package me.clip.placeholderapi.util;

import com.google.common.hash.Hashing;
import com.google.common.io.Files;
import com.google.common.io.Resources;
import me.clip.placeholderapi.PlaceholderAPIPlugin;
import me.clip.placeholderapi.expansion.manager.CloudExpansionManager;
import org.jetbrains.annotations.NotNull;

import java.io.BufferedReader;
import java.io.File;
import java.io.InputStreamReader;
import java.net.URI;
import java.net.URL;
import java.net.URLConnection;
import java.nio.charset.StandardCharsets;
import java.util.Arrays;
import java.util.HashSet;
import java.util.Set;
import java.util.logging.Level;
import java.util.stream.Collectors;

public final class ExpansionSafetyCheck {
    private static final String MESSAGE =
            "\n###############################################\n" +
                    "###############################################\n" +
                    "PlaceholderAPI performs checks at startup and /papi reload for known malicious expansions. If you're seeing this message, there are the following malicious expansions in plugins/PlaceholderAPI/expansions.\n" +
                    "%s" +
                    "To prevent further infection PlaceholderAPI has stopped the server.\n" +
                    "If you're seeing this message after updating PAPI, your server may have been infected for some time, so best practice is a complete system wipe and reinstall of your server software and plugins to be safe.\n" +
                    "If you're seeing this after downloading an expansion however, PAPI hasn't loaded any of the malicious expansions above so you should be safe to simply delete the expansion in question.\n" +
                    "###############################################\n" +
                    "###############################################";

    private final PlaceholderAPIPlugin main;

    public ExpansionSafetyCheck(@NotNull final PlaceholderAPIPlugin main) {
        this.main = main;
    }

    public boolean runChecks() {
        if (!main.getPlaceholderAPIConfig().detectMaliciousExpansions()) {
            return false;
        }

        final File expansionsFolder = new File(main.getDataFolder(), "expansions");

        if (!expansionsFolder.exists()) {
            return false;
        }

        final Set<String> knownMaliciousExpansions;

        try {
            final URLConnection connection = new URI("https://check.placeholderapi.com").toURL().openConnection();
            connection.setRequestProperty("User-Agent", CloudExpansionManager.USER_AGENT);
            final String hashes = new BufferedReader(new InputStreamReader(connection.getInputStream(), StandardCharsets.UTF_8))
                    .lines().collect(Collectors.joining(System.lineSeparator()));
            knownMaliciousExpansions = Arrays.stream(hashes.split("\n")).collect(Collectors.toSet());
        } catch (Exception e) {
            main.getLogger().log(Level.SEVERE, "Failed to download anti malware hash check list from https://check.placeholderapi.com", e);
            return false;
        }

        final Set<String> maliciousPaths = new HashSet<>();
        final File[] files = expansionsFolder.listFiles();

        if (files == null) {
            return false;
        }

        for (File file : files) {
            try {
                if (!file.isFile()) {
                    continue;
                }

                final String hash = Hashing.sha256().hashBytes(Files.asByteSource(file).read()).toString();

                if (knownMaliciousExpansions.contains(hash)) {
                    maliciousPaths.add(file.getAbsolutePath());
                }
            } catch (Exception e) {
                main.getLogger().log(Level.SEVERE, "Error occurred while trying to read " + file.getAbsolutePath(), e);
            }
        }

        if (maliciousPaths.isEmpty()) {
            return false;
        }

        main.getLogger().severe(String.format(MESSAGE, maliciousPaths.stream().map(p -> "HASH OF " + p + " MATCHES KNOWN MALICIOUS EXPANSION DELETE IMMEDIATELY\n").collect(Collectors.joining())));

        main.getServer().shutdown();
        return true;
    }
}