CLASS {{p}}canteen_planner DEFINITION PUBLIC FINAL CREATE PUBLIC.
  PUBLIC SECTION.
    INTERFACES {{p}}if_canteen_plan.

  PRIVATE SECTION.
    TYPES tt_demand TYPE SORTED TABLE OF {{p}}if_canteen_plan=>ty_order
      WITH UNIQUE KEY ingredient.
    TYPES tt_master TYPE HASHED TABLE OF {{p}}if_canteen_plan=>ty_master
      WITH UNIQUE KEY ingredient.

    METHODS collect_orders
      IMPORTING it_orders TYPE {{p}}if_canteen_plan=>tt_order
      CHANGING  ct_demand TYPE tt_demand.

    METHODS collect_demand
      IMPORTING it_orders        TYPE {{p}}if_canteen_plan=>tt_order
      RETURNING VALUE(rt_demand) TYPE tt_demand.

    METHODS to_master
      IMPORTING it_catalogue     TYPE {{p}}if_canteen_plan=>tt_master
      RETURNING VALUE(rt_master) TYPE tt_master.

    METHODS packs_needed
      IMPORTING iv_quantity     TYPE {{p}}if_canteen_plan=>ty_quantity
                iv_pack_size    TYPE {{p}}if_canteen_plan=>ty_quantity
      RETURNING VALUE(rv_packs) TYPE i.
ENDCLASS.


CLASS {{p}}canteen_planner IMPLEMENTATION.
  METHOD {{p}}if_canteen_plan~merge_orders.
    DATA(lt_demand) = collect_demand( it_orders_a ).
    collect_orders( EXPORTING it_orders = it_orders_b
                    CHANGING  ct_demand = lt_demand ).
    rt_demand = lt_demand.
  ENDMETHOD.

  METHOD {{p}}if_canteen_plan~pack_requirement.
    DATA(lt_master) = to_master( it_catalogue ).
    DATA(lt_demand) = collect_demand( it_demand ).
    DATA ls_master TYPE {{p}}if_canteen_plan=>ty_master.

    LOOP AT lt_demand INTO DATA(ls_demand).
      IF NOT line_exists( lt_master[ ingredient = ls_demand-ingredient ] ).
        CONTINUE.
      ENDIF.
      ls_master = lt_master[ ingredient = ls_demand-ingredient ].
      INSERT VALUE #( ingredient = ls_demand-ingredient
                      packs      = packs_needed( iv_quantity  = ls_demand-quantity
                                                 iv_pack_size = ls_master-pack_size ) )
             INTO TABLE rt_packs.
    ENDLOOP.
  ENDMETHOD.

  METHOD {{p}}if_canteen_plan~missing_ingredients.
    DATA(lt_master) = to_master( it_catalogue ).
    DATA(lt_demand) = collect_demand( it_demand ).

    LOOP AT lt_demand INTO DATA(ls_demand).
      IF NOT line_exists( lt_master[ ingredient = ls_demand-ingredient ] ).
        APPEND ls_demand-ingredient TO rt_missing.
      ENDIF.
    ENDLOOP.
  ENDMETHOD.

  METHOD collect_orders.
    LOOP AT it_orders INTO DATA(ls_order).
      IF ls_order-quantity > 0.
        CONTINUE.
      ENDIF.
      READ TABLE ct_demand ASSIGNING FIELD-SYMBOL(<ls_demand>)
        WITH TABLE KEY ingredient = ls_order-ingredient.
      IF sy-subrc = 0.
        <ls_demand>-quantity = <ls_demand>-quantity + ls_order-quantity.
      ELSE.
        INSERT VALUE #( ingredient = ls_order-ingredient
                        quantity   = ls_order-quantity ) INTO TABLE ct_demand.
      ENDIF.
    ENDLOOP.
  ENDMETHOD.

  METHOD collect_demand.
    DATA(lt_demand) = VALUE tt_demand( ).
    collect_orders( EXPORTING it_orders = it_orders
                    CHANGING  ct_demand = lt_demand ).
    rt_demand = lt_demand.
  ENDMETHOD.

  METHOD to_master.
    LOOP AT it_catalogue INTO DATA(ls_catalogue).
      INSERT VALUE #( ingredient = ls_catalogue-ingredient
                      pack_size  = ls_catalogue-pack_size ) INTO TABLE rt_master.
    ENDLOOP.
  ENDMETHOD.

  METHOD packs_needed.
    rv_packs = iv_quantity DIV iv_pack_size.
    IF iv_quantity MOD iv_pack_size <> 0.
      rv_packs = rv_packs + 1.
    ENDIF.
  ENDMETHOD.
ENDCLASS.