# -*- coding: utf-8 -*-
from .mom import mom
from ..utils import get_offset, verify_series

def roc(close, length=None, offset=None, **kwargs):
    """Indicator: Rate of Change (ROC)"""
    # Validate Arguments
    close = verify_series(close)
    length = int(length) if length and length > 0 else 10
    min_periods = int(kwargs['min_periods']) if 'min_periods' in kwargs and kwargs['min_periods'] is not None else length
    offset = get_offset(offset)

    # Calculate Result
    roc = 100 * mom(close=close, length=length) / close.shift(length)

    # Offset
    if offset != 0:
        roc = roc.shift(offset)

    # Handle fills
    if 'fillna' in kwargs:
        roc.fillna(kwargs['fillna'], inplace=True)
    if 'fill_method' in kwargs:
        roc.fillna(method=kwargs['fill_method'], inplace=True)

    # Name and Categorize it
    roc.name = f"ROC_{length}"
    roc.category = 'momentum'

    return roc



roc.__doc__ = \
"""Rate of Change (ROC)

Rate of Change is an indicator is also referred to as Momentum (yeah, confusingly).
It is a pure momentum oscillator that measures the percent change in price with the
previous price 'n' (or length) periods ago.

Sources:
    https://www.tradingview.com/wiki/Rate_of_Change_(ROC)

Calculation:
    Default Inputs:
        length=1
    MOM = Momentum
    ROC = 100 * MOM(close, length) / close.shift(length)

Args:
    close (pd.Series): Series of 'close's
    length (int): It's period.  Default: 1
    offset (int): How many periods to offset the result.  Default: 0

Kwargs:
    fillna (value, optional): pd.DataFrame.fillna(value)
    fill_method (value, optional): Type of fill method

Returns:
    pd.Series: New feature generated.
"""