# Python program that can be executed to report whether particular
# python packages are available on the system.

import math
import os
import sys


def test_is_python_35():
    major = sys.version_info.major
    minor = sys.version_info.minor
    if major == 3:
        pass 
    else:
        print("You are running Python {}, but we need Python {}.".format(major, 3))
        print("Download and install the Anaconda distribution for Python 3.")
        print("Stopping here.")

        # Let's stop here
        sys.exit(1)
        return None
        # assert major == 3, "Stopping here - we need Python 3."

    if minor >= 5:
        print("Testing Python version-> py{}.{} OK".format(major, minor))
    else:
        print("Warning: You should be running Python 3.5 or newer, " +
              "you have Python {}.{}.".format(major, minor))
        
        
def test_numpy():
    try:
        import numpy as np
    except ImportError:
        print("Could not import numpy -> numpy failed")
        return None
    # Simple test
    a = np.arange(0, 100, 1)
    assert np.sum(a) == sum(a)
    print("Testing numpy...      -> numpy OK")


def test_scipy():
    try:
        import scipy
    except ImportError:
        print("Could not import 'scipy' -> scipy failed")
        return None
    # Simple test
    import scipy.integrate
    assert abs(scipy.integrate.quad(lambda x: x * x, 0, 6)[0] - 72.0) < 1e-6
    print("Testing scipy ...     -> scipy OK")


def test_pylab():
    """Actually testing matplotlib, as pylab is part of matplotlib."""
    try:
        import pylab
    except ImportError:
            print("Could not import 'matplotlib/pylab' -> failed")
            return None
    # Creata plot for testing purposes
    xvalues = [i * 0.1 for i in range(100)]
    yvalues = [math.sin(x) for x in xvalues]
    pylab.plot(xvalues, yvalues, "-o", label="sin(x)")
    pylab.legend()
    pylab.xlabel('x')
    testfilename='pylab-testfigure.png'

    # check that file does not exist yet:
    if os.path.exists(testfilename):
        print("Skipping plotting to file as file {} exists already."\
            .format(testfilename))
    else:
        # Write plot to file
        pylab.savefig(testfilename)
        # Then check that file exists
        assert os.path.exists(testfilename)
        print("Testing matplotlib... -> pylab OK")
        os.remove(testfilename)


def test_sympy():
    try:
        import sympy
    except ImportError:
            print("Could not import 'sympy' -> fail")
            return None
    # simple test
    x = sympy.Symbol('x')
    my_f = x ** 2
    assert sympy.diff(my_f,x) == 2 * x
    print("Testing sympy         -> sympy OK")


def test_pytest():
    try:
        import pytest
    except ImportError:
            print("Could not import 'pytest' -> fail")
            return None
    print("Testing pytest        -> pytest OK")


if __name__ == "__main__":

    print("Running using Python {}".format(sys.version))
    test_is_python_35()
    test_numpy()
    test_scipy()
    test_pylab()
    test_sympy()
    test_pytest()