# ctrlutil.py - control system utility functions
#
# Author: Richard M. Murray
# Date: 24 May 09
# 
# These are some basic utility functions that are used in the control
# systems library and that didn't naturally fit anyplace else.
#
# Copyright (c) 2009 by California Institute of Technology
# All rights reserved.
#
# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following conditions
# are met:
#
# 1. Redistributions of source code must retain the above copyright
#    notice, this list of conditions and the following disclaimer.
# 
# 2. Redistributions in binary form must reproduce the above copyright
#    notice, this list of conditions and the following disclaimer in the
#    documentation and/or other materials provided with the distribution.
# 
# 3. Neither the name of the California Institute of Technology nor
#    the names of its contributors may be used to endorse or promote
#    products derived from this software without specific prior
#    written permission.
# 
# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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# SUCH DAMAGE.
# 
# $Id$

# Packages that we need access to
import scipy as sp
import statesp
import xferfcn 

# Specific functions that we use
from scipy import pi

# Utility function to unwrap an angle measurement

def unwrap(angle, period=2*pi):
    """Unwrap a phase angle to give a continuous curve
    
    Parameters
    ----------
    X : array_like
        Input array
    period : number
        Input period (usually either 2``*``pi or 360)

    Returns
    -------
    Y : array_like
        Output array, with jumps of period/2 eliminated
    
    Examples
    --------
    >>> import numpy as np
    >>> X = [5.74, 5.97, 6.19, 0.13, 0.35, 0.57]
    >>> unwrap(X, period=2 * np.pi)
    [5.74, 5.97, 6.19, 6.413185307179586, 6.633185307179586, 6.8531853071795865]

    """
    wrap = 0;
    last = angle[0];

    for k in range(len(angle)):
        # See if we need to account for angle wrapping
        if (angle[k] - last > period/2):
            wrap -= period
        elif (last - angle[k] > period/2):
            wrap += period

        # Update the last value we have sene
        last = angle[k]

        # Add in the wrap angle if nonzer
        if (wrap != 0):
            angle[k] += wrap;

    # return the updated list
    return angle

# Determine if an object is a system
def issys(object):
    # Check for a member of one of the classes that we define here
    #! TODO: this should probably look for an LTI object instead??
    if (isinstance(object, (statesp.StateSpace, xferfcn.TransferFunction))): 
        return True
    
    # Didn't find anything that matched
    return False
