import os
import sys
import subprocess

from .inwinreg import register_interpreter

EXE_DIR = os.path.abspath(os.path.dirname(sys.executable))
if EXE_DIR.endswith('.app/Contents/MacOS'):
    EXE_DIR = os.path.dirname(EXE_DIR.rsplit('.app')[0])

def make_abs(path):
    if path.startswith('.'):
        return os.path.abspath(os.path.join(EXE_DIR, path))
    return path


class PythonInterpreter:
    """ Class to represent a Python interpreter. It has properties
    to get the path and version. Upon creation the version number is
    acquired by calling the interpreter in a subprocess. If this fails,
    the version becomes ''.
    
    """
    def __init__(self, path):
        if not isinstance(path, str):
            raise ValueError('Path for PythonInterpreter is not a string: %r' % path)
        if not os.path.isfile(make_abs(path)):
            raise ValueError('Path for PythonInterpreter is invalid: %r' % path)
        self._path = path if path.startswith('.') else os.path.normpath(os.path.abspath(path))
        self._normpath = os.path.normcase(self._path)
        self._problem = ''
        self._version = None
        # Set prefix
        self._prefix = os.path.dirname(self.path)
        if os.path.basename(self._prefix) == 'bin':
            self._prefix = os.path.dirname(self._prefix) 
    
    def __repr__(self):
        cls_name = self.__class__.__name__
        return '<%s version %s at %s>' % (cls_name, self.version, self.path)
    
    def __hash__(self):
        return hash(self._normpath)
    
    def __eq__(self, other):
        return self._normpath == other._normpath
    
    @property
    def path(self):
        """ The path to the executable of the Python interpreter.
        If relative (starting with a dot), it is relative to the current
        sys.executable.
        """
        return self._path
    
    @property
    def prefix(self):
        """ The prefix of this executable.
        """
        return self._prefix
    
    @property
    def is_conda(self):
        """ Whether this interpreter is part of a conda environment (either
        a root or an env).
        """
        return os.path.isdir(os.path.join(make_abs(self._prefix), 'conda-meta'))
    
    @property
    def version(self):
        """ The version number as a string, usually 3 numbers.
        """
        if self._version is None:
            self._version = self._getversion()
        return self._version
    
    @property
    def version_info(self):
        """ The version number as a tuple of integers. For comparing.
        """
        return versionStringToTuple(self.version)
    
    def register(self):
        """ Register this Python intepreter. On Windows this modifies
        the CURRENT_USER. On All other OS's this is a no-op.
        """
        if sys.platform.startswith('win'):
            path = os.path.split(make_abs(self.path))[0] # Remove "python.exe"
            register_interpreter(self.version[:3], path)
    
    def _getversion(self):
        path = make_abs(self._path)
        
        # Check if path is even a file
        if not os.path.isfile(path):
            self._problem = '%s is not a valid file.'
            return ''
        
        # Poll Python executable (--version does not work on 2.4)
        # shell=True prevents loads of command windows popping up on Windows,
        # but if used on Linux it would enter interpreter mode
        cmd = [path, '-V']
        try:
            v = subprocess.check_output(cmd, stderr=subprocess.STDOUT, 
                                        shell=sys.platform.startswith('win'))
        except (OSError, IOError, subprocess.CalledProcessError) as e:
            self._problem = str(e)
            return ''
        
        # Extract the version, apply some defensive programming
        v = v.decode('ascii','ignore').strip().lower()
        if v.startswith('python'):
            v = v.split(' ')[1]
        v = v.split(' ')[0]
        
        # Try turning it into version_info
        try:
            versionStringToTuple(v)
        except ValueError:
            return ''
        
        # Done
        return v


def versionStringToTuple(version):
    # Truncate version number to first occurance of non-numeric character
    tversion = ''
    for c in version:
        if c in '0123456789.':  tversion += c
    # Split by dots, make each number an integer
    tversion = tversion.strip('.')
    return tuple( [int(a) for a in tversion.split('.') if a] )
