/*
 * Copyright (C) 2024  Minecon724
 * Tweaks724 is licensed under the GNU General Public License. See the LICENSE.md file
 * in the project root for the full license text.
 */

package eu.m724.tweaks.updater;

import eu.m724.tweaks.updater.cache.ResourceVersion;

import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.util.HashSet;
import java.util.Set;

public class VersionCheckCache {
    private static final byte FILE_VERSION = 1;

    public static Set<ResourceVersion> loadAll(FileInputStream inputStream) throws IOException {
        byte fileVersion = (byte) inputStream.read();
        if (fileVersion != FILE_VERSION) throw new FileVersionMismatchException(fileVersion, FILE_VERSION);

        Set<ResourceVersion> versions = new HashSet<>();
        int i = 0;

        byte[] buffer = new byte[8]; // 3 + 2 + 3
        while (inputStream.available() > 0) {
            int read = inputStream.read(buffer);
            if (read < 8) break; // end of file
            if (++i > 10000) throw new RuntimeException("Cache file is too large");

            ResourceVersion resourceVersion = getResourceVersion(buffer);
            versions.add(resourceVersion);
        }

        return versions;
    }

    private static ResourceVersion getResourceVersion(byte[] bytes) {
        int resourceId = ((bytes[0] & 0xFF) << 16) | ((bytes[1] & 0xFF) << 8) | (bytes[2] & 0xFF);
        int page = ((bytes[3] & 0xFF) << 8) | (bytes[4] & 0xFF);
        int versionId = ((bytes[5] & 0xFF) << 16) | ((bytes[6] & 0xFF) << 8) | (bytes[7] & 0xFF);

        return new ResourceVersion(resourceId, page, versionId, null, null);
    }

    private static void writeResourceVersion(ResourceVersion resourceVersion, OutputStream outputStream) throws IOException {
        int resourceId = resourceVersion.resourceId();
        outputStream.write((resourceId >> 16) & 0xFF);
        outputStream.write((resourceId >> 8) & 0xFF);
        outputStream.write(resourceId & 0xFF);

        int page = resourceVersion.page();
        outputStream.write((page >> 8) & 0xFF);
        outputStream.write(page & 0xFF);

        int versionId = resourceVersion.updateId();
        outputStream.write((versionId >> 16) & 0xFF);
        outputStream.write((versionId >> 8) & 0xFF);
        outputStream.write(versionId & 0xFF);
    }

    public static void writeAll(FileOutputStream outputStream, Set<ResourceVersion> versions) throws IOException {
        outputStream.write(FILE_VERSION);
        for (ResourceVersion version : versions) {
            writeResourceVersion(version, outputStream);
        }
    }

    public static class FileVersionMismatchException extends RuntimeException {
        public final byte fileVersion, expectedVersion;

        public FileVersionMismatchException(byte fileVersion, byte expectedVersion) {
            this.fileVersion = fileVersion;
            this.expectedVersion = expectedVersion;
        }
    }
}