import os
import subprocess
import re
from utils import *
from method_missing import MethodMissingMixin
from errors import GitCommandError

# Enables debugging of GitPython's git commands
GIT_PYTHON_TRACE = os.environ.get("GIT_PYTHON_TRACE", False)

class Git(MethodMissingMixin):
    """
    The Git class manages communication with the Git binary
    """
    def __init__(self, git_dir=None):
        super(Git, self).__init__()
        if git_dir:
            self.find_git_dir(git_dir)
        else:
            self.find_git_dir(os.getcwd())

    def find_git_dir(self, path):
        """Find the best value for self.git_dir.
        For bare repositories, this is the path to the bare repository.
        For repositories with work trees, this is the work tree path.

        When barerepo.git is passed in,  self.git_dir = barerepo.git
        When worktree/.git is passed in, self.git_dir = worktree
        When worktree is passed in,      self.git_dir = worktree
        """

        path = os.path.abspath(path)
        self.git_dir = path

        cdup = self.execute(["git", "rev-parse", "--show-cdup"])
        if cdup:
            path = os.path.abspath(os.path.join(self.git_dir, cdup))
        else:
            is_bare_repository =\
                self.rev_parse(is_bare_repository=True) == "true"
            is_inside_git_dir =\
                self.rev_parse(is_inside_git_dir=True) == "true"

            if not is_bare_repository and is_inside_git_dir:
                path = os.path.dirname(self.git_dir)

        self.git_dir = path

    @property
    def get_dir(self):
        return self.git_dir

    def execute(self, command,
                istream = None,
                with_status = False,
                with_stderr = False,
                with_exceptions = False,
                with_raw_output = False,
                ):
        """
        Handles executing the command on the shell and consumes and returns
        the returned information (stdout)

        ``command``
            The command argument list to execute

        ``istream``
            Standard input filehandle passed to subprocess.Popen.

        ``with_status``
            Whether to return a (status, str) tuple.

        ``with_stderr``
            Whether to combine stderr into the output.

        ``with_exceptions``
            Whether to raise an exception when git returns a non-zero status.

        ``with_raw_output``
            Whether to avoid stripping off trailing whitespace.

        Returns
            str(output)                     # with_status = False (Default)
            tuple(int(status), str(output)) # with_status = True
        """

        if GIT_PYTHON_TRACE:
            print command

        # Allow stderr to be merged into stdout when with_stderr is True.
        # Otherwise, throw stderr away.
        if with_stderr:
            stderr = subprocess.STDOUT
        else:
            stderr = subprocess.PIPE

        # Start the process
        proc = subprocess.Popen(command,
                                cwd = self.git_dir,
                                stdin = istream,
                                stderr = stderr,
                                stdout = subprocess.PIPE
                                )

        # Wait for the process to return
        stdout_value = proc.stdout.read()
        status = proc.wait()
        proc.stdout.close()

        # Strip off trailing whitespace by default
        if not with_raw_output:
            stdout_value = stdout_value.rstrip()

        # Grab the exit status
        status = proc.poll()
        if with_exceptions and status != 0:
            raise GitCommandError("%s returned exit status %d"
                                  % (str(command), status))

        # Allow access to the command's status code
        if with_status:
            return (status, stdout_value)
        else:
            return stdout_value

    def transform_kwargs(self, **kwargs):
        """
        Transforms Python style kwargs into git command line options.
        """
        args = []
        for k, v in kwargs.items():
            if len(k) == 1:
                if v is True:
                    args.append("-%s" % k)
                else:
                    args.append("-%s%s" % (k, v))
            else:
                if v is True:
                    args.append("--%s" % dashify(k))
                else:
                    args.append("--%s=%s" % (dashify(k), v))
        return args

    def method_missing(self, method, *args, **kwargs):
        """
        Run the given git command with the specified arguments and return
        the result as a String

        ``method``
            is the command

        ``args``
            is the list of arguments

        ``kwargs``
            is a dict of keyword arguments.
            This function accepts the same optional keyword arguments
            as execute().

        Examples
            git.rev_list('master', max_count=10, header=True)

        Returns
            Same as execute()
        """

        # Handle optional arguments prior to calling transform_kwargs
        # otherwise these'll end up in args, which is bad.
        istream = kwargs.pop("istream", None)
        with_status = kwargs.pop("with_status", None)
        with_stderr = kwargs.pop("with_stderr", None)
        with_exceptions = kwargs.pop("with_exceptions", None)
        with_raw_output = kwargs.pop("with_raw_output", None)

        # Prepare the argument list
        opt_args = self.transform_kwargs(**kwargs)
        ext_args = map(str, args)
        args = opt_args + ext_args

        call = ["git", dashify(method)]
        call.extend(args)

        return self.execute(call,
                            istream = istream,
                            with_status = with_status,
                            with_stderr = with_stderr,
                            with_exceptions = with_exceptions,
                            with_raw_output = with_raw_output,
                            )