Longest winning streak

# Table: Matches
# 
# +-------------+------+
# | Column Name | Type |
# +-------------+------+
# | player_id   | int  |
# | match_day   | date |
# | result      | enum |
# +-------------+------+
# (player_id, match_day) is the primary key (combination of columns with unique values) for this table.
# Each row of this table contains the ID of a player, the day of the match they played, and the result of that match.
# The result column is an ENUM (category) type of ('Win', 'Draw', 'Lose').
# 
#  
# 
# The winning streak of a player is the number of consecutive wins uninterrupted by draws or losses.
# 
# Write a solution to count the longest winning streak for each player.
# 
# Return the result table in any order.
# 
# The result format is in the following example.
#
# Example 1:
# Input:
# Matches table:
# +-----------+------------+--------+
# | player_id | match_day  | result |
# +-----------+------------+--------+
# | 1         | 2022-01-17 | Win    |
# | 1         | 2022-01-18 | Win    |
# | 1         | 2022-01-25 | Win    |
# | 1         | 2022-01-31 | Draw   |
# | 1         | 2022-02-08 | Win    |
# | 2         | 2022-02-06 | Lose   |
# | 2         | 2022-02-08 | Lose   |
# | 3         | 2022-03-30 | Win    |
# +-----------+------------+--------+
# Output:
# +-----------+----------------+
# | player_id | longest_streak |
# +-----------+----------------+
# | 1         | 3              |
# | 2         | 0              |
# | 3         | 1              |
# +-----------+----------------+
# Explanation:
# Player 1:
# From 2022-01-17 to 2022-01-25, player 1 won 3 consecutive matches.
# On 2022-01-31, player 1 had a draw.
# On 2022-02-08, player 1 won a match.
# The longest winning streak was 3 matches.
# 
# Player 2:
# From 2022-02-06 to 2022-02-08, player 2 lost 2 consecutive matches.
# The longest winning streak was 0 matches.
# 
# Player 3:
# On 2022-03-30, player 3 won a match.
# The longest winning streak was 1 match.

import pandas as pd

def longest_winning_streak(matches: pd.DataFrame) -> pd.DataFrame:
  if matches.empty:
    return pd.DataFrame({'player_id': pd.Series(dtype='int'), 'longest_streak': pd.Series(dtype='int')})
  matches = matches.sort_values(['player_id', 'match_day']).reset_index(drop=True)
  matches['is_win'] = (matches['result'] == 'Win').astype(int)
  matches['grp'] = ((matches['player_id'] != matches['player_id'].shift()) | (matches['is_win'] != matches['is_win'].shift())).cumsum()
  streaks = matches[matches['is_win'] == 1].groupby(['player_id', 'grp']).size().reset_index(name='streak')
  max_streaks = streaks.groupby('player_id')['streak'].max().reset_index(name='longest_streak')
  all_players = matches[['player_id']].drop_duplicates()
  result = all_players.merge(max_streaks, on='player_id', how='left')
  result['longest_streak'] = result['longest_streak'].fillna(0).astype(int)
  return result[['player_id', 'longest_streak']]