"""Unit: sources-version counter helpers (phase 53, task 01).

``app.rag.sources_meta`` runs against the local compose Postgres
(``podman compose up -d db``) — the house DB-test pattern: the helpers
are thin session wrappers whose contract (seeded single row, flush-not
commit, defensive absence) only holds against a real database. Skips
with clear instructions when the stack is not up.

A fixture resets ``sources_meta`` to the migration-0010 seed state
(id 1, version 0) before and after every test, so the suite leaves the
dev DB exactly as the migration left it.
"""
from __future__ import annotations

import pytest
from sqlalchemy import text
from sqlalchemy.orm import Session

from app.db import SessionLocal
from app.models import SourcesMeta
from app.rag.sources_meta import bump_sources_version, current_sources_version


@pytest.fixture()
def seeded_sources_meta(db: Session):
    """Reset the counter to the migration-0010 seed (id 1, version 0)."""
    db.execute(text("DELETE FROM sources_meta"))
    db.add(SourcesMeta(id=1, version=0))
    db.commit()
    yield
    db.execute(text("DELETE FROM sources_meta"))
    db.add(SourcesMeta(id=1, version=0))
    db.commit()


def test_current_absent_row_returns_zero_without_raising(
    db: Session, seeded_sources_meta: None
) -> None:
    """Defensive: a deleted seed row reads as 0 — never an exception."""
    db.execute(text("DELETE FROM sources_meta"))
    db.commit()
    assert current_sources_version(db) == 0


def test_first_bump_zero_to_one(db: Session, seeded_sources_meta: None) -> None:
    """Seeded at 0 (the pre-counter KB), the first bump returns 1 and
    ``current`` reflects it."""
    assert current_sources_version(db) == 0
    assert bump_sources_version(db) == 1
    db.commit()  # the caller commits — the helper only flushes
    assert current_sources_version(db) == 1


def test_second_bump_increments(db: Session, seeded_sources_meta: None) -> None:
    """Bumps are monotonic: 0 → 1 → 2, one step per KB-changing sync."""
    assert bump_sources_version(db) == 1
    db.commit()
    assert bump_sources_version(db) == 2
    db.commit()
    assert current_sources_version(db) == 2


def test_bump_absent_row_upserts_to_one(db: Session, seeded_sources_meta: None) -> None:
    """Upsert semantics: a deleted seed row is recreated by the first
    bump (version 0 → 1), never left dangling."""
    db.execute(text("DELETE FROM sources_meta"))
    db.commit()
    assert bump_sources_version(db) == 1
    db.commit()
    row = db.get(SourcesMeta, 1)
    assert row is not None, "the single row must be recreated"
    assert row.id == 1
    assert row.version == 1
    assert row.updated_at is not None, "updated_at must be server-stamped"


def test_bump_flushes_without_committing(db: Session, seeded_sources_meta: None) -> None:
    """The helper flushes, it does not commit: a rolled-back session
    must roll the bump back with it (each sync path owns its
    transaction)."""
    assert bump_sources_version(db) == 1
    db.rollback()
    assert current_sources_version(db) == 0, "the uncommitted bump must roll back"


def test_bumps_in_separate_sessions_progress(db: Session, seeded_sources_meta: None) -> None:
    """One writer at a time is the deployment reality, but two bumps in
    two sessions must not race to the same value: the second session
    sees the committed increment and lands on the next generation."""
    assert bump_sources_version(db) == 1
    db.commit()

    other = SessionLocal()
    try:
        assert bump_sources_version(other) == 2
        other.commit()
    finally:
        other.close()

    db.expire_all()  # drop the stale identity-map state
    assert current_sources_version(db) == 2