"""Alembic migration smoke test.

We do not boot a real Postgres in CI; instead we point Alembic at an in-process
SQLite database and verify:

- ``alembic upgrade head`` succeeds offline (SQL generation) using the real
  migration files, exercising every column type and constraint declaration;
- ``downgrade base`` rewinds without errors.

This catches typos and broken migration ordering early without requiring the
full backing-service compose stack to be online.
"""

from __future__ import annotations

import sys
from pathlib import Path

import pytest
from alembic import command
from alembic.config import Config
from alembic.script import ScriptDirectory

ROOT = Path(__file__).resolve().parents[1]
sys.path.insert(0, str(ROOT))


@pytest.fixture
def alembic_cfg(tmp_path, monkeypatch):
    """Configure Alembic against an isolated SQLite file."""
    db_file = tmp_path / "legacyhub.db"
    monkeypatch.setenv("POSTGRES_HOST", "127.0.0.1")
    monkeypatch.setenv("POSTGRES_PORT", "5432")
    cfg = Config(str(ROOT / "alembic.ini"))
    cfg.set_main_option("script_location", str(ROOT / "app" / "db" / "migrations"))
    cfg.set_main_option("sqlalchemy.url", f"sqlite:///{db_file}")
    return cfg


def test_migration_offline_emits_sql(alembic_cfg, tmp_path):
    """Offline mode generates SQL for every table; verify ``documents`` appears
    and the TeamHUB AssetManifest ingest job table is part of the linear head.
    SQLite has no JSONB but Alembic's offline mode happily emits the raw DDL for
    inspection.
    """
    out_file = tmp_path / "upgrade.sql"
    # ``--sql`` mode bypasses dialect-specific runtime, perfect for a fast check.
    with out_file.open("w", encoding="utf-8") as f:
        old_stdout = sys.stdout
        sys.stdout = f
        try:
            command.upgrade(alembic_cfg, "head", sql=True)
        finally:
            sys.stdout = old_stdout

    sql = out_file.read_text(encoding="utf-8")
    assert "CREATE TABLE documents" in sql
    assert "CREATE TABLE chunks" in sql
    assert "CREATE TABLE processing_events" in sql
    assert "CREATE TABLE asset_ingest_jobs" in sql
    assert "CREATE TABLE audit_log" in sql
    # Constraint sanity
    assert "uq_chunks_doc_idx" in sql
    assert "uq_pages_doc_page" in sql
    assert "uq_asset_ingest_identity" in sql


def test_revision_history_is_linear(alembic_cfg):
    """The project keeps a single linear migration head."""
    script = ScriptDirectory.from_config(alembic_cfg)
    heads = script.get_heads()
    assert len(heads) == 1, f"expected one head, got: {heads}"
    assert heads == ["0003_audit_log"]
    revisions = [rev.revision for rev in script.walk_revisions()]
    assert revisions == ["0003_audit_log", "0002_asset_ingest_jobs", "0001_initial"]