"""Migration 036: provenance, the operator switch, and membership intervals.

The migration makes two irreversible-feeling judgement calls, and both need to
be pinned:

1. **Existing rows become ``manual``.** Provenance cannot be recovered from
   ``created_at``, and manual is the fail-safe guess — manual rows are never
   pruned, so a wrong guess costs an un-pruned symbol rather than one swept out
   of the scanner.
2. **Existing "off" states are carried into ``scan_disabled_on``.** Whoever set
   ``untracked_on`` is ambiguous, and re-entry clears the prune flag. Copying it
   is what stops an automated sync reactivating something switched off by hand.
"""

from __future__ import annotations

import importlib.util
from pathlib import Path

import sqlalchemy as sa
from alembic.migration import MigrationContext
from alembic.operations import Operations


def _load_migration_module():
    path = (
        Path(__file__).resolve().parents[2]
        / "alembic"
        / "versions"
        / "036_universe_membership.py"
    )
    spec = importlib.util.spec_from_file_location("migration_036", path)
    assert spec is not None and spec.loader is not None
    module = importlib.util.module_from_spec(spec)
    spec.loader.exec_module(module)
    return module


def _tickers_table(connection: sa.Connection) -> None:
    """The schema as migration 035 leaves it."""
    connection.execute(sa.text(
        """
        CREATE TABLE tickers (
            id INTEGER PRIMARY KEY,
            symbol VARCHAR(10) NOT NULL,
            delisted_on DATE,
            untracked_on DATE
        )
        """
    ))
    connection.execute(sa.text(
        "INSERT INTO tickers (id, symbol, delisted_on, untracked_on) VALUES "
        "(1, 'AAPL', NULL, NULL), "
        "(2, 'OFF', NULL, '2026-08-01')"
    ))


def _columns(connection: sa.Connection, table: str) -> set[str]:
    return {row[1] for row in connection.execute(sa.text(f"PRAGMA table_info({table})"))}


def test_upgrade_defaults_existing_rows_to_manual():
    migration = _load_migration_module()
    engine = sa.create_engine("sqlite://")

    with engine.begin() as connection:
        _tickers_table(connection)
        with Operations.context(MigrationContext.configure(connection)):
            migration.upgrade()

        rows = dict(connection.execute(
            sa.text("SELECT symbol, tracking_source FROM tickers")
        ).all())
        assert rows == {"AAPL": "manual", "OFF": "manual"}


def test_upgrade_carries_an_existing_off_state_into_the_operator_switch():
    migration = _load_migration_module()
    engine = sa.create_engine("sqlite://")

    with engine.begin() as connection:
        _tickers_table(connection)
        with Operations.context(MigrationContext.configure(connection)):
            migration.upgrade()

        rows = dict(connection.execute(
            sa.text("SELECT symbol, scan_disabled_on FROM tickers")
        ).all())
        # The ambiguous existing "off" is preserved on the column no sync clears.
        assert rows["OFF"] == "2026-08-01"
        # A row that was never off stays on.
        assert rows["AAPL"] is None


def test_upgrade_creates_the_membership_table_empty():
    migration = _load_migration_module()
    engine = sa.create_engine("sqlite://")

    with engine.begin() as connection:
        _tickers_table(connection)
        with Operations.context(MigrationContext.configure(connection)):
            migration.upgrade()

        assert {"ticker_id", "universe", "first_seen_on", "absent_since"} <= _columns(
            connection, "universe_memberships"
        )
        # History starts at first observation — the migration invents none.
        count = connection.execute(
            sa.text("SELECT COUNT(*) FROM universe_memberships")
        ).scalar_one()
        assert count == 0


def test_downgrade_removes_the_new_state_and_keeps_the_tickers():
    migration = _load_migration_module()
    engine = sa.create_engine("sqlite://")

    with engine.begin() as connection:
        _tickers_table(connection)
        with Operations.context(MigrationContext.configure(connection)):
            migration.upgrade()
        with Operations.context(MigrationContext.configure(connection)):
            migration.downgrade()

        columns = _columns(connection, "tickers")
        assert "tracking_source" not in columns
        assert "scan_disabled_on" not in columns
        # 035's column and the rows themselves are untouched.
        assert "untracked_on" in columns
        assert connection.execute(
            sa.text("SELECT symbol FROM tickers ORDER BY symbol")
        ).all() == [("AAPL",), ("OFF",)]