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

from typing import Callable, List, Optional, Sequence, TypeVar, Union

from .._utils import find_one
from ..exc import UnknownEnumValue, UnknownType
from ..lang.visitor import DispatchingVisitor
from ..schema import (
    Argument,
    Directive,
    EnumType,
    EnumValue,
    Field,
    GraphQLCompositeType,
    InputField,
    InputObjectType,
    InterfaceType,
    ListType,
    ObjectType,
    is_input_type,
    is_output_type,
    nullable_type,
    unwrap_type,
)
from ..schema.introspection import (
    SCHEMA_INTROSPECTION_FIELD,
    TYPE_INTROSPECTION_FIELD,
    TYPE_NAME_INTROSPECTION_FIELD,
)

T = TypeVar("T")


OptList = List[Optional[T]]


def _peek(
    lst: Sequence[T], count: int = 1, default: Optional[T] = None
) -> Optional[T]:
    return lst[-1 * count] if len(lst) >= count else default


def _or_none(value: T, predicate: Callable[[T], bool] = bool) -> Optional[T]:
    return value if predicate(value) else None


def _get_field_def(schema, parent_type, field):
    name = field.name.value
    if parent_type is schema.query_type:
        if name == SCHEMA_INTROSPECTION_FIELD.name:
            return SCHEMA_INTROSPECTION_FIELD
        if name == TYPE_INTROSPECTION_FIELD.name:
            return TYPE_INTROSPECTION_FIELD

    if (
        isinstance(parent_type, GraphQLCompositeType)
        and name == TYPE_NAME_INTROSPECTION_FIELD.name
    ):
        return TYPE_NAME_INTROSPECTION_FIELD

    if isinstance(parent_type, (ObjectType, InterfaceType)):
        return parent_type.field_map.get(name, None)

    return None


# This is a very basic re-implementation of the reference javascript
# implementation which is compatible with our version of AST visitors
# and it can most likley be improved.
class TypeInfoVisitor(DispatchingVisitor):
    """
    Utility visitor that recurisvely track the current types and field
    definitions while traversing a Document.

    All tracked types are considered with regards to the provided schema,
    however unknown types and other unexpected errors will be downgraded to
    null values in order to not crash the traversal. This leaves the consumer
    responsible to handle such cases.

    Warning:
        When using this alongside other visitors (such as when using
        :class:`py_gql.lang.visitor.ParallelVisitor`), this visitor **must**
        to be the first one to visit the nodes in order for the information
        provided donwstream to be accurate.

    Args:
        schema (py_gql.schema.Schema): Reference schema to extract types from

    Attributes:

        type (Optional[py_gql.schema.ObjectType]):
            Current type if applicable

        parent_typ (Optional[py_gql.schema.ObjectType]):
            Current type if applicable_stack, 1)

        input_typ (Optional[py_gql.schema.InputObjectType]):
            Current input type if applicable (when visiting arguments)

        parent_input_typ (Optional[py_gql.schema.InputObjectType]):
            Current parent input type if applicable (when visiting input objects)

        fiel (Optional[py_gql.schema.Field]):
            Current field definition if applicable (when visiting object)

        input_value_def (Optional[Union[py_gql.schema.Argument, \
                py_gql.schema.InputField]]):
            Current input value definition (e.g. arg def, input field) if applicable
    """

    __slots__ = (
        "_schema",
        "_type_stack",
        "_input_type_stack",
        "_parent_type_stack",
        "_field_stack",
        "_input_value_def_stack",
        "directive",
        "argument",
        "enum_value",
    )

    def __init__(self, schema):
        self._schema = schema

        self._type_stack = []  # type: OptList[ObjectType]
        self._parent_type_stack = []  # type: OptList[ObjectType]
        self._input_type_stack = []  # type: OptList[InputObjectType]
        self._field_stack = []  # type: OptList[Field]
        self._input_value_def_stack = (
            []
        )  # type: OptList[Union[Argument, InputField]]

        self.directive = None  # type: Optional[Directive]
        self.argument = None  # type: Optional[Argument]
        self.enum_value = None  # type: Optional[EnumValue]

    @property
    def type(self) -> Optional[ObjectType]:
        return _peek(self._type_stack)

    @property
    def parent_type(self) -> Optional[ObjectType]:
        return _peek(self._parent_type_stack, 1)

    @property
    def input_type(self) -> Optional[InputObjectType]:
        return _peek(self._input_type_stack, 1)

    @property
    def parent_input_type(self) -> Optional[InputObjectType]:
        return _peek(self._input_type_stack, 2)

    @property
    def field(self) -> Optional[Field]:
        return _peek(self._field_stack)

    @property
    def input_value_def(self) -> Optional[Union[Argument, InputField]]:
        return _peek(self._input_value_def_stack)

    def _get_field_def(self, node):
        parent_type = self.parent_type
        return (
            _get_field_def(self._schema, parent_type, node)
            if parent_type
            else None
        )

    def _type_from_ast(self, type_node):
        try:
            return self._schema.get_type_from_literal(type_node)
        except UnknownType:
            return None

    def _leave_input_value(self):
        self._input_type_stack.pop()
        self._input_value_def_stack.pop()

    def enter_selection_set(self, node):
        named_type = unwrap_type(self.type)
        self._parent_type_stack.append(
            _or_none(named_type, lambda x: isinstance(x, GraphQLCompositeType))
        )
        return node

    def leave_selection_set(self, _node):
        self._parent_type_stack.pop()

    def enter_field(self, node):
        field_def = self._get_field_def(node)
        self._field_stack.append(field_def)
        if field_def:
            self._type_stack.append(_or_none(field_def.type, is_output_type))
        else:
            self._type_stack.append(None)
        return node

    def leave_field(self, _node):
        self._type_stack.pop()
        self._field_stack.pop()

    def enter_directive(self, node):
        self.directive = self._schema.directives.get(node.name.value)
        return node

    def leave_directive(self, _node):
        self.directive = None

    def enter_operation_definition(self, node):
        type_ = {
            "query": self._schema.query_type,
            "mutation": self._schema.mutation_type,
            "subscription": self._schema.subscription_type,
        }.get(node.operation, None)
        self._type_stack.append(
            type_ if isinstance(type_, ObjectType) else None
        )
        return node

    def leave_operation_definition(self, _node):
        self._type_stack.pop()

    def enter_fragment_definition(self, node):
        self._type_stack.append(
            _or_none(self._type_from_ast(node.type_condition), is_output_type)
        )
        return node

    def leave_fragment_definition(self, _node):
        self._type_stack.pop()

    def enter_inline_fragment(self, node):
        if node.type_condition:
            self._type_stack.append(
                _or_none(
                    self._type_from_ast(node.type_condition), is_output_type
                )
            )
        else:
            self._type_stack.append(_or_none(self.type, is_output_type))
        return node

    def leave_inline_fragment(self, _node):
        self._type_stack.pop()

    def enter_variable_definition(self, node):
        self._input_type_stack.append(
            _or_none(self._type_from_ast(node.type), is_input_type)
        )
        return node

    def leave_variable_definition(self, _node):
        self._input_type_stack.pop()

    def enter_argument(self, node):
        ctx = self.directive or self.field
        if ctx:
            name = node.name.value
            self.argument = find_one(ctx.arguments, lambda a: a.name == name)
            self._input_value_def_stack.append(self.argument)
            self._input_type_stack.append(
                self.argument.type
                if self.argument and is_input_type(self.argument.type)
                else None
            )
        else:
            self.argument = None
            self._input_type_stack.append(None)
            self._input_value_def_stack.append(None)
        return node

    def leave_argument(self, _node):
        self.argument = None
        self._leave_input_value()

    def enter_list_value(self, node):
        list_type = nullable_type(self.input_type)
        item_type = (
            unwrap_type(list_type) if isinstance(list_type, ListType) else None
        )
        self._input_type_stack.append(
            _or_none(item_type, is_input_type)
            if item_type is not None
            else None
        )
        # List positions never have a default value.
        self._input_value_def_stack.append(None)
        return node

    def leave_list_value(self, _node):
        self._leave_input_value()

    def enter_object_field(self, node):
        object_type = unwrap_type(self.input_type)
        if isinstance(object_type, InputObjectType):
            name = node.name.value
            field_def = find_one(object_type.fields, lambda f: f.name == name)
            self._input_value_def_stack.append(field_def)
            self._input_type_stack.append(
                field_def.type
                if field_def and is_input_type(field_def.type)
                else None
            )
        else:
            self._input_type_stack.append(None)
            self._input_value_def_stack.append(None)
        return node

    def leave_object_field(self, _node):
        self._leave_input_value()

    def enter_enum_value(self, node):
        enum = unwrap_type(self.input_type)
        if isinstance(enum, EnumType):
            try:
                self.enum_value = enum.get_value(node.value)
            except UnknownEnumValue:
                self.enum_value = None
        return node

    def leave_enum_value(self, _node):
        self.enum_value = None
