# tree.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
import blob
import base
import binascii
import git.diff as diff
import utils
from git.utils import join_path

def sha_to_hex(sha):
    """Takes a string and returns the hex of the sha within"""
    hexsha = binascii.hexlify(sha)
    assert len(hexsha) == 40, "Incorrect length of sha1 string: %d" % hexsha
    return hexsha


class Tree(base.IndexObject, diff.Diffable, utils.Traversable):
	"""
	Tress represent a ordered list of Blobs and other Trees. Hence it can be 
	accessed like a list.
	
	Tree's will cache their contents after first retrieval to improve efficiency.
	
	``Tree as a list``::
		
		Access a specific blob using the  
		tree['filename'] notation.
		
		You may as well access by index
		blob = tree[0]
		
		
	"""
	
	type = "tree"
	__slots__ = "_cache"
	
	# using ascii codes for comparison 
	commit_id = 016		
	blob_id = 010
	symlink_id = 012
	tree_id = 040
	
	
	def __init__(self, repo, sha, mode=0, path=None):
		super(Tree, self).__init__(repo, sha, mode, path)

	@classmethod
	def _get_intermediate_items(cls, index_object):
		if index_object.type == "tree":
			return index_object._cache
		return tuple()


	def _set_cache_(self, attr):
		if attr == "_cache":
			# Set the data when we need it
			self._cache = self._get_tree_cache()
		else:
			super(Tree, self)._set_cache_(attr)

	def _get_tree_cache(self):
		"""
		Return
			list(object_instance, ...)
		
		``treeish``
			sha or ref identifying a tree  
		"""
		out = list()
		for obj in self._iter_from_data():
			if obj is not None:
				out.append(obj)
			# END if object was handled
		# END for each line from ls-tree
		return out
		
		
	def _iter_from_data(self):
		"""
		Reads the binary non-pretty printed representation of a tree and converts
		it into Blob, Tree or Commit objects.
		
		Note: This method was inspired by the parse_tree method in dulwich.
		
		Returns
			list(IndexObject, ...)
		"""
		ord_zero = ord('0')
		data = self.data
		len_data = len(data)
		i = 0
		while i < len_data:
			mode = 0
			mode_boundary = i + 6
			
			# read type
			type_id = ((ord(data[i])-ord_zero)<<3) + (ord(data[i+1])-ord_zero)
			i += 2
			
			while data[i] != ' ':
				# move existing mode integer up one level being 3 bits
				# and add the actual ordinal value of the character
				mode = (mode << 3) + (ord(data[i]) - ord_zero)
				i += 1
			# END while reading mode
			
			# byte is space now, skip it
			i += 1
			
			# parse name, it is NULL separated
			
			ns = i
			while data[i] != '\0':
				i += 1
			# END while not reached NULL
			name = data[ns:i]
			path = join_path(self.path, name)
			
			# byte is NULL, get next 20
			i += 1
			sha = data[i:i+20]
			i = i + 20
			
			mode |= type_id<<12
			hexsha = sha_to_hex(sha)
			if type_id == self.blob_id or type_id == self.symlink_id:
				yield blob.Blob(self.repo, hexsha, mode, path)
			elif type_id == self.tree_id:
				yield Tree(self.repo, hexsha, mode, path)
			elif type_id == self.commit_id:
				# todo 
				yield None
			else:
				raise TypeError( "Unknown type found in tree data: %i" % type_id )
		# END for each byte in data stream


	def __div__(self, file):
		"""
		Find the named object in this tree's contents

		Examples::

			>>> Repo('/path/to/python-git').tree/'lib'
			<git.Tree "6cc23ee138be09ff8c28b07162720018b244e95e">
			>>> Repo('/path/to/python-git').tree/'README.txt'
			<git.Blob "8b1e02c0fb554eed2ce2ef737a68bb369d7527df">

		Returns
			``git.Blob`` or ``git.Tree``
		
		Raise 
			KeyError if given file or tree does not exist in tree
		"""
		msg = "Blob or Tree named %r not found"
		if '/' in file:
			tree = self
			item = self
			tokens = file.split('/')
			for i,token in enumerate(tokens):
				item = tree[token]
				if item.type == 'tree':
					tree = item
				else:
					# safety assertion - blobs are at the end of the path
					if i != len(tokens)-1:
						raise KeyError(msg % file)  
					return item
				# END handle item type
			# END for each token of split path
			if item == self:
				raise KeyError(msg % file)
			return item
		else:
			for obj in self._cache:
				if obj.name == file:
					return obj
			# END for each obj
			raise KeyError( msg % file )
		# END handle long paths


	def __repr__(self):
		return '<git.Tree "%s">' % self.sha
			
	@property
	def trees(self):
		"""
		Returns
			list(Tree, ...) list of trees directly below this tree
		"""
		return [ i for i in self if i.type == "tree" ]
		
	@property
	def blobs(self):
		"""
		Returns
			list(Blob, ...) list of blobs directly below this tree
		"""
		return [ i for i in self if i.type == "blob" ]


	def traverse( self, predicate = lambda i,d: True,
						   prune = lambda i,d: False, depth = -1, branch_first=True,
						   visit_once = False, ignore_self=1 ):
		"""For documentation, see utils.Traversable.traverse
		
		Trees are set to visist_once = False to gain more performance in the traversal"""
		return super(Tree, self).traverse(predicate, prune, depth, branch_first, visit_once, ignore_self)

	# List protocol
	def __getslice__(self,i,j):
		return self._cache[i:j]
		
	def __iter__(self):
		return iter(self._cache)
		
	def __len__(self):
		return len(self._cache)
		
	def __getitem__(self,item):
		if isinstance(item, int):
			return self._cache[item]
		
		if isinstance(item, basestring):
			# compatability
			return self.__div__(item)
		# END index is basestring 
		
		raise TypeError( "Invalid index type: %r" % item )
		
		
	def __contains__(self,item):
		if isinstance(item, base.IndexObject):
			return item in self._cache
		
		# compatability
		for obj in self._cache:
			if item == obj.path:
				return True
		# END for each item
		return False
	
	def __reversed__(self):
		return reversed(self._cache)