/**
 * Pushes this machine's full configuration — settings, broker credentials,
 * instruments, manual assignments — to the master, so a dead VPS can be
 * replaced by restoring the backup (lib/backup-restore.ts) and adopting this
 * instance's uuid.
 *
 * This is the deliberate exception to "credentials never leave the machine":
 * the payload goes over HTTPS to the bearer-gated /api/instances/backup and is
 * AES-encrypted at rest on the master. It never rides the unauthenticated
 * control socket.
 *
 * Push policy: on bootstrap, then every POLL_INTERVAL, but only when the
 * content actually changed (hash comparison) — plus an immediate debounced
 * push whenever settings or credentials are edited (scheduleBackupPush, called
 * from the mutation routes).
 */

import { createHash } from 'node:crypto';
import {
    getSetting,
    setSetting,
    listSettings,
    listCredentials,
    getInstruments,
    listAllAssignments,
    type FirmCredentialRow,
    type AssignmentRow,
} from './db';

export interface BackupPayload {
    v: 1;
    savedAt: string;
    settings: Record<string, string>;
    credentials: FirmCredentialRow[];
    instruments: { symbol: string; enabled: boolean }[];
    assignments: AssignmentRow[];
}

const BACKUP_PATH = '/api/instances/backup';
const POLL_INTERVAL_MS = 5 * 60_000;
const DEBOUNCE_MS = 5_000;
const FETCH_TIMEOUT_MS = 10_000;

const g = globalThis as typeof globalThis & {
    __backupSyncTimer?: ReturnType<typeof setTimeout>;
    __backupDebounceTimer?: ReturnType<typeof setTimeout>;
    __backupLastHash?: string;
};

// Bookkeeping that describes this process run, not the configuration worth
// restoring. Excluded from the hash so a heartbeat doesn't look like a change
// worth pushing. (The restore side has its own skip-set; these still travel in
// the payload so a restore debugger can see them.)
const VOLATILE_KEYS = new Set([
    'runner_heartbeat',
    'catalog_last_sync_at',
    'catalog_last_error',
    'backup_last_push_at',
    'backup_last_error',
]);

export function collectBackup(): BackupPayload {
    return {
        v: 1,
        savedAt: new Date().toISOString(),
        settings: listSettings(),
        credentials: listCredentials(),
        instruments: getInstruments().map((i) => ({ symbol: i.symbol, enabled: Boolean(i.enabled) })),
        assignments: listAllAssignments(),
    };
}

/** Stable digest of everything restorable, so unchanged config never pushes. */
function contentHash(payload: BackupPayload): string {
    const settings = Object.entries(payload.settings)
        .filter(([k]) => !VOLATILE_KEYS.has(k))
        .sort(([a], [b]) => (a < b ? -1 : a > b ? 1 : 0));
    return createHash('sha256')
        .update(JSON.stringify({
            settings,
            credentials: payload.credentials,
            instruments: payload.instruments,
            assignments: payload.assignments,
        }))
        .digest('hex');
}

function preconditions(): { masterUrl: string; id: string; token: string } | null {
    const masterUrl = getSetting('master_dashboard_url');
    const token = getSetting('master_backup_token');
    // No uuid yet = the master has never said welcome; there is nothing stable
    // to key the backup by, so wait for the first hello to complete.
    const id = getSetting('instance_id');
    if (!masterUrl || !token || !id) return null;
    return { masterUrl, id, token };
}

export async function pushBackup(force = false): Promise<{ ok: boolean; skipped?: boolean; error?: string }> {
    const pre = preconditions();
    if (!pre) return { ok: false, skipped: true, error: 'master url, backup token or instance uuid not set' };

    const payload = collectBackup();
    const hash = contentHash(payload);
    if (!force && hash === g.__backupLastHash) return { ok: true, skipped: true };

    let url: URL;
    try {
        url = new URL(BACKUP_PATH, pre.masterUrl);
    } catch {
        return { ok: false, error: `master_dashboard_url is not a URL: ${pre.masterUrl}` };
    }

    try {
        const res = await fetch(url, {
            method: 'PUT',
            headers: {
                'content-type': 'application/json',
                authorization: `Bearer ${pre.token}`,
            },
            body: JSON.stringify({
                id: pre.id,
                name: getSetting('instance_name') ?? '',
                payload,
            }),
            signal: AbortSignal.timeout(FETCH_TIMEOUT_MS),
        });
        if (!res.ok) {
            const detail = await res.json().then((b) => b?.error).catch(() => '');
            throw new Error(`master returned ${res.status}${detail ? ` — ${detail}` : ''}`);
        }
        g.__backupLastHash = hash;
        setSetting('backup_last_push_at', new Date().toISOString());
        setSetting('backup_last_error', '');
        console.log('[backup] pushed to master');
        return { ok: true };
    } catch (err) {
        const error = err instanceof Error ? err.message : String(err);
        console.error('[backup] push failed:', error);
        setSetting('backup_last_error', error);
        return { ok: false, error };
    }
}

/** Debounced push for the mutation routes: a settings PATCH or credential PUT
 *  lands on the master seconds later instead of at the next poll. */
export function scheduleBackupPush(): void {
    if (g.__backupDebounceTimer) clearTimeout(g.__backupDebounceTimer);
    g.__backupDebounceTimer = setTimeout(() => { void pushBackup(); }, DEBOUNCE_MS);
}

export function startBackupSync(): void {
    stopBackupSync();
    const tick = async () => {
        await pushBackup();
        // Jitter so a fleet restarting together doesn't push in lockstep.
        g.__backupSyncTimer = setTimeout(tick, POLL_INTERVAL_MS + Math.floor(Math.random() * 30_000));
    };
    void tick();
}

export function stopBackupSync(): void {
    if (g.__backupSyncTimer) {
        clearTimeout(g.__backupSyncTimer);
        g.__backupSyncTimer = undefined;
    }
}