package com.keuin.kbackupfabric.backup.incremental;

import org.jetbrains.annotations.NotNull;

import java.io.*;
import java.nio.file.Files;
import java.nio.file.Path;
import java.util.Iterator;
import java.util.Objects;

/**
 * Serialize and deserialize ObjectCollection from/to the disk file.
 * Now we want to save additional metadata in incremental backups. So the serializer on pure ObjectCollection is depreciated.
 */
public class ObjectCollectionSerializer {

    /**
     * This doesn't work with the latest format. Use IncBackupInfoSerializer instead.
     */
    @Deprecated
    public static ObjectCollection2 fromFile(File file) throws IOException {
        Objects.requireNonNull(file);
        ObjectCollection2 collection;
        try (FileInputStream fileInputStream = new FileInputStream(file)) {
            try (ObjectInputStream objectInputStream = new ObjectInputStream(fileInputStream)) {
                collection = (ObjectCollection2) objectInputStream.readObject();
            } catch (ClassNotFoundException ignored) {
                // this should not happen
                return null;
            }
        }
        return collection;
    }

    /**
     * Only used for testing backward-compatibility with legacy backups.
     */
    public static void toFile(ObjectCollection2 collection, File file) throws IOException {
        Objects.requireNonNull(collection);
        Objects.requireNonNull(file);
        try (FileOutputStream fileOutputStream = new FileOutputStream(file)) {
            try (ObjectOutputStream objectOutputStream = new ObjectOutputStream(fileOutputStream)) {
                objectOutputStream.writeObject(collection);
            }
        }
    }

    public static Iterable<ObjectCollection2> fromDirectory(File directory) throws IOException {

        if (!directory.isDirectory()) {
            throw new IllegalArgumentException("Given directory is invalid.");
        }
        return new Iterable<ObjectCollection2>() {
            private final Iterator<ObjectCollection2> iter = new Iterator<ObjectCollection2>() {
                private final Iterator<Path> i = Files.walk(directory.toPath(), 1).filter(p -> {
                    File f = p.toFile();
                    return f.isFile() && f.getName().endsWith(".kbi");
                }).iterator();

                @Override
                public boolean hasNext() {
                    return i.hasNext();
                }

                @Override
                public ObjectCollection2 next() {
                    try {
                        return fromFile(i.next().toFile());
                    } catch (IOException e) {
                        throw new RuntimeException(e);
                    }
                }
            };

            @NotNull
            @Override
            public Iterator<ObjectCollection2> iterator() {
                return iter;
            }
        };

    }
}