import os
from typing import Callable, Dict, Optional, Union, cast

from mypy.checker import TypeChecker
from mypy.nodes import MemberExpr, NameExpr, TypeInfo
from mypy.options import Options
from mypy.plugin import (
    AttributeContext, ClassDefContext, FunctionContext, MethodContext, Plugin,
)
from mypy.types import (
    AnyType, CallableType, Instance, NoneTyp, Type, TypeOfAny, TypeType, UnionType,
)

from mypy_django_plugin import helpers, monkeypatch
from mypy_django_plugin.config import Config
from mypy_django_plugin.transformers import fields, init_create
from mypy_django_plugin.transformers.forms import (
    make_meta_nested_class_inherit_from_any,
)
from mypy_django_plugin.transformers.migrations import (
    determine_model_cls_from_string_for_migrations, get_string_value_from_expr,
)
from mypy_django_plugin.transformers.models import process_model_class
from mypy_django_plugin.transformers.settings import (
    AddSettingValuesToDjangoConfObject, get_settings_metadata,
)


def transform_model_class(ctx: ClassDefContext) -> None:
    try:
        sym = ctx.api.lookup_fully_qualified(helpers.MODEL_CLASS_FULLNAME)
    except KeyError:
        # models.Model is not loaded, skip metadata model write
        pass
    else:
        if sym is not None and isinstance(sym.node, TypeInfo):
            sym.node.metadata['django']['model_bases'][ctx.cls.fullname] = 1
    process_model_class(ctx)


def transform_manager_class(ctx: ClassDefContext) -> None:
    sym = ctx.api.lookup_fully_qualified_or_none(helpers.MANAGER_CLASS_FULLNAME)
    if sym is not None and isinstance(sym.node, TypeInfo):
        sym.node.metadata['django']['manager_bases'][ctx.cls.fullname] = 1


def transform_form_class(ctx: ClassDefContext) -> None:
    sym = ctx.api.lookup_fully_qualified_or_none(helpers.BASEFORM_CLASS_FULLNAME)
    if sym is not None and isinstance(sym.node, TypeInfo):
        sym.node.metadata['django']['baseform_bases'][ctx.cls.fullname] = 1

    make_meta_nested_class_inherit_from_any(ctx)


def determine_proper_manager_type(ctx: FunctionContext) -> Type:
    api = cast(TypeChecker, ctx.api)
    ret = ctx.default_return_type
    if not api.tscope.classes:
        # not in class
        return ret
    outer_model_info = api.tscope.classes[0]
    if not outer_model_info.has_base(helpers.MODEL_CLASS_FULLNAME):
        return ret
    if not isinstance(ret, Instance):
        return ret

    for i, base in enumerate(ret.type.bases):
        if base.type.fullname() in {helpers.MANAGER_CLASS_FULLNAME,
                                    helpers.RELATED_MANAGER_CLASS_FULLNAME,
                                    helpers.BASE_MANAGER_CLASS_FULLNAME}:
            ret.type.bases[i] = Instance(base.type, [Instance(outer_model_info, [])])
            return ret
    return ret


def return_user_model_hook(ctx: FunctionContext) -> Type:
    api = cast(TypeChecker, ctx.api)
    setting_expr = helpers.get_setting_expr(api, 'AUTH_USER_MODEL')
    if setting_expr is None:
        return ctx.default_return_type

    model_path = get_string_value_from_expr(setting_expr)
    if model_path is None:
        return ctx.default_return_type

    app_label, _, model_class_name = model_path.rpartition('.')
    if app_label is None:
        return ctx.default_return_type

    model_fullname = helpers.get_model_fullname(app_label, model_class_name,
                                                all_modules=api.modules)
    if model_fullname is None:
        api.fail(f'"{app_label}.{model_class_name}" model class is not imported so far. Try to import it '
                 f'(under if TYPE_CHECKING) at the beginning of the current file',
                 context=ctx.context)
        return ctx.default_return_type

    model_info = helpers.lookup_fully_qualified_generic(model_fullname,
                                                        all_modules=api.modules)
    if model_info is None or not isinstance(model_info, TypeInfo):
        return ctx.default_return_type
    return TypeType(Instance(model_info, []))


def _extract_referred_to_type_info(typ: Union[UnionType, Instance]) -> Optional[TypeInfo]:
    if isinstance(typ, Instance):
        return typ.type
    else:
        # should be Union[TYPE, None]
        typ = helpers.make_required(typ)
        if isinstance(typ, Instance):
            return typ.type
    return None


def extract_and_return_primary_key_of_bound_related_field_parameter(ctx: AttributeContext) -> Type:
    if not isinstance(ctx.default_attr_type, Instance) or not (ctx.default_attr_type.type.fullname() == 'builtins.int'):
        return ctx.default_attr_type

    if not isinstance(ctx.type, Instance) or not ctx.type.type.has_base(helpers.MODEL_CLASS_FULLNAME):
        return ctx.default_attr_type

    field_name = ctx.context.name.split('_')[0]
    sym = ctx.type.type.get(field_name)
    if sym and isinstance(sym.type, Instance) and len(sym.type.args) > 0:
        referred_to = sym.type.args[1]
        if isinstance(referred_to, AnyType):
            return AnyType(TypeOfAny.implementation_artifact)

        model_type = _extract_referred_to_type_info(referred_to)
        if model_type is None:
            return AnyType(TypeOfAny.implementation_artifact)

        primary_key_type = helpers.extract_primary_key_type_for_get(model_type)
        if primary_key_type:
            return primary_key_type

    is_nullable = helpers.get_fields_metadata(ctx.type.type).get(field_name, {}).get('null', False)
    if is_nullable:
        return helpers.make_optional(ctx.default_attr_type)

    return ctx.default_attr_type


def return_integer_type_for_id_for_non_defined_primary_key_in_models(ctx: AttributeContext) -> Type:
    if isinstance(ctx.type, Instance) and ctx.type.type.has_base(helpers.MODEL_CLASS_FULLNAME):
        return ctx.api.named_generic_type('builtins.int', [])
    return ctx.default_attr_type


class ExtractSettingType:
    def __init__(self, module_fullname: str):
        self.module_fullname = module_fullname

    def __call__(self, ctx: AttributeContext) -> Type:
        api = cast(TypeChecker, ctx.api)
        original_module = api.modules.get(self.module_fullname)
        if original_module is None:
            return ctx.default_attr_type

        definition = ctx.context
        if isinstance(definition, MemberExpr):
            sym = original_module.names.get(definition.name)
            if sym and sym.type:
                return sym.type

        return ctx.default_attr_type


def transform_form_view(ctx: ClassDefContext) -> None:
    form_class_value = helpers.get_assigned_value_for_class(ctx.cls.info, 'form_class')
    if isinstance(form_class_value, NameExpr):
        helpers.get_django_metadata(ctx.cls.info)['form_class'] = form_class_value.fullname


def extract_proper_type_for_get_form_class(ctx: MethodContext) -> Type:
    object_type = ctx.type
    if not isinstance(object_type, Instance):
        return ctx.default_return_type

    form_class_fullname = helpers.get_django_metadata(object_type.type).get('form_class', None)
    if not form_class_fullname:
        return ctx.default_return_type

    return TypeType(ctx.api.named_generic_type(form_class_fullname, []))


def extract_proper_type_for_get_form(ctx: MethodContext) -> Type:
    object_type = ctx.type
    if not isinstance(object_type, Instance):
        return ctx.default_return_type

    form_class_type = helpers.get_argument_type_by_name(ctx, 'form_class')
    if form_class_type is None or isinstance(form_class_type, NoneTyp):
        # extract from specified form_class in metadata
        form_class_fullname = helpers.get_django_metadata(object_type.type).get('form_class', None)
        if not form_class_fullname:
            return ctx.default_return_type

        return ctx.api.named_generic_type(form_class_fullname, [])

    if isinstance(form_class_type, TypeType) and isinstance(form_class_type.item, Instance):
        return form_class_type.item

    if isinstance(form_class_type, CallableType) and isinstance(form_class_type.ret_type, Instance):
        return form_class_type.ret_type

    return ctx.default_return_type


class DjangoPlugin(Plugin):
    def __init__(self, options: Options) -> None:
        super().__init__(options)

        monkeypatch.restore_original_load_graph()
        monkeypatch.restore_original_dependencies_handling()

        config_fpath = os.environ.get('MYPY_DJANGO_CONFIG', 'mypy_django.ini')
        if config_fpath and os.path.exists(config_fpath):
            self.config = Config.from_config_file(config_fpath)
            self.django_settings_module = self.config.django_settings_module
        else:
            self.config = Config()
            self.django_settings_module = None

        if 'DJANGO_SETTINGS_MODULE' in os.environ:
            self.django_settings_module = os.environ['DJANGO_SETTINGS_MODULE']

        settings_modules = ['django.conf.global_settings']
        if self.django_settings_module:
            settings_modules.append(self.django_settings_module)

        monkeypatch.add_modules_as_a_source_seed_files(settings_modules)
        monkeypatch.inject_modules_as_dependencies_for_django_conf_settings(settings_modules)

    def _get_current_model_bases(self) -> Dict[str, int]:
        model_sym = self.lookup_fully_qualified(helpers.MODEL_CLASS_FULLNAME)
        if model_sym is not None and isinstance(model_sym.node, TypeInfo):
            return (helpers.get_django_metadata(model_sym.node)
                    .setdefault('model_bases', {helpers.MODEL_CLASS_FULLNAME: 1}))
        else:
            return {}

    def _get_current_manager_bases(self) -> Dict[str, int]:
        model_sym = self.lookup_fully_qualified(helpers.MANAGER_CLASS_FULLNAME)
        if model_sym is not None and isinstance(model_sym.node, TypeInfo):
            return (helpers.get_django_metadata(model_sym.node)
                    .setdefault('manager_bases', {helpers.MANAGER_CLASS_FULLNAME: 1}))
        else:
            return {}

    def _get_current_form_bases(self) -> Dict[str, int]:
        model_sym = self.lookup_fully_qualified(helpers.BASEFORM_CLASS_FULLNAME)
        if model_sym is not None and isinstance(model_sym.node, TypeInfo):
            return (helpers.get_django_metadata(model_sym.node)
                    .setdefault('baseform_bases', {helpers.BASEFORM_CLASS_FULLNAME: 1,
                                                   helpers.FORM_CLASS_FULLNAME: 1,
                                                   helpers.MODELFORM_CLASS_FULLNAME: 1}))
        else:
            return {}

    def get_function_hook(self, fullname: str
                          ) -> Optional[Callable[[FunctionContext], Type]]:
        if fullname == 'django.contrib.auth.get_user_model':
            return return_user_model_hook

        manager_bases = self._get_current_manager_bases()
        if fullname in manager_bases:
            return determine_proper_manager_type

        sym = self.lookup_fully_qualified(fullname)
        if sym is not None and isinstance(sym.node, TypeInfo):
            if sym.node.has_base(helpers.FIELD_FULLNAME):
                return fields.adjust_return_type_of_field_instantiation

            if sym.node.metadata.get('django', {}).get('generated_init'):
                return init_create.redefine_and_typecheck_model_init

    def get_method_hook(self, fullname: str
                        ) -> Optional[Callable[[MethodContext], Type]]:
        class_name, _, method_name = fullname.rpartition('.')
        if method_name == 'get_form_class':
            sym = self.lookup_fully_qualified(class_name)
            if sym and isinstance(sym.node, TypeInfo) and sym.node.has_base(helpers.FORM_MIXIN_CLASS_FULLNAME):
                return extract_proper_type_for_get_form_class

        if method_name == 'get_form':
            sym = self.lookup_fully_qualified(class_name)
            if sym and isinstance(sym.node, TypeInfo) and sym.node.has_base(helpers.FORM_MIXIN_CLASS_FULLNAME):
                return extract_proper_type_for_get_form

        if fullname in {'django.apps.registry.Apps.get_model',
                        'django.db.migrations.state.StateApps.get_model'}:
            return determine_model_cls_from_string_for_migrations

        manager_classes = self._get_current_manager_bases()
        class_fullname, _, method_name = fullname.rpartition('.')
        if class_fullname in manager_classes and method_name == 'create':
            return init_create.redefine_and_typecheck_model_create
        return None

    def get_base_class_hook(self, fullname: str
                            ) -> Optional[Callable[[ClassDefContext], None]]:
        if fullname == helpers.DUMMY_SETTINGS_BASE_CLASS:
            settings_modules = ['django.conf.global_settings']
            if self.django_settings_module:
                settings_modules.append(self.django_settings_module)
            return AddSettingValuesToDjangoConfObject(settings_modules,
                                                      self.config.ignore_missing_settings)

        if fullname in self._get_current_model_bases():
            return transform_model_class

        if fullname in self._get_current_manager_bases():
            return transform_manager_class

        if fullname in self._get_current_form_bases():
            return transform_form_class

        sym = self.lookup_fully_qualified(fullname)
        if sym and isinstance(sym.node, TypeInfo) and sym.node.has_base(helpers.FORM_MIXIN_CLASS_FULLNAME):
            return transform_form_view

        return None

    def get_attribute_hook(self, fullname: str
                           ) -> Optional[Callable[[AttributeContext], Type]]:
        if fullname == 'builtins.object.id':
            return return_integer_type_for_id_for_non_defined_primary_key_in_models

        module, _, name = fullname.rpartition('.')
        sym = self.lookup_fully_qualified('django.conf.LazySettings')
        if sym and isinstance(sym.node, TypeInfo):
            metadata = get_settings_metadata(sym.node)
            if module == 'builtins.object' and name in metadata:
                return ExtractSettingType(module_fullname=metadata[name])

        return extract_and_return_primary_key_of_bound_related_field_parameter


def plugin(version):
    return DjangoPlugin