#-- we need to know the platform and Python version, so we need
#   access to the system module
import sys
import os

fail = False
#-- these are the packages that need to be tested
version_IPython = '0.11'
version_numpy = '1.6.0'
version_matplotlib = '1.2.0'
version_scipy = '0.9.0'

#-- it's easier to test numbers than strings, so these small functions
#   convert a string to a list of floats, and test whether or not the version
#   is at least the required one.
def string_to_triple(current):
    # remember major, minor and micro if available
    version = [0,0,0]
    current = current.split('.')
    for i,value in enumerate(current):
        try:        
            version[i] = float(value)
        except:
            version[i] = 0
    return version

def check_version_info(current,required):
    # check if all of major, minor and micro are greater or equal to the required
    # version
    current = string_to_triple(current)
    required = string_to_triple(required)
    if all([(i>=j) for i,j in zip(current,required)]):
        return True

#-- check Python version
if sys.version_info[0]<2 or sys.version_info[1]<7:
    print("You need to have Python 2.7 at least, it makes the transition to Python 3 easier")
    fail = True
else:
    print("Your Python version is up-to-date")

#-- check all other packages: I was lazy in naming variables, so I can just
#   cycle over all the variables that are defined here. Whenever it says "version_*"
#   the variable hold the name of the package and the value is the required version
for version_package in locals().keys():
    # of course we have other global variables as well, we want to skip those
    if not 'version'==version_package.split('_')[0]: continue
    # derive the package name and required version
    package = "_".join(version_package.split('_')[1:])
    required_version = locals()[version_package]
    # try to import, and check the version
    try:
        mypackage = __import__(package)
        if not check_version_info(mypackage.__version__,required_version):
            print("Package {:s} is old (version {:s} instead of {:s}). Please upgrade.".format(package,mypackage.__version__,required_version))
        else:
            print("Package {:s} is installed and up-to-date".format(package))
    except ImportError:
        print("Package {:s} is not installed. You will not be able to run all tutorial examples. Please install.".format(package))
        fail = True
        

if not fail:
    print('All tests passed successfully')
else:
    print("Some tests failed")