Python3高级核心技术 第八章 MyOrm

import numbers
import collections
from helper import MysqlHelper


OrderByTuple = collections.namedtuple("OrderByTuple", ["name", "direction"])


class Field:
    pass


class IntField(Field):
    # 数据描述符
    def __init__(self, db_column, min_value=None, max_value=None):
        self._name = 'i_' + db_column
        self.min_value = min_value
        self.max_value = max_value
        self.db_column = db_column
        if min_value is not None:
            if not isinstance(min_value, numbers.Integral):
                raise ValueError("min_value must be int")
            elif min_value < 0:
                raise ValueError("min_value must be positive int")
        if max_value is not None:
            if not isinstance(max_value, numbers.Integral):
                raise ValueError("max_value must be int")
            elif max_value < 0:
                raise ValueError("max_value must be positive int")
        if min_value is not None and max_value is not None:
            if min_value > max_value:
                raise ValueError("min_value must be smaller than max_value")

    def __get__(self, instance, owner):
        return getattr(instance, self._name)

    def __set__(self, instance, value):
        if not isinstance(value, numbers.Integral):
            raise ValueError("int value need")
        if (self.min_value is not None and value < self.min_value) or 
                (self.max_value is not None and value > self.max_value):
            raise ValueError("value must between min_value and max_value")
        setattr(instance, self._name, value)


class CharField(Field):
    def __init__(self, db_column, max_length=None):
        self._name = 's_' + db_column
        self.db_column = db_column
        if max_length is None:
            raise ValueError("you must spcify max_lenth for charfiled")
        self.max_length = max_length

    def __get__(self, instance, owner):
        return getattr(instance, self._name)

    def __set__(self, instance, value):
        if not isinstance(value, str):
            raise ValueError("string value need")
        if len(value) > self.max_length:
            raise ValueError("value len excess len of max_length")
        setattr(instance, self._name, value)


class PrimaryKeyMixIn:
    id = IntField(db_column="id")


class ModelMetaClass(type):
    def __new__(cls, name, bases, attrs):
        if name == "BaseModel":
            return super().__new__(cls, name, bases, attrs)
        fields = {"id": IntField(db_column="id")}
        for key, value in attrs.items():
            if isinstance(value, Field):
                fields[key] = value
        attrs_meta = attrs.get("Meta", None)
        _meta = {}
        db_table = name.lower()
        if attrs_meta is not None:
            table = getattr(attrs_meta, "db_table", None)
            if table is not None:
                db_table = table
        _meta["db_table"] = db_table
        attrs["_meta"] = _meta
        attrs["fields"] = fields
        del attrs["Meta"]
        return super().__new__(cls, name, bases, attrs)


class BaseModel(metaclass=ModelMetaClass):
    def __init__(self, *args, **kwargs):
        for key, value in kwargs.items():
            setattr(self, key, value)
        super().__init__()

    def save(self):
        fields = []
        values = []
        for key, value in self.fields.items():
            db_column = value.db_column
            if db_column is None:
                db_column = key.lower()
            fields.append(db_column)
            value = getattr(self, key)
            if isinstance(value, str):
                values.append("'" + value + "'")
            else:
                values.append(str(value))
        # insert user(id, name) values (1, 'admin')
        sql = "insert {db_table}({fields}) values ({values})".format(db_table=self._meta["db_table"],
                                                                     fields=",".join(fields),
                                                                     values=",".join(values))
        print(sql)
        db = MysqlHelper()
        db.insert(sql)

    def delete(self):
        conditions = []
        for key, value in self.fields.items():
            db_column = value.db_column
            if db_column is None:
                db_column = key.lower()
            value = getattr(self, key)
            if value is not None:
                if isinstance(value, str):
                    conditions.append(db_column + " = '" + value + "'")
                else:
                    conditions.append(db_column + " = " + str(value))
        # delete from user where id = 3
        sql = "delete from " + self._meta["db_table"] + " where " + " and ".join(conditions)
        print(sql)
        db = MysqlHelper()
        db.delete(sql)

    @classmethod
    def batch_delete(cls, ids):
        # delete from user where id in (9, 10, 11)
        sql = "delete from " + cls._meta["db_table"] + " where id in (" + ",".join([str(p_key) for p_key in ids]) + ")"
        print(sql)
        db = MysqlHelper()
        db.delete(sql)

    def update(self):
        conditions = []
        primary_key = getattr(self, 'id', None)
        if primary_key is None:
            raise KeyError("primary key cannot be empty")
        for key, value in self.fields.items():
            db_column = value.db_column
            if db_column is None:
                db_column = key.lower()
            value = getattr(self, key)
            if isinstance(value, str):
                conditions.append(db_column + " = '" + value + "'")
            else:
                conditions.append(db_column + " = " + str(value))
        # update user set name = 'test' where id = 4
        sql = "update " + self._meta["db_table"] + " set " + ", ".join(conditions) + " where id = " + str(primary_key)
        print(sql)
        db = MysqlHelper()
        db.update(sql)

    @classmethod
    def batch_update(cls, obs):
        conditions = []
        fields = set()
        ids = []
        for item in obs:
            ids.append(item.id)
            for key, value in cls.fields.items():
                value = getattr(item, key, None)
                if value is not None:
                    fields.add(key)

        for key in fields:
            db_column = cls.fields[key].db_column
            if db_column is None:
                db_column = key.lower()
            when_tens = []
            for p_key in ids:
                instance = list(filter(lambda x: x.id == p_key, obs))[0]
                value = getattr(instance, key)
                if isinstance(value, str):
                    when_tens.append("when " + str(p_key) + " then '" + value + "'")
                else:
                    when_tens.append("when " + str(p_key) + " then " + str(value))

            conditions.append(db_column + " = case id " + " ".join(when_tens) + " end")

        # update user set
        # id = case id when 1 then 1 when 2 then 2 when 3 then 3 end,
        # title = case id when 1 then 'test1' when 2 then 'test2' when 3 then 'test3' end
        # where id in (1,2,3)
        sql = "update " + cls._meta["db_table"] + " set "
        sql += ", ".join(conditions) + " "
        sql += "where id in (" + ",".join([str(p_key) for p_key in ids]) + ")"
        print(sql)
        db = MysqlHelper()
        db.update(sql)

    @classmethod
    def all(cls, **kwargs):
        sql = "select * from " + cls._meta["db_table"] + " "
        order_by = kwargs.get("order_by", None)
        if order_by is not None:
            options = []
            for item in order_by:
                option = item.name + " " + item.direction
                options.append(option)
            sql += "order by " + ", ".join(options)
        # select * from user order by id desc, name asc
        print(sql)
        db = MysqlHelper()
        res = db.get_all_obj(sql, cls._meta["db_table"])
        obs = []
        for item in res:
            obj = cls()
            for k, v in item.items():
                setattr(obj, k, v)
            obs.append(obj)
        return obs

    @classmethod
    def filter(cls, **kwargs):
        conditions = []
        has_order_by = False
        for key, value in kwargs.items():
            if key == "order_by":
                has_order_by = True
                continue
            field_value = cls.fields.get(key, None)
            if field_value is None:
                raise KeyError("the field " + key + " does not exist")
            db_column = field_value.db_column
            if db_column is None:
                db_column = key.lower()
            if isinstance(value, str):
                conditions.append(db_column + " like '%" + value + "%'")
            else:
                conditions.append(db_column + " = " + str(value))
        sql = "select * from " + cls._meta["db_table"] + " where " + " and ".join(conditions) + " "
        options = []
        if has_order_by:
            order_by = kwargs.get("order_by", None)
            if order_by is not None:
                for item in order_by:
                    option = item.name + " " + item.direction
                    options.append(option)
        if len(options) > 0:
            sql += "order by " + ", ".join(options)
        # select * from user where name = 'admin' order by id desc, name asc
        print(sql)
        db = MysqlHelper()
        res = db.get_all_obj(sql, cls._meta["db_table"])
        obs = []
        for item in res:
            obj = cls()
            for k, v in item.items():
                setattr(obj, k, v)
            obs.append(obj)
        return obs

    @classmethod
    def one(cls, **kwargs):
        conditions = []
        for key, value in kwargs.items():
            field_value = cls.fields.get(key, None)
            if field_value is None:
                raise KeyError("the field " + key + " does not exist")
            db_column = field_value.db_column
            if db_column is None:
                db_column = key.lower()
            if isinstance(value, str):
                conditions.append(db_column + " = '%" + value + "%'")
            else:
                conditions.append(db_column + " = " + str(value))
        # select * from user where name = 'admin'
        sql = "select * from " + cls._meta["db_table"] + " where " + " and ".join(conditions)
        print(sql)
        db = MysqlHelper()
        item = db.get_one_obj(sql, cls._meta["db_table"])
        if item is None:
            return None
        obj = cls()
        for k, v in item.items():
            setattr(obj, k, v)
        return obj