import { config } from '../config.js';
import { db } from '../db/index.js';
import { komodoInspectHealthy, komodoRestart, komodoRuntimeAction } from '../integrations/komodo.js';
import { rconStatusResult } from '../integrations/rcon.js';
import { beginDeployment, deploymentStage, finishDeployment } from '../fleet/deployments.js';

// Komodo queues restart work. Don't mistake the still-running old container
// for a completed restart when an API kick immediately follows the request.
const HEALTH_POLL_MS = 15_000;
const requestsInFlight = new Set<string>();

interface RestartSlot {
    server: string;
    requested_at: string;
    checked_at: string | null;
    healthy_at: string | null;
    players: number | null;
    error: string | null;
    operation_id: string | null;
}

function slotFor(server: string): RestartSlot | undefined {
    return db().prepare('SELECT * FROM restart_rollout WHERE server = ?').get(server) as RestartSlot | undefined;
}

/** The queued restart may still expose the previous healthy container. */
export function restartSettling(server: string): boolean {
    const slot = slotFor(server);
    return requestsInFlight.has(server) || !!(slot && !slot.healthy_at
        && Date.now() - Date.parse(slot.requested_at) < HEALTH_POLL_MS);
}

export function rolloutWaitReason(server: string, operationId = ''): string | null {
    if (db().prepare(`SELECT 1 FROM server_deployments WHERE server = ? AND id != ?
        AND ((action IN ('start','stop','rebuild') AND state IN ('running','awaiting-health'))
            OR (action = 'destroy' AND state IN ('waiting','running')))`).get(server, operationId)) {
        return 'Waiting for the current provisioning operation';
    }
    const slot = slotFor(server);
    if (slot?.healthy_at === null) {
        return `Waiting for the previous restart of this server to recover${slot.error ? `: ${slot.error}` : ''}`;
    }
    const { n } = db().prepare('SELECT COUNT(*) AS n FROM restart_rollout WHERE healthy_at IS NULL').get() as { n: number };
    return n >= config.restartConcurrency ? 'Queued for a rolling restart; waiting for another server to recover' : null;
}

export type RolloutRestartResult =
    | { kind: 'started' }
    | { kind: 'queued'; message: string }
    | { kind: 'failed'; message: string };

/** Reserve capacity before any async I/O; callers still check for players first. */
export async function restartInRollout(server: string, options: { operationId?: string; action?: 'start' | 'restart'; triggeredBy?: string } = {}): Promise<RolloutRestartResult> {
    let operationId = options.operationId;
    const waitReason = db().transaction(() => {
        const reason = rolloutWaitReason(server, operationId);
        if (reason) return reason;
        operationId ??= beginDeployment(server, options.action ?? 'restart', options.triggeredBy ?? 'automation');
        db().prepare(`INSERT INTO restart_rollout (server, requested_at, operation_id) VALUES (?, ?, ?)
            ON CONFLICT(server) DO UPDATE SET requested_at = excluded.requested_at,
                checked_at = NULL, healthy_at = NULL, players = NULL, error = NULL, operation_id = excluded.operation_id`)
            .run(server, new Date().toISOString(), operationId);
        deploymentStage(operationId, options.action === 'start' ? 'Starting container' : 'Restarting container');
        return null;
    }).immediate();
    if (waitReason) return { kind: 'queued', message: waitReason };

    requestsInFlight.add(server);
    db().prepare(`UPDATE servers SET container_state = 'restarting', last_error = NULL, last_reply_snippet = NULL,
        game_started_at = NULL, game_ended_at = NULL WHERE name = ?`).run(server);
    try {
        const result = options.action === 'start' ? await komodoRuntimeAction(server, 'start') : await komodoRestart(server);
        if (result.ok) {
            db().prepare("UPDATE server_deployments SET state = 'awaiting-health' WHERE id = ?").run(operationId);
            deploymentStage(operationId!, 'Waiting for container and RCON health');
            return { kind: 'started' };
        }
        // These failures cannot have queued a remote restart. Other failures
        // (especially a timeout) may have: retain capacity until recovery.
        if (result.kind === 'no-name' || result.kind === 'unconfigured') {
            db().prepare('DELETE FROM restart_rollout WHERE server = ?').run(server);
        } else {
            db().prepare('UPDATE restart_rollout SET error = ? WHERE server = ?').run(`komodo: ${result.message}`, server);
        }
        finishDeployment(operationId!, { ok: false, message: `komodo: ${result.message}` });
        return { kind: 'failed', message: `komodo: ${result.message}` };
    } catch (err) {
        const message = `komodo: ${(err as Error).message}`;
        db().prepare('UPDATE restart_rollout SET error = ? WHERE server = ?').run(message, server);
        finishDeployment(operationId!, { ok: false, message });
        return { kind: 'failed', message };
    } finally {
        // Start the grace period at completion, including slow/failed requests.
        db().prepare('UPDATE restart_rollout SET requested_at = ? WHERE server = ?')
            .run(new Date().toISOString(), server);
        requestsInFlight.delete(server);
    }
}

let refreshInFlight: Promise<void> | null = null;

/** Poll all occupied slots, even if their originating beta was already closed. */
export function refreshRestartRollout(): Promise<void> {
    if (refreshInFlight) return refreshInFlight;
    refreshInFlight = refresh().finally(() => { refreshInFlight = null; });
    return refreshInFlight;
}

async function refresh(): Promise<void> {
    // Adopt work started before this feature was installed. INSERT OR IGNORE
    // preserves completed slots and never resets a newer restart's progress.
    db().prepare(`INSERT OR IGNORE INTO restart_rollout (server, requested_at)
        SELECT server, MAX(restarted_at) FROM deployment_servers
        WHERE restart_state IN ('pending','failed') AND restarted_at IS NOT NULL GROUP BY server`).run();
    db().prepare(`INSERT OR IGNORE INTO restart_rollout (server, requested_at)
        SELECT bs.server, MAX(COALESCE(bs.restarted_at, bs.updated_at))
        FROM beta_servers bs JOIN betas b ON b.id = bs.beta_id
        WHERE b.state = 'running' AND bs.stage IN ('restarting','awaiting-health') GROUP BY bs.server`).run();

    const slots = db().prepare('SELECT * FROM restart_rollout WHERE healthy_at IS NULL ORDER BY requested_at, server')
        .all() as RestartSlot[];
    for (const slot of slots) {
        if (requestsInFlight.has(slot.server)) continue;
        if (Date.now() - Date.parse(slot.checked_at ?? slot.requested_at) < HEALTH_POLL_MS) continue;
        let error: string | null = null;
        let players: number | null = null;
        try {
            const health = await komodoInspectHealthy(slot.server);
            if (!health.ok) {
                error = `unhealthy: ${health.reason}${health.snippet ? ` snippet=${health.snippet.slice(0, 400)}` : ''}`;
            } else {
                const rcon = await rconStatusResult(slot.server);
                if (!rcon.ok) error = `rcon not answering: ${rcon.reason}`;
                else players = rcon.status.players;
            }
        } catch (err) {
            error = `health check: ${(err as Error).message}`;
        }
        const now = new Date().toISOString();
        db().prepare(`UPDATE restart_rollout SET checked_at = ?, healthy_at = ?, players = ?, error = ?
            WHERE server = ? AND requested_at = ? AND healthy_at IS NULL`)
            .run(now, error ? null : now, players, error, slot.server, slot.requested_at);
        if (slot.operation_id && db().prepare("SELECT 1 FROM server_deployments WHERE id = ? AND state = 'awaiting-health'").get(slot.operation_id)) {
            if (error) deploymentStage(slot.operation_id, 'Waiting for health: ' + error);
            else {
                deploymentStage(slot.operation_id, 'Verified container and RCON health');
                finishDeployment(slot.operation_id, { ok: true });
            }
        }
    }
}

export function rolloutHealth(server: string): { ok: true; players: number } | { ok: false; reason: string } {
    const slot = slotFor(server);
    if (slot?.healthy_at) return { ok: true, players: slot.players ?? 0 };
    return { ok: false, reason: slot?.error ?? 'Waiting for restart recovery and health checks' };
}