# Copyright (C) 2010, 2011 Sebastian Thiel (byronimo@gmail.com) and contributors
#
# This module is part of GitDB and is released under
# the New BSD License: http://www.opensource.org/licenses/bsd-license.php
"""Module with basic data structures - they are designed to be lightweight and fast"""
from util import (
		bin_to_hex,
		zlib
	)

from fun import (
					type_id_to_type_map,
					type_to_type_id_map
				)

__all__ = ('OInfo', 'OPackInfo', 'ODeltaPackInfo', 
			'OStream', 'OPackStream', 'ODeltaPackStream',
			'IStream', 'InvalidOInfo', 'InvalidOStream' )

#{ ODB Bases

class OInfo(tuple):
	"""Carries information about an object in an ODB, provding information 
	about the binary sha of the object, the type_string as well as the uncompressed size
	in bytes.
	
	It can be accessed using tuple notation and using attribute access notation::
	
		assert dbi[0] == dbi.binsha
		assert dbi[1] == dbi.type
		assert dbi[2] == dbi.size
	
	The type is designed to be as lighteight as possible."""
	__slots__ = tuple()
	
	def __new__(cls, sha, type, size):
		return tuple.__new__(cls, (sha, type, size))
	
	def __init__(self, *args):
		tuple.__init__(self)
	
	#{ Interface 
	@property
	def binsha(self):
		""":return: our sha as binary, 20 bytes"""
		return self[0]
	
	@property
	def hexsha(self):
		""":return: our sha, hex encoded, 40 bytes"""
		return bin_to_hex(self[0])
		
	@property
	def type(self):
		return self[1]
	
	@property
	def type_id(self):
		return type_to_type_id_map[self[1]]
		
	@property
	def size(self):
		return self[2]
	#} END interface
	
	
class OPackInfo(tuple):
	"""As OInfo, but provides a type_id property to retrieve the numerical type id, and 
	does not include a sha.
	
	Additionally, the pack_offset is the absolute offset into the packfile at which 
	all object information is located. The data_offset property points to the abosolute
	location in the pack at which that actual data stream can be found."""
	__slots__ = tuple()
	
	def __new__(cls, packoffset, type, size):
		return tuple.__new__(cls, (packoffset,type, size))
	
	def __init__(self, *args):
		tuple.__init__(self)
		
	#{ Interface 
	
	@property
	def pack_offset(self):
		return self[0]
	
	@property
	def type(self):
		return type_id_to_type_map[self[1]]
	
	@property
	def type_id(self):
		return self[1]
		
	@property
	def size(self):
		return self[2]
		
	#} END interface
		
		
class ODeltaPackInfo(OPackInfo):
	"""Adds delta specific information, 
	Either the 20 byte sha which points to some object in the database, 
	or the negative offset from the pack_offset, so that pack_offset - delta_info yields
	the pack offset of the base object"""
	__slots__ = tuple()
	
	def __new__(cls, packoffset, type, size, delta_info):
		return tuple.__new__(cls, (packoffset, type, size, delta_info))
		
	#{ Interface 
	@property
	def delta_info(self):
		return self[3]
	#} END interface 
	
	
class OStream(OInfo):
	"""Base for object streams retrieved from the database, providing additional 
	information about the stream.
	Generally, ODB streams are read-only as objects are immutable"""
	__slots__ = tuple()
	
	def __new__(cls, sha, type, size, stream, *args, **kwargs):
		"""Helps with the initialization of subclasses"""
		return tuple.__new__(cls, (sha, type, size, stream))
	
	
	def __init__(self, *args, **kwargs):
		tuple.__init__(self)
	
	#{ Stream Reader Interface 
	
	def read(self, size=-1):
		return self[3].read(size)
		
	@property
	def stream(self):
		return self[3]
		
	#} END stream reader interface
	
	
class ODeltaStream(OStream):
	"""Uses size info of its stream, delaying reads"""
	
	def __new__(cls, sha, type, size, stream, *args, **kwargs):
		"""Helps with the initialization of subclasses"""
		return tuple.__new__(cls, (sha, type, size, stream))
	
	#{ Stream Reader Interface
	
	@property
	def size(self):
		return self[3].size
		
	#} END stream reader interface
	
	
class OPackStream(OPackInfo):
	"""Next to pack object information, a stream outputting an undeltified base object
	is provided"""
	__slots__ = tuple()
	
	def __new__(cls, packoffset, type, size, stream, *args):
		"""Helps with the initialization of subclasses"""
		return tuple.__new__(cls, (packoffset, type, size, stream))
		
	#{ Stream Reader Interface 
	def read(self, size=-1):
		return self[3].read(size)
		
	@property
	def stream(self):
		return self[3]
	#} END stream reader interface

	
class ODeltaPackStream(ODeltaPackInfo):
	"""Provides a stream outputting the uncompressed offset delta information"""
	__slots__ = tuple()
	
	def __new__(cls, packoffset, type, size, delta_info, stream):
		return tuple.__new__(cls, (packoffset, type, size, delta_info, stream))


	#{ Stream Reader Interface 
	def read(self, size=-1):
		return self[4].read(size)
		
	@property
	def stream(self):
		return self[4]
	#} END stream reader interface


class IStream(list):
	"""Represents an input content stream to be fed into the ODB. It is mutable to allow 
	the ODB to record information about the operations outcome right in this instance.
	
	It provides interfaces for the OStream and a StreamReader to allow the instance
	to blend in without prior conversion.
	
	The only method your content stream must support is 'read'"""
	__slots__ = tuple()
	
	def __new__(cls, type, size, stream, sha=None):
		return list.__new__(cls, (sha, type, size, stream, None))
		
	def __init__(self, type, size, stream, sha=None):
		list.__init__(self, (sha, type, size, stream, None))
	
	#{ Interface 
	@property
	def hexsha(self):
		""":return: our sha, hex encoded, 40 bytes"""
		return bin_to_hex(self[0])
		
	def _error(self):
		""":return: the error that occurred when processing the stream, or None"""
		return self[4]
		
	def _set_error(self, exc):
		"""Set this input stream to the given exc, may be None to reset the error"""
		self[4] = exc
			
	error = property(_error, _set_error)
	
	#} END interface
	
	#{ Stream Reader Interface
	
	def read(self, size=-1):
		"""Implements a simple stream reader interface, passing the read call on 
			to our internal stream"""
		return self[3].read(size)
		
	#} END stream reader interface 
	
	#{  interface
	
	def _set_binsha(self, binsha):
		self[0] = binsha
		
	def _binsha(self):
		return self[0]
		
	binsha = property(_binsha, _set_binsha)
	
	
	def _type(self):
		return self[1]
	
	def _set_type(self, type):
		self[1] = type
		
	type = property(_type, _set_type)
	
	def _size(self):
		return self[2]
		
	def _set_size(self, size):
		self[2] = size
	
	size = property(_size, _set_size)
	
	def _stream(self):
		return self[3]
		
	def _set_stream(self, stream):
		self[3] = stream
	
	stream = property(_stream, _set_stream)
	
	#} END odb info interface 
		

class InvalidOInfo(tuple):
	"""Carries information about a sha identifying an object which is invalid in 
	the queried database. The exception attribute provides more information about
	the cause of the issue"""
	__slots__ = tuple()
	
	def __new__(cls, sha, exc):
		return tuple.__new__(cls, (sha, exc))
		
	def __init__(self, sha, exc):
		tuple.__init__(self, (sha, exc))
	
	@property
	def binsha(self):
		return self[0]
		
	@property
	def hexsha(self):
		return bin_to_hex(self[0])
		
	@property
	def error(self):
		""":return: exception instance explaining the failure"""
		return self[1]


class InvalidOStream(InvalidOInfo):
	"""Carries information about an invalid ODB stream"""
	__slots__ = tuple()
	
#} END ODB Bases

