"""Test cases for the constraint solver used in type inference."""

from __future__ import annotations

from mypy.constraints import SUBTYPE_OF, SUPERTYPE_OF, Constraint
from mypy.solve import solve_constraints
from mypy.test.helpers import Suite, assert_equal
from mypy.test.typefixture import TypeFixture
from mypy.types import Type, TypeVarId, TypeVarType


class SolveSuite(Suite):
    def setUp(self) -> None:
        self.fx = TypeFixture()

    def test_empty_input(self) -> None:
        self.assert_solve([], [], [])

    def test_simple_supertype_constraints(self) -> None:
        self.assert_solve(
            [self.fx.t.id], [self.supc(self.fx.t, self.fx.a)], [(self.fx.a, self.fx.o)]
        )
        self.assert_solve(
            [self.fx.t.id],
            [self.supc(self.fx.t, self.fx.a), self.supc(self.fx.t, self.fx.b)],
            [(self.fx.a, self.fx.o)],
        )

    def test_simple_subtype_constraints(self) -> None:
        self.assert_solve([self.fx.t.id], [self.subc(self.fx.t, self.fx.a)], [self.fx.a])
        self.assert_solve(
            [self.fx.t.id],
            [self.subc(self.fx.t, self.fx.a), self.subc(self.fx.t, self.fx.b)],
            [self.fx.b],
        )

    def test_both_kinds_of_constraints(self) -> None:
        self.assert_solve(
            [self.fx.t.id],
            [self.supc(self.fx.t, self.fx.b), self.subc(self.fx.t, self.fx.a)],
            [(self.fx.b, self.fx.a)],
        )

    def test_unsatisfiable_constraints(self) -> None:
        # The constraints are impossible to satisfy.
        self.assert_solve(
            [self.fx.t.id],
            [self.supc(self.fx.t, self.fx.a), self.subc(self.fx.t, self.fx.b)],
            [None],
        )

    def test_exactly_specified_result(self) -> None:
        self.assert_solve(
            [self.fx.t.id],
            [self.supc(self.fx.t, self.fx.b), self.subc(self.fx.t, self.fx.b)],
            [(self.fx.b, self.fx.b)],
        )

    def test_multiple_variables(self) -> None:
        self.assert_solve(
            [self.fx.t.id, self.fx.s.id],
            [
                self.supc(self.fx.t, self.fx.b),
                self.supc(self.fx.s, self.fx.c),
                self.subc(self.fx.t, self.fx.a),
            ],
            [(self.fx.b, self.fx.a), (self.fx.c, self.fx.o)],
        )

    def test_no_constraints_for_var(self) -> None:
        self.assert_solve([self.fx.t.id], [], [self.fx.uninhabited])
        self.assert_solve(
            [self.fx.t.id, self.fx.s.id], [], [self.fx.uninhabited, self.fx.uninhabited]
        )
        self.assert_solve(
            [self.fx.t.id, self.fx.s.id],
            [self.supc(self.fx.s, self.fx.a)],
            [self.fx.uninhabited, (self.fx.a, self.fx.o)],
        )

    def test_simple_constraints_with_dynamic_type(self) -> None:
        self.assert_solve(
            [self.fx.t.id], [self.supc(self.fx.t, self.fx.anyt)], [(self.fx.anyt, self.fx.anyt)]
        )
        self.assert_solve(
            [self.fx.t.id],
            [self.supc(self.fx.t, self.fx.anyt), self.supc(self.fx.t, self.fx.anyt)],
            [(self.fx.anyt, self.fx.anyt)],
        )
        self.assert_solve(
            [self.fx.t.id],
            [self.supc(self.fx.t, self.fx.anyt), self.supc(self.fx.t, self.fx.a)],
            [(self.fx.anyt, self.fx.anyt)],
        )

        self.assert_solve(
            [self.fx.t.id], [self.subc(self.fx.t, self.fx.anyt)], [(self.fx.anyt, self.fx.anyt)]
        )
        self.assert_solve(
            [self.fx.t.id],
            [self.subc(self.fx.t, self.fx.anyt), self.subc(self.fx.t, self.fx.anyt)],
            [(self.fx.anyt, self.fx.anyt)],
        )
        # self.assert_solve([self.fx.t.id],
        #                   [self.subc(self.fx.t, self.fx.anyt),
        #                    self.subc(self.fx.t, self.fx.a)],
        #                   [(self.fx.anyt, self.fx.anyt)])
        # TODO: figure out what this should be after changes to meet(any, X)

    def test_both_normal_and_any_types_in_results(self) -> None:
        # If one of the bounds is any, we promote the other bound to
        # any as well, since otherwise the type range does not make sense.
        self.assert_solve(
            [self.fx.t.id],
            [self.supc(self.fx.t, self.fx.a), self.subc(self.fx.t, self.fx.anyt)],
            [(self.fx.anyt, self.fx.anyt)],
        )

        self.assert_solve(
            [self.fx.t.id],
            [self.supc(self.fx.t, self.fx.anyt), self.subc(self.fx.t, self.fx.a)],
            [(self.fx.anyt, self.fx.anyt)],
        )

    def assert_solve(
        self,
        vars: list[TypeVarId],
        constraints: list[Constraint],
        results: list[None | Type | tuple[Type, Type]],
    ) -> None:
        res: list[Type | None] = []
        for r in results:
            if isinstance(r, tuple):
                res.append(r[0])
            else:
                res.append(r)
        actual = solve_constraints(vars, constraints)
        assert_equal(str(actual), str(res))

    def supc(self, type_var: TypeVarType, bound: Type) -> Constraint:
        return Constraint(type_var.id, SUPERTYPE_OF, bound)

    def subc(self, type_var: TypeVarType, bound: Type) -> Constraint:
        return Constraint(type_var.id, SUBTYPE_OF, bound)