import { readFileSync, statSync } from 'fs';
import path from 'path';
import { countPendingLocate } from '@/lib/db';
import { corsJson, corsPreflight } from '../cors';

/** The extension version this checkout ships.
 *
 *  Read out of the manifest rather than kept as a constant here: the manifest is
 *  the file Chrome actually loads, so the two cannot drift apart. Cached on
 *  mtime because every browser polls this every few seconds and the file only
 *  changes when an update lands. Null when there is no extension folder beside
 *  the server — the extension then leaves itself alone, which is the right
 *  answer for a dashboard that cannot see what it is supposed to be running. */
let manifestCache: { mtimeMs: number; version: string | null } | null = null;

function shippedExtensionVersion(): string | null {
    const file = path.join(process.cwd(), 'extension', 'manifest.json');
    try {
        const { mtimeMs } = statSync(file);
        if (!manifestCache || manifestCache.mtimeMs !== mtimeMs) {
            const parsed = JSON.parse(readFileSync(file, 'utf8')) as { version?: string };
            manifestCache = { mtimeMs, version: parsed.version ?? null };
        }
        return manifestCache.version;
    } catch {
        return null;
    }
}

/** Polled by the Chromium extension every few seconds, and by the AutoBuyer page.
 *  The AutoBuyer has no on/off switch — it is ready whenever the runner is — so
 *  the only things worth reporting here are whether clicks are waiting to be
 *  served, and which extension build this checkout expects to be talking to. */
export async function GET() {
    return corsJson({
        pendingLocate: countPendingLocate(),
        extensionVersion: shippedExtensionVersion(),
    });
}

export async function OPTIONS() {
    return corsPreflight();
}