import { db } from '../db/index.js';
import type { RebalanceCandidate, RebalanceSettings } from '../../rebalancing.js';
import { rebalanceMoveBlocker } from './planner.js';
import { rebalanceSnapshot } from './snapshot.js';

/** A delivered migration must finish even after the operator stops its parent run. */
export function rebalanceAdmission(operationId: string): string | null {
    const operation = db()
        .prepare('SELECT triggered_by FROM server_deployments WHERE id=?')
        .get(operationId) as { triggered_by: string } | undefined;
    if (!operation?.triggered_by.startsWith('rebalance:')) return null;
    const migration = db()
        .prepare(
            'SELECT remove_operation_id,removed_at FROM ec_host_migrations WHERE deployment_id=?'
        )
        .get(operationId) as
        { remove_operation_id: string | null; removed_at: string | null } | undefined;
    if (migration?.remove_operation_id || migration?.removed_at) return null;
    const row = db()
        .prepare(
            `SELECT m.candidate,r.settings,r.state FROM rebalancing_moves m
        JOIN rebalancing_runs r ON r.id=m.run_id WHERE m.operation_id=? AND m.state='moving'`
        )
        .get(operationId) as { candidate: string; settings: string; state: string } | undefined;
    if (!row || row.state !== 'running') return 'Rebalance run is no longer requesting this move.';
    const settings = JSON.parse(row.settings) as RebalanceSettings;
    return rebalanceMoveBlocker(
        rebalanceSnapshot(settings, operationId),
        JSON.parse(row.candidate) as RebalanceCandidate
    );
}

/** Cancelling an individual uncommitted move also withdraws the rest of that run. */
export function requestRebalanceStopForOperation(operationId: string): void {
    db()
        .prepare(
            `UPDATE rebalancing_runs SET state='stopping',updated_at=?,message='Stopping after the current move.'
        WHERE state='running' AND id IN (SELECT run_id FROM rebalancing_moves WHERE operation_id=?)`
        )
        .run(new Date().toISOString(), operationId);
}