# util.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
"""
Module for general utility functions
"""
import re
from collections import deque as Deque
from git.actor import Actor
import platform

from string import digits
import time
import os

__all__ = ('get_object_type_by_name', 'get_user_id', 'parse_date', 'parse_actor_and_date', 
			'ProcessStreamAdapter', 'Traversable')

def get_object_type_by_name(object_type_name):
	"""
	Returns
		type suitable to handle the given object type name.
		Use the type to create new instances.
		
	``object_type_name``
		Member of TYPES
		
	Raises
		ValueError: In case object_type_name is unknown
	"""
	if object_type_name == "commit":
		import commit
		return commit.Commit
	elif object_type_name == "tag":
		import tag
		return tag.TagObject
	elif object_type_name == "blob":
		import blob
		return blob.Blob
	elif object_type_name == "tree":
		import tree
		return tree.Tree
	else:
		raise ValueError("Cannot handle unknown object type: %s" % object_type_name)
		

def get_user_id():
	""":return: string identifying the currently active system user as name@node
	:note: user can be set with the 'USER' environment variable, usually set on windows"""
	ukn = 'UNKNOWN'
	username = os.environ.get('USER', ukn)
	if username == ukn and hasattr(os, 'getlogin'):
		username = os.getlogin()
	# END get username from login
	return "%s@%s" % (username, platform.node())
		

def _utc_tz_to_altz(utctz):
	"""we convert utctz to the timezone in seconds, it is the format time.altzone
	returns. Git stores it as UTC timezon which has the opposite sign as well, 
	which explains the -1 * ( that was made explicit here )
	:param utctz: git utc timezone string, i.e. +0200"""
	return -1 * int(float(utctz)/100*3600)

def _verify_utctz(offset):
	""":raise ValueError: if offset is incorrect
	:return: offset"""
	fmt_exc = ValueError("Invalid timezone offset format: %s" % offset)
	if len(offset) != 5:
		raise fmt_exc
	if offset[0] not in "+-":
		raise fmt_exc
	if	offset[1] not in digits or \
		offset[2] not in digits or \
		offset[3] not in digits or \
		offset[4] not in digits:
		raise fmt_exc
	# END for each char
	return offset

def parse_date(string_date):
	"""
	Parse the given date as one of the following
		* Git internal format: timestamp offset
		* RFC 2822: Thu, 07 Apr 2005 22:13:13 +0200. 
		* ISO 8601 2005-04-07T22:13:13
		 The T can be a space as well
		 
	:return: Tuple(int(timestamp), int(offset), both in seconds since epoch
	:raise ValueError: If the format could not be understood
	:note: Date can also be YYYY.MM.DD, MM/DD/YYYY and DD.MM.YYYY 
	"""
	# git time
	try:
		if string_date.count(' ') == 1 and string_date.rfind(':') == -1:
			timestamp, offset = string_date.split()
			timestamp = int(timestamp)
			return timestamp, _utc_tz_to_altz(_verify_utctz(offset))
		else:
			offset = "+0000"					# local time by default
			if string_date[-5] in '-+':
				offset = _verify_utctz(string_date[-5:])
				string_date = string_date[:-6]	# skip space as well
			# END split timezone info
			
			# now figure out the date and time portion - split time
			date_formats = list()
			splitter = -1
			if ',' in string_date:
				date_formats.append("%a, %d %b %Y")
				splitter = string_date.rfind(' ')
			else:
				# iso plus additional
				date_formats.append("%Y-%m-%d")
				date_formats.append("%Y.%m.%d")
				date_formats.append("%m/%d/%Y")
				date_formats.append("%d.%m.%Y")
				
				splitter = string_date.rfind('T')
				if splitter == -1:
					splitter = string_date.rfind(' ')
				# END handle 'T' and ' '
			# END handle rfc or iso 
			
			assert splitter > -1
			
			# split date and time
			time_part = string_date[splitter+1:]	# skip space
			date_part = string_date[:splitter]
			
			# parse time
			tstruct = time.strptime(time_part, "%H:%M:%S")
			
			for fmt in date_formats:
				try:
					dtstruct = time.strptime(date_part, fmt)
					fstruct = time.struct_time((dtstruct.tm_year, dtstruct.tm_mon, dtstruct.tm_mday, 
												tstruct.tm_hour, tstruct.tm_min, tstruct.tm_sec,
												dtstruct.tm_wday, dtstruct.tm_yday, tstruct.tm_isdst))
					return int(time.mktime(fstruct)), _utc_tz_to_altz(offset)
				except ValueError:
					continue
				# END exception handling
			# END for each fmt
			
			# still here ? fail
			raise ValueError("no format matched")
		# END handle format
	except Exception:
		raise ValueError("Unsupported date format: %s" % string_date)  
	# END handle exceptions

	
# precompiled regex
_re_actor_epoch = re.compile(r'^.+? (.*) (\d+) ([+-]\d+).*$')

def parse_actor_and_date(line):
	"""
	Parse out the actor (author or committer) info from a line like::
	
	 author Tom Preston-Werner <tom@mojombo.com> 1191999972 -0700
	
	Returns
		[Actor, int_seconds_since_epoch, int_timezone_offset]
	"""
	m = _re_actor_epoch.search(line)
	actor, epoch, offset = m.groups()
	return (Actor._from_string(actor), int(epoch), _utc_tz_to_altz(offset))
	
	
	
class ProcessStreamAdapter(object):
	"""
	Class wireing all calls to the contained Process instance.
	
	Use this type to hide the underlying process to provide access only to a specified 
	stream. The process is usually wrapped into an AutoInterrupt class to kill 
	it if the instance goes out of scope.
	"""
	__slots__ = ("_proc", "_stream")
	def __init__(self, process, stream_name):
		self._proc = process
		self._stream = getattr(process, stream_name)
	
	def __getattr__(self, attr):
		return getattr(self._stream, attr)
		
		
class Traversable(object):
	"""Simple interface to perforam depth-first or breadth-first traversals 
	into one direction.
	Subclasses only need to implement one function.
	Instances of the Subclass must be hashable"""
	__slots__ = tuple()
	
	@classmethod
	def _get_intermediate_items(cls, item):
		"""
		Returns:
			List of items connected to the given item.
			Must be implemented in subclass
		"""
		raise NotImplementedError("To be implemented in subclass")
			
	
	def traverse( self, predicate = lambda i,d: True,
						   prune = lambda i,d: False, depth = -1, branch_first=True,
						   visit_once = True, ignore_self=1, as_edge = False ):
		"""
		``Returns``
			iterator yieling of items found when traversing self
			
		``predicate``
			f(i,d) returns False if item i at depth d should not be included in the result
			
		``prune``
			f(i,d) return True if the search should stop at item i at depth d.
			Item i will not be returned.
			
		``depth``
			define at which level the iteration should not go deeper
			if -1, there is no limit
			if 0, you would effectively only get self, the root of the iteration
			i.e. if 1, you would only get the first level of predessessors/successors
			
		``branch_first``
			if True, items will be returned branch first, otherwise depth first
			
		``visit_once``
			if True, items will only be returned once, although they might be encountered
			several times. Loops are prevented that way.
		
		``ignore_self``
			if True, self will be ignored and automatically pruned from
			the result. Otherwise it will be the first item to be returned.
			If as_edge is True, the source of the first edge is None
			
		``as_edge``
			if True, return a pair of items, first being the source, second the 
			destinatination, i.e. tuple(src, dest) with the edge spanning from 
			source to destination"""
		visited = set()
		stack = Deque()
		stack.append( ( 0 ,self, None ) )		# self is always depth level 0
	
		def addToStack( stack, item, branch_first, depth ):
			lst = self._get_intermediate_items( item )
			if not lst:
				return
			if branch_first:
				stack.extendleft( ( depth , i, item ) for i in lst )
			else:
				reviter = ( ( depth , lst[i], item ) for i in range( len( lst )-1,-1,-1) )
				stack.extend( reviter )
		# END addToStack local method
	
		while stack:
			d, item, src = stack.pop()			# depth of item, item, item_source
			
			if visit_once and item in visited:
				continue
				
			if visit_once:
				visited.add(item)
			
			rval = ( as_edge and (src, item) ) or item
			if prune( rval, d ):
				continue
	
			skipStartItem = ignore_self and ( item == self )
			if not skipStartItem and predicate( rval, d ):
				yield rval
	
			# only continue to next level if this is appropriate !
			nd = d + 1
			if depth > -1 and nd > depth:
				continue
	
			addToStack( stack, item, branch_first, nd )
		# END for each item on work stack