import os
import subprocess
import re
import sys


def which(cmd):
    for p in os.environ["PATH"].split(os.pathsep):
        clang_path = os.path.join(p, cmd)
        if os.path.exists(clang_path):
            return clang_path
    return None


CLANG_VERSION_REGEX = ".*version\s*([0-9]*\.[0-9]*)\.*"
clang_path = which("clang++")
clang_version_major = 0
clang_version_minor = 0

if clang_path:
    clang_version_out = subprocess.Popen([clang_path, "--version"], stdout=subprocess.PIPE).communicate()[0]
    clang_version_match = re.search(CLANG_VERSION_REGEX, clang_version_out)
    clang_version_str = clang_version_match.group(1)
    clang_version_array = clang_version_str.split('.')
    clang_version_major = int(clang_version_array[0])
    clang_version_minor = int(clang_version_array[1])

if clang_version_major >= 3 and clang_version_minor >= 5:
    print ""
else:
    # Loop in support clang version only
    clang_version_major = 3
    clang_version_minor = 9
    while clang_version_major >= 3 and clang_version_minor >= 5:
        clang_version_str = "%d.%d" % (clang_version_major, clang_version_minor)
        clang_path = which("clang++-" + clang_version_str)
        if clang_path:
            print clang_version_str
            sys.exit(0)
        clang_version_minor -= 1
        if clang_version_minor < 0:
            clang_version_minor = 9
            clang_version_major -= 1
    print "None"