package com.mydreamjob.skill;

import com.fasterxml.jackson.core.type.TypeReference;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.mydreamjob.profile.StudentProfile;
import com.mydreamjob.profile.StudentProfileRepository;
import com.mydreamjob.skill.domain.SkillAlias;
import com.mydreamjob.skill.dto.SkillCloudItem;
import com.mydreamjob.skill.dto.SkillCloudResponse;
import com.mydreamjob.skill.dto.SkillMatchResponse;
import com.mydreamjob.skill.repository.SkillAliasRepository;
import lombok.extern.slf4j.Slf4j;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Transactional;

import java.util.ArrayList;
import java.util.Collection;
import java.util.HashMap;
import java.util.HashSet;
import java.util.List;
import java.util.Map;
import java.util.Set;

@Slf4j
@Service
@Transactional(readOnly = true)
public class SkillMatchService {

    private static final int TOP_LIMIT = 10;

    private final SkillCloudQueryService skillCloudQueryService;
    private final StudentProfileRepository studentProfileRepository;
    private final SkillAliasRepository skillAliasRepository;
    private final SkillNameNormalizer skillNameNormalizer;
    private final ObjectMapper objectMapper;

    public SkillMatchService(SkillCloudQueryService skillCloudQueryService,
                             StudentProfileRepository studentProfileRepository,
                             SkillAliasRepository skillAliasRepository,
                             SkillNameNormalizer skillNameNormalizer,
                             ObjectMapper objectMapper) {
        this.skillCloudQueryService = skillCloudQueryService;
        this.studentProfileRepository = studentProfileRepository;
        this.skillAliasRepository = skillAliasRepository;
        this.skillNameNormalizer = skillNameNormalizer;
        this.objectMapper = objectMapper;
    }

    public SkillMatchResponse match(Long studentUserId,
                                    Long industryId,
                                    Long occupationId,
                                    Long categoryId) {
        SkillCloudResponse cloud = skillCloudQueryService.query(industryId, occupationId, categoryId);
        int actualTopSize = Math.min(TOP_LIMIT, cloud.items().size());
        List<SkillCloudItem> topSkills = cloud.items().subList(0, actualTopSize);
        Set<String> studentSkills = loadStudentSkills(studentUserId);
        Map<Long, List<SkillAlias>> aliasesBySkillId = loadAliases(topSkills);

        List<SkillCloudItem> matchedSkills = new ArrayList<>();
        List<SkillCloudItem> missingSkills = new ArrayList<>();
        for (SkillCloudItem skill : topSkills) {
            if (matches(skill, studentSkills, aliasesBySkillId.getOrDefault(skill.skillId(), List.of()))) {
                matchedSkills.add(skill);
            } else {
                missingSkills.add(skill);
            }
        }

        int matchScore = actualTopSize == 0
                ? 0
                : (int) Math.round(matchedSkills.size() * 100.0 / actualTopSize);
        return new SkillMatchResponse(
                matchScore,
                matchedSkills.size(),
                actualTopSize,
                matchedSkills,
                missingSkills
        );
    }

    private Set<String> loadStudentSkills(Long studentUserId) {
        if (studentUserId == null) {
            return Set.of();
        }

        StudentProfile profile = studentProfileRepository.findByUserId(studentUserId).orElse(null);
        if (profile == null || profile.getSkillsJson() == null || profile.getSkillsJson().isBlank()) {
            return Set.of();
        }

        try {
            List<String> parsed = objectMapper.readValue(
                    profile.getSkillsJson(),
                    new TypeReference<List<String>>() {}
            );
            if (parsed == null || parsed.isEmpty()) {
                return Set.of();
            }

            Set<String> normalizedSkills = new HashSet<>();
            for (String skill : parsed) {
                if (skill == null) {
                    continue;
                }
                String normalized = skillNameNormalizer.normalize(skill);
                if (!normalized.isBlank()) {
                    normalizedSkills.add(normalized);
                }
            }
            return Set.copyOf(normalizedSkills);
        } catch (Exception exception) {
            log.warn("Failed to parse student skills JSON: profileId={}, errorType={}",
                    profile.getId(), exception.getClass().getSimpleName());
            return Set.of();
        }
    }

    private Map<Long, List<SkillAlias>> loadAliases(List<SkillCloudItem> topSkills) {
        Collection<Long> skillIds = topSkills.stream()
                .map(SkillCloudItem::skillId)
                .filter(java.util.Objects::nonNull)
                .toList();
        if (skillIds.isEmpty()) {
            return Map.of();
        }

        Map<Long, List<SkillAlias>> aliasesBySkillId = new HashMap<>();
        for (SkillAlias alias : skillAliasRepository.findAllBySkillIdInOrderByIdAsc(skillIds)) {
            aliasesBySkillId.computeIfAbsent(alias.getSkillId(), ignored -> new ArrayList<>()).add(alias);
        }
        return aliasesBySkillId;
    }

    private boolean matches(SkillCloudItem skill,
                            Set<String> studentSkills,
                            List<SkillAlias> aliases) {
        if (containsNormalized(studentSkills, skill.nameZh())
                || containsNormalized(studentSkills, skill.nameEn())
                || containsNormalized(studentSkills, skill.skillCode())) {
            return true;
        }
        return aliases.stream().anyMatch(alias -> containsNormalized(studentSkills, alias.getAlias()));
    }

    private boolean containsNormalized(Set<String> studentSkills, String candidate) {
        if (candidate == null) {
            return false;
        }
        String normalized = skillNameNormalizer.normalize(candidate);
        return !normalized.isBlank() && studentSkills.contains(normalized);
    }
}