from __future__ import annotations

from typing import Optional, Sequence

import libcst as cst
import libcst.matchers as m
from libcst._nodes.expression import BaseExpression, Call  # noqa: TCH002
from libcst.codemod import CodemodContext, VisitorBasedCodemodCommand
from libcst.codemod.visitors import AddImportsVisitor, RemoveImportsVisitor


def _find_named_argument(args: Sequence[cst.Arg], name: str) -> cst.Arg | None:
    return next(
        (arg for arg in args if arg.keyword and arg.keyword.value == name),
        None,
    )


def _find_positional_argument(
    args: Sequence[cst.Arg], search_index: int
) -> cst.Arg | None:
    for index, arg in enumerate(args):
        if index > search_index:
            return None

        if index == search_index and arg.keyword is None:
            return arg

    return None


class ConvertUnionToAnnotatedUnion(VisitorBasedCodemodCommand):
    DESCRIPTION: str = (
        "Converts strawberry.union(..., types=(...)) to "
        "Annotated[Union[...], strawberry.union(...)]"
    )

    def __init__(
        self,
        context: CodemodContext,
        use_pipe_syntax: bool = True,
        use_typing_extensions: bool = False,
    ) -> None:
        self._is_using_named_import = False
        self.use_pipe_syntax = use_pipe_syntax
        self.use_typing_extensions = use_typing_extensions

        super().__init__(context)

    def visit_Module(self, node: cst.Module) -> Optional[bool]:
        self._is_using_named_import = False

        return super().visit_Module(node)

    @m.visit(
        m.ImportFrom(
            m.Name("strawberry"),
            [
                m.ZeroOrMore(),
                m.ImportAlias(m.Name("union")),
                m.ZeroOrMore(),
            ],
        )
    )
    def visit_import_from(self, original_node: cst.ImportFrom) -> None:
        self._is_using_named_import = True

    @m.leave(
        m.Call(
            func=m.Attribute(value=m.Name("strawberry"), attr=m.Name("union"))
            | m.Name("union")
        )
    )
    def leave_union_call(
        self, original_node: Call, updated_node: Call
    ) -> BaseExpression:
        if not self._is_using_named_import and isinstance(original_node.func, cst.Name):
            return original_node

        types = _find_named_argument(original_node.args, "types")
        union_name = _find_named_argument(original_node.args, "name")

        if types is None:
            types = _find_positional_argument(original_node.args, 1)

        # this is probably a strawberry.union(name="...") so we skip the conversion
        # as it is going to be used in the new way already 😊

        if types is None:
            return original_node

        AddImportsVisitor.add_needed_import(
            self.context,
            "typing_extensions" if self.use_typing_extensions else "typing",
            "Annotated",
        )

        RemoveImportsVisitor.remove_unused_import(self.context, "strawberry", "union")

        if union_name is None:
            union_name = _find_positional_argument(original_node.args, 0)

        assert union_name
        assert isinstance(types.value, (cst.Tuple, cst.List))

        types = types.value.elements  # type: ignore
        union_name = union_name.value  # type: ignore

        description = _find_named_argument(original_node.args, "description")
        directives = _find_named_argument(original_node.args, "directives")

        if self.use_pipe_syntax:
            union_node = self._create_union_node_with_pipe_syntax(types)  # type: ignore
        else:
            AddImportsVisitor.add_needed_import(self.context, "typing", "Union")

            union_node = cst.Subscript(
                value=cst.Name(value="Union"),
                slice=[
                    cst.SubscriptElement(slice=cst.Index(value=t.value))
                    for t in types  # type: ignore
                ],
            )

        union_call_args = [
            cst.Arg(
                value=union_name,  # type: ignore
                keyword=cst.Name(value="name"),
                equal=cst.AssignEqual(
                    whitespace_before=cst.SimpleWhitespace(""),
                    whitespace_after=cst.SimpleWhitespace(""),
                ),
            )
        ]

        additional_args = {"description": description, "directives": directives}

        union_call_args.extend(
            cst.Arg(
                value=arg.value,
                keyword=cst.Name(name),
                equal=cst.AssignEqual(
                    whitespace_before=cst.SimpleWhitespace(""),
                    whitespace_after=cst.SimpleWhitespace(""),
                ),
            )
            for name, arg in additional_args.items()
            if arg is not None
        )

        union_call_node = cst.Call(
            func=cst.Attribute(
                value=cst.Name(value="strawberry"),
                attr=cst.Name(value="union"),
            ),
            args=union_call_args,
        )

        return cst.Subscript(
            value=cst.Name(value="Annotated"),
            slice=[
                cst.SubscriptElement(
                    slice=cst.Index(
                        value=union_node,
                    ),
                ),
                cst.SubscriptElement(
                    slice=cst.Index(
                        value=union_call_node,
                    ),
                ),
            ],
        )

    @classmethod
    def _create_union_node_with_pipe_syntax(
        cls, types: Sequence[cst.BaseElement]
    ) -> cst.BaseExpression:
        type_names = [t.value for t in types]

        if not all(isinstance(t, cst.Name) for t in type_names):
            raise ValueError("Only names are supported for now")

        expression = " | ".join(name.value for name in type_names)  # type: ignore

        return cst.parse_expression(expression)