"""Tests for the extension registry and its immutable build product."""

from __future__ import annotations

import pytest

from deerflow.extensions.registry import EMPTY_EXTENSIONS, ExtensionRegistry


class _Contributor:
    def __init__(self, tag: str = "") -> None:
        self.tag = tag


def test_empty_registry_builds_with_all_flags_false():
    loaded = ExtensionRegistry().build()
    assert loaded.has_middleware_contributors is False
    assert loaded.needs_task_store is False


def test_empty_singleton_matches_an_empty_build():
    assert EMPTY_EXTENSIONS.has_middleware_contributors is False
    assert EMPTY_EXTENSIONS.needs_task_store is False


def test_middleware_contributions_require_a_task_store():
    registry = ExtensionRegistry()
    with registry.attributed_to("demo:install"):
        registry.middlewares(_Contributor())

    assert registry.build().needs_task_store is True


def test_entries_carry_their_source():
    registry = ExtensionRegistry()
    contributor = _Contributor("mw")
    with registry.attributed_to("demo_ext:install"):
        registry.middlewares(contributor)
    loaded = registry.build()
    assert loaded.middleware_contributors == (("demo_ext:install", contributor),)
    assert loaded.has_middleware_contributors is True


def test_registration_order_is_preserved():
    registry = ExtensionRegistry()
    first, second = _Contributor("a"), _Contributor("b")
    with registry.attributed_to("a_ext:install"):
        registry.middlewares(first)
    with registry.attributed_to("b_ext:install"):
        registry.middlewares(second)
    loaded = registry.build()
    assert [source for source, _ in loaded.middleware_contributors] == ["a_ext:install", "b_ext:install"]


def test_discard_removes_every_entry_of_one_source():
    """A partially-registered extension is worse than an absent one: the data
    it produces looks complete but is not."""
    registry = ExtensionRegistry()
    keep, drop = _Contributor("keep"), _Contributor("drop")
    with registry.attributed_to("good:install"):
        registry.middlewares(keep)
    with registry.attributed_to("bad:install"):
        registry.middlewares(drop)
    registry.discard("bad:install")
    loaded = registry.build()
    assert loaded.middleware_contributors == (("good:install", keep),)


def test_registering_outside_attributed_to_raises():
    registry = ExtensionRegistry()
    with pytest.raises(RuntimeError, match="attributed_to"):
        registry.middlewares(_Contributor())


def test_build_result_is_frozen():
    loaded = ExtensionRegistry().build()
    with pytest.raises(Exception):
        loaded.middleware_contributors = ()  # type: ignore[misc]


def test_app_store_is_created_at_build_time():
    """The app store must exist before binding so the registration phase and
    the binding phase see the same object."""
    loaded = ExtensionRegistry().build()
    assert loaded.app_store is not None
    assert loaded.app_store.scope_id == "app"