take two lists of operations ones that will be used for the database and ones that will be used for the state change this allows operations that don t support state change to have it applied or have operations that affect the state or not the database or so on we calculate state separately in here since our state functions aren t useful we calculate state separately in here since our state functions aren t useful tostate now has the states of all the databaseoperations applied which is the fromstate for the backwards migration of the last operation run some raw sql a reverse sql statement may be provided also accept a list of operations that represent the state change effected by this sql change in case it s custom columntable creationdeletion run python code in a context suitable for doing versioned orm operations forwards code reverse code runpython objects have no state effect to add some combine this with separatedatabaseandstate runpython has access to all models ensure that all models are reloaded in case any are delayed we now execute the python code in a context that contains a models object representing the versioned models as an app registry we could try to override the global cache but then people will still use direct imports so we go with a documentation approach instead take two lists of operations ones that will be used for the database and ones that will be used for the state change this allows operations that don t support state change to have it applied or have operations that affect the state or not the database or so on we calculate state separately in here since our state functions aren t useful we calculate state separately in here since our state functions aren t useful to_state now has the states of all the database_operations applied which is the from_state for the backwards migration of the last operation run some raw sql a reverse sql statement may be provided also accept a list of operations that represent the state change effected by this sql change in case it s custom column table creation deletion run python code in a context suitable for doing versioned orm operations forwards code reverse code runpython objects have no state effect to add some combine this with separatedatabaseandstate runpython has access to all models ensure that all models are reloaded in case any are delayed we now execute the python code in a context that contains a models object representing the versioned models as an app registry we could try to override the global cache but then people will still use direct imports so we go with a documentation approach instead
from django.db import router

from .base import Operation


class SeparateDatabaseAndState(Operation):
    

    serialization_expand_args = ["database_operations", "state_operations"]

    def __init__(self, database_operations=None, state_operations=None):
        self.database_operations = database_operations or []
        self.state_operations = state_operations or []

    def deconstruct(self):
        kwargs = {}
        if self.database_operations:
            kwargs["database_operations"] = self.database_operations
        if self.state_operations:
            kwargs["state_operations"] = self.state_operations
        return (self.__class__.__qualname__, [], kwargs)

    def state_forwards(self, app_label, state):
        for state_operation in self.state_operations:
            state_operation.state_forwards(app_label, state)

    def database_forwards(self, app_label, schema_editor, from_state, to_state):
        
        for database_operation in self.database_operations:
            to_state = from_state.clone()
            database_operation.state_forwards(app_label, to_state)
            database_operation.database_forwards(
                app_label, schema_editor, from_state, to_state
            )
            from_state = to_state

    def database_backwards(self, app_label, schema_editor, from_state, to_state):
        
        to_states = {}
        for dbop in self.database_operations:
            to_states[dbop] = to_state
            to_state = to_state.clone()
            dbop.state_forwards(app_label, to_state)
        
        
        
        for database_operation in reversed(self.database_operations):
            from_state = to_state
            to_state = to_states[database_operation]
            database_operation.database_backwards(
                app_label, schema_editor, from_state, to_state
            )

    def describe(self):
        return "Custom state/database change combination"


class RunSQL(Operation):
    

    noop = ""

    def __init__(
        self, sql, reverse_sql=None, state_operations=None, hints=None, elidable=False
    ):
        self.sql = sql
        self.reverse_sql = reverse_sql
        self.state_operations = state_operations or []
        self.hints = hints or {}
        self.elidable = elidable

    def deconstruct(self):
        kwargs = {
            "sql": self.sql,
        }
        if self.reverse_sql is not None:
            kwargs["reverse_sql"] = self.reverse_sql
        if self.state_operations:
            kwargs["state_operations"] = self.state_operations
        if self.hints:
            kwargs["hints"] = self.hints
        return (self.__class__.__qualname__, [], kwargs)

    @property
    def reversible(self):
        return self.reverse_sql is not None

    def state_forwards(self, app_label, state):
        for state_operation in self.state_operations:
            state_operation.state_forwards(app_label, state)

    def database_forwards(self, app_label, schema_editor, from_state, to_state):
        if router.allow_migrate(
            schema_editor.connection.alias, app_label, **self.hints
        ):
            self._run_sql(schema_editor, self.sql)

    def database_backwards(self, app_label, schema_editor, from_state, to_state):
        if self.reverse_sql is None:
            raise NotImplementedError("You cannot reverse this operation")
        if router.allow_migrate(
            schema_editor.connection.alias, app_label, **self.hints
        ):
            self._run_sql(schema_editor, self.reverse_sql)

    def describe(self):
        return "Raw SQL operation"

    def _run_sql(self, schema_editor, sqls):
        if isinstance(sqls, (list, tuple)):
            for sql in sqls:
                params = None
                if isinstance(sql, (list, tuple)):
                    elements = len(sql)
                    if elements == 2:
                        sql, params = sql
                    else:
                        raise ValueError("Expected a 2-tuple but got %d" % elements)
                schema_editor.execute(sql, params=params)
        elif sqls != RunSQL.noop:
            statements = schema_editor.connection.ops.prepare_sql_script(sqls)
            for statement in statements:
                schema_editor.execute(statement, params=None)


class RunPython(Operation):
    

    reduces_to_sql = False

    def __init__(
        self, code, reverse_code=None, atomic=None, hints=None, elidable=False
    ):
        self.atomic = atomic
        
        if not callable(code):
            raise ValueError("RunPython must be supplied with a callable")
        self.code = code
        
        if reverse_code is None:
            self.reverse_code = None
        else:
            if not callable(reverse_code):
                raise ValueError("RunPython must be supplied with callable arguments")
            self.reverse_code = reverse_code
        self.hints = hints or {}
        self.elidable = elidable

    def deconstruct(self):
        kwargs = {
            "code": self.code,
        }
        if self.reverse_code is not None:
            kwargs["reverse_code"] = self.reverse_code
        if self.atomic is not None:
            kwargs["atomic"] = self.atomic
        if self.hints:
            kwargs["hints"] = self.hints
        return (self.__class__.__qualname__, [], kwargs)

    @property
    def reversible(self):
        return self.reverse_code is not None

    def state_forwards(self, app_label, state):
        
        
        pass

    def database_forwards(self, app_label, schema_editor, from_state, to_state):
        
        
        from_state.clear_delayed_apps_cache()
        if router.allow_migrate(
            schema_editor.connection.alias, app_label, **self.hints
        ):
            
            
            
            
            self.code(from_state.apps, schema_editor)

    def database_backwards(self, app_label, schema_editor, from_state, to_state):
        if self.reverse_code is None:
            raise NotImplementedError("You cannot reverse this operation")
        if router.allow_migrate(
            schema_editor.connection.alias, app_label, **self.hints
        ):
            self.reverse_code(from_state.apps, schema_editor)

    def describe(self):
        return "Raw Python operation"

    @staticmethod
    def noop(apps, schema_editor):
        return None