"""Reclassify cached Alpha checks without changing upstream evidence."""

import sqlalchemy as sa
from alembic import op

revision = "0018"
down_revision = "0017"
branch_labels = None
depends_on = None


def check_type(checks, separate_limits):
    """Frozen classification for reversible data migration; never import mutable app code."""
    checks = checks if isinstance(checks, list) else []
    if separate_limits:
        checks = [c for c in checks if not (isinstance(c, dict) and c.get("name") == "REGULAR_SUBMISSION")]
    valid = [c for c in checks if isinstance(c, dict)]
    failures = sum(c.get("result") == "FAIL" for c in valid)
    if failures:
        return "FAIL_1" if failures == 1 else "FAIL_2"
    if not checks or len(valid) != len(checks) or any(c.get("result") != "PASS" for c in valid):
        return "PENDING"
    return "PASS" if any(c.get("name") == "PROD_CORRELATION" for c in valid) else "PRE_CHECK"


def reclassify(separate_limits):
    """Update only affected derived columns, in bounded batches; raw snapshots stay intact."""
    table = sa.table("alphas", sa.column("id", sa.String()), sa.column("checks", sa.JSON()),
                     sa.column("check_type", sa.String()))
    connection = op.get_bind()
    last_id = None
    while True:
        query = sa.select(table.c.id, table.c.checks).order_by(table.c.id).limit(500)
        if last_id is not None:
            query = query.where(table.c.id > last_id)
        rows = connection.execute(query).mappings().all()
        if not rows:
            break
        updates = [
            {"snapshot_id": row["id"], "classification": check_type(row["checks"], separate_limits)}
            for row in rows if isinstance(row["checks"], list) and any(
                isinstance(c, dict) and c.get("name") == "REGULAR_SUBMISSION" for c in row["checks"])
        ]
        if updates:
            connection.execute(table.update().where(table.c.id == sa.bindparam("snapshot_id"))
                               .values(check_type=sa.bindparam("classification")), updates)
        last_id = rows[-1]["id"]


def upgrade():
    reclassify(True)


def downgrade():
    reclassify(False)