#!/usr/bin/env python

"""computes probabilities for the kolmogorov distribution.

Translated from R 2.4 by Gavin Huttley
"""
from __future__ import division
from numpy import sqrt, log, pi, exp, fabs, floor, zeros, asarray,\
            dot as matrixmultiply, ones, array, reshape, ravel, sum, arange
from cogent.maths.stats.special import combinations

__author__ = "Gavin Huttley"
__copyright__ = "Copyright 2007-2009, The Cogent Project"
__credits__ = ["Gavin Huttley"]
__license__ = "GPL"
__version__ = "1.3"
__maintainer__ = "Gavin Huttley"
__email__ = "gavin.huttley@anu.edu.au"
__status__ = "Production"

PIO4 = pi/4
PIO2 = pi/2
INVSQRT2PI = 1/sqrt(2*pi)

def mpower(A, exponent):
    """matrix power"""
    new = A
    for i in range(1, exponent):
        new = matrixmultiply(new, A)
    return new

def pkolmogorov1x(statistic, n):
    """Probability function for the one-sided one sample Kolmogorov statistics.
    
    Translated from R 2.4."""
    statistic = asarray(statistic)
    if statistic <= 0:
        return 0.
    if statistic >= 1:
        return 1.
    to = floor(n * (1-statistic))+1
    j = arange(0, to)
    coeffs = asarray([log(combinations(n, i)) for i in j])
    p = sum(exp(coeffs + (n-j)*log(1-statistic-j/n) + \
                                            (j-1)*(log(statistic+j/n))))
    return 1 - statistic * p

def pkolmogorov2x(statistic, n):
    """Probability function for Kolmogorovs distribution."""
    k=int(n*statistic)+1
    m=2*k-1
    h=k-n*statistic
    H = ones(m**2, 'd')
    Q = zeros(m**2, 'd')
    for i in range(m):
        for j in range(m):
            if(i-j+1<0):
                H[i*m+j]=0
    
    for i in range(m):
        H[i*m] -= h**(i+1)
        H[(m-1) * m+i] -= h**(m-i)
    H[(m-1)*m] += [0, (2*h-1)**m][2 * h - 1 > 0]
    for i in range(m):
        for j in range(m):
            if(i-j+1>0):
                for g in range(1, i-j+2):
                    H[i*m+j] /= g
    Q = ravel(mpower(reshape(H, (m,m)), n))
    s = Q[(k-1)*m+k-1]
    for i in range(1,n+1):
        s *= i/n
    return s

def pkstwo(x_vector, tolerance=1e-6):
    """Probability from the Kolmogorov asymptotic distribution."""
    #if isinstance(x_vector, float):
    #    x_vector = asarray(x_vector)
    x_vector = array(x_vector, ndmin=1)
    size = len(x_vector)
    k_max = int(sqrt(2-log(tolerance)))
    for i in range(size):
        if x_vector[i] < 1:
            z = -(PIO2 * PIO4) / x_vector[i]**2
            w = log(x_vector[i])
            s = 0
            for k in range(1, k_max, 2):
                s += exp(k**2 * z - w)
            x_vector[i] = s / INVSQRT2PI
        else:
            z = -2 * x_vector[i]**2
            s = -1
            k = 1
            old = 0
            new = 1
            while fabs(old - new) > tolerance:
                old = new
                new += (2 * s * exp(z * k**2))
                s *= -1
                k += 1
            x_vector[i] = new
    
    return x_vector

def psmirnov2x(statistic, least, most):
    if least > most:
        least, most = most, least
    q = floor(statistic * most * least - 1e-7) / (least * most)
    u_vector = zeros(most+1, 'd')
    for j in range(most+1):
        #SUPPORT2425
        u_vector[j] = [1,0][int(j / most > q)]
    for i in range(1,least+1):
        w = i / (i+most)
        if i/least > q:
            u_vector[0] = 0
        else:
            u_vector[0] = w * u_vector[0]
        for j in range(1, most+1):
            if fabs(i/least - j/most) > q:
                u_vector[j] = 0
            else:
                u_vector[j] = w * u_vector[j] + u_vector[j-1]
    
    return u_vector[most]
