CLASS {{p}}roast_merger DEFINITION PUBLIC FINAL CREATE PUBLIC.
  PUBLIC SECTION.
    TYPES:
      ty_batch_id TYPE c LENGTH 10,
      ty_plant    TYPE c LENGTH 4,
      ty_lot_id   TYPE c LENGTH 8,
      ty_weight   TYPE p LENGTH 7 DECIMALS 2,
      BEGIN OF ty_batch,
        batch_id   TYPE ty_batch_id,
        plant      TYPE ty_plant,
        lot_id     TYPE ty_lot_id,
        roast_date TYPE d,
        roasted_kg TYPE ty_weight,
      END OF ty_batch,
      tt_batches TYPE STANDARD TABLE OF ty_batch WITH EMPTY KEY,
      BEGIN OF ty_lot_total,
        lot_id      TYPE ty_lot_id,
        batch_count TYPE i,
        total_kg    TYPE ty_weight,
        last_date   TYPE d,
      END OF ty_lot_total,
      tt_lot_totals TYPE STANDARD TABLE OF ty_lot_total WITH EMPTY KEY.

    METHODS merge
      IMPORTING it_plant_a       TYPE tt_batches
                it_plant_b       TYPE tt_batches
      RETURNING VALUE(rt_totals) TYPE tt_lot_totals.

  PRIVATE SECTION.
    TYPES tt_unique TYPE HASHED TABLE OF ty_batch WITH UNIQUE KEY batch_id.

    METHODS add_batches
      IMPORTING it_batches TYPE tt_batches
      CHANGING  ct_unique  TYPE tt_unique.

    METHODS build_totals
      IMPORTING it_unique        TYPE tt_unique
      RETURNING VALUE(rt_totals) TYPE tt_lot_totals.
ENDCLASS.


CLASS {{p}}roast_merger IMPLEMENTATION.
  METHOD merge.
    DATA lt_unique TYPE tt_unique.
    add_batches( EXPORTING it_batches = it_plant_a
                 CHANGING  ct_unique  = lt_unique ).
    add_batches( EXPORTING it_batches = it_plant_b
                 CHANGING  ct_unique  = lt_unique ).
    rt_totals = build_totals( lt_unique ).
  ENDMETHOD.

  METHOD add_batches.
    LOOP AT it_batches INTO DATA(ls_batch).
      IF ls_batch-batch_id IS INITIAL OR ls_batch-roasted_kg <= 0.
        CONTINUE.
      ENDIF.
      READ TABLE ct_unique WITH TABLE KEY batch_id = ls_batch-batch_id
        ASSIGNING FIELD-SYMBOL(<ls_kept>).
      IF sy-subrc <> 0.
        INSERT ls_batch INTO TABLE ct_unique.
      ELSEIF ls_batch-roasted_kg > <ls_kept>-roasted_kg.
        <ls_kept> = ls_batch.
      ENDIF.
    ENDLOOP.
  ENDMETHOD.

  METHOD build_totals.
    DATA lt_totals TYPE SORTED TABLE OF ty_lot_total WITH UNIQUE KEY lot_id.
    LOOP AT it_unique INTO DATA(ls_batch).
      READ TABLE lt_totals WITH TABLE KEY lot_id = ls_batch-lot_id
        ASSIGNING FIELD-SYMBOL(<ls_total>).
      IF sy-subrc <> 0.
        INSERT VALUE #( lot_id      = ls_batch-lot_id
                        batch_count = 1
                        total_kg    = ls_batch-roasted_kg
                        last_date   = ls_batch-roast_date )
               INTO TABLE lt_totals.
        CONTINUE.
      ENDIF.
      <ls_total>-batch_count = <ls_total>-batch_count + 1.
      <ls_total>-total_kg    = <ls_total>-total_kg + ls_batch-roasted_kg.
      IF ls_batch-roast_date > <ls_total>-last_date.
        <ls_total>-last_date = ls_batch-roast_date.
      ENDIF.
    ENDLOOP.
    rt_totals = lt_totals.
  ENDMETHOD.
ENDCLASS.