#! /usr/bin/env python
'''Libraries for machine learning algorithms'''

import numpy as np


class Model(object):
    '''Abstract class for loading/saving model'''    
    def load(self, filename):
        from os import path
        if path.exists(filename):
            self.model.load(filename)
        else:
            print('Provided filename {} does not exist: model not loaded!'.format(filename))

    def save(self, filename):
        self.model.save(filename)

class SVM(Model):
    '''wrapper for OpenCV SimpleVectorMachine algorithm'''

    def __init__(self):
        import cv2
        self.model = cv2.SVM()

    def train(self, samples, responses, svm_type, kernel_type, degree = 0, gamma = 1, coef0 = 0, Cvalue = 1, nu = 0, p = 0):
        self.params = dict(svm_type = svm_type, kernel_type = kernel_type, degree = degree, gamma = gamma, coef0 = coef0, Cvalue = Cvalue, nu = nu, p = p)
        self.model.train(samples, responses, params = self.params)

    def predict(self, hog):
        return self.model.predict(hog)


class Centroid(object):
    'Wrapper around instances to add a counter'

    def __init__(self, instance, nInstances = 1):
        self.instance = instance
        self.nInstances = nInstances

    # def similar(instance2):
    #     return self.instance.similar(instance2)

    def add(self, instance2):
        self.instance = self.instance.multiply(self.nInstances)+instance2
        self.nInstances += 1
        self.instance = self.instance.multiply(1/float(self.nInstances))

    def average(c):
        inst = self.instance.multiply(self.nInstances)+c.instance.multiply(instance.nInstances)
        inst.multiply(1/(self.nInstances+instance.nInstances))
        return Centroid(inst, self.nInstances+instance.nInstances)

    def plot(self, options = ''):
        from matplotlib.pylab import text
        self.instance.plot(options)
        text(self.instance.position.x+1, self.instance.position.y+1, str(self.nInstances))

def kMedoids(similarityMatrix, initialCentroids = None, k = None):
    '''Algorithm that clusters any dataset based on a similarity matrix
    Either the initialCentroids or k are passed'''
    pass

def assignCluster(data, similarFunc, initialCentroids = None, shuffleData = True):
    '''k-means algorithm with similarity function
    Two instances should be in the same cluster if the sameCluster function returns true for two instances. It is supposed that the average centroid of a set of instances can be computed, using the function. 
    The number of clusters will be determined accordingly

    data: list of instances
    averageCentroid: '''

    from random import shuffle
    from copy import copy, deepcopy
    localdata = copy(data) # shallow copy to avoid modifying data
    if shuffleData:
        shuffle(localdata)
    if initialCentroids is None:
        centroids = [Centroid(localdata[0])]
    else:
        centroids = deepcopy(initialCentroids)
    for instance in localdata[1:]:
        i = 0
        while i<len(centroids) and not similarFunc(centroids[i].instance, instance):
            i += 1
        if i == len(centroids):
            centroids.append(Centroid(instance))
        else:
            centroids[i].add(instance)

    return centroids

# TODO recompute centroids for each cluster: instance that minimizes some measure to all other elements

def spectralClustering(similarityMatrix, k, iter=20):
	'''Spectral Clustering algorithm'''
	n = len(similarityMatrix)
	# create Laplacian matrix
	rowsum = np.sum(similarityMatrix,axis=0)
	D = np.diag(1 / np.sqrt(rowsum))
	I = np.identity(n)
	L = I - np.dot(D,np.dot(similarityMatrix,D))
	# compute eigenvectors of L
	U,sigma,V = np.linalg.svd(L)
	# create feature vector from k first eigenvectors
	# by stacking eigenvectors as columns
	features = np.array(V[:k]).T
	# k-means
	from scipy.cluster.vq import kmeans, whiten, vq
	features = whiten(features)
	centroids,distortion = kmeans(features,k, iter)
	code,distance = vq(features,centroids) # code starting from 0 (represent first cluster) to k-1 (last cluster)
	return code,sigma	

def prototypeCluster(instances, similarityMatrix, minSimilarity, minClusterSize = None, randomInitialization = False):
    '''Finds exemplar (prototype) instance that represent each cluster
    Returns the prototype indices (in the instances list) and the cluster label of each instance

    the elements in the instances list must have a length (method __len__), or one can use the random initialization
    the positions in the instances list corresponds to the similarityMatrix

    if an instance is different enough (<minSimilarity), 
    it will become a new prototype. 
    Non-prototype instances will be assigned to an existing prototype
    if minClusterSize is not None, the clusters will be refined by removing iteratively the smallest clusters
    and reassigning all elements in the cluster until no cluster is smaller than minClusterSize'''

    # sort instances based on length
    indices = range(similarityMatrix.shape[0])
    if randomInitialization:
        indices = np.random.permutation(indices)
    else:
        def compare(i, j):
            if len(instances[i]) > len(instances[j]):
                return -1
            elif len(instances[i]) == len(instances[j]):
                return 0
            else:
                return 1
        indices.sort(compare)
    # go through all instances
    prototypeIndices = [indices[0]]
    for i in indices[1:]:
        if similarityMatrix[i][prototypeIndices].max() < minSimilarity:
             prototypeIndices.append(i)

    # assignment
    indices = [i for i in range(similarityMatrix.shape[0]) if i not in prototypeIndices]
    assign = True
    while assign:
        labels = [-1]*similarityMatrix.shape[0]
        for i in prototypeIndices:
            labels[i] = i
        for i in indices:
            prototypeIndex = similarityMatrix[i][prototypeIndices].argmax()
            labels[i] = prototypeIndices[prototypeIndex]
        clusterSizes = {i: sum(np.array(labels) == i) for i in prototypeIndices}
        smallestClusterIndex = min(clusterSizes, key = clusterSizes.get) 
        assign = (clusterSizes[smallestClusterIndex] < minClusterSize)
        if assign:
            prototypeIndices.remove(smallestClusterIndex)
            indices.append(smallestClusterIndex)

    return prototypeIndices, labels
