from git.util import (
						join_path,
						Actor,
						LockedFD,
						LockFile,
						assure_directory_exists,
						to_native_path,
						bin_to_hex,
						join,
						file_contents_ro_filepath
					)

from git.objects.util import (
								parse_date,
								Serializable, 
								utctz_to_altz,
								altz_to_utctz_str,
							)

import time
import os
import re

__all__ = ["RefLog", "RefLogEntry"]


class RefLogEntry(tuple):
	"""Named tuple allowing easy access to the revlog data fields"""
	_fmt = "%s %s %s <%s> %i %s\t%s\n"
	_re_hexsha_only = re.compile('^[0-9A-Fa-f]{40}$')
	__slots__ = tuple()
	
	def __repr__(self):
		"""Representation of ourselves in git reflog format"""
		act = self.actor
		time = self.time
		return self._fmt % (self.oldhexsha, self.newhexsha, act.name, act.email, 
							time[0], altz_to_utctz_str(time[1]), self.message)
	
	@property
	def oldhexsha(self):
		"""The hexsha to the commit the ref pointed to before the change""" 
		return self[0]
		
	@property
	def newhexsha(self):
		"""The hexsha to the commit the ref now points to, after the change"""
		return self[1]
		
	@property
	def actor(self):
		"""Actor instance, providing access"""
		return self[2]
		
	@property
	def time(self):
		"""time as tuple:
		
		* [0] = int(time)
		* [1] = int(timezone_offset) in time.altzone format """
		return self[3]
		
	@property
	def message(self):
		"""Message describing the operation that acted on the reference"""
		return self[4]
	
	@classmethod
	def new(self, oldhexsha, newhexsha, actor, time, tz_offset, message):
		""":return: New instance of a RefLogEntry"""
		if not isinstance(actor, Actor):
			raise ValueError("Need actor instance, got %s" % actor)
		# END check types 
		return RefLogEntry((oldhexsha, newhexsha, actor, (time, tz_offset), message))
		
	@classmethod
	def from_line(cls, line):
		""":return: New RefLogEntry instance from the given revlog line.
		:param line: line without trailing newline
		:raise ValueError: If line could not be parsed"""
		try:
			info, msg = line.split('\t', 2)
		except ValueError:
			raise ValueError("line is missing tab separator")
		#END handle first plit
		oldhexsha = info[:40]
		newhexsha = info[41:81]
		for hexsha in (oldhexsha, newhexsha):
			if not cls._re_hexsha_only.match(hexsha):
				raise ValueError("Invalid hexsha: %s" % hexsha)
			# END if hexsha re doesn't match
		#END for each hexsha
		
		email_end = info.find('>', 82)
		if email_end == -1:
			raise ValueError("Missing token: >")
		#END handle missing end brace
		
		actor = Actor._from_string(info[82:email_end+1])
		time, tz_offset = parse_date(info[email_end+2:])
		
		return RefLogEntry((oldhexsha, newhexsha, actor, (time, tz_offset), msg))
		

class RefLog(list, Serializable):
	"""A reflog contains reflog entries, each of which defines a certain state
	of the head in question. Custom query methods allow to retrieve log entries 
	by date or by other criteria.
	
	Reflog entries are orded, the first added entry is first in the list, the last
	entry, i.e. the last change of the head or reference, is last in the list."""
	
	__slots__ = ('_path', )
	
	def __new__(cls, filepath=None):
		inst = super(RefLog, cls).__new__(cls)
		return inst
		
	def __init__(self, filepath=None):
		"""Initialize this instance with an optional filepath, from which we will
		initialize our data. The path is also used to write changes back using 
		the write() method"""
		self._path = filepath
		if filepath is not None:
			self._read_from_file()
		# END handle filepath
	
	def _read_from_file(self):
		fmap = file_contents_ro_filepath(self._path, stream=False, allow_mmap=True)
		try:
			self._deserialize(fmap)
		finally:
			fmap.close()
		#END handle closing of handle
	
	#{ Interface
	
	@classmethod
	def from_file(cls, filepath):
		"""
		:return: a new RefLog instance containing all entries from the reflog 
			at the given filepath
		:param filepath: path to reflog 
		:raise ValueError: If the file could not be read or was corrupted in some way"""
		return cls(filepath)
	
	@classmethod
	def path(cls, ref):
		"""
		:return: string to absolute path at which the reflog of the given ref 
			instance would be found. The path is not guaranteed to point to a valid 
			file though.
		:param ref: SymbolicReference instance"""
		return join(ref.repo.git_dir, "logs", to_native_path(ref.path))
		
	@classmethod
	def iter_entries(cls, stream):
		"""
		:return: Iterator yielding RefLogEntry instances, one for each line read 
			sfrom the given stream.
		:param stream: file-like object containing the revlog in its native format
			or basestring instance pointing to a file to read"""
		new_entry = RefLogEntry.from_line
		if isinstance(stream, basestring):
			stream = file_contents_ro_filepath(stream)
		#END handle stream type
		while True:
			line = stream.readline()
			if not line:
				return
			yield new_entry(line.strip())
		#END endless loop
		
	@classmethod
	def entry_at(cls, filepath, index):
		""":return: RefLogEntry at the given index
		:param filepath: full path to the index file from which to read the entry
		:param index: python list compatible index, i.e. it may be negative to 
			specifiy an entry counted from the end of the list
			
		:raise IndexError: If the entry didn't exist
		
		.. note:: This method is faster as it only parses the entry at index, skipping
			all other lines. Nonetheless, the whole file has to be read if 
			the index is negative
		"""
		fp = open(filepath, 'rb')
		if index < 0:
			return RefLogEntry.from_line(fp.readlines()[index].strip())
		else:
			# read until index is reached
			for i in xrange(index+1):
				line = fp.readline()
				if not line:
					break
				#END abort on eof
			#END handle runup
			
			if i != index or not line:
				raise IndexError
			#END handle exception
			
			return RefLogEntry.from_line(line.strip())
		#END handle index
	
	def to_file(self, filepath):
		"""Write the contents of the reflog instance to a file at the given filepath.
		:param filepath: path to file, parent directories are assumed to exist"""
		lfd = LockedFD(filepath)
		assure_directory_exists(filepath, is_file=True)
		
		fp = lfd.open(write=True, stream=True)
		try:
			self._serialize(fp)
			lfd.commit()
		except:
			# on failure it rolls back automatically, but we make it clear
			lfd.rollback()
			raise
		#END handle change
		
	@classmethod
	def append_entry(cls, config_reader, filepath, oldbinsha, newbinsha, message):
		"""Append a new log entry to the revlog at filepath.
		
		:param config_reader: configuration reader of the repository - used to obtain
			user information. May be None
		:param filepath: full path to the log file
		:param oldbinsha: binary sha of the previous commit
		:param newbinsha: binary sha of the current commit
		:param message: message describing the change to the reference
		:param write: If True, the changes will be written right away. Otherwise
			the change will not be written
		:return: RefLogEntry objects which was appended to the log
		:note: As we are append-only, concurrent access is not a problem as we 
			do not interfere with readers."""
		if len(oldbinsha) != 20 or len(newbinsha) != 20:
			raise ValueError("Shas need to be given in binary format")
		#END handle sha type
		assure_directory_exists(filepath, is_file=True)
		entry = RefLogEntry((bin_to_hex(oldbinsha), bin_to_hex(newbinsha), Actor.committer(config_reader), (int(time.time()), time.altzone), message))
		
		lf = LockFile(filepath)
		lf._obtain_lock_or_raise()
		
		fd = open(filepath, 'a')
		try:
			fd.write(repr(entry))
		finally:
			fd.close()
			lf._release_lock()
		#END handle write operation
		
		return entry
		
	def write(self):
		"""Write this instance's data to the file we are originating from
		:return: self"""
		if self._path is None:
			raise ValueError("Instance was not initialized with a path, use to_file(...) instead")
		#END assert path
		self.to_file(self._path)
		return self
	
	#} END interface
	
	#{ Serializable Interface
	def _serialize(self, stream):
		lm1 = len(self) - 1
		write = stream.write
		
		# write all entries
		for e in self:
			write(repr(e))
		#END for each entry
	
	def _deserialize(self, stream):
		self.extend(self.iter_entries(stream))
	#} END serializable interface
