import { db } from '../db/index.js';
import { planScaling } from './planner.js';
import { scalingSnapshot } from './snapshot.js';
import { liveScaling, type ScalingPolicy, type ScalingDecision } from '../../autoscaling.js';
import { deploymentStage } from '../provisioning/history.js';

export interface ScalingIntent { policy_id: string; revision: number; decision: string; operation_id: string }
export function scalingIntent(operationId: string): ScalingIntent | undefined {
    return db().prepare('SELECT policy_id,revision,decision,operation_id FROM autoscaling_decisions WHERE operation_id=? AND resolved=0').get(operationId) as ScalingIntent | undefined;
}
/** Rechecked before placement, after asynchronous preparation, and before dispatch. */
export function scalingAdmission(operationId: string): string | null {
    const intent = scalingIntent(operationId);
    if (!intent) return null;
    const row = db().prepare('SELECT * FROM autoscaling_policies WHERE id=?').get(intent.policy_id) as { id: string; settings: string; mode: ScalingPolicy['mode']; revision: number; paused_reason: string | null; owns_map: number } | undefined;
    let reason: string | null = null;
    const paused = (db().prepare("SELECT value FROM settings WHERE key='autoscaling_paused'").get() as { value: string } | undefined)?.value === '1';
    if (!row || !liveScaling(row.mode) || !row.owns_map || row.revision !== intent.revision || row.paused_reason || paused) reason = 'Autoscaling policy is paused or changed.';
    else {
        const policy: ScalingPolicy = { ...JSON.parse(row.settings), id: row.id, mode: row.mode, revision: row.revision, nextActionAt: 0, pausedReason: null, updatedAt: '' };
        const requested = JSON.parse(intent.decision) as ScalingDecision;
        if (requested.action === 'destroy' && row.mode !== 'create-destroy') return 'Automatic removal is disabled.';
        const snapshot = scalingSnapshot(policy, Date.now(), operationId);
        if (requested.action === 'create') {
            snapshot.reservedNames = snapshot.reservedNames.filter(n => n !== requested.server);
            snapshot.blockers = snapshot.blockers.filter(b => b !== `Unresolved native instance ${requested.server}.`);
        }
        const current = planScaling(policy, snapshot, Date.now());
        if (current.action !== requested.action || current.server !== requested.server) reason = `Autoscaling intent no longer eligible: ${current.reason}`;
    }
    if (reason) deploymentStage(operationId, reason, { blocker: { code: 'autoscaling', message: reason, automatic: true } });
    return reason;
}