package com.mydreamjob.talentinvitation;

import com.mydreamjob.talentdiscovery.CandidateKeyGenerator;
import com.mydreamjob.talentdiscovery.TalentDiscoveryCandidateSource;
import lombok.RequiredArgsConstructor;
import org.springframework.stereotype.Component;

import java.nio.charset.StandardCharsets;
import java.security.MessageDigest;
import java.time.LocalDate;
import java.time.LocalDateTime;
import java.util.Map;
import java.util.List;

/** 在当前 V41 合格候选池内重算 opaque key，绝不通过 key 反解学生 ID。 */
@Component
@RequiredArgsConstructor
public class TalentInvitationCandidateResolver {
    private final TalentDiscoveryCandidateSource candidateSource;
    private final CandidateKeyGenerator candidateKeyGenerator;

    public Resolution resolve(Long companyId, Long jobId, String candidateKey, LocalDateTime capturedNow) {
        if (companyId == null || jobId == null || candidateKey == null || capturedNow == null) {
            return Resolution.none();
        }
        byte[] expected = candidateKey.getBytes(StandardCharsets.UTF_8);
        Long match = null;
        int matches = 0;
        List<TalentDiscoveryCandidateSource.CandidateSeed> candidates = candidateSource.findEligibleCandidates(companyId);
        List<Long> candidateIds = candidates.stream().map(TalentDiscoveryCandidateSource.CandidateSeed::studentUserId).toList();
        Map<Long, TalentDiscoveryCandidateSource.PreferenceSignal> preferences = safeMap(candidateSource.findPreferences(candidateIds));
        Map<Long, TalentDiscoveryCandidateSource.ScoreSignal> riasec = safeMap(candidateSource.findLatestRiasec(candidateIds));
        Map<Long, TalentDiscoveryCandidateSource.ScoreSignal> ability = safeMap(candidateSource.findLatestAbility(candidateIds, capturedNow));
        LocalDate bucket = capturedNow.toLocalDate();
        for (TalentDiscoveryCandidateSource.CandidateSeed candidate : candidates) {
            // 候选池要求至少有一个可用推荐信号；缺失信号不得按 0 分放行。
            if (!hasSignal(candidate.studentUserId(), preferences, riasec, ability)) continue;
            String generated = candidateKeyGenerator.generate(companyId, jobId, candidate.studentUserId(), bucket);
            if (MessageDigest.isEqual(expected, generated.getBytes(StandardCharsets.UTF_8))) {
                match = candidate.studentUserId();
                matches++;
            }
        }
        return matches == 1 ? new Resolution(match, true) : Resolution.none();
    }

    private boolean hasSignal(Long studentId,
                              Map<Long, TalentDiscoveryCandidateSource.PreferenceSignal> preferences,
                              Map<Long, TalentDiscoveryCandidateSource.ScoreSignal> riasec,
                              Map<Long, TalentDiscoveryCandidateSource.ScoreSignal> ability) {
        TalentDiscoveryCandidateSource.PreferenceSignal p = preferences.get(studentId);
        if (p != null && (p.expectedSalaryMin() != null || p.expectedSalaryMax() != null
                || !p.cities().isEmpty() || !p.employmentTypes().isEmpty()
                || !p.industries().isEmpty() || !p.jobTypes().isEmpty())) return true;
        TalentDiscoveryCandidateSource.ScoreSignal i = riasec.get(studentId);
        if (i != null && i.scores() != null && !i.scores().isEmpty()) return true;
        TalentDiscoveryCandidateSource.ScoreSignal a = ability.get(studentId);
        return a != null && a.scores() != null && !a.scores().isEmpty();
    }

    private <K, V> Map<K, V> safeMap(Map<K, V> value) {
        return value == null ? Map.of() : value;
    }

    public record Resolution(Long studentUserId, boolean matched) {
        public static Resolution none() { return new Resolution(null, false); }
    }
}