# index.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 containing Index implementation, allowing to perform all kinds of index
manipulations such as querying and merging.
"""
import struct
import binascii
import mmap
import objects
import tempfile
import os
import sys
import stat
import git.diff as diff

from git.objects import Blob, Tree, Object
from git.utils import SHA1Writer, LazyMixin, ConcurrentWriteOperation


class _TemporaryFileSwap(object):
	"""
	Utility class moving a file to a temporary location within the same directory
	and moving it back on to where on object deletion.
	"""
	__slots__ = ("file_path", "tmp_file_path")
	
	def __init__(self, file_path):
		self.file_path = file_path
		self.tmp_file_path = self.file_path + tempfile.mktemp('','','')
		os.rename(self.file_path, self.tmp_file_path)
		
	def __del__(self):
		if os.path.isfile(self.tmp_file_path):
			if sys.platform == "win32" and os.path.exists(self.file_path):
				os.remove(self.file_path)
			os.rename(self.tmp_file_path, self.file_path)
		# END temp file exists
	

class IndexEntry(tuple):
	"""
	Allows convenient access to IndexEntry data without completely unpacking it.
	
	Attributes usully accessed often are cached in the tuple whereas others are 
	unpacked on demand.
	
	See the properties for a mapping between names and tuple indices.
	"""
	@property
	def ctime(self):
		"""
		Returns
			Tuple(int_time_seconds_since_epoch, int_nano_seconds) of the 
			file's creation time
		"""
		return struct.unpack(">LL", self[0])
		
	@property
	def mtime(self):
		"""
		See ctime property, but returns modification time
		"""
		return struct.unpack(">LL", self[1])
	
	@property
	def dev(self):
		"""
		Device ID
		"""
		return self[2] 
	
	@property
	def inode(self):
		"""
		Inode ID
		"""
		return self[3]
		
	@property
	def mode(self):
		"""
		File Mode, compatible to stat module constants
		"""
		return self[4]
		
	@property
	def uid(self):
		"""
		User ID
		"""
		return self[5]
		
	@property
	def gid(self):
		"""
		Group ID
		"""
		return self[6]

	@property
	def size(self):
		"""
		Uncompressed size of the blob
		
		Note
			Will be 0 if the stage is not 0 ( hence it is an unmerged entry )
		"""
		return self[7]
		
	@property
	def sha(self):
		"""
		hex sha of the blob
		"""
		return self[8]
		
	@property
	def stage(self):
		"""
		Stage of the entry, either:
			0 = default stage
			1 = stage before a merge or common ancestor entry in case of a 3 way merge
			2 = stage of entries from the 'left' side of the merge
			3 = stage of entries from the right side of the merge
		Note:
			For more information, see http://www.kernel.org/pub/software/scm/git/docs/git-read-tree.html
		"""
		return self[9]

	@property
	def path(self):
		return self[10]
		
		
	@classmethod
	def from_blob(cls, blob):
		"""
		Returns
			Minimal entry resembling the given blob objecft
		"""
		time = struct.pack(">LL", 0, 0)
		return IndexEntry((time, time, 0, 0, blob.mode, 0, 0, blob.size, blob.id, 0, blob.path))


class IndexFile(LazyMixin, diff.Diffable):
	"""
	Implements an Index that can be manipulated using a native implementation in 
	order to save git command function calls wherever possible.
	
	It provides custom merging facilities allowing to merge without actually changing
	your index or your working tree. This way you can perform own test-merges based
	on the index only without having to deal with the working copy. This is useful 
	in case of partial working trees.
	
	``Entries``
	The index contains an entries dict whose keys are tuples of type IndexEntry
	to facilitate access.
	
	As opposed to the Index type, the IndexFile represents the index on file level.
	This can be considered an alternate, file-based implementation of the Index class
	with less support for common functions. Use it for very special and custom index 
	handling.
	"""
	__slots__ = ( "repo", "version", "entries", "_extension_data", "_file_path" )
	_VERSION = 2			# latest version we support
	S_IFGITLINK	= 0160000
	
	def __init__(self, repo, file_path=None):
		"""
		Initialize this Index instance, optionally from the given ``file_path``.
		If no file_path is given, we will be created from the current index file.
		
		If a stream is not given, the stream will be initialized from the current 
		repository's index on demand.
		"""
		self.repo = repo
		self.version = self._VERSION
		self._extension_data = ''
		self._file_path = file_path or self._index_path()
	
	def _set_cache_(self, attr):
		if attr == "entries":
			# read the current index
			# try memory map for speed
			fp = open(self._file_path, "r")
			stream = fp
			try:
				stream = mmap.mmap(fp.fileno(), 0, access=mmap.ACCESS_READ)
			except Exception:
				pass
			# END memory mapping
			
			try:
				self._read_from_stream(stream)
			finally:
				fp.close()
			# END read from default index on demand
		else:
			super(IndexFile, self)._set_cache_(attr)
	
	def _index_path(self):
		return os.path.join(self.repo.path, "index")
	
	
	@property
	def path(self):
		"""
		Returns 
			Path to the index file we are representing
		"""
		return self._file_path
	
	@classmethod
	def _read_entry(cls, stream):
		"""Return: One entry of the given stream"""
		beginoffset = stream.tell()
		ctime = struct.unpack(">8s", stream.read(8))[0]
		mtime = struct.unpack(">8s", stream.read(8))[0]
		(dev, ino, mode, uid, gid, size, sha, flags) = \
			struct.unpack(">LLLLLL20sH", stream.read(20 + 4 * 6 + 2))
		path_size = flags & 0x0fff
		path = stream.read(path_size)
		
		real_size = ((stream.tell() - beginoffset + 8) & ~7)
		data = stream.read((beginoffset + real_size) - stream.tell())
		return IndexEntry((ctime, mtime, dev, ino, mode, uid, gid, size, 
				binascii.hexlify(sha), flags >> 12, path))
		
	@classmethod
	def _read_header(cls, stream):
		"""Return tuple(version_long, num_entries) from the given stream"""
		type_id = stream.read(4)
		if type_id != "DIRC":
			raise AssertionError("Invalid index file header: %r" % type_id)
		version, num_entries = struct.unpack(">LL", stream.read(4 * 2))
		assert version in (1, 2)
		return version, num_entries
		
	def _read_from_stream(self, stream):
		"""
		Initialize this instance with index values read from the given stream
		"""
		self.version, num_entries = self._read_header(stream)
		count = 0
		self.entries = dict()
		while count < num_entries:
			entry = self._read_entry(stream)
			self.entries[(entry.path, entry.stage)] = entry
			count += 1
		# END for each entry
		
		# the footer contains extension data and a sha on the content so far
		# Keep the extension footer,and verify we have a sha in the end
		self._extension_data = stream.read(~0)
		assert len(self._extension_data) > 19, "Index Footer was not at least a sha on content as it was only %i bytes in size" % len(self._extension_data)
		
		content_sha = self._extension_data[-20:]
		
		# truncate the sha in the end as we will dynamically create it anyway 
		self._extension_data = self._extension_data[:-20]
	
	
	@classmethod
	def _write_cache_entry(cls, stream, entry):
		"""
		Write an IndexEntry to a stream
		"""
		beginoffset = stream.tell()
		stream.write(entry[0])			# ctime
		stream.write(entry[1])			# mtime
		path = entry[10]
		plen = len(path) & 0x0fff		# path length
		assert plen == len(path), "Path %s too long to fit into index" % entry[10]
		flags = plen | (entry[9] << 12)# stage and path length are 2 byte flags
		stream.write(struct.pack(">LLLLLL20sH", entry[2], entry[3], entry[4], 
									entry[5], entry[6], entry[7], binascii.unhexlify(entry[8]), flags))
		stream.write(path)
		real_size = ((stream.tell() - beginoffset + 8) & ~7)
		stream.write("\0" * ((beginoffset + real_size) - stream.tell()))

	def write(self, file_path = None):
		"""
		Write the current state to our file path or to the given one
		
		``file_path``
			If None, we will write to our stored file path from which we have 
			been initialized. Otherwise we write to the given file path.
			Please note that this will change the file_path of this index to 
			the one you gave.
		
		Returns
			self
		
		Note
			Index writing based on the dulwich implementation
		"""
		write_op = ConcurrentWriteOperation(file_path or self._file_path)
		stream = write_op._begin_writing()
		
		stream = SHA1Writer(stream)
		
		# header
		stream.write("DIRC")
		stream.write(struct.pack(">LL", self.version, len(self.entries)))
		
		# body
		entries_sorted = self.entries.values()
		entries_sorted.sort(key=lambda e: (e[10], e[9]))		# use path/stage as sort key
		for entry in entries_sorted:
			self._write_cache_entry(stream, entry)
		# END for each entry
		
		# write previously cached extensions data
		stream.write(self._extension_data)
		
		# write the sha over the content
		stream.write_sha()
		write_op._end_writing()
		
		# make sure we represent what we have written
		if file_path is not None:
			self._file_path = file_path
	
	@classmethod
	def from_tree(cls, repo, *treeish, **kwargs):
		"""
		Merge the given treeish revisions into a new index which is returned.
		The original index will remain unaltered
		
		``repo``
			The repository treeish are located in.
			
		``*treeish``
			One, two or three Tree Objects or Commits. The result changes according to the 
			amount of trees.
			If 1 Tree is given, it will just be read into a new index
			If 2 Trees are given, they will be merged into a new index using a 
			 two way merge algorithm. Tree 1 is the 'current' tree, tree 2 is the 'other'
			 one. It behaves like a fast-forward.
			If 3 Trees are given, a 3-way merge will be performed with the first tree
			 being the common ancestor of tree 2 and tree 3. Tree 2 is the 'current' tree, 
			 tree 3 is the 'other' one
			 
		``**kwargs``
			Additional arguments passed to git-read-tree
			
		Returns
			New IndexFile instance. It will point to a temporary index location which 
			does not exist anymore. If you intend to write such a merged Index, supply
			an alternate file_path to its 'write' method.
			
		Note:
			In the three-way merge case, --aggressive will be specified to automatically
			resolve more cases in a commonly correct manner. Specify trivial=True as kwarg
			to override that.
			
			As the underlying git-read-tree command takes into account the current index, 
			it will be temporarily moved out of the way to assure there are no unsuspected
			interferences.
		"""
		if len(treeish) == 0 or len(treeish) > 3:
			raise ValueError("Please specify between 1 and 3 treeish, got %i" % len(treeish))
		
		arg_list = list()
		# ignore that working tree and index possibly are out of date
		if len(treeish)>1:
			# drop unmerged entries when reading our index and merging
			arg_list.append("--reset")	
			# handle non-trivial cases the way a real merge does
			arg_list.append("--aggressive")	
		# END merge handling
		
		# tmp file created in git home directory to be sure renaming 
		# works - /tmp/ dirs could be on another device
		tmp_index = tempfile.mktemp('','',repo.path)
		arg_list.append("--index-output=%s" % tmp_index)
		arg_list.extend(treeish)
		
		# move current index out of the way - otherwise the merge may fail
		# as it considers existing entries. moving it essentially clears the index.
		# Unfortunately there is no 'soft' way to do it.
		# The _TemporaryFileSwap assure the original file get put back
		index_handler = _TemporaryFileSwap(os.path.join(repo.path, 'index'))
		try:
			repo.git.read_tree(*arg_list, **kwargs)
			index = cls(repo, tmp_index)
			index.entries		# force it to read the file
		finally:
			if os.path.exists(tmp_index):
				os.remove(tmp_index)
		# END index merge handling
		
		return index
	
	@classmethod
	def _index_mode_to_tree_index_mode(cls, index_mode):
		"""
		Cleanup a index_mode value.
		This will return a index_mode that can be stored in a tree object.
		
		``index_mode``
			Index_mode to clean up.
		"""
		if stat.S_ISLNK(index_mode):
			return stat.S_IFLNK
		elif stat.S_ISDIR(index_mode):
			return stat.S_IFDIR
		elif stat.S_IFMT(index_mode) == cls.S_IFGITLINK:
			return cls.S_IFGITLINK
		ret = stat.S_IFREG | 0644
		ret |= (index_mode & 0111)
		return ret
	
	def iter_blobs(self, predicate = lambda t: True):
		"""
		Returns
			Iterator yielding tuples of Blob objects and stages, tuple(stage, Blob)
			
		``predicate``
			Function(t) returning True if tuple(stage, Blob) should be yielded by the 
			iterator
		"""
		for entry in self.entries.itervalues():
			mode = self._index_mode_to_tree_index_mode(entry.mode)
			blob = Blob(self.repo, entry.sha, mode, entry.path)
			blob.size = entry.size
			output = (entry.stage, blob)
			if predicate(output):
				yield output
		# END for each entry 
	
	def unmerged_blobs(self):
		"""
		Returns
			Iterator yielding dict(path : list( tuple( stage, Blob, ...))), being 
			a dictionary associating a path in the index with a list containing 
			stage/blob pairs
			
		Note:
			Blobs that have been removed in one side simply do not exist in the 
			given stage. I.e. a file removed on the 'other' branch whose entries
			are at stage 3 will not have a stage 3 entry.
		"""
		is_unmerged_blob = lambda t: t[0] != 0
		path_map = dict()
		for stage, blob in self.iter_blobs(is_unmerged_blob):
			path_map.setdefault(blob.path, list()).append((stage, blob))
		# END for each unmerged blob
		
		return path_map
	
	def resolve_blobs(self, iter_blobs):
		"""
		Resolve the blobs given in blob iterator. This will effectively remove the 
		index entries of the respective path at all non-null stages and add the given 
		blob as new stage null blob.
		
		For each path there may only be one blob, otherwise a ValueError will be raised
		claiming the path is already at stage 0.
		
		Raise
			ValueError if one of the blobs already existed at stage 0
		
		Returns:
			self
		"""
		for blob in iter_blobs:
			stage_null_key = (blob.path, 0)
			if stage_null_key in self.entries:
				raise ValueError( "Blob %r already at stage 0" % blob )
			# END assert blob is not stage 0 already 
			
			# delete all possible stages
			for stage in (1, 2, 3):
				try:
					del( self.entries[(blob.path, stage)] )
				except KeyError:
					pass 
				# END ignore key errors
			# END for each possible stage
			
			self.entries[stage_null_key] = IndexEntry.from_blob(blob) 
		# END for each blob
		
		return self
	
	def write_tree(self):
		"""
		Writes the Index in self to a corresponding Tree file into the repository
		object database and returns it as corresponding Tree object.
		
		Returns
			Tree object representing this index
		"""
		index_path = self._index_path()
		tmp_index_mover = _TemporaryFileSwap(index_path)
		
		self.write(index_path)
		tree_sha = self.repo.git.write_tree()
		
		return Tree(self.repo, tree_sha, 0, '')
		
	def _process_diff_args(self, args):
		try:
			args.pop(args.index(self))
		except IndexError:
			pass
		# END remove self
		return args
		
	def diff(self, other=diff.Diffable.Index, paths=None, create_patch=False, **kwargs):
		"""
		Diff this index against the working copy or a Tree or Commit object
		
		For a documentation of the parameters and return values, see 
		Diffable.diff
		
		Note
			Will only work with indices that represent the default git index as 
			they have not been initialized with a stream.
		"""
		# perhaps we shouldn't diff these at all, or we swap them in place first
		if self._file_path != self._index_path():
			raise AssertionError( "Cannot diff custom indices as they do not represent the default git index" )
		
		# index against index is always empty
		if other is self.Index:
			return diff.DiffIndex()
			
		# index against anything but None is a reverse diff with the respective
		# item. Handle existing -R flags properly. Transform strings to the object
		# so that we can call diff on it
		if isinstance(other, basestring):
			other = Object.new(self.repo, other)
		# END object conversion
		
		if isinstance(other, Object):
			# invert the existing R flag
			cur_val = kwargs.get('R', False)
			kwargs['R'] = not cur_val
			return other.diff(self.Index, paths, create_patch, **kwargs)
		# END diff against other item handlin
		
		# if other is not None here, something is wrong 
		if other is not None:
			raise ValueError( "other must be None, Diffable.Index, a Tree or Commit, was %r" % other )
		
		# diff against working copy - can be handled by superclass natively
		return super(IndexFile, self).diff(other, paths, create_patch, **kwargs)