package com.mydreamjob.skill;

import com.mydreamjob.common.exception.BusinessException;
import com.mydreamjob.common.exception.ErrorCode;
import com.mydreamjob.skill.domain.SkillCategory;
import com.mydreamjob.skill.domain.SkillIndustry;
import com.mydreamjob.skill.domain.SkillOccupation;
import com.mydreamjob.skill.dto.SkillCloudItem;
import com.mydreamjob.skill.dto.SkillCloudNode;
import com.mydreamjob.skill.dto.SkillCloudResponse;
import com.mydreamjob.skill.dto.SkillCloudSkillProjection;
import com.mydreamjob.skill.repository.OccupationSkillRepository;
import com.mydreamjob.skill.repository.SkillCategoryRepository;
import com.mydreamjob.skill.repository.SkillIndustryRepository;
import com.mydreamjob.skill.repository.SkillOccupationRepository;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Transactional;

import java.math.BigDecimal;
import java.util.Comparator;
import java.util.List;
import java.util.stream.IntStream;

@Service
@Transactional(readOnly = true)
public class SkillCloudQueryService {

    private static final Comparator<SkillCloudSkillProjection> SKILL_ORDER = (left, right) -> {
        int heatComparison = compareHeat(left.importance(), right.importance());
        if (heatComparison != 0) {
            return heatComparison;
        }

        int nameComparison = compareNullable(left.nameZh(), right.nameZh());
        if (nameComparison != 0) {
            return nameComparison;
        }

        return compareNullable(left.skillId(), right.skillId());
    };

    private final SkillIndustryRepository industryRepository;
    private final SkillOccupationRepository occupationRepository;
    private final SkillCategoryRepository categoryRepository;
    private final OccupationSkillRepository occupationSkillRepository;

    public SkillCloudQueryService(SkillIndustryRepository industryRepository,
                                  SkillOccupationRepository occupationRepository,
                                  SkillCategoryRepository categoryRepository,
                                  OccupationSkillRepository occupationSkillRepository) {
        this.industryRepository = industryRepository;
        this.occupationRepository = occupationRepository;
        this.categoryRepository = categoryRepository;
        this.occupationSkillRepository = occupationSkillRepository;
    }

    public SkillCloudResponse query(Long industryId, Long occupationId, Long categoryId) {
        long validatedIndustryId = requirePositive(industryId, "industryId");
        long validatedOccupationId = requirePositive(occupationId, "occupationId");
        Long validatedCategoryId = categoryId == null ? null : requirePositive(categoryId, "categoryId");

        SkillIndustry industry = industryRepository.findById(validatedIndustryId)
                .orElseThrow(() -> badRequest("industry not found: industryId=" + validatedIndustryId));
        SkillOccupation occupation = occupationRepository.findById(validatedOccupationId)
                .orElseThrow(() -> badRequest("occupation not found: occupationId=" + validatedOccupationId));
        if (!occupation.getIndustryId().equals(validatedIndustryId)) {
            throw badRequest("occupation does not belong to industry: occupationId="
                    + validatedOccupationId + ", industryId=" + validatedIndustryId);
        }

        SkillCategory category = null;
        if (validatedCategoryId != null) {
            category = categoryRepository.findById(validatedCategoryId)
                    .orElseThrow(() -> badRequest("category not found: categoryId=" + validatedCategoryId));
            if (!category.getOccupationId().equals(validatedOccupationId)) {
                throw badRequest("category does not belong to occupation: categoryId="
                        + validatedCategoryId + ", occupationId=" + validatedOccupationId);
            }
        }

        List<SkillCloudSkillProjection> projections = validatedCategoryId == null
                ? occupationSkillRepository.findSkillProjectionsByOccupationId(validatedOccupationId)
                : occupationSkillRepository.findSkillProjectionsByOccupationIdAndCategoryId(
                        validatedOccupationId, validatedCategoryId);

        List<SkillCloudSkillProjection> sortedProjections = projections.stream()
                .sorted(SKILL_ORDER)
                .toList();
        List<SkillCloudItem> items = IntStream.range(0, sortedProjections.size())
                .mapToObj(index -> toItem(sortedProjections.get(index), index + 1))
                .toList();

        return new SkillCloudResponse(
                toNode(industry.getId(), industry.getCode(), industry.getNameZh()),
                toNode(occupation.getId(), occupation.getCode(), occupation.getNameZh()),
                category == null ? null : toNode(category.getId(), category.getCode(), category.getNameZh()),
                items.size(),
                items
        );
    }

    private SkillCloudItem toItem(SkillCloudSkillProjection projection, int rank) {
        return new SkillCloudItem(
                rank,
                projection.skillId(),
                projection.skillCode(),
                projection.nameZh(),
                projection.nameEn(),
                projection.sourceType(),
                projection.sourceCode(),
                projection.categoryId(),
                projection.categoryName(),
                projection.importance(),
                projection.importanceSourceCode(),
                projection.importanceElementId(),
                projection.importanceIsProxy()
        );
    }

    private static int compareHeat(BigDecimal left, BigDecimal right) {
        if (left == null && right == null) {
            return 0;
        }
        if (left == null) {
            return 1;
        }
        if (right == null) {
            return -1;
        }
        return right.compareTo(left);
    }

    private static <T extends Comparable<? super T>> int compareNullable(T left, T right) {
        if (left == null && right == null) {
            return 0;
        }
        if (left == null) {
            return 1;
        }
        if (right == null) {
            return -1;
        }
        return left.compareTo(right);
    }

    private static SkillCloudNode toNode(Long id, String code, String name) {
        return new SkillCloudNode(id, code, name);
    }

    private static long requirePositive(Long value, String parameterName) {
        if (value == null || value <= 0) {
            throw badRequest(parameterName + " must be a positive integer");
        }
        return value;
    }

    private static BusinessException badRequest(String detail) {
        return new BusinessException(ErrorCode.BAD_REQUEST, detail);
    }
}