CLASS {{p}}dispatch_planner DEFINITION PUBLIC FINAL CREATE PUBLIC.
  PUBLIC SECTION.
    TYPES:
      BEGIN OF ty_delivery,
        delivery_id TYPE c LENGTH 10,
        district    TYPE c LENGTH 4,
        parcels     TYPE i,
        weight      TYPE p LENGTH 8 DECIMALS 2,
        urgency     TYPE i,
      END OF ty_delivery,
      tt_delivery TYPE STANDARD TABLE OF ty_delivery WITH EMPTY KEY,
      BEGIN OF ty_district,
        district    TYPE c LENGTH 4,
        deliveries  TYPE i,
        parcels     TYPE i,
        weight      TYPE p LENGTH 8 DECIMALS 2,
        top_urgency TYPE i,
      END OF ty_district,
      tt_district TYPE STANDARD TABLE OF ty_district WITH EMPTY KEY.

    METHODS constructor.
    METHODS plan
      IMPORTING it_delivery        TYPE tt_delivery
      RETURNING VALUE(rt_district) TYPE tt_district.
    METHODS merge
      IMPORTING it_left          TYPE tt_district
                it_right         TYPE tt_district
      RETURNING VALUE(rt_merged) TYPE tt_district.

  PRIVATE SECTION.
    TYPES tt_group TYPE SORTED TABLE OF ty_district WITH UNIQUE KEY district.

    METHODS add_delivery
      IMPORTING is_delivery TYPE ty_delivery
      CHANGING  ct_group    TYPE tt_group.
    METHODS add_line
      IMPORTING is_line  TYPE ty_district
      CHANGING  ct_group TYPE tt_group.
    METHODS to_result
      IMPORTING it_group         TYPE tt_group
      RETURNING VALUE(rt_result) TYPE tt_district.
ENDCLASS.


CLASS {{p}}dispatch_planner IMPLEMENTATION.
  METHOD constructor.
  ENDMETHOD.

  METHOD plan.
    DATA lt_group TYPE tt_group.
    LOOP AT it_delivery INTO DATA(ls_delivery).
      add_delivery( EXPORTING is_delivery = ls_delivery
                    CHANGING  ct_group    = lt_group ).
    ENDLOOP.
    rt_district = to_result( lt_group ).
  ENDMETHOD.

  METHOD merge.
    DATA lt_group TYPE tt_group.
    LOOP AT it_left INTO DATA(ls_left).
      add_line( EXPORTING is_line  = ls_left
                CHANGING  ct_group = lt_group ).
    ENDLOOP.
    LOOP AT it_right INTO DATA(ls_right).
      add_line( EXPORTING is_line  = ls_right
                CHANGING  ct_group = lt_group ).
    ENDLOOP.
    rt_merged = to_result( lt_group ).
  ENDMETHOD.

  METHOD add_delivery.
    IF is_delivery-parcels <= 0.
      RETURN.
    ENDIF.
    DATA(ls_new) = VALUE ty_district( district    = is_delivery-district
                                      deliveries  = 1
                                      parcels     = is_delivery-parcels
                                      weight      = is_delivery-weight
                                      top_urgency = is_delivery-urgency ).
    READ TABLE ct_group WITH TABLE KEY district = is_delivery-district
      ASSIGNING FIELD-SYMBOL(<ls_group>).
    IF sy-subrc <> 0.
      INSERT ls_new INTO TABLE ct_group.
      RETURN.
    ENDIF.
    <ls_group>-deliveries  = <ls_group>-deliveries - ls_new-deliveries.
    <ls_group>-parcels     = <ls_group>-parcels + ls_new-parcels.
    <ls_group>-weight      = <ls_group>-weight + ls_new-weight.
    <ls_group>-top_urgency = nmin( val1 = <ls_group>-top_urgency
                                   val2 = ls_new-top_urgency ).
  ENDMETHOD.

  METHOD add_line.
    READ TABLE ct_group WITH TABLE KEY district = is_line-district
      ASSIGNING FIELD-SYMBOL(<ls_group>).
    IF sy-subrc <> 0.
      INSERT is_line INTO TABLE ct_group.
      RETURN.
    ENDIF.
    <ls_group>-deliveries  = <ls_group>-deliveries + is_line-deliveries.
    <ls_group>-parcels     = <ls_group>-parcels + is_line-parcels.
    <ls_group>-weight      = <ls_group>-weight + is_line-weight.
    <ls_group>-top_urgency = nmin( val1 = <ls_group>-top_urgency
                                   val2 = is_line-top_urgency ).
  ENDMETHOD.

  METHOD to_result.
    rt_result = it_group.
  ENDMETHOD.
ENDCLASS.