package com.evsuite.abrp;

import android.content.Context;
import android.net.ConnectivityManager;
import android.net.Network;
import android.net.NetworkCapabilities;
import android.net.NetworkInfo;

import java.io.IOException;
import java.net.HttpURLConnection;
import java.net.InetAddress;
import java.net.URL;
import java.util.ArrayList;
import java.util.List;

/**
 * What an update check writes down about the connection before and after it fails: the networks
 * Android sees, whether the server's name can be looked up, and whether the internet answers at
 * all, which tells a SIM without data from a server that is down. Blocking: background thread.
 * Never logs the server's address or anything about the car. — UNSTABLE BUILDS ONLY.
 */
final class UpdateNetworkCheck {

    /** Android's own connectivity test, as Android itself uses it; no data about the car is sent. */
    private static final String INTERNET_TEST = "https://www.gstatic.com/generate_204";
    private static final int TIMEOUT_MS = 10_000;

    private UpdateNetworkCheck() {}

    /** One line per network, or one saying there is none. */
    static List<String> networks(Context app) {
        List<String> out = new ArrayList<>();
        try {
            ConnectivityManager cm = (ConnectivityManager) app.getSystemService(Context.CONNECTIVITY_SERVICE);
            if (cm == null) {
                out.add("Network: no connectivity service");
                return out;
            }
            Network active = cm.getActiveNetwork();
            if (active == null) out.add("Network: none in use");
            for (Network network : cm.getAllNetworks()) {
                NetworkCapabilities caps = cm.getNetworkCapabilities(network);
                if (caps == null) continue;
                NetworkInfo info = cm.getNetworkInfo(network);
                out.add("Network: " + UpdateDiagnosis.network(transports(caps),
                        caps.hasCapability(NetworkCapabilities.NET_CAPABILITY_INTERNET),
                        caps.hasCapability(NetworkCapabilities.NET_CAPABILITY_VALIDATED),
                        network.equals(active), info != null && info.isRoaming()));
            }
        } catch (RuntimeException e) {
            out.add("Network: unreadable (" + e.getClass().getSimpleName() + ")");
        }
        return out;
    }

    private static List<String> transports(NetworkCapabilities caps) {
        List<String> out = new ArrayList<>();
        if (caps.hasTransport(NetworkCapabilities.TRANSPORT_CELLULAR)) out.add("cellular");
        if (caps.hasTransport(NetworkCapabilities.TRANSPORT_WIFI)) out.add("Wi-Fi");
        if (caps.hasTransport(NetworkCapabilities.TRANSPORT_ETHERNET)) out.add("ethernet");
        if (caps.hasTransport(NetworkCapabilities.TRANSPORT_BLUETOOTH)) out.add("Bluetooth");
        if (caps.hasTransport(NetworkCapabilities.TRANSPORT_VPN)) out.add("VPN");
        return out;
    }

    /** Whether the host's name resolves, without saying the name. */
    static String lookup(String host) {
        long started = System.currentTimeMillis();
        try {
            InetAddress.getByName(host);
            return "Server's name: found in " + (System.currentTimeMillis() - started) + " ms";
        } catch (IOException | RuntimeException e) {
            return "Server's name: " + UpdateDiagnosis.failure(e);
        }
    }

    /** Whether the world outside the car server answers. */
    static String internet() {
        HttpURLConnection conn = null;
        try {
            conn = (HttpURLConnection) new URL(INTERNET_TEST).openConnection();
            conn.setInstanceFollowRedirects(false);
            conn.setConnectTimeout(TIMEOUT_MS);
            conn.setReadTimeout(TIMEOUT_MS);
            return "Internet test: " + UpdateDiagnosis.internet(conn.getResponseCode());
        } catch (IOException | RuntimeException e) {
            return "Internet test: " + UpdateDiagnosis.failure(e);
        } finally {
            if (conn != null) conn.disconnect();
        }
    }
}