    bool                       is_dl;
    const ue_carrier_params_t* ue;
  };
  srsran::bounded_vector<alloc_record, 2 * MAX_GRANTS> dci_list;
  pdcch_dl_list_t&                                     pdcch_dl_list;
  pdcch_ul_list_t&                                     pdcch_ul_list;

  // DFS decision tree of PDCCH grants
  struct tree_node {
    uint16_t              rnti        = SRSRAN_INVALID_RNTI;
    uint32_t              record_idx  = 0;
    uint32_t              dci_pos_idx = 0;
    srsran_dci_location_t dci_pos     = {0, 0};
    /// Accumulation of all PDCCH masks for the current solution (DFS path)
    coreset_bitmap total_mask, current_mask;
  };
  using alloc_tree_dfs_t = std::vector<tree_node>;
  alloc_tree_dfs_t dfs_tree, saved_dfs_tree;

  srsran::span<const uint32_t> get_cce_loc_table(const alloc_record& record) const;
  bool                         alloc_dfs_node(const alloc_record& record, uint32_t dci_idx);
  bool                         get_next_dfs();
};

/**
 * Class to handle the allocation of REs for a BWP PDCCH in a specific slot
 */
class bwp_pdcch_allocator
{
public:
  bwp_pdcch_allocator(const bwp_params_t& bwp_cfg_,
                      uint32_t            slot_idx,
                      pdcch_dl_list_t&    pdcch_dl_list,
                      pdcch_ul_list_t&    pdcch_ul_list);

  /**
   * Clear current slot allocations
   */
  void reset();

  /**
   * Allocates RE space for DL DCI in PDCCH, avoiding in the process collisions with other PDCCH allocations
   * @param rnti_type type of RNTI (e.g. SI, RA, C, TC)
   * @param ss_id Search space ID
   * @param aggr_idx Aggregation level index (0..4)
   * @param user UE object or null in case of broadcast/RAR/paging allocation
   * @return pdcch object if the allocation was successful
   */
  pdcch_dl_t* alloc_dl_pdcch(srsran_rnti_type_t         rnti_type,
                             uint32_t                   ss_id,
                             uint32_t                   aggr_idx,
                             const ue_carrier_params_t* user = nullptr);

  /**
   * Allocates RE space for UL DCI in PDCCH, avoiding in the process collisions with other PDCCH allocations
   * @param ss_id Search space ID
   * @param aggr_idx Aggregation level index (0..4)
   * @param user UE object parameters
   * @return pdcch object if the allocation was successful
   */
  pdcch_ul_t* alloc_ul_pdcch(uint32_t ss_id, uint32_t aggr_idx, const ue_carrier_params_t* user);

  /**
   * Cancel and remove last PDCCH allocation
   * @param ss_id Search space ID
   */
  void rem_last_pdcch(uint32_t ss_id);

  /// Returns the number of PDCCH allocations made in the slot
  uint32_t nof_allocations() const;

private:
  using slot_coreset_list = srsran::optional_array<coreset_region, SRSRAN_UE_DL_NR_MAX_NOF_CORESET>;

  bool check_args_valid(srsran_rnti_type_t         rnti_type,
                        uint32_t                   ss_id,
                        uint32_t                   aggr_idx,
                        const ue_carrier_params_t* user,
                        bool                       is_dl) const;

  // args
  const bwp_params_t&   bwp_cfg;
  srslog::basic_logger& logger;
  const uint32_t        slot_idx;

  pdcch_dl_list_t&  pdcch_dl_list;
  pdcch_ul_list_t&  pdcch_ul_list;
  slot_coreset_list coresets;
};

} // namespace sched_nr_impl

} // namespace srsenb

#endif // SRSRAN_SCHED_NR_PDCCH_H