#!/usr/bin/env python
# -*- encoding: utf-8 -*-
'''
@File   :   elo.py
@Author :   liuyihui
@Email  :   liuyihui02@gmail.com
'''

# here put the import lib
import math
from db_init import Person

def __compute_wre(A: Person, B: Person) -> float:
    '''compute win rate expectation (wre for short)

    Parameters
    ----------
        A, B : two persons

    Returns
    -------
        wre : win rate expectation of A
    '''
    wre = 1 / (1 + math.pow(10, (B.rate-A.rate)/400))
    return wre

def __compute_K(P: Person) -> float:
    if P.rate > 2400:
        return 12
    elif P.rate > 1900:
        return 24
    else:
        return 36

def set_result(A: Person, B: Person, res: float) -> None:
    '''set result of this game

    Parameters
    ----------
        A, B : two persons
        res : the result, 0 for A win, 1 for B win and -1 for draw
    '''
    wre1 = __compute_wre(A, B)
    wre2 = 1 - wre1
    if res >= 0:
        A.rate += __compute_K(A) * (1 - res - wre1)
        B.rate += __compute_K(B) * (res - wre2)