Namespace std.collections

#rem monkeydoc @hidden Convenience type alias for Deque\<Int\>.
#end
Alias IntDeque:Deque<Int>

#rem monkeydoc @hidden Convenience type alias for Deque\<Float\>.
#end
Alias FloatDeque:Deque<Float>

#rem monkeydoc @hidden Convenience type alias for Deque\<String\>.
#end
Alias StringDeque:Deque<String>

#rem monkeydoc @hidden
#end
Class Deque<T> Implements IContainer<T>

	Struct Iterator Implements IIterator<T>
	
		Private
		
		Field _deque:Deque
		Field _index:Int
		Field _seq:Int
		
		Method AssertSeq()
			DebugAssert( _seq=_deque._seq,"Concurrent list modification" )
		End
		
		Method AssertCurrent()
			DebugAssert( Not AtEnd,"Invalid list iterator" )
		End
		
		Method New( deque:Deque,index:Int )
			_deque=deque
			_index=index
			_seq=deque._seq
		End
		
		Public
		
		#rem monkeydoc Checks if the iterator has reached the end of the deque.
		#end
		Property AtEnd:Bool()
			AssertSeq()
			Return _index=_deque._tail
		End
		
		#rem monkeydoc The value currently pointed to by the iterator.
		#end
		Property Current:T()
			AssertCurrent()
			Return _deque._data[_index]
		Setter( current:T )
			AssertCurrent()
			_deque._data[_index]=current
		End
		
		#rem monkeydoc Bumps the iterator so it points to the next value in the deqeue.
		#end
		Method Bump()
			AssertCurrent()
			_index+=1
			If _index=_deque.Capacity _index=0
		End
		
		Method Erase()
			RuntimeError( "Erase not supported for Deques" )
		End
		
		#rem monkeydoc Safely inserts a value before the value pointed to by the iterator.

		After calling this method, the iterator will point to the newly added value.
		
		#end
		Method Insert( value:T )
			RuntimeError( "Insert not supported for Deques" )
		End
	End
	
	Private

	Field _data:T[]
	Field _head:Int
	Field _tail:Int
	Field _seq:Int	
	
	Method Normalize( capacity:Int )
	
		Local length:=Length
		
		Local data:=New T[capacity]
		
		If _head<=_tail
			_data.CopyTo( data,_head,0,length )
		Else
			Local n:=Capacity-_head
			_data.CopyTo( data,_head,0,n )
			_data.CopyTo( data,0,n,_tail )
		Endif
		
		_data=data
		_tail=length
		_head=0
		_seq+=1
	End
	
	Public

	#rem monkeydoc Creates a new deque.
	
	@param length Initalize length of the deque.

	#end	
	Method New()
		_data=New T[10]
	End
	
	Method New( length:Int )
		_tail=length
		_data=New T[_tail+1]
	End

	#rem monkeydoc True if deque is empty.
	#end
	Property Empty:Bool()
		Return _head=_tail
	End

	#rem monkeydoc Gets the storage capacity of the deque.
	
	The capacity of a deque is the number of values it can contain before memory needs to be reallocated to store more values.
	
	If a deque's length equals its capacity, then the next Add or Insert operation will need to allocate more memory to 'grow' the deque.
	
	You don't normally need to worry about deque capacity, but it can be useful to use [[Reserve]] to preallocate deque storage if you know in advance
	how many values a deque is likely to contain, in order to prevent the overhead of excessive memory allocation.
	
	@return The current deque capacity.
	
	#end
	Property Capacity:Int()
		Return _data.Length
	End
	
	#rem monkeydoc Gets the number of values in the deque.
	
	@return The number of values in the deque.
	
	#end
	Property Length:Int()
		If _head<=_tail Return _tail-_head
		Return Capacity-_head+_tail
	End

	#rem monkeydoc Gets the underlying array used by the deque.
	
	Note that the returned array may be longer than the deque length.
	
	@return The array used internally by the deque.
	
	#end
	Property Data:T[]()

		If Not _head Return _data
		
		Normalize( Capacity )
		
		Return _data
	End
	
	#rem monkeydoc Gets an iterator for visiting deque values.
	
	Returns an iterator suitable for use with [[Eachin]], or for manual iteration.
	
	@return A deque iterator.
	
	#end
	Method All:Iterator()
	
		Return New Iterator( Self,_head )
	End
	
	#rem monkeydoc Converts the deque to an array.
	
	@return An array containing each element of the deque.
	
	#end
	Method ToArray:T[]()
	
		Local data:=New T[Length]
		
		If _head<=_tail
			_data.CopyTo( data,_head,0,Length )
		Else
			Local n:=Capacity-_head
			_data.CopyTo( data,_head,0,n )
			_data.CopyTo( data,0,n,_tail )
		Endif
		
		Return data
	End
	
	#rem monkeydoc Reserves deque storage capacity.
	
	The capacity of a deque is the number of values it can contain before memory needs to be reallocated to store more values.
	
	If a deque's length equals its capacity, then the next Add, Insert or Push operation will need to allocate more memory to 'grow' the deque.
	
	You don't normally need to worry about deque capacity, but it can be useful to use [[Reserve]] to preallocate deque storage if you know in advance
	how many values a deque is likely to contain, in order to prevent the overhead of excessive memory allocation.
	
	@param capacity The new capacity.
	
	#end
	Method Reserve( capacity:Int )
		DebugAssert( capacity>=0 )
		
		If Capacity>=capacity Return

		capacity=Max( Length*2+Length,capacity )
		
		Normalize( capacity )
	End
	
	#rem monkeydoc Clears the deque.
	#end
	Method Clear()
		If _head<=_tail
			For Local i:=_head Until _tail
				_data[i]=Null
			Next
		Else
			For Local i:=0 Until _tail
				_data[i]=Null
			Next
			For Local i:=_head Until Capacity
				_data[i]=Null
			Next
		Endif
		_head=0
		_tail=0
		_seq+=1
	End
	
	#rem monkeydoc Adds a value at the start of the deque.
	#end
	Method PushFirst( value:T )
		If Length+1=Capacity Reserve( Capacity+1 )

		_head-=1
		If _head=-1 _head=Capacity-1
		_data[_head]=value
		_seq+=1
	End
	
	#rem monkeydoc Adds a value at the end of the deque.
	#end
	Method PushLast( value:T )
		If Length+1=Capacity Reserve( Capacity+1 )

		_data[_tail]=value
		_tail+=1
		If _tail=Capacity _tail=0
		_seq+=1
	End
	
	#rem monkeydoc Removes and returns the first value in a deque.
	
	In debug builds, a runtime error will occur if the deque is empty.
	
	#end
	Method PopFirst:T()
		DebugAssert( Not Empty,"Illegal operation on empty deque" )

		Local value:=_data[_head]
		_data[_head]=Null
		_head+=1
		If _head=Capacity _head=0
		_seq+=1
		Return value
	End
	
	#rem monkeydoc Removes and returns the last value in a deque.

	In debug builds, a runtime error will occur if the deque is empty.

	#end
	Method PopLast:T()
		DebugAssert( Not Empty,"Illegal operation on empty deque" )
		
		_tail-=1
		If _tail=-1 _tail=Capacity-1
		Local value:=_data[_tail]
		_data[_tail]=Null
		_seq+=1
		Return value
	End
	
	#rem monkeydoc Returns the first value in the deque.

	In debug builds, a runtime error will occur if the deque is empty.

	#end
	Method First:T()
		DebugAssert( Not Empty,"Illegal operation on empty deque" )
		
		Return _data[_head]
	End
	
	#rem monkeydoc Returns the last value in the deque.

	In debug builds, a runtime error will occur if the deque is empty.

	#end
	Method Last:T()
		DebugAssert( Not Empty,"Illegal operation on empty deque" )
		
		Return _data[ _tail>=0 ? _tail-1 Else Capacity-1 ]
	End
	
	#rem monkedoc Gets the value of a deque element.
	
	In debug builds, a runtime error will occur if `index` is less than 0, or greater than or equal to the length of the deque.
	
	#end
	Method Get:T( index:Int )
		DebugAssert( index>=0 And  index<Length,"Deque index out of range" )
		
		Return _data[ index Mod Capacity ]
	End
	
	#rem monkedoc Sets the value of a deque element.

	In debug builds, a runtime error will occur if `index` is less than 0, or greater than or equal to the length of the deque.
	
	#end
	Method Set( index:Int,value:T )
		DebugAssert( index>=0 And index<Length,"Deque index out of range" )
		
		_data[ index Mod Capacity ]=value
	End
	
	#rem monkedoc Gets the value of a deque element.

	In debug builds, a runtime error will occur if `index` is less than 0, or greater than or equal to the length of the deque.
	
	#end
	Operator[]:T( index:Int )
		DebugAssert( index>=0 And index<Length,"Deque index out of range" )
		
		Return _data[ index Mod Capacity ]
	End
	
	#rem monkedoc Sets the value of a deque element.

	In debug builds, a runtime error will occur if `index` is less than 0, or greater than or equal to the length of the deque.
	
	#end
	Operator[]=( index:Int,value:T )
		DebugAssert( index>=0 And index<Length,"Deque index out of range" )
		
		_data[ index Mod Capacity ]=value
	End
	
End