# -*- coding: utf-8 -*-

#

from itertools import chain

from .utils import lazyproperty

class Stack(list):

def is_empty(self):

return len(self) == 0

@property

def top(self):

if self.is_empty():

return None

return self[-1]

@property

def bottom(self):

if self.is_empty():

return None

return self[0]

def size(self):

return len(self)

def push(self, item):

self.append(item)

class QuerySetChain:

def __init__(self, querysets):

self.querysets = querysets

@lazyproperty

def querysets_counts(self):

counts = [s.count() for s in self.querysets]

return counts

def count(self):

return self.total_count

@lazyproperty

def total_count(self):

return sum(self.querysets_counts)

def __iter__(self):

self._chain = chain(*self.querysets)

return self

def __next__(self):

return next(self._chain)

def __getitem__(self, ndx):

querysets_count_zip = zip(self.querysets, self.querysets_counts)

length = 0 # 加上本数组后的大数组长度

pre_length = 0 # 不包含本数组的大数组长度

items = [] # 返回的值

loop = 0

if isinstance(ndx, slice):

ndx_start = ndx.start or 0

ndx_stop = ndx.stop or self.total_count

ndx_step = ndx.step or 1

else:

ndx_start = ndx

ndx_stop, ndx_step = None, None

for queryset, count in querysets_count_zip:

length += count

loop += 1

# 取当前数组的start角标, 存在3中情况

# 1. start角标在当前数组

if length > ndx_start >= pre_length:

start = ndx_start - pre_length

# print("[loop {}] Start is: {}".format(loop, start))

if ndx_step is None:

return queryset[start]

# 2. 不包含当前数组，因为起始已经超过了当前数组的长度

elif ndx_start >= length:

pre_length += count

continue

# 3. 不在当前数组，但是应该从当前数组0开始计算

else:

start = 0

# 可能取单个值, ndx_stop 为None, 不应该再找

if ndx_stop is None:

pre_length += count

continue

# 取当前数组的stop角标, 存在2中情况

# 不存在第3中情况是因为找到了会提交结束循环

# 1. 结束角标小于length代表 结束位在当前数组上

if ndx_stop < length:

stop = ndx_stop - pre_length

# 2. 结束位置包含改数组到了最后

else:

stop = count

# print("[loop {}] Slice: {} {} {}".format(loop, start, stop, ndx_step))

items.extend(list(queryset[slice(start, stop, ndx_step)]))

pre_length += count

# 如果结束再当前数组，则结束循环

if ndx_stop < length:

break

return items