project/src/main/java/internal/hw/crawler/commands/SaveCommand.java

package internal.hw.crawler.commands;

import com.google.gson.Gson;
import internal.hw.crawler.models.Article;
import internal.hw.crawler.repositories.ArticleRepository;
import internal.hw.crawler.views.CommandOutput;

import java.io.*;
import java.util.*;
import java.util.stream.Collectors;

public class SaveCommand implements Command {
    Gson gson = new Gson();
    private final ArticleRepository articleRepository;
    private final CommandOutput out;

    public SaveCommand(ArticleRepository articleRepository, CommandOutput out) {
        this.articleRepository = articleRepository;
        this.out = out;
    }

    @Override
    public String getName() {
        return "save";
    }

    @Override
    public void execute(String[] args) {
        String filename = "articles.output.json";

        List<Article> articles = getExistingArticles(filename);
        Map<String, Article> articleMap = articles.stream().collect(Collectors.toMap(this::articleMapId, it -> it));

        // Update existing articles with new articles
        for (Article article : articleRepository.getAll()) {
            articleMap.put(articleMapId(article), article);
        }

        Article[] articlesToSave = articleMap.values().toArray(new Article[0]);

        try (BufferedWriter writer = new BufferedWriter(new FileWriter(filename));) {
            writer.write(gson.toJson(articlesToSave));
            out.success(String.format("Wrote %d articles to %s", articlesToSave.length, filename));
        } catch (IOException e) {
            throw new RuntimeException(e);
        }
    }

    private String articleMapId(Article article) {
        return String.format("%s-%s", article.getSource(), article.getId());
    }

    private List<Article> getExistingArticles(String filename) {
        try (BufferedReader reader = new BufferedReader(new FileReader(filename))) {
            Article[] articles = gson.fromJson(reader, Article[].class);
            return Arrays.asList(articles);
        } catch (IOException e) {
            return List.of();
        }
    }
}