import { db } from '../db/index.js';
import { config, komodoConfigured, rconConfigured } from '../config.js';
import { getServer, listServers } from './servers.js';
import { rconGetPlayerCount, rconPlutoniumVersion } from '../integrations/rcon.js';
import { refreshRestartRollout, restartInRollout, rolloutHealth, rolloutWaitReason } from '../pipeline/restart-rollout.js';
import { nextMaintenanceAt, parsePlutoniumManifest, PLUTONIUM_MANIFEST_URL } from '../../plutonium.js';
import type { MaintenanceJob, MaintenanceSchedule, PlutoniumRelease, PlutoniumStatus, PlutoniumVersion } from '../../plutonium.js';

const HOUR = 60 * 60 * 1000;
const nowIso = () => new Date().toISOString();
function readSetting<T>(key: string, fallback: T): T {
    const row = db().prepare('SELECT value FROM settings WHERE key = ?').get(key) as { value: string } | undefined;
    return row ? JSON.parse(row.value) : fallback;
}
function writeSetting(key: string, value: unknown): void {
    db().prepare('INSERT INTO settings (key, value) VALUES (?, ?) ON CONFLICT(key) DO UPDATE SET value = excluded.value')
        .run(key, JSON.stringify(value));
}
function release(): PlutoniumRelease {
    return readSetting('plutonium_release', { revision: null, checkedAt: null, error: null });
}
function schedule(): MaintenanceSchedule {
    // Legacy schedules were explicitly UTC. Preserve their timing until saved.
    return { timeZone: 'UTC', ...readSetting('plutonium_schedule', { enabled: false, time: '06:00', nextAt: null }) };
}
export function saveMaintenanceSchedule(enabled: boolean, time: string, timeZone: string): void {
    const nextAt = nextMaintenanceAt(time, new Date(), timeZone);
    writeSetting('plutonium_schedule', { enabled, time, timeZone, nextAt: enabled ? nextAt : null });
}
export function plutoniumStatus(): PlutoniumStatus {
    const versions = db().prepare('SELECT * FROM plutonium_versions').all() as PlutoniumVersion[];
    return {
        release: release(), schedule: schedule(),
        servers: listServers().map(s => versions.find(v => v.server === s.name)
            ?? { server: s.name, revision: null, checked_at: null, error: null }),
        jobs: db().prepare(`SELECT * FROM maintenance_jobs WHERE state IN ('queued','restarting')
            OR id IN (SELECT id FROM maintenance_jobs ORDER BY id DESC LIMIT 100) ORDER BY id DESC`).all() as MaintenanceJob[]
    };
}

async function probeVersion(server: string): Promise<number | null> {
    const recovering = db().prepare('SELECT 1 FROM restart_rollout WHERE server = ? AND healthy_at IS NULL').get(server);
    const result = recovering ? { revision: null, error: 'Waiting for restart recovery.' }
        : await rconPlutoniumVersion(server).catch(() => ({ revision: null, error: 'Version check failed.' }));
    // Clear the old revision on failure: it is no longer evidence of what is running.
    db().prepare(`INSERT INTO plutonium_versions (server, revision, checked_at, error) VALUES (?, ?, ?, ?)
        ON CONFLICT(server) DO UPDATE SET revision = excluded.revision, checked_at = excluded.checked_at, error = excluded.error`)
        .run(server, result.revision, nowIso(), result.error);
    return result.revision;
}

let checking: Promise<void> | null = null;
export function checkPlutonium(): Promise<void> {
    if (checking) return checking;
    checking = check().finally(() => { checking = null; });
    return checking;
}
async function check(): Promise<void> {
    const previous = release();
    try {
        const response = await fetch(PLUTONIUM_MANIFEST_URL, { signal: AbortSignal.timeout(config.httpTimeoutMs), redirect: 'error' });
        if (!response.ok) throw new Error(`Updater manifest request failed (HTTP ${response.status}).`);
        const body = await response.text();
        if (body.length > 2_000_000) throw new Error('Updater manifest response was too large.');
        writeSetting('plutonium_release', { revision: parsePlutoniumManifest(JSON.parse(body)), checkedAt: nowIso(), error: null });
    } catch (err) {
        writeSetting('plutonium_release', { ...previous, checkedAt: nowIso(), error: (err as Error).message });
    }
    const servers = listServers();
    for (let i = 0; i < servers.length; i += 4) {
        await Promise.all(servers.slice(i, i + 4).map(s => probeVersion(s.name)));
    }
}

export function queueMaintenance(servers: string[]): number {
    const names = new Set(listServers().map(s => s.name));
    if (!servers.length || servers.some(s => !names.has(s))) throw new Error('Choose existing fleet servers.');
    return db().transaction(() => {
        const latest = release();
        // An old cached release is still displayed, but never used as a fresh target.
        const target = !latest.error && latest.checkedAt && Date.now() - Date.parse(latest.checkedAt) < HOUR
            ? latest.revision : null;
        let added = 0;
        for (const server of new Set(servers)) {
            added += db().prepare(`INSERT OR IGNORE INTO maintenance_jobs (server, target_revision, requested_at)
                VALUES (?, ?, ?)`).run(server, target, nowIso()).changes;
        }
        return added;
    })();
}
export function cancelMaintenance(id: number): boolean {
    return db().prepare(`UPDATE maintenance_jobs SET state = 'cancelled', finished_at = ?, detail = 'Cancelled by operator'
        WHERE id = ? AND state = 'queued'`).run(nowIso(), id).changes > 0;
}

function conflictingWork(server: string): boolean {
    return !!db().prepare(`SELECT 1 FROM server_deployments WHERE server = ? AND state IN ('queued','running','awaiting-health')
        UNION ALL SELECT 1 FROM deployment_servers WHERE server = ? AND restart_state IN ('pending','failed')
        UNION ALL SELECT 1 FROM beta_servers bs JOIN betas b ON b.id = bs.beta_id
            WHERE bs.server = ? AND b.state IN ('running','ready-promote') LIMIT 1`).get(server, server, server);
}
function finish(job: MaintenanceJob, state: 'done' | 'failed' | 'cancelled', detail: string) {
    db().prepare('UPDATE maintenance_jobs SET state = ?, detail = ?, finished_at = ? WHERE id = ?')
        .run(state, detail, nowIso(), job.id);
}
function hold(job: MaintenanceJob, detail: string) {
    db().prepare('UPDATE maintenance_jobs SET detail = ? WHERE id = ?').run(detail, job.id);
}

let ticking: Promise<void> | null = null;
export function maintenanceTick(): Promise<void> {
    if (ticking) return ticking;
    ticking = runTick().finally(() => { ticking = null; });
    return ticking;
}
async function runTick(): Promise<void> {
    const latest = release();
    if (!latest.checkedAt || Date.now() - Date.parse(latest.checkedAt) >= HOUR) await checkPlutonium();
    db().transaction(() => {
        const plan = schedule();
        if (plan.enabled && plan.nextAt && plan.nextAt <= nowIso()) {
            const names = listServers().map(s => s.name);
            if (names.length) queueMaintenance(names);
            // Coalesce missed days after downtime into one run; no restart backlog.
            writeSetting('plutonium_schedule', { ...plan, nextAt: nextMaintenanceAt(plan.time, new Date(), plan.timeZone) });
        }
    })();
    await refreshRestartRollout();
    const jobs = db().prepare(`SELECT * FROM maintenance_jobs WHERE state IN ('queued','restarting') ORDER BY id`).all() as MaintenanceJob[];
    for (const job of jobs) {
        try { await processJob(job); }
        catch { hold(job, 'Maintenance check failed; waiting for the next check.'); }
    }
    db().prepare(`DELETE FROM maintenance_jobs WHERE finished_at < ? AND state IN ('done','failed','cancelled')`)
        .run(new Date(Date.now() - 30 * 24 * HOUR).toISOString());
}
async function processJob(job: MaintenanceJob): Promise<void> {
    const server = getServer(job.server);
    if (!server || server.destroyed_at) return finish(job, 'cancelled', 'Server removed.');
    if (job.state === 'restarting') {
        const slot = db().prepare('SELECT requested_at FROM restart_rollout WHERE server = ?').get(job.server) as { requested_at: string } | undefined;
        if (!slot || !job.restarted_at || slot.requested_at < job.restarted_at) {
            return finish(job, 'failed', 'Restart submission was interrupted. Inspect the server before queuing another restart.');
        }
        const health = rolloutHealth(job.server);
        if (!health.ok) return hold(job, health.reason);
        const revision = await probeVersion(job.server);
        if (job.target_revision && (revision === null || revision < job.target_revision)) {
            return finish(job, 'failed', `Server recovered, but r${job.target_revision} was not verified (${revision === null ? 'version unknown' : `running r${revision}`}). Check Plutainer auto-update settings.`);
        }
        return finish(job, 'done', `Server recovered; ${revision === null ? 'running revision unknown' : `running r${revision}`}.`);
    }
    if (!komodoConfigured() || !rconConfigured()) return hold(job, 'Configure Komodo and RCON before restarting.');
    if (conflictingWork(job.server)) return hold(job, 'Waiting for deployment or beta work on this server.');
    const reason = rolloutWaitReason(job.server);
    if (reason) return hold(job, reason);
    const players = await rconGetPlayerCount(job.server);
    if (players === null || players > 0) return hold(job, players === null ? 'Waiting for a fresh RCON player count.' : `Waiting for ${players} player(s) to leave.`);
    // Recheck after async I/O; cancellation and lifecycle operations may have arrived.
    const current = getServer(job.server);
    if (!current || current.destroyed_at) return finish(job, 'cancelled', 'Server removed.');
    if (conflictingWork(job.server)) return hold(job, 'Waiting for deployment or beta work on this server.');
    const claimed = db().prepare(`UPDATE maintenance_jobs SET state = 'restarting', restarted_at = ?, detail = 'Restart requested'
        WHERE id = ? AND state = 'queued'`).run(nowIso(), job.id);
    if (!claimed.changes) return;
    db().prepare('UPDATE plutonium_versions SET revision = NULL, error = ? WHERE server = ?')
        .run('Waiting for restart recovery.', job.server);
    // Persist intent before remote I/O. An ambiguous timeout must never cause an automatic second restart.
    const result = await restartInRollout(job.server);
    if (result.kind === 'queued') {
        db().prepare(`UPDATE maintenance_jobs SET state = 'queued', restarted_at = NULL, detail = ? WHERE id = ?`).run(result.message, job.id);
    } else if (result.kind === 'failed') finish(job, 'failed', result.message);
}