Issue #18, #19 resolved

Added pagination and sorting to the /api/pokemon endpoint

src/main/java/nl/utwente/mod4/pokemon/dao/PokemonDao.java

+package nl.utwente.mod4.pokemon.dao;
+
+import com.fasterxml.jackson.core.util.DefaultPrettyPrinter;
+import com.fasterxml.jackson.databind.ObjectMapper;
+import com.fasterxml.jackson.databind.ObjectWriter;
+import jakarta.ws.rs.BadRequestException;
+import jakarta.ws.rs.NotFoundException;
+import java.io.File;
+import java.io.IOException;
+import java.time.Instant;
+import java.time.ZoneId;
+import java.time.format.DateTimeFormatter;
+import java.util.*;
+import nl.utwente.mod4.pokemon.Utils;
+import nl.utwente.mod4.pokemon.model.Pokemon;
+import nl.utwente.mod4.pokemon.model.Trainer;
+
+public enum PokemonDao {
+
+    INSTANCE;
+
+    private static final String ORIGINAL_POKEMON = Utils.getAbsolutePathToResources() + "/default-pokemon-dataset.json";
+    private static final String POKEMON = Utils.getAbsolutePathToResources() + "/pokemon.json";
+    private final DateTimeFormatter dateFormatter = DateTimeFormatter.ofPattern("dd/MM/yyyy");
+
+    private HashMap<String, Pokemon> pokemons = new HashMap<>();
+
+    public void delete(String id) {
+        if(pokemons.containsKey(id)) {
+            pokemons.remove(id);
+        } else {
+            throw new NotFoundException("Pokemon '" + id + "' not found.");
+        }
+    }
+
+    public List<Pokemon> getPokemon(int pageSize, int pageNumber) {
+        var list = new ArrayList<>(pokemons.values());
+        return (List<Pokemon>) Utils.pageSlice(list,pageSize,pageNumber);
+    }
+
+    public Pokemon getTrainer(String id) {
+        var pt = pokemons.get(id);
+
+        if (pt == null) {
+            throw new NotFoundException("Pokemon '" + id + "' not found!");
+        }
+
+        return pt;
+    }
+
+    public void load() throws IOException {
+        ObjectMapper mapper = new ObjectMapper();
+        File source = existsPokemon() ?
+                new File(POKEMON) :
+                new File(ORIGINAL_POKEMON);
+        Pokemon[] arr = mapper.readValue(source, Pokemon[].class);
+
+        Arrays.stream(arr).forEach(pokemon -> pokemons.put(pokemon.id, pokemon));
+    }
+
+    public void save() throws IOException {
+        ObjectMapper mapper = new ObjectMapper();
+        ObjectWriter writer = mapper.writer(new DefaultPrettyPrinter());
+        File destination = new File(POKEMON);
+
+        writer.writeValue(destination, pokemons.values());
+    }
+
+    private boolean existsPokemon() {
+        File f = new File(POKEMON);
+        return f.exists() && !f.isDirectory();
+    }
+
+    private int getMaxId() {
+        Set<String> ids = pokemons.keySet();
+        return ids.isEmpty() ? 0 : ids.stream()
+                .map(Integer::parseInt)
+                .max(Integer::compareTo)
+                .get();
+    }
+
+
+    public Pokemon create(Pokemon newPokemon) {
+        String nextId = "" + (getMaxId() + 1);
+
+        newPokemon.id = nextId;
+        Instant now = Instant.now();
+        newPokemon.created = dateFormatter.format(now.atZone(ZoneId.systemDefault()).toLocalDateTime());
+        newPokemon.lastUpDate = dateFormatter.format(now.atZone(ZoneId.systemDefault()).toLocalDateTime());
+        pokemons.put(nextId,newPokemon);
+
+        return newPokemon;
+    }
+
+    public Pokemon replace(Pokemon updated) {
+        if(!updated.checkIsValid())
+            throw new BadRequestException("Invalid pokemon.");
+        if(pokemons.get(updated.id) == null)
+            throw new NotFoundException("Pokemon id '" + updated.id + "' not found.");
+
+        Instant now = Instant.now();
+        updated.created = pokemons.get(updated.id).created;
+        updated.lastUpDate = dateFormatter.format(now.atZone(ZoneId.systemDefault()).toLocalDateTime());
+        pokemons.put(updated.id,updated);
+
+        return updated;
+    }
+
+    public int getTotalPokemon() {
+        return pokemons.keySet().size();
+    }
+}