"""Fix frozen timestamp defaults from 0006 and add model indexes never migrated.

0006 declared ``server_default="now()"`` as a plain string. SQLAlchemy renders
that as the literal ``'now()'``, which PostgreSQL casts to a timestamp once,
when the column is created — every later row got that same fixed instant
instead of the insert time (agents.created_at/updated_at, jobs.created_at).
The models rely on the server default, so Jobs and Agents registered after
0006 all carried the migration's timestamp. Existing rows are left as they
are: their real creation time is not recoverable.

The models also declare ``index=True`` on three columns that no migration
ever indexed.

Revision ID: 0019_fix_timestamp_defaults
Revises: 0018_blocker_installation
"""
from alembic import op
import sqlalchemy as sa

revision = "0019_fix_timestamp_defaults"
down_revision = "0018_blocker_installation"
branch_labels = None
depends_on = None

_TIMESTAMP_COLUMNS = (("agents", "created_at"), ("agents", "updated_at"), ("jobs", "created_at"))
_MISSING_INDEXES = (
    ("ix_kb_observations_tenant_id", "kb_observations", "tenant_id"),
    ("ix_kb_observations_company_key", "kb_observations", "company_key"),
    ("ix_tenant_product_context_company_key", "tenant_product_context", "company_key"),
)


def upgrade():
    for table, column in _TIMESTAMP_COLUMNS:
        op.alter_column(table, column, server_default=sa.func.now(), existing_type=sa.DateTime(timezone=True), existing_nullable=False)
    for name, table, column in _MISSING_INDEXES:
        op.create_index(name, table, [column])


def downgrade():
    # The frozen-timestamp defaults are a bug and are deliberately not restored.
    for name, table, _column in reversed(_MISSING_INDEXES):
        op.drop_index(name, table_name=table)