# -*- coding: utf-8 -*-
"""
Day_2 参考解答
=============
主题：字典与字符串。
建议：先自己写，写不出来再看；看完后关掉文件自己默写一遍。
"""

# ============================================================
# 题目一：模拟查询结果的处理（热身）
# ============================================================

users = [
    {"name": "zhangsan", "age": 20, "city": "青岛"},
    {"name": "lisi",     "age": 17, "city": "济南"},
    {"name": "wangwu",   "age": 22, "city": "北京"},
]

# 1. 筛选年龄 ≥ 18
adults = [u for u in users if u["age"] >= 18]

# 2. 按年龄从大到小排序（key 指定按哪个字段排，reverse=True 表示降序）
adults_sorted = sorted(adults, key=lambda u: u["age"], reverse=True)

# 3. 格式化成字符串列表
formatted = [f"{u['name']}({u['age']}岁)" for u in adults_sorted]

# 4. 进阶：拼成一个字符串
joined = ", ".join(formatted)

if __name__ == '__main__':
    print(adults)
    print([u["name"] for u in adults_sorted])
    print(formatted)
    print(joined)
    # [{'name': 'zhangsan', 'age': 20, 'city': '青岛'}, {'name': 'wangwu', 'age': 22, 'city': '北京'}]
    # ['wangwu', 'zhangsan']
    # ['wangwu(22岁)', 'zhangsan(20岁)']
    # wangwu(22岁), zhangsan(20岁)


# ============================================================
# 题目二：解析 URL 查询参数
# ============================================================

def parse_query_string(query):
    """把 'username=zhangsan&age=20' 解析成 {'username': 'zhangsan', 'age': '20'}"""
    result = {}
    if not query:                       # 边界 1：空输入
        return result
    for item in query.split('&'):       # 先按 & 切成若干段
        if '=' in item:
            key, value = item.split('=', 1)   # maxsplit=1：值里可能也含有 '='，只切第一个
        else:
            key, value = item, ''       # 边界 3：没有 = 的参数，值记为空字符串
        result[key] = value             # 字典赋值天然处理"重复键覆盖"和"值为空"
    return result


# 进阶：URL 编码还原（把 + 和 %20 还原成空格）
def url_decode(value):
    return value.replace('+', ' ').replace('%20', ' ')


def parse_query_string_advanced(query):
    result = {}
    if not query:
        return result
    for item in query.split('&'):
        if '=' in item:
            key, value = item.split('=', 1)
        else:
            key, value = item, ''
        result[key] = url_decode(value)
    return result


if __name__ == '__main__':
    print(parse_query_string('username=zhangsan&age=20&city=qingdao'))
    # {'username': 'zhangsan', 'age': '20', 'city': 'qingdao'}
    print(parse_query_string('name=a&name=b&flag'))
    # {'name': 'b', 'flag': ''}
    print(parse_query_string(''))
    # {}
    print(parse_query_string_advanced('name=Zhang+San&city=A%20B'))
    # {'name': 'Zhang San', 'city': 'A B'}