"""The `lesson` kind — its trigger, its title, and its place in the vocabulary.

WHY THIS EXISTS (milestone 385 step 2, #3729)

A lesson is a note that must be findable by WHEN IT APPLIES rather than by what
it is about. That is a document-shape fact: the trigger has to reach the
embedded text, and decision #4157 put it in `notes.data` with a mirror in the
title and the head of the body — the shape snippets already use.

THE ONE THAT MATTERS MOST

`test_one_join_builds_every_trigger_title`. Three kinds now rank on a
`{subject} — {trigger}` title: rules, snippets and lessons. That join had three
implementations before this step and would have had four; #3207 records what
that costs. The guard is behavioural rather than `assert a is b`, because the
three are reached through different public names and a test that compared
identities would pass on a re-implementation that merely re-exported.

WHAT IS DELIBERATELY NOT TESTED HERE

That the database accepts `note_type='lesson'`. `note_type` carries no CHECK —
only `task_kind` does — so there is nothing to assert against in a unit test,
and asserting the absence would pin the schema's current shape rather than the
behaviour that matters. The real guard is in the integration lane, where a
lesson is written and read back: it holds whether or not a constraint exists,
and goes red the day one is added without this value.
"""
from types import SimpleNamespace

from scribe.services import knowledge as knowledge_svc
from scribe.services import lessons as lessons_svc
from scribe.services import snippets as snippets_svc
from scribe.services.embeddings import trigger_title


def _note(data=None, body=""):
    return SimpleNamespace(data=data, body=body)


def test_the_trigger_is_read_from_the_indexed_mirror():
    note = _note(data={"when_to_apply": "a stack trace, and it is still broken"})
    assert lessons_svc.lesson_trigger(note) == "a stack trace, and it is still broken"


def test_the_body_answers_when_the_mirror_is_absent():
    """Not dead code. A row written before the mirror existed is still readable,
    and an absent mirror has to degrade to the right answer rather than to
    silence — the discipline `snippet_fields` follows for the same reason."""
    note = _note(body="**When to apply:** about to reach for a second hypothesis\n\nbody")
    assert lessons_svc.lesson_trigger(note) == "about to reach for a second hypothesis"


def test_the_mirror_wins_when_both_are_present():
    note = _note(
        data={"when_to_apply": "from the mirror"},
        body="**When to apply:** from the body",
    )
    assert lessons_svc.lesson_trigger(note) == "from the mirror"


def test_no_trigger_reads_as_empty_rather_than_raising():
    """A lesson with no trigger is unreachable, not broken. Whatever refuses to
    write one belongs on the write path; a reader's job is to say so plainly."""
    assert lessons_svc.lesson_trigger(_note()) == ""
    assert lessons_svc.lesson_trigger(_note(data={}, body="no trigger line here")) == ""


def test_one_join_builds_every_trigger_title():
    """THE GUARD. Rules, snippets and lessons rank on the same title shape.

    Behavioural on purpose — see the module docstring. Each of the three is
    called through the name its own callers use, so a fourth hand-rolled copy
    fails here even though it would look correct in isolation.
    """
    subject, trigger = "Pace hard debugging", "a stack trace and it is still broken"
    expected = f"{subject} — {trigger}"

    assert trigger_title(subject, trigger) == expected
    assert lessons_svc.compose_title(subject, trigger) == expected
    assert snippets_svc.compose_title(subject, trigger) == expected


def test_a_subject_with_no_trigger_degrades_to_the_subject():
    """It still embeds, just less sharply — an argument for backfilling
    triggers, not for padding the title with whatever text is to hand."""
    assert trigger_title("debounce", "") == "debounce"
    assert lessons_svc.compose_title("  debounce  ") == "debounce"
    assert trigger_title("", "when it applies") == "when it applies"


def test_the_kind_is_in_the_browse_vocabulary():
    """A kind the browse surface does not know is a record nobody can filter to.

    Asserted through the public table rather than a literal, because the door's
    validation, the counts and both dialects of the type filter are all
    generated from it (#3161) — so this is the one place that decides.
    """
    assert lessons_svc.LESSON_NOTE_TYPE in knowledge_svc.FACET_TYPES
    assert lessons_svc.LESSON_NOTE_TYPE in knowledge_svc.NON_TASK_FACETS


def test_the_global_kinds_list_names_the_lesson_and_nothing_else():
    """`embeddings.GLOBAL_NOTE_TYPES` spells "lesson" as a literal because
    `services.lessons` imports `trigger_title` from that module, so importing
    it back would close a cycle (milestone 385 step 3). The copy is pinned
    here instead — the one thing a literal costs is that it can drift, and
    this is what stops it.
    """
    from scribe.services.embeddings import GLOBAL_NOTE_TYPES

    assert GLOBAL_NOTE_TYPES == (lessons_svc.LESSON_NOTE_TYPE,)


def test_a_lesson_is_not_a_task_on_either_arm_of_the_filter():
    """The cell left empty on purpose (#3163).

    `is_task` IS `status is not None`, so a lesson that acquired a status would
    become a task and start appearing in open-work listings — the one way
    filling a field in by accident changes what the record IS.
    """
    assert knowledge_svc.facet_is_task(lessons_svc.LESSON_NOTE_TYPE) is False
    lesson = SimpleNamespace(note_type="lesson", is_task=False, task_kind="work")
    assert knowledge_svc.matches_facet(lesson, "lesson") is True
    assert knowledge_svc.matches_facet(lesson, "task") is False
    # And it does not answer to another kind's facet.
    assert knowledge_svc.matches_facet(lesson, "note") is False