import { fleetSettings } from '../settings.js';
import { db } from '../db/index.js';
import { komodoInspectHealthy, komodoRestart, komodoRuntimeAction } from '../integrations/komodo.js';
import { probeServerStatus } from '../fleet/status-evidence.js';
import { deploymentStage, finishDeployment } from './history.js';
import { applyStagedFilesForOperation } from '../fleet/staged-files.js';
import type { RuntimeAction } from '../../provisioning.js';
import type { ProvisioningBlocker } from '../../provisioning-detail.js';
import { recordProgress, type ProgressUpdate } from './progress.js';
import { nativeDeployment } from '../backends/native.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 Map<string, string>();
export const restartRequestInFlight = (server: string) => requestsInFlight.has(server);

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;
}

export function restartRecoveryPending(server: string): boolean {
    return slotFor(server)?.healthy_at === null;
}

/** 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 = '', action: RuntimeAction = 'restart'): string | null {
    return rolloutBlocker(server, operationId, action)?.message ?? null;
}

export function rolloutBlocker(server: string, operationId = '', action: RuntimeAction = 'restart'): ProvisioningBlocker | null {
    const conflict = db().prepare(`SELECT id FROM server_deployments WHERE server = ? AND id != ? AND server_deleted_at IS NULL
        AND ((action IN ('start','stop','rebuild') AND state IN ('running','awaiting-health'))
            OR (action = 'destroy' AND state IN ('waiting','running')))`).get(server, operationId) as { id: string } | undefined;
    if (conflict) {
        return { code: 'operation-conflict', message: 'Waiting for the current provisioning operation', automatic: true,
            href: `/provisioning/${encodeURIComponent(conflict.id)}`, label: 'Blocking operation' };
    }
    const slot = slotFor(server);
    const ownHandoff = slot?.operation_id === operationId && !!db().prepare(`SELECT 1 FROM server_deployments d
        WHERE d.id = ? AND d.server_deleted_at IS NULL AND d.action IN ('restart','rebuild') AND EXISTS (
            SELECT 1 FROM provisioning_sources s WHERE s.operation_id = d.id AND s.kind = 'watchdog')`).get(operationId);
    if (slot?.healthy_at === null && !ownHandoff) {
        return { code: 'previous-recovery', message: `Waiting for this server to recover from its previous operation${slot.error ? `: ${slot.error}` : ''}`, automatic: true,
            href: slot.operation_id ? `/provisioning/${encodeURIComponent(slot.operation_id)}` : null, label: 'Previous operation' };
    }
    const { n } = db().prepare('SELECT COUNT(*) AS n FROM restart_rollout WHERE healthy_at IS NULL').get() as { n: number };
    return n - (ownHandoff && slot?.healthy_at === null ? 1 : 0) >= fleetSettings().restartConcurrency
        ? { code: 'restart-capacity', message: `Queued to ${action}; waiting for another server to recover`, automatic: true } : 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' }): Promise<RolloutRestartResult> {
    const operationId = options.operationId;
    const waitReason = db().transaction(() => {
        if (!db().prepare('SELECT 1 FROM server_deployments WHERE id = ? AND server_deleted_at IS NULL').get(operationId)) return 'Original server was deleted';
        const reason = rolloutWaitReason(server, operationId, options.action);
        if (reason) return reason;
        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);
        recordProgress(operationId, { blocker: null, recovery: { state: 'held', message: 'Restart recovery capacity reserved.', operationId } });
        return null;
    }).immediate();
    if (waitReason) return { kind: 'queued', message: waitReason };

    // Every gate, including rollout capacity, has cleared. No async work may
    // intervene between applying these files and submitting the restart.
    try {
        applyStagedFilesForOperation(operationId, server);
    } catch (err) {
        const message = `File activation failed: ${(err as Error).message}`;
        db().transaction(() => {
            db().prepare('DELETE FROM restart_rollout WHERE server = ? AND operation_id = ?').run(server, operationId);
            recordProgress(operationId, { recovery: { state: 'released', message: 'Capacity released before any remote command: file activation failed.', operationId } });
            finishDeployment(operationId, { ok: false, message });
        })();
        return { kind: 'failed', message };
    }
    db().transaction(() => {
        db().prepare('UPDATE server_deployments SET submitted_at = ? WHERE id = ?').run(new Date().toISOString(), operationId);
        deploymentStage(operationId, options.action === 'start' ? 'Starting container' : 'Restarting container', {
            phase: 'container-action', blocker: null, checks: [], checkpoint: { key: 'eligibility', label: 'Eligibility checks passed' },
            command: { state: 'attempted', message: `${options.action === 'start' ? 'Start' : 'Restart'} submission attempted.` }
        });
    })();
    requestsInFlight.set(server, operationId);
    db().prepare(`UPDATE servers SET container_state = 'restarting', last_error = NULL, rcon_failures = 0, 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 (!db().prepare('SELECT 1 FROM server_deployments WHERE id = ? AND server_deleted_at IS NULL').get(operationId)) return { kind: 'failed', message: 'Original server was deleted' };
        if (result.ok) {
            db().transaction(() => {
                db().prepare("UPDATE server_deployments SET state = 'awaiting-health' WHERE id = ? AND server_deleted_at IS NULL").run(operationId);
                deploymentStage(operationId!, 'Waiting for container and game health (RCON or fresh telemetry)', {
                    phase: 'verify-container', command: { state: 'accepted', message: 'Komodo accepted the request; recovery still requires verification.' },
                    checkpoint: { key: 'container-action', label: 'Container command accepted' },
                    blocker: { code: 'recovery-settling', message: 'Waiting for the recovery settling interval before checking health.', automatic: true }
                });
            })();
            return { kind: 'started' };
        }
        // These failures cannot have queued a remote restart. Other failures
        // (especially a timeout) may have: retain capacity until recovery.
        db().transaction(() => {
            if (result.kind === 'no-name' || result.kind === 'unconfigured') {
                db().prepare('DELETE FROM restart_rollout WHERE server = ? AND operation_id = ?').run(server, operationId);
                recordProgress(operationId, { command: { state: 'rejected', message: 'The command could not be submitted: ' + result.message },
                    recovery: { state: 'released', message: 'Capacity released because no remote command could be submitted.', operationId } });
            } else {
                db().prepare('UPDATE restart_rollout SET error = ? WHERE server = ? AND operation_id = ?').run(`komodo: ${result.message}`, server, operationId);
                recordProgress(operationId, { command: { state: 'uncertain', message: 'The command may have reached Komodo: ' + result.message } });
            }
            finishDeployment(operationId!, { ok: false, message: `komodo: ${result.message}` });
        })();
        return { kind: 'failed', message: `komodo: ${result.message}` };
    } catch (err) {
        if (!db().prepare('SELECT 1 FROM server_deployments WHERE id = ? AND server_deleted_at IS NULL').get(operationId)) return { kind: 'failed', message: 'Original server was deleted' };
        const message = `komodo: ${(err as Error).message}`;
        db().transaction(() => {
            db().prepare('UPDATE restart_rollout SET error = ? WHERE server = ? AND operation_id = ?').run(message, server, operationId);
            recordProgress(operationId, { command: { state: 'uncertain', message: 'The command may have reached Komodo: ' + (err as Error).message } });
            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 = ? AND operation_id = ?')
            .run(new Date().toISOString(), server, operationId);
        if (requestsInFlight.get(server) === operationId) 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> {
    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 (slot.operation_id && nativeDeployment(slot.operation_id)) continue;
        if (requestsInFlight.has(slot.server)) continue;
        // Recovery capacity transferred to a rebuild remains reserved until
        // teardown. Its health is verified by the creation worker, never here.
        if (slot.operation_id && db().prepare(`SELECT 1 FROM server_deployments d WHERE d.id = ? AND d.server_deleted_at IS NULL AND (
            (d.action = 'rebuild' AND d.state IN ('waiting','queued','running','awaiting-health'))
            OR (d.action = 'restart' AND d.state = 'waiting' AND d.submitted_at IS NULL AND EXISTS (
                SELECT 1 FROM provisioning_sources s WHERE s.operation_id = d.id AND s.kind = 'watchdog')))`)
            .get(slot.operation_id)) 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;
        const checks: NonNullable<ProgressUpdate['checks']> = [];
        try {
            const health = await komodoInspectHealthy(slot.server);
            checks.push({ key: 'container', label: 'Container readiness', result: health.ok ? 'pass' : 'waiting', source: 'komodo', actual: health.state ?? null,
                checkedAt: new Date().toISOString(), message: health.ok ? null : health.reason });
            if (!health.ok) {
                error = `unhealthy: ${health.reason}${health.snippet ? ` snippet=${health.snippet.slice(0, 400)}` : ''}`;
            } else {
                const status = await probeServerStatus(slot.server, slot.requested_at);
                checks.push({ key: 'game', label: 'Game status', result: status.ok ? 'pass' : 'waiting', source: status.ok ? status.source : null,
                    checkedAt: status.observedAt, receivedAt: status.ok ? status.receivedAt : null, actual: status.ok ? status.players : null,
                    message: status.ok ? null : status.reason });
                if (!status.ok) error = `rcon not answering and no fresh telemetry: ${status.reason}`;
                else players = status.players;
            }
        } catch (err) {
            error = `health check: ${(err as Error).message}`;
            checks.push({ key: checks.length ? 'game' : 'container', label: checks.length ? 'Game status' : 'Container readiness', result: 'unknown', source: null, message: error });
        }
        const now = new Date().toISOString();
        db().transaction(() => {
            const checked = db().prepare(`UPDATE restart_rollout SET checked_at = ?, healthy_at = ?, players = ?, error = ?
                WHERE server = ? AND requested_at = ? AND operation_id IS ? AND healthy_at IS NULL`)
                .run(now, error ? null : now, players, error, slot.server, slot.requested_at, slot.operation_id);
            if (!checked.changes) return;
            if (slot.operation_id) recordProgress(slot.operation_id, {
                phase: checks.some(check => check.key === 'game') ? 'verify-game' : 'verify-container', checks, observedAt: now,
                blocker: error ? { code: 'recovery-health', message: error, automatic: true } : null,
                recovery: { state: error ? 'held' : 'released', at: now, operationId: slot.operation_id,
                    message: error ? 'Restart capacity remains reserved while recovery is checked.' : 'Container and game recovery verified; restart capacity released.' },
                checkpoints: error ? [] : [{ key: 'verify-container', label: 'Container readiness verified', at: now }, { key: 'verify-game', label: 'Game status verified', at: now }]
            });
            if (slot.operation_id && db().prepare("SELECT 1 FROM server_deployments WHERE id = ? AND server_deleted_at IS NULL AND state = 'awaiting-health'").get(slot.operation_id)) {
                db().prepare('UPDATE server_deployments SET checked_at = ?, players = ? WHERE id = ?').run(now, players, slot.operation_id);
                if (error) deploymentStage(slot.operation_id, 'Waiting for health: ' + error);
                else {
                    deploymentStage(slot.operation_id, 'Verified container and game health (RCON or fresh telemetry)');
                    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' };
}