BoltLink-backendAlex/UrlShortener.java

package backendAlex;

import java.io.IOException;
import java.net.URI;
import java.net.URISyntaxException;
import java.nio.charset.StandardCharsets;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.util.List;
import java.security.SecureRandom;
import java.util.HashSet;

import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.core.type.TypeReference;
import com.fasterxml.jackson.databind.ObjectMapper;

public class UrlShortener {
    private Path file = Paths.get("/Users/alexandrawerner/project/urlShortenerTest/data.json");
    private List<UrlShortenerData> urlData;

    private String linkPrefix = "https://bolt-link.de/";  //https://shorturl.at/RDKwO
    private static final String CHARACTERS = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
    private static final int CODE_LENGTH = 6;
    private static final SecureRandom random = new SecureRandom();

    public String getShortUrl(String longUrl){
        readJson();
        boolean newUrl = true;
        String shortUrl = new String();
        for (UrlShortenerData url : urlData) {
            if(url.getLongUrl().equals(longUrl)){
                shortUrl = url.getShortUrl();
                newUrl = false;
                break;
            }
        }
        if(newUrl){
            shortUrl = createShortUrl();
            setNewUrl(shortUrl, longUrl);
        }
        return shortUrl;
    }

    public String getLongUrl(String shortUrl){
        readJson();
        String longUrl = "url not found";
        for (UrlShortenerData url : urlData) {
            if(url.getLongUrl().equals(shortUrl)){
                longUrl = url.getShortUrl();
            }
        }
        return longUrl;
    }

    private String createShortUrl(){
        String url = linkPrefix + generateUniqueCode();
        return url;
    }

    private String generateUniqueCode() {
        HashSet<String> usedCodes = new HashSet<>();
        usedCodes = getAllLinkSuffix();

        String code;
        do {
            code = generateRandomCode();
        } while (usedCodes.contains(code)); // Check if already used //TODO mit equals checken und nicht mir contains
        
        usedCodes.add(code);
        return code;
    }
    
    private String generateRandomCode() {
        StringBuilder sb = new StringBuilder(CODE_LENGTH);
        
        for (int i = 0; i < CODE_LENGTH; i++) {
            int index = random.nextInt(CHARACTERS.length());
            sb.append(CHARACTERS.charAt(index));
        }
        
        return sb.toString();
    }

    private HashSet<String> getAllLinkSuffix() {
    readJson();
    HashSet<String> usedCodes = new HashSet<>();
    
    for (UrlShortenerData url : urlData) {
        String shortUrl = url.getShortUrl();
        try{
            URI uri = new URI(shortUrl);
            
            String path = uri.getPath();

            if (path.contains("/")) {
                usedCodes.add(path.substring(path.lastIndexOf('/') + 1));
            }
        }catch(URISyntaxException e){
            e.printStackTrace();
        }
    }
    return usedCodes; 
    }

    private void setNewUrl(String shortUrl, String longUrl){
        readJson();
        UrlShortenerData newUrl = new UrlShortenerData(longUrl, shortUrl);
        urlData.add(newUrl);
        writeJson();
    }

    private void readJson(){
        try {
            String contentWithCharset = Files.readString(file, StandardCharsets.UTF_8);
            ObjectMapper mapper = new ObjectMapper();
            urlData  = mapper.readValue(contentWithCharset, new TypeReference<List<UrlShortenerData>>(){});
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    private void writeJson(){
        try{
            ObjectMapper mapper = new ObjectMapper();
            // Liste -> JSON Array
            String jsonString = mapper.writeValueAsString(urlData);
            Files.writeString(file, jsonString);       
        }catch(IOException e){
            e.printStackTrace();
        }
    }

    //test function
    public void printJson(){
        readJson();
        ObjectMapper mapper = new ObjectMapper();
        try{
        String prettyJson = mapper.writerWithDefaultPrettyPrinter().writeValueAsString(urlData);
        System.out.println(prettyJson);
        }catch(JsonProcessingException e){
            e.printStackTrace();
            System.out.println(e);
        }
    }
}