file.java

// AddDiaryFoodRequest.java
package com.diettracker.backend.requests;
public class AddDiaryFoodRequest {
    private Long diaryId;
    private Long foodId;
    private double weight;

    // Getters and setters
    public Long getDiaryId() { return diaryId; }
    public void setDiaryId(Long diaryId) { this.diaryId = diaryId; }
    public Long getFoodId() { return foodId; }
    public void setFoodId(Long foodId) { this.foodId = foodId; }
    public double getWeight() { return weight; }
    public void setWeight(double weight) { this.weight = weight; }
}

// diary
package com.diettracker.backend.models;

import jakarta.persistence.*;

import java.util.Set;

@Entity
@Table(name = "diary")
public class Diary {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    @Enumerated(EnumType.STRING)
    private DiaryType name;

//    @OneToMany(mappedBy = "diary", cascade = CascadeType.ALL, orphanRemoval = true)
//    private Set<DiaryFood> diaryFoods;

    public Diary() {
    }

    public Diary(DiaryType name) {
        this.name = name;
    }

    public Long getId() {
        return id;
    }

    public void setId(Long id) {
        this.id = id;
    }

    public DiaryType getName() {
        return name;
    }

    public void setName(DiaryType name) {
        this.name = name;
    }
}

// DiaryController.java
package com.diettracker.backend.controllers;

import com.diettracker.backend.dto.DiaryFoodDTO;
import com.diettracker.backend.models.Diary;
import com.diettracker.backend.models.DiaryFood;
import com.diettracker.backend.models.DiaryType;
import com.diettracker.backend.models.Food;
import com.diettracker.backend.repositories.DiaryFoodRepository;
import com.diettracker.backend.repositories.DiaryRepository;
import com.diettracker.backend.requests.AddDiaryFoodRequest;
import com.diettracker.backend.services.DiaryService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.*;

import java.util.List;
import java.util.Optional;

@RestController
@RequestMapping("/api/diary")
public class DiaryController {

    private final DiaryRepository diaryRepository;
    private final DiaryFoodRepository diaryFoodRepository;
    private final DiaryService diaryService;

    public DiaryController(DiaryRepository diaryRepository, DiaryFoodRepository diaryFoodRepository, DiaryService diaryService) {
        this.diaryRepository = diaryRepository;
        this.diaryFoodRepository = diaryFoodRepository;
        this.diaryService = diaryService;
    }

    @GetMapping
    public List<DiaryFood> getAllDiaries() {
        return diaryFoodRepository.findAll();
    }

    @GetMapping("/{id}")
    public ResponseEntity<Diary> getDiaryById(@PathVariable Long id) {
        Optional<Diary> diary = diaryRepository.findById(id);
        return diary.map(ResponseEntity::ok).orElseGet(() -> ResponseEntity.notFound().build());
    }

    @PostMapping
    public ResponseEntity<DiaryFoodDTO> addFoodToDiary(@RequestBody AddDiaryFoodRequest request) {
        DiaryFood diaryFood = diaryService.addFoodToDiary(
                request.getDiaryId(),
                request.getFoodId(),
                request.getWeight()
        );
        return ResponseEntity.ok(convertToDTO(diaryFood));
    }

    private DiaryFoodDTO convertToDTO(DiaryFood diaryFood) {
        Food food = diaryFood.getFood();
        double weightRatio = diaryFood.getWeight() / food.getWeight();

        return new DiaryFoodDTO(
                diaryFood.getId(),
                diaryFood.getDiary().getId(),
                food.getId(),
                food.getName(),
                diaryFood.getWeight(),
                Math.round(food.getCalories() * weightRatio * 10.0) / 10.0,
                Math.round(food.getProteins() * weightRatio * 10.0) / 10.0,
                Math.round(food.getFats() * weightRatio * 10.0) / 10.0,
                Math.round(food.getCarbs() * weightRatio * 10.0) / 10.0,
                diaryFood.getCreatedAt(),
                diaryFood.getUpdatedAt()
        );
    }
}

// DiaryFoodDTO
package com.diettracker.backend.dto;

import java.time.LocalDateTime;

public class DiaryFoodDTO {
    private final Long id;
    private final Long diaryId;
    private final Long foodId;
    private final String foodName;
    private final double weight;
    private final double calories;
    private final double proteins;
    private final double fats;
    private final double carbs;
    private final LocalDateTime createdAt;
    private final LocalDateTime updatedAt;

    public DiaryFoodDTO(
            Long id, Long diaryId, Long foodId, String foodName,
            double weight, double calories, double proteins,
            double fats, double carbs, LocalDateTime createdAt,
            LocalDateTime updatedAt) {
        this.id = id;
        this.diaryId = diaryId;
        this.foodId = foodId;
        this.foodName = foodName;
        this.weight = weight;
        this.calories = calories;
        this.proteins = proteins;
        this.fats = fats;
        this.carbs = carbs;
        this.createdAt = createdAt;
        this.updatedAt = updatedAt;
    }

    // Getters
    public Long getId() { return id; }
    public Long getDiaryId() { return diaryId; }
    public Long getFoodId() { return foodId; }
    public String getFoodName() { return foodName; }
    public double getWeight() { return weight; }
    public double getCalories() { return calories; }
    public double getProteins() { return proteins; }
    public double getFats() { return fats; }
    public double getCarbs() { return carbs; }
    public LocalDateTime getCreatedAt() { return createdAt; }
    public LocalDateTime getUpdatedAt() { return updatedAt; }
}

// Diary Food Repository 
package com.diettracker.backend.repositories;

import com.diettracker.backend.models.DiaryFood;
import org.springframework.data.jpa.repository.JpaRepository;

public interface DiaryFoodRepository extends JpaRepository<DiaryFood, Long> {
}

// Diary Service

package com.diettracker.backend.services;

import com.diettracker.backend.models.Diary;
import com.diettracker.backend.models.DiaryFood;
import com.diettracker.backend.models.DiaryType;
import com.diettracker.backend.models.Food;
import com.diettracker.backend.repositories.DiaryFoodRepository;
import com.diettracker.backend.repositories.DiaryRepository;
import com.diettracker.backend.repositories.FoodRepository;
import jakarta.persistence.EntityNotFoundException;
import jakarta.transaction.Transactional;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

@Service
@Transactional
public class DiaryService {
    @Autowired
    private DiaryRepository diaryRepository;

    @Autowired
    private FoodRepository foodRepository;

    @Autowired
    private DiaryFoodRepository diaryFoodRepository;

    public DiaryFood addFoodToDiary(Long diaryId, Long foodId, double weight) {
        // First, get the persistent entities from the database
        Diary diary;
        if (diaryId == null) {
            diary = new Diary(DiaryType.BREAKFAST); // Default type, you might want to make this configurable
            diary = diaryRepository.save(diary);
        } else {
            diary = diaryRepository.findById(diaryId).orElseThrow(() -> new EntityNotFoundException("Diary not found"));
        }


        Food food = foodRepository.findById(foodId).orElseThrow(() -> new EntityNotFoundException("Food not found"));

        // Create new DiaryFood with the persistent entities
        DiaryFood diaryFood = new DiaryFood();
        diaryFood.setDiary(diary);
        diaryFood.setFood(food);
        diaryFood.setWeight(weight);

        // Add to diary's collection
//        diary.addDiaryFood(diaryFood);

        // Save and return
        return diaryFoodRepository.save(diaryFood);
    }
}