CLASS {{p}}league_table DEFINITION PUBLIC FINAL CREATE PUBLIC.
  PUBLIC SECTION.
    TYPES ty_team TYPE c LENGTH 10.

    TYPES:
      BEGIN OF ty_match,
        home_team  TYPE ty_team,
        away_team  TYPE ty_team,
        home_goals TYPE i,
        away_goals TYPE i,
      END OF ty_match.
    TYPES tt_match TYPE STANDARD TABLE OF ty_match WITH EMPTY KEY.

    TYPES:
      BEGIN OF ty_row,
        rank          TYPE i,
        team          TYPE ty_team,
        played        TYPE i,
        won           TYPE i,
        drawn         TYPE i,
        lost          TYPE i,
        goals_for     TYPE i,
        goals_against TYPE i,
        goal_diff     TYPE i,
        points        TYPE i,
      END OF ty_row.
    TYPES tt_row TYPE STANDARD TABLE OF ty_row WITH EMPTY KEY.

    METHODS evaluate
      IMPORTING it_matches      TYPE tt_match
      RETURNING VALUE(rt_table) TYPE tt_row.

  PRIVATE SECTION.
    TYPES tt_work TYPE HASHED TABLE OF ty_row WITH UNIQUE KEY team.

    METHODS is_invalid
      IMPORTING is_match      TYPE ty_match
      RETURNING VALUE(rv_bad) TYPE abap_bool.

    METHODS add_result
      IMPORTING iv_team          TYPE ty_team
                iv_goals_for     TYPE i
                iv_goals_against TYPE i
      CHANGING  ct_work          TYPE tt_work.

    METHODS assign_rank
      CHANGING ct_table TYPE tt_row.
ENDCLASS.


CLASS {{p}}league_table IMPLEMENTATION.
  METHOD evaluate.
    DATA lt_work TYPE tt_work.

    LOOP AT it_matches INTO DATA(ls_match).
      IF is_invalid( ls_match ) = abap_false.
        add_result( EXPORTING iv_team          = ls_match-home_team
                              iv_goals_for     = ls_match-home_goals
                              iv_goals_against = ls_match-away_goals
                    CHANGING  ct_work          = lt_work ).
        add_result( EXPORTING iv_team          = ls_match-away_team
                              iv_goals_for     = ls_match-away_goals
                              iv_goals_against = ls_match-home_goals
                    CHANGING  ct_work          = lt_work ).
      ENDIF.
    ENDLOOP.

    rt_table = lt_work.
    SORT rt_table BY points    DESCENDING
                     goal_diff DESCENDING
                     goals_for DESCENDING
                     team      ASCENDING.
    assign_rank( CHANGING ct_table = rt_table ).
  ENDMETHOD.

  METHOD is_invalid.
    rv_bad = xsdbool( is_match-home_team IS INITIAL
                   OR is_match-away_team IS INITIAL
                   OR is_match-home_team = is_match-away_team
                   OR is_match-home_goals < 0
                   OR is_match-away_goals < 0 ).
  ENDMETHOD.

  METHOD add_result.
    ASSIGN ct_work[ team = iv_team ] TO FIELD-SYMBOL(<ls_row>).
    IF sy-subrc <> 0.
      INSERT VALUE ty_row( team = iv_team ) INTO TABLE ct_work ASSIGNING <ls_row>.
    ENDIF.

    <ls_row>-played        = <ls_row>-played + 1.
    <ls_row>-goals_for     = <ls_row>-goals_for + iv_goals_for.
    <ls_row>-goals_against = <ls_row>-goals_against + iv_goals_against.
    <ls_row>-goal_diff     = <ls_row>-goals_for - <ls_row>-goals_against.

    IF iv_goals_for > iv_goals_against.
      <ls_row>-won    = <ls_row>-won + 1.
      <ls_row>-points = <ls_row>-points + 3.
    ELSEIF iv_goals_for = iv_goals_against.
      <ls_row>-drawn  = <ls_row>-drawn + 1.
      <ls_row>-points = <ls_row>-points + 1.
    ELSE.
      <ls_row>-lost   = <ls_row>-lost + 1.
    ENDIF.
  ENDMETHOD.

  METHOD assign_rank.
    DATA lv_rank     TYPE i.
    DATA lv_position TYPE i.
    DATA ls_previous TYPE ty_row.

    LOOP AT ct_table ASSIGNING FIELD-SYMBOL(<ls_row>).
      lv_position = lv_position + 1.
      IF lv_position = 1
         OR <ls_row>-points    <> ls_previous-points
         OR <ls_row>-goal_diff <> ls_previous-goal_diff
         OR <ls_row>-goals_for <> ls_previous-goals_for.
        lv_rank = lv_position.
      ENDIF.
      <ls_row>-rank = lv_rank.
      ls_previous = <ls_row>.
    ENDLOOP.
  ENDMETHOD.
ENDCLASS.