import megamek.common.loaders.MekSummaryCache;

/**
 * Force MegaMek to build data/mekfiles/units.cache at image-build time.
 *
 * <p>MegaMek does not ship the cache. Building it means walking ~11k unit files:
 * 20.2s cold versus 2.9s to load a prebuilt one. Paying that once per image
 * instead of once per match is the single largest cold-start saving measured.
 *
 * <p>Run with the single-file source launcher against the stock jar; it needs no
 * compiler in the runtime image because only the resulting cache file is copied
 * forward. Must run with MegaMek's install dir as the working directory -
 * MegaMek resolves data/ relative to cwd.
 */
public final class PrimeUnitsCache {

    public static void main(String[] args) throws Exception {
        long start = System.currentTimeMillis();
        MekSummaryCache cache = MekSummaryCache.getInstance();
        long deadline = start + 300_000L;
        while (!cache.isInitialized()) {
            if (System.currentTimeMillis() > deadline) {
                System.err.println("units.cache did not initialise within 300s");
                System.exit(1);
            }
            Thread.sleep(250L);
        }
        System.out.printf("units.cache primed in %.1fs%n", (System.currentTimeMillis() - start) / 1000.0);
    }
}