package com.chaegeon.niro;

import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;

/** Root-only, per-run E2E evidence. No request, location or secret is stored. */
final class WeatherRefreshCounters {
    private final File directory;
    private long signal;
    private long callback;

    WeatherRefreshCounters(File directory) throws IOException {
        if (!directory.isDirectory()
                || !directory.getCanonicalPath().equals(directory.getAbsolutePath())) {
            throw new IOException("invalid counter directory");
        }
        this.directory = directory;
        writeAtomic("signal.counter", 0L);
        writeAtomic("callback.counter", 0L);
    }

    synchronized void signalAccepted() throws IOException {
        if (signal == Long.MAX_VALUE) {
            throw new IOException("signal counter overflow");
        }
        writeAtomic("signal.counter", signal + 1L);
        ++signal;
    }

    synchronized void freshCallbackCompleted() throws IOException {
        if (callback == Long.MAX_VALUE) {
            throw new IOException("callback counter overflow");
        }
        writeAtomic("callback.counter", callback + 1L);
        ++callback;
    }

    private void writeAtomic(String name, long value) throws IOException {
        File target = new File(directory, name);
        File pending = new File(directory, name + ".new");
        if (pending.exists() || !pending.getCanonicalPath().equals(pending.getAbsolutePath())
                || !target.getCanonicalPath().equals(target.getAbsolutePath())) {
            throw new IOException("counter path not safe");
        }
        FileOutputStream output = new FileOutputStream(pending);
        try {
            if (!pending.setReadable(false, false)
                    || !pending.setWritable(false, false)
                    || !pending.setExecutable(false, false)
                    || !pending.setReadable(true, true)
                    || !pending.setWritable(true, true)) {
                throw new IOException("counter permission failure");
            }
            output.write((Long.toString(value) + "\n").getBytes("US-ASCII"));
            output.getFD().sync();
        } finally {
            output.close();
        }
        if (!pending.renameTo(target)) {
            throw new IOException("counter replacement failed");
        }
    }
}