"""Alerts notice silence: per-rule sample tracking and a no-data mark

Revision ID: 0029_alert_no_data
Revises: 0028_alert_resolve_and_reset
Create Date: 2026-10-06
"""
from typing import Sequence, Union
from alembic import op
import sqlalchemy as sa

revision: str = "0029_alert_no_data"
down_revision: Union[str, None] = "0028_alert_resolve_and_reset"
branch_labels: Union[str, Sequence[str], None] = None
depends_on: Union[str, Sequence[str], None] = None


def upgrade() -> None:
    op.add_column("alert_rules", sa.Column("notify_no_data", sa.Boolean,
                                           nullable=False, server_default=sa.true()))
    op.add_column("alert_states", sa.Column("last_sample_at", sa.DateTime(timezone=True),
                                            nullable=True))
    op.add_column("alert_states", sa.Column("sample_interval_s", sa.Float, nullable=True))
    op.add_column("alert_states", sa.Column("no_data_since", sa.DateTime(timezone=True),
                                            nullable=True))
    # Seed each existing rule's last sample and usual gap from the last day of
    # its series, so the first silence check after the upgrade judges every
    # rule against what it has actually been receiving.
    op.execute("""
        UPDATE alert_states s
        SET last_sample_at = k.last_at, sample_interval_s = k.gap
        FROM (
            SELECT r.id AS rule_id, max(m.recorded_at) AS last_at,
                   EXTRACT(EPOCH FROM max(m.recorded_at) - min(m.recorded_at))
                       / NULLIF(count(*) - 1, 0) AS gap
            FROM alert_rules r
            JOIN plugin_metrics m
              ON m.source_module = r.source_module AND m.resource_name = r.resource_name
             AND m.metric_name = r.metric_name AND m.recorded_at > now() - interval '1 day'
            GROUP BY r.id
        ) k
        WHERE s.rule_id = k.rule_id
    """)


def downgrade() -> None:
    op.drop_column("alert_states", "no_data_since")
    op.drop_column("alert_states", "sample_interval_s")
    op.drop_column("alert_states", "last_sample_at")
    op.drop_column("alert_rules", "notify_no_data")