#
# -*- coding: utf-8 -*-
#
 
from numpy import array, zeros, convolve, dot, roll, sqrt, concatenate
 
class AbstractFilter():
 
    def __init__(self):
        pass
 
    def __call__ (self, samples):
        """
        Apply the filter to samples. This method has to be
        overloaded from the specific filter class
        """
        pass
 
 
class FIR(AbstractFilter):
 
    def __init__(self, coefficients):
 
        self.coefficients = coefficients
 
    def __call__(self, samples):
        """Apply the FIR to samples"""
        # Per ora tronchiamo brutalmente la convoluzione, anche se
        # questo vuol dire perdere dei samples finali. d'altronde
        # sembra essere l'unico modo per prevere i delay.
        sz = len(samples)
        return convolve (self.coefficients, samples)[0:sz]
 
 
    def GetResponse(self):
        """
        Obtain the vector of coefficients.
        """
        return self.coefficients
 
    def __mul__(self, other):
        return FIR(convolve(self.coefficients, other.GetResponse()))
 
 
 
def DownSample(samples):
 
    return array(samples[::2])
 
def UpSample(samples):
 
    s = zeros(2 * len(samples))
    s[::2] = samples
    return array(s)
 
class WaveletStack():
 
    def __init__(self):
        """
        Creates a new WaveletTransformedSignal to
        store the samples from the filterbank
        """
        self.samples_number = None
        self.low_samples = []
        self.high_samples = []
        self.end = []
        self.end_effect = []
 
    def PushEndSamples(self, samples):
        """Push end samples, i.e. the samples that exceeds the
        ideal dimensione pow(2,m) where m is the depth of the
        filterbank."""
        self.end = samples
 
    def PopEndSamples(self):
        return self.end
 
    def PushEndEffectSamples(self, samples):
        """Push some end samples to preserve them to
        end effect"""
        self.end_effect = samples
 
    def PopEndEffectSamples(self):
        return self.end_effect
 
    def PushHighSamples(self, samples):
        """
        Add a new High Sample
        """
        if self.samples_number is None:
            self.samples_number = len(samples)
            self.high_samples.append(samples)
        else:
            if len(samples) != (self.samples_number / 2):
                raise IndexError("High frequency samples do not have the expected length")
            else:
                self.high_samples.append (samples)
                self.samples_number = len(samples)
 
    def PushLowSamples(self, samples):
        """
        Add the Low samples
        """
        if self.samples_number != len(samples):
            raise IndexError("Low frequency samples do not have the expected length")
        else:
            self.low_samples.append(samples)
 
    def PopLowSamples(self):
        """
        Get the low frequency samples
        """
        try:
            return self.low_samples.pop()
        except:
            raise IndexError("No low samples in the WaveletStack")
 
    def GetLowSamplesNumber(self):
        """Get the length of the lowsample array, i.e. how many low
        samples track do we have pushed."""
        return len(self.low_samples)
 
    def GetHighSamplesNumber(self):
        """Get the length of the lowsample array, i.e. how many low
        samples track do we have pushed."""
        return len(self.high_samples)
 
    def GetAllSamplesNumber(self):
        return sum(map(len, self.low_samples)) + sum(map(len,self.high_samples)) + len(self.end_effect) + len(self.end)
 
    def GetNumSamples(self):
        """Get the total number of samples in the WaveletStack."""
        return len(self.low_samples) + len(self.high_samples)
 
    def GetSamplesMaxValue(self):
        """Get the maximum abs value of the lowsample and
        high sample array"""
        m = [0]
        for low in self.low_samples:
            m.append (max(abs(low)))
        for high in self.high_samples:
            m.append(max(abs(high)))
        return max(m)
 
    def PopHighSamples(self):
        """
        Get the high frequency samples
        """
        try:
            return self.high_samples.pop ()
        except:
            raise IndexError("No more high samples in the stack")
 
 
class FilterBank():
 
    def __init__(self):
        """Create a new empty filter bank"""
        self.lowPassFilter = None
        self.highPassFilter = None
        self.highPassInverseFilter = None
        self.lowPassInverseFilter = None
 
        self.depth = 1
 
    def SetFilterMatrix(self, filter_matrix):
        """
        Set the filter matrix for the filter bank.
        It must have this shape:
 
          [ h0 , h1, f0, f1 ]
 
        Where h0 is the lowPass coefficients vector,
        h1 the high pass one, f0 the inverse low pass
        and f1 the inverse high pass.
        This method can only use FIR filters, if you are
        looking for more freedom use SetLowPassFilter ()
        and similar.
        """
        self.lowPassFilter = FIR (filter_matrix[0])
        self.highPassFilter = FIR (filter_matrix[1])
        self.lowPassInverseFilter = FIR (filter_matrix[2])
        self.highPassInverseFilter = FIR (filter_matrix[3])
 
    def _Truncate(self, samples):
        """
        Returns the samples truncated to make
        recursive split possibile
        (i.e. len(samples) % 2^depth = 0)
        """
        toRemove = len(samples) % pow(2,self.depth)
        if toRemove is 0:
            return samples, []
        else:
            return samples[:-1 * toRemove], samples[-1 * toRemove:]
 
    def SetDepth(self, depth):
        """
        Set the depth of the filter, i.e. how many recursion
        will be done when filtering and downsampling
        """
        self.depth = depth
 
    def SetLowPassFilter(self, lowpass):
        """
        Set the LowPassFilter for the filterbank.
        It has to be a callable that transform the
        samples. It will usually be a FIR
        """
        self.lowPassFilter = lowpass
 
        # Sembra che la lunghezza del filtro debba essere
        # la metà del filtro lowpass, arrotondata per eccesso
        self.SetLength ( int((len(lowpass) + 1)/2) )
 
    def SetHighPassFilter(self, highpass):
        """
        Set the High pass filter. It is usually
        a FIR but can be a generic callable that
        returns the filtered samples
        """
        self.highPassFilter = highpass
 
    def SetLowPassInverseFilter(self, lowpass):
        """
        Set the LowPass inverse filter to be used
        in reconstruction.
        """
        self.lowPassInverseFilter = lowpass
 
    def SetHighPassInverseFilter(self, highpass):
        """
        Set the HighPass inverse filter to be used
        in signal reconstruction
        """
        self.highPassInverseFilter = highpass
 
    def SetLength(self, length):
        """
        Set the length of the filter, i.e how much
        will be the delay when recovering
        """
        self.length = length
 
    def Split(self, samples):
        """
        Split the samples using the filter provided
        by the user. It returns a WaveletStack that
        contains the details and the last average.
        The original signal can be rebuilt collapsing
        all these downsampled signals with the Rebuild
        method.
        """
 
        samplesStack = WaveletStack()
        low, end = self._Truncate(samples)
        samplesStack.PushEndSamples (end)
 
        # Non sono proprio sicuro che questo sia il modo migliore per farlo.
        end_effect_number = (-2) * self.depth * len(self.lowPassFilter.GetResponse())
        samplesStack.PushEndEffectSamples (low[end_effect_number:])
 
        # Do the real filtering and downsampling. Store the downsampled
        # details in the array.
        for recursion in xrange(0, self.depth):
            samplesStack.PushHighSamples (DownSample (self.highPassFilter (low)))
            low = DownSample (self.lowPassFilter (low))
 
        # In the end append the low downsampled data to the array
        samplesStack.PushLowSamples (low)
 
        return samplesStack
 
    def Rebuild(self, samplesStack):
        """
        Rebuild an array of samples obtained by the Split()
        method.
        """
 
        low = samplesStack.PopLowSamples ()
        end = samplesStack.PopEndSamples ()
 
        counter = 0
 
        # high = samplesStack.PopHighSamples ()
        while(samplesStack.GetHighSamplesNumber() > 0):
 
            # Otteniamo l'high samples dallo stack
            high = samplesStack.PopHighSamples ()
 
            # E li filtriamo insieme ai low samples.
            low = self.lowPassInverseFilter (UpSample (low))
            low += self.highPassInverseFilter (UpSample (high))
 
            # Facciamo shiftare l'array in modo che il delay dei sample
            # ricostruiti non disturbi la ricostruzione dei prossimi.
            # Sfortunatamente questo ci rovinerà tutta l'ultima parte del
            # segnale, ma per ora non vedo una soluzione comoda.
            low = roll(low, -1 * self.length)
 
        # Riparo gli eventuali end effect
        low[-2*self.depth*len(self.lowPassFilter.GetResponse()):] = samplesStack.PopEndEffectSamples ()
 
        # Riattacchiamo la coda
        return concatenate ((low, end))
 
 
DaubechiesFilterBank = FilterBank ()
DaubechiesFilterBank.SetFilterMatrix ( [
        0.125 * array([ 1 + sqrt(3), 3 + sqrt(3), 3 - sqrt(3), 1 - sqrt(3)]),
        0.125 * array([ 1 - sqrt(3),-3 + sqrt(3), 3 + sqrt(3),-1 - sqrt(3)]),
        0.25  * array([ 1 - sqrt(3), 3 - sqrt(3), 3 + sqrt(3), 1 + sqrt(3)]),
        0.25  * array([-1 - sqrt(3), 3 + sqrt(3),-3 + sqrt(3), 1 - sqrt(3)])
        ])
DaubechiesFilterBank.SetLength (3)
 
HaarFilterBank = FilterBank ()
HaarFilterBank.SetFilterMatrix ( [
        [0.5, 0.5],
        [-0.5 ,0.5],
        [1 , 1 ],
        [1 , -1]
        ])
HaarFilterBank.SetLength(1)
 
LeoFilterBank = FilterBank()
LeoFilterBank.SetFilterMatrix ( [
        [0.25 , 0.5 , 0.25 ],
        [0.25 , -0.5, 0.25] ,
        [0.5 , 1, 0.5],
        [0.5, -1, 0.5]
        ])
LeoFilterBank.SetLength(3)
 
StrangFilterBank = FilterBank ()
StrangFilterBank.SetFilterMatrix ( [
        0.125 * array([-1,2,6,2,-1]),
        0.25 * array([1,-2,1]),
        0.5 * array([1,2,1]),
        0.25 * array([1,2,-6,2,1])
        ])
StrangFilterBank.SetLength(3)
 
def PRCheck(f):
 
    a = 0.5 * (f.lowPassFilter * f.lowPassInverseFilter).GetResponse ()
    b = 0.5 * (f.highPassFilter * f.highPassInverseFilter).GetResponse ()
    return a + b
 
 
h0 = StrangFilterBank.lowPassFilter
h1 = StrangFilterBank.highPassFilter
f0 = StrangFilterBank.lowPassInverseFilter
f1 = StrangFilterBank.highPassInverseFilter