"""The newest sample of each metric, kept beside plugin_metrics (#5208)

Revision ID: 0030_plugin_metric_latest
Revises: 0029_alert_no_data
Create Date: 2026-10-07
"""
from typing import Sequence, Union
from alembic import op
import sqlalchemy as sa

revision: str = "0030_plugin_metric_latest"
down_revision: Union[str, None] = "0029_alert_no_data"
branch_labels: Union[str, Sequence[str], None] = None
depends_on: Union[str, Sequence[str], None] = None


def upgrade() -> None:
    op.create_table(
        "plugin_metric_latest",
        sa.Column("source_module", sa.String(64), primary_key=True),
        sa.Column("resource_name", sa.String(255), primary_key=True),
        sa.Column("metric_name", sa.String(128), primary_key=True),
        sa.Column("value", sa.Float, nullable=False),
        sa.Column("recorded_at", sa.DateTime(timezone=True), nullable=False),
    )
    # Seed from history without a full scan: step through the distinct keys of
    # the (source, resource, metric, recorded_at) index one probe at a time,
    # then take each key's newest row with a backward probe of the same index.
    op.execute("""
        WITH RECURSIVE k AS (
            (SELECT source_module, resource_name, metric_name FROM plugin_metrics
             ORDER BY source_module, resource_name, metric_name LIMIT 1)
            UNION ALL
            SELECT n.source_module, n.resource_name, n.metric_name
            FROM k, LATERAL (
                SELECT p.source_module, p.resource_name, p.metric_name FROM plugin_metrics p
                WHERE (p.source_module, p.resource_name, p.metric_name)
                    > (k.source_module, k.resource_name, k.metric_name)
                ORDER BY p.source_module, p.resource_name, p.metric_name LIMIT 1
            ) n
        )
        INSERT INTO plugin_metric_latest
            (source_module, resource_name, metric_name, value, recorded_at)
        SELECT k.source_module, k.resource_name, k.metric_name, l.value, l.recorded_at
        FROM k, LATERAL (
            SELECT p.value, p.recorded_at FROM plugin_metrics p
            WHERE p.source_module = k.source_module AND p.resource_name = k.resource_name
              AND p.metric_name = k.metric_name
            ORDER BY p.recorded_at DESC LIMIT 1
        ) l
    """)


def downgrade() -> None:
    op.drop_table("plugin_metric_latest")