"""Harden V3 heartbeat identity and concurrent updates.

Revision ID: 202607260001
Revises: 202607150001
Create Date: 2026-07-26
"""

from alembic import op
import sqlalchemy as sa


revision = "202607260001"
down_revision = "202607150001"
branch_labels = None
depends_on = None

HEARTBEAT_TABLE = "system_heartbeats"
HEARTBEAT_IDENTITY_CONSTRAINT = "uq_system_heartbeat_component_instance"


def upgrade() -> None:
    op.execute(
        sa.text(
            """
            DELETE FROM system_heartbeats
            WHERE id IN (
                SELECT id
                FROM (
                    SELECT
                        id,
                        ROW_NUMBER() OVER (
                            PARTITION BY component, instance_id
                            ORDER BY last_seen_at DESC, id DESC
                        ) AS duplicate_rank
                    FROM system_heartbeats
                ) ranked
                WHERE duplicate_rank > 1
            )
            """
        )
    )
    with op.batch_alter_table(HEARTBEAT_TABLE) as batch_op:
        batch_op.create_unique_constraint(
            HEARTBEAT_IDENTITY_CONSTRAINT,
            ["component", "instance_id"],
        )


def downgrade() -> None:
    with op.batch_alter_table(HEARTBEAT_TABLE) as batch_op:
        batch_op.drop_constraint(HEARTBEAT_IDENTITY_CONSTRAINT, type_="unique")