import os
import subprocess
import shlex
import signal
import sys
import locale

from pexpect.popen_spawn import PopenSpawn

# Include `unicode` in STR_TYPES for Python 2.X
try:
    STR_TYPES = (str, unicode)
except NameError:
    STR_TYPES = (str, )

TIMEOUT = 30

class Command(object):

    def __init__(self, cmd, timeout=TIMEOUT):
        super(Command, self).__init__()
        self.cmd = cmd
        self.timeout = timeout
        self.subprocess = None
        self.blocking = None
        self.was_run = False
        self.__out = None
        self.__err = None

    def __repr__(self):
        return '<Command {!r}>'.format(self.cmd)

    @property
    def _popen_args(self):
        return self.cmd

    @property
    def _default_popen_kwargs(self):
        return {
            'env': os.environ.copy(),
            'stdin': subprocess.PIPE,
            'stdout': subprocess.PIPE,
            'stderr': subprocess.PIPE,
            'shell': True,
            'universal_newlines': True,
            'bufsize': 0,
        }

    @property
    def _default_pexpect_kwargs(self):
        encoding = 'utf-8'
        if sys.platform == 'win32':
            default_encoding = locale.getdefaultlocale()[1]
            if default_encoding is not None:
                encoding = default_encoding
        return {
            'env': os.environ.copy(),
            'encoding': encoding,
            'timeout': self.timeout
        }

    @property
    def _uses_subprocess(self):
        return isinstance(self.subprocess, subprocess.Popen)

    @property
    def _uses_pexpect(self):
        return isinstance(self.subprocess, PopenSpawn)

    @property
    def std_out(self):
        return self.subprocess.stdout

    @property
    def _pexpect_out(self):
        if self.subprocess.encoding:
            result = ''
        else:
            result = b''

        if self.subprocess.before:
            result += self.subprocess.before

        if self.subprocess.after:
            result += self.subprocess.after

        result += self.subprocess.read()
        return result

    @property
    def out(self):
        """Std/out output (cached)"""
        if self.__out is not None:
            return self.__out

        if self._uses_subprocess:
            self.__out = self.std_out.read()
        else:
            self.__out = self._pexpect_out

        return self.__out

    @property
    def std_err(self):
        return self.subprocess.stderr

    @property
    def err(self):
        """Std/err output (cached)"""
        if self.__err is not None:
            return self.__err

        if self._uses_subprocess:
            self.__err = self.std_err.read()
            return self.__err
        else:
            return self._pexpect_out

    @property
    def pid(self):
        """The process' PID."""
        # Support for pexpect's functionality.
        if hasattr(self.subprocess, 'proc'):
            return self.subprocess.proc.pid
        # Standard subprocess method.
        return self.subprocess.pid

    @property
    def return_code(self):
        # Support for pexpect's functionality.
        if self._uses_pexpect:
            return self.subprocess.exitstatus
        # Standard subprocess method.
        return self.subprocess.returncode

    @property
    def std_in(self):
        return self.subprocess.stdin

    def run(self, block=True, binary=False):
        """Runs the given command, with or without pexpect functionality enabled."""
        self.blocking = block

        # Use subprocess.
        if self.blocking:
            popen_kwargs = self._default_popen_kwargs.copy()
            popen_kwargs['universal_newlines'] = not binary
            s = subprocess.Popen(self._popen_args, **popen_kwargs)
        # Otherwise, use pexpect.
        else:
            pexpect_kwargs = self._default_pexpect_kwargs.copy()
            if binary:
                pexpect_kwargs['encoding'] = None
            # Enable Python subprocesses to work with expect functionality.
            pexpect_kwargs['env']['PYTHONUNBUFFERED'] = '1'
            s = PopenSpawn(self._popen_args, **pexpect_kwargs)
        self.subprocess = s
        self.was_run = True

    def expect(self, pattern, timeout=-1):
        """Waits on the given pattern to appear in std_out"""

        if self.blocking:
            raise RuntimeError('expect can only be used on non-blocking commands.')

        self.subprocess.expect(pattern=pattern, timeout=timeout)

    def send(self, s, end=os.linesep, signal=False):
        """Sends the given string or signal to std_in."""

        if self.blocking:
            raise RuntimeError('send can only be used on non-blocking commands.')

        if not signal:
            if self._uses_subprocess:
                return self.subprocess.communicate(s + end)
            else:
                return self.subprocess.send(s + end)
        else:
            self.subprocess.send_signal(s)

    def terminate(self):
        self.subprocess.terminate()

    def kill(self):
        self.subprocess.kill(signal.SIGINT)

    def block(self):
        """Blocks until process is complete."""
        if self._uses_subprocess:
            # consume stdout and stderr
            try:
                stdout, stderr = self.subprocess.communicate()
                self.__out = stdout
                self.__err = stderr
            except ValueError:
                pass  # Don't read from finished subprocesses.
        else:
            self.subprocess.wait()

    def pipe(self, command, timeout=None):
        """Runs the current command and passes its output to the next
        given process.
        """
        if not timeout:
            timeout = self.timeout

        if not self.was_run:
            self.run(block=False)

        data = self.out

        if timeout:
            c = Command(command, timeout)
        else:
            c = Command(command)

        c.run(block=False)
        if data:
            c.send(data)
            c.subprocess.sendeof()
        c.block()
        return c


def _expand_args(command):
    """Parses command strings and returns a Popen-ready list."""

    # Prepare arguments.
    if isinstance(command, STR_TYPES):
        splitter = shlex.shlex(command.encode('utf-8'))
        splitter.whitespace = '|'
        splitter.whitespace_split = True
        command = []

        while True:
            token = splitter.get_token()
            if token:
                command.append(token)
            else:
                break

        command = list(map(shlex.split, command))

    return command


def chain(command, timeout=TIMEOUT):
    commands = _expand_args(command)
    data = None

    for command in commands:

        c = run(command, block=False, timeout=timeout)

        if data:
            c.send(data)
            c.subprocess.sendeof()

        data = c.out

    return c


def run(command, block=True, binary=False, timeout=TIMEOUT):
    c = Command(command, timeout=timeout)
    c.run(block=block, binary=binary)

    if block:
        c.block()

    return c
