#Created by: Chen Da

"""
佇列類似生活中的排隊，為FIFO結構。

兩個基本操作：入隊push和出隊pop。

用單鏈表可以實現，雙鏈表雖然可以，但是操作比較複雜。
"""

#先實現一個單鏈表
class Node(object):
    def __init__(self,value=None,next=None):
        self.value,self.next = value,next

class LinkedList(object):
    def __init__(self,max_size=None):
        self.max_size = max_size
        self.root = Node()
        self.length = 0
        self.tail_node = None
    
    def __len__(self):
        return self.length

    def append(self,value):
        if self.max_size is not None and self.length > max_size:
            raise Exception("The LinkedNode is Full!")
        node = Node(value)
        tail_node = self.tail_node
        if tail_node is None:          #只有根節點
            self.root.next = node
        else:
            tail_node.next = node
        self.tail_node = node               #將尾節點指向新增的節點
        self.length += 1

    def append_left(self,value):
        if self.max_size is not None and self.length > max_size:
            raise Exception("The LinkedNode is Full!")
        head_node = self.root.next
        node = Node(value)
        self.root.next = node
        node.next = head_node
        self.length += 1

    def iter_node(self):
        cur_node = self.root.next
        while cur_node.next is not None:
            yield cur_node
            cur_node = cur_node.next
        yield cur_node

    def __iter__(self):
        for node in self.iter_node():
            yield node.value

    def remove(self,value):
        pre_node = self.root
        cur_node = self.root.next
        for cur_node in self.iter_node():
            if cur_node.value == value:
                pre_node.next = cur_node.next
            if cur_node is self.tail_node:
                self.tail_node = pre_node
            del cur_node
            self.length -= 1
            return 1
        else:
            pre_node = cur_node
        return -1

    def find(self,value):
        index = 0
        for node in self.iter_node():
            if node.value == value:
                return index
            index += 1
        return -1

    def pop_left(self):
        if self.root.next is None:
            raise Exception("單鏈表已空")
        head_node = self.root.next
        self.root.next = head_node.next
        self.length -= 1
        value = head_node.value
        del head_node
        return value

    def clear(self):
        for node in self.iter_node():
            del node
        self.root.next = None
        self.length = 0


#################################
#以下是Queue
#################################
class FullError(Exception):
    pass

class EmptyError(Exception):
    pass


class Queue(object):
    def __init__(self,max_size=None):
        self.max_size = max_size
        self._item_linked_list = LinkedList()

    def __len__(self):
        return len(self._item_linked_list)

    def push(self,value):
        if self.max_size is not None and len(self) > max_size:
            raise FullError("Queue is Full!")
        return self._item_linked_list.append(value)

    def pop(self):
        if len(self) == 0:
            raise EmptyError("Queue is empty!")
        return self._item_linked_list.pop_left()
        

#寫一個單測（這裡寫的不全）
def test_queue():
    q = Queue()
    q.push(0)
    q.push(1)
    q.push(2)

    assert len(q) == 3

    assert q.pop() == 0
    assert q.pop() == 1
    assert q.pop() == 2

if __name__ == "__main__":
    test_queue()