# cmd.py
# Copyright (C) 2008, 2009 Michael Trier (mtrier@gmail.com) and contributors
#
# This module is part of GitPython and is released under
# the BSD License: http://www.opensource.org/licenses/bsd-license.php

import os, sys
from util import (
                    LazyMixin, 
                    stream_copy
                )
from exc import GitCommandError

from subprocess import (
                            call, 
                            Popen,
                            PIPE
                        )

execute_kwargs = ('istream', 'with_keep_cwd', 'with_extended_output',
                  'with_exceptions', 'as_process', 
                  'output_stream' )

__all__ = ('Git', )

def dashify(string):
    return string.replace('_', '-')


class Git(LazyMixin):
    """
    The Git class manages communication with the Git binary.
    
    It provides a convenient interface to calling the Git binary, such as in::
    
     g = Git( git_dir )
     g.init()                   # calls 'git init' program
     rval = g.ls_files()        # calls 'git ls-files' program
    
    ``Debugging``
        Set the GIT_PYTHON_TRACE environment variable print each invocation 
        of the command to stdout.
        Set its value to 'full' to see details about the returned values.
    """
    __slots__ = ("_working_dir", "cat_file_all", "cat_file_header", "_version_info",
                 "_git_options")
    
    # CONFIGURATION
    # The size in bytes read from stdout when copying git's output to another stream
    max_chunk_size = 1024*64
    
    git_exec_name = "git"           # default that should work on linux and windows
    git_exec_name_win = "git.cmd"   # alternate command name, windows only
    
    # Enables debugging of GitPython's git commands
    GIT_PYTHON_TRACE = os.environ.get("GIT_PYTHON_TRACE", False)
    
    # Provide the full path to the git executable. Otherwise it assumes git is in the path
    _git_exec_env_var = "GIT_PYTHON_GIT_EXECUTABLE"
    GIT_PYTHON_GIT_EXECUTABLE = os.environ.get(_git_exec_env_var, git_exec_name)
    
    
    class AutoInterrupt(object):
        """Kill/Interrupt the stored process instance once this instance goes out of scope. It is 
        used to prevent processes piling up in case iterators stop reading.
        Besides all attributes are wired through to the contained process object.
        
        The wait method was overridden to perform automatic status code checking
        and possibly raise."""
        __slots__= ("proc", "args")
        
        def __init__(self, proc, args ):
            self.proc = proc
            self.args = args
            
        def __del__(self):
            self.proc.stdout.close()
            self.proc.stderr.close()

            # did the process finish already so we have a return code ?
            if self.proc.poll() is not None:
                return
                
            # can be that nothing really exists anymore ... 
            if os is None:
                return
                
            # try to kill it
            try:
                os.kill(self.proc.pid, 2)   # interrupt signal
            except OSError:
                pass # ignore error when process already died
            except AttributeError:
                # try windows 
                # for some reason, providing None for stdout/stderr still prints something. This is why 
                # we simply use the shell and redirect to nul. Its slower than CreateProcess, question 
                # is whether we really want to see all these messages. Its annoying no matter what.
                call(("TASKKILL /F /T /PID %s 2>nul 1>nul" % str(self.proc.pid)), shell=True)
            # END exception handling 
            
        def __getattr__(self, attr):
            return getattr(self.proc, attr)
            
        def wait(self):
            """Wait for the process and return its status code. 
            
            :raise GitCommandError: if the return status is not 0"""
            status = self.proc.wait()
            self.proc.stdout.close()
            self.proc.stderr.close()
            if status != 0:
                raise GitCommandError(self.args, status, self.proc.stderr.read())
            # END status handling 
            return status
    # END auto interrupt
    
    class CatFileContentStream(object):
        """Object representing a sized read-only stream returning the contents of 
        an object.
        It behaves like a stream, but counts the data read and simulates an empty 
        stream once our sized content region is empty.
        If not all data is read to the end of the objects's lifetime, we read the 
        rest to assure the underlying stream continues to work"""
        
        __slots__ = ('_stream', '_nbr', '_size')
        
        def __init__(self, size, stream):
            self._stream = stream
            self._size = size
            self._nbr = 0           # num bytes read
            
            # special case: if the object is empty, has null bytes, get the 
            # final newline right away.
            if size == 0:
                stream.read(1)
            # END handle empty streams
            
        def read(self, size=-1):
            bytes_left = self._size - self._nbr
            if bytes_left == 0:
                return ''
            if size > -1:
                # assure we don't try to read past our limit
                size = min(bytes_left, size)
            else:
                # they try to read all, make sure its not more than what remains
                size = bytes_left
            # END check early depletion
            data = self._stream.read(size)
            self._nbr += len(data)
            
            # check for depletion, read our final byte to make the stream usable by others
            if self._size - self._nbr == 0:
                self._stream.read(1)    # final newline
            # END finish reading
            return data
            
        def readline(self, size=-1):
            if self._nbr == self._size:
                return ''
            
            # clamp size to lowest allowed value
            bytes_left = self._size - self._nbr
            if size > -1:
                size = min(bytes_left, size)
            else:
                size = bytes_left
            # END handle size
            
            data = self._stream.readline(size)
            self._nbr += len(data)
            
            # handle final byte
            if self._size - self._nbr == 0:
                self._stream.read(1)
            # END finish reading
            
            return data
            
        def readlines(self, size=-1):
            if self._nbr == self._size:
                return list()
            
            # leave all additional logic to our readline method, we just check the size
            out = list()
            nbr = 0
            while True:
                line = self.readline()
                if not line:
                    break
                out.append(line)
                if size > -1:
                    nbr += len(line)
                    if nbr > size:
                        break
                # END handle size constraint
            # END readline loop
            return out
            
        def __iter__(self):
            return self
            
        def next(self):
            line = self.readline()
            if not line:
                raise StopIteration
            return line
            
        def __del__(self):
            bytes_left = self._size - self._nbr
            if bytes_left:
                # read and discard - seeking is impossible within a stream
                # includes terminating newline
                self._stream.read(bytes_left + 1)
            # END handle incomplete read
    
    
    def __init__(self, working_dir=None):
        """Initialize this instance with:
        
        :param working_dir:
           Git directory we should work in. If None, we always work in the current 
           directory as returned by os.getcwd().
           It is meant to be the working tree directory if available, or the 
           .git directory in case of bare repositories."""
        super(Git, self).__init__()
        self._working_dir = working_dir
        self._git_options = ()

        # cached command slots
        self.cat_file_header = None
        self.cat_file_all = None

    def __getattr__(self, name):
        """A convenience method as it allows to call the command as if it was 
        an object.
        :return: Callable object that will execute call _call_process with your arguments."""
        if name[0] == '_':
            return LazyMixin.__getattr__(self, name)
        return lambda *args, **kwargs: self._call_process(name, *args, **kwargs)

    def _set_cache_(self, attr):
        if attr == '_version_info':
            # We only use the first 4 numbers, as everthing else could be strings in fact (on windows)
            version_numbers = self._call_process('version').split(' ')[2]
            self._version_info = tuple(int(n) for n in version_numbers.split('.')[:4] if n.isdigit())
        else:
            super(Git, self)._set_cache_(attr)
        #END handle version info
            

    @property
    def working_dir(self):
        """:return: Git directory we are working on"""
        return self._working_dir
        
    @property
    def version_info(self):
        """
        :return: tuple(int, int, int, int) tuple with integers representing the major, minor
            and additional version numbers as parsed from git version.
            This value is generated on demand and is cached"""
        return self._version_info

    def execute(self, command,
                istream=None,
                with_keep_cwd=False,
                with_extended_output=False,
                with_exceptions=True,
                as_process=False, 
                output_stream=None, 
                **subprocess_kwargs
                ):
        """Handles executing the command on the shell and consumes and returns
        the returned information (stdout)

        :param command:
            The command argument list to execute.
            It should be a string, or a sequence of program arguments. The
            program to execute is the first item in the args sequence or string.

        :param istream:
            Standard input filehandle passed to subprocess.Popen.

        :param with_keep_cwd:
            Whether to use the current working directory from os.getcwd().
            The cmd otherwise uses its own working_dir that it has been initialized
            with if possible.

        :param with_extended_output:
            Whether to return a (status, stdout, stderr) tuple.

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

        :param as_process:
            Whether to return the created process instance directly from which 
            streams can be read on demand. This will render with_extended_output and 
            with_exceptions ineffective - the caller will have 
            to deal with the details himself.
            It is important to note that the process will be placed into an AutoInterrupt
            wrapper that will interrupt the process once it goes out of scope. If you 
            use the command in iterators, you should pass the whole process instance 
            instead of a single stream.
            
        :param output_stream:
            If set to a file-like object, data produced by the git command will be 
            output to the given stream directly.
            This feature only has any effect if as_process is False. Processes will
            always be created with a pipe due to issues with subprocess.
            This merely is a workaround as data will be copied from the 
            output pipe to the given output stream directly.
            
        :param subprocess_kwargs:
            Keyword arguments to be passed to subprocess.Popen. Please note that 
            some of the valid kwargs are already set by this method, the ones you 
            specify may not be the same ones.
            
        :return:
            * str(output) if extended_output = False (Default)
            * tuple(int(status), str(stdout), str(stderr)) if extended_output = True
             
            if ouput_stream is True, the stdout value will be your output stream:
            * output_stream if extended_output = False
            * tuple(int(status), output_stream, str(stderr)) if extended_output = True

            Note git is executed with LC_MESSAGES="C" to ensure consitent
            output regardless of system language.
            
        :raise GitCommandError:
        
        :note:
           If you add additional keyword arguments to the signature of this method, 
           you must update the execute_kwargs tuple housed in this module."""
        if self.GIT_PYTHON_TRACE and not self.GIT_PYTHON_TRACE == 'full':
            print ' '.join(command)

        # Allow the user to have the command executed in their working dir.
        if with_keep_cwd or self._working_dir is None:
          cwd = os.getcwd()
        else:
          cwd=self._working_dir
          
        # Start the process
        proc = Popen(command,
                        env={"LC_MESSAGES": "C"},
                        cwd=cwd,
                        stdin=istream,
                        stderr=PIPE,
                        stdout=PIPE,
                        close_fds=(os.name=='posix'),# unsupported on linux
                        **subprocess_kwargs
                        )
        if as_process:
            return self.AutoInterrupt(proc, command)
        
        # Wait for the process to return
        status = 0
        stdout_value = ''
        stderr_value = ''
        try:
            if output_stream is None:
                stdout_value, stderr_value = proc.communicate() 
                # strip trailing "\n"
                if stdout_value.endswith("\n"):
                    stdout_value = stdout_value[:-1]
                if stderr_value.endswith("\n"):
                    stderr_value = stderr_value[:-1]
                status = proc.returncode
            else:
                stream_copy(proc.stdout, output_stream, self.max_chunk_size)
                stdout_value = output_stream
                stderr_value = proc.stderr.read()
                # strip trailing "\n"
                if stderr_value.endswith("\n"):
                    stderr_value = stderr_value[:-1]
                status = proc.wait()
            # END stdout handling
        finally:
            proc.stdout.close()
            proc.stderr.close()

        if self.GIT_PYTHON_TRACE == 'full':
            cmdstr = " ".join(command)
            if stderr_value:
                print "%s -> %d; stdout: '%s'; stderr: '%s'" % (cmdstr, status, stdout_value, stderr_value)
            elif stdout_value:
                print "%s -> %d; stdout: '%s'" % (cmdstr, status, stdout_value)
            else:
                print "%s -> %d" % (cmdstr, status)
        # END handle debug printing

        if with_exceptions and status != 0:
            if with_extended_output:
                raise GitCommandError(command, status, stderr_value, stdout_value)
            else:
                raise GitCommandError(command, status, stderr_value)

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

    def transform_kwargs(self, split_single_char_options=False, **kwargs):
        """Transforms Python style kwargs into git command line options."""
        args = list()
        for k, v in kwargs.items():
            if len(k) == 1:
                if v is True:
                    args.append("-%s" % k)
                elif type(v) is not bool:
                    if split_single_char_options:
                        args.extend(["-%s" % k, "%s" % v])
                    else:
                        args.append("-%s%s" % (k, v))
            else:
                if v is True:
                    args.append("--%s" % dashify(k))
                elif type(v) is not bool:
                    args.append("--%s=%s" % (dashify(k), v))
        return args

    @classmethod
    def __unpack_args(cls, arg_list):
        if not isinstance(arg_list, (list,tuple)):
            if isinstance(arg_list, unicode):
                return [arg_list.encode('utf-8')]
            return [ str(arg_list) ]
            
        outlist = list()
        for arg in arg_list:
            if isinstance(arg_list, (list, tuple)):
                outlist.extend(cls.__unpack_args( arg ))
            elif isinstance(arg_list, unicode):
                outlist.append(arg_list.encode('utf-8'))
            # END recursion 
            else:
                outlist.append(str(arg))
        # END for each arg
        return outlist

    def __call__(self, **kwargs):
        """Specify command line options to the git executable
        for a subcommand call

        :param kwargs:
            is a dict of keyword arguments.
            these arguments are passed as in _call_process
            but will be passed to the git command rather than
            the subcommand.

        ``Examples``::
            git(work_tree='/tmp').difftool()"""
        self._git_options = self.transform_kwargs(
            split_single_char_options=True, **kwargs)
        return self

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

        :param method:
            is the command. Contained "_" characters will be converted to dashes,
            such as in 'ls_files' to call 'ls-files'.

        :param args:
            is the list of arguments. If None is included, it will be pruned.
            This allows your commands to call git more conveniently as None
            is realized as non-existent

        :param 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)

        :return: Same as ``execute``"""
        # Handle optional arguments prior to calling transform_kwargs
        # otherwise these'll end up in args, which is bad.
        _kwargs = dict()
        for kwarg in execute_kwargs:
            try:
                _kwargs[kwarg] = kwargs.pop(kwarg)
            except KeyError:
                pass

        # Prepare the argument list
        opt_args = self.transform_kwargs(**kwargs)
        
        ext_args = self.__unpack_args([a for a in args if a is not None])
        args = opt_args + ext_args
        
        def make_call():
            call = [self.GIT_PYTHON_GIT_EXECUTABLE]

            # add the git options, the reset to empty
            # to avoid side_effects
            call.extend(self._git_options)
            self._git_options = ()

            call.extend([dashify(method)])
            call.extend(args)
            return call
        #END utility to recreate call after changes
        
        if sys.platform == 'win32':
            try:
                try:
                    return self.execute(make_call(), **_kwargs)
                except WindowsError:
                    # did we switch to git.cmd already, or was it changed from default ? permanently fail
                    if self.GIT_PYTHON_GIT_EXECUTABLE != self.git_exec_name:
                        raise
                    #END handle overridden variable
                    type(self).GIT_PYTHON_GIT_EXECUTABLE = self.git_exec_name_win
                    call = [self.GIT_PYTHON_GIT_EXECUTABLE] + list(args)
                    
                    try:
                        return self.execute(make_call(), **_kwargs)
                    finally:
                        import warnings
                        msg = "WARNING: Automatically switched to use git.cmd as git executable, which reduces performance by ~70%."
                        msg += "Its recommended to put git.exe into the PATH or to set the %s environment variable to the executable's location" % self._git_exec_env_var 
                        warnings.warn(msg)
                    #END print of warning
                #END catch first failure
            except WindowsError:
                raise WindowsError("The system cannot find or execute the file at %r" % self.GIT_PYTHON_GIT_EXECUTABLE)
            #END provide better error message
        else:
            return self.execute(make_call(), **_kwargs)
        #END handle windows default installation
        
    def _parse_object_header(self, header_line):
        """
        :param header_line:
            <hex_sha> type_string size_as_int
            
        :return: (hex_sha, type_string, size_as_int)
            
        :raise ValueError: if the header contains indication for an error due to 
            incorrect input sha"""
        tokens = header_line.split()
        if len(tokens) != 3:
            if not tokens:
                raise ValueError("SHA could not be resolved, git returned: %r" % (header_line.strip()))
            else:
                raise ValueError("SHA %s could not be resolved, git returned: %r" % (tokens[0], header_line.strip()))
            # END handle actual return value
        # END error handling
        
        if len(tokens[0]) != 40:
            raise ValueError("Failed to parse header: %r" % header_line) 
        return (tokens[0], tokens[1], int(tokens[2]))
    
    def __prepare_ref(self, ref):
        # required for command to separate refs on stdin
        refstr = str(ref)               # could be ref-object
        if refstr.endswith("\n"):
            return refstr
        return refstr + "\n"
    
    def __get_persistent_cmd(self, attr_name, cmd_name, *args,**kwargs):
        cur_val = getattr(self, attr_name)
        if cur_val is not None:
            return cur_val
            
        options = { "istream" : PIPE, "as_process" : True }
        options.update( kwargs )
        
        cmd = self._call_process( cmd_name, *args, **options )
        setattr(self, attr_name, cmd )
        return cmd
    
    def __get_object_header(self, cmd, ref):
        cmd.stdin.write(self.__prepare_ref(ref))
        cmd.stdin.flush()
        return self._parse_object_header(cmd.stdout.readline())
    
    def get_object_header(self, ref):
        """ Use this method to quickly examine the type and size of the object behind 
        the given ref. 
        
        :note: The method will only suffer from the costs of command invocation 
            once and reuses the command in subsequent calls. 
        
        :return: (hexsha, type_string, size_as_int)"""
        cmd = self.__get_persistent_cmd("cat_file_header", "cat_file", batch_check=True)
        return self.__get_object_header(cmd, ref)
        
    def get_object_data(self, ref):
        """ As get_object_header, but returns object data as well
        :return: (hexsha, type_string, size_as_int,data_string)
        :note: not threadsafe"""
        hexsha, typename, size, stream = self.stream_object_data(ref)
        data = stream.read(size)
        del(stream)
        return (hexsha, typename, size, data)
        
    def stream_object_data(self, ref):
        """As get_object_header, but returns the data as a stream
        :return: (hexsha, type_string, size_as_int, stream)
        :note: This method is not threadsafe, you need one independent  Command instance
            per thread to be safe !"""
        cmd = self.__get_persistent_cmd("cat_file_all", "cat_file", batch=True)
        hexsha, typename, size = self.__get_object_header(cmd, ref)
        return (hexsha, typename, size, self.CatFileContentStream(size, cmd.stdout))
        
    def clear_cache(self):
        """Clear all kinds of internal caches to release resources.
        
        Currently persistent commands will be interrupted.
        
        :return: self"""
        self.cat_file_all = None
        self.cat_file_header = None
        return self
