package com.goldenchart.service;

import com.fasterxml.jackson.core.type.TypeReference;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.goldenchart.dto.TrendSearchRequest;
import com.goldenchart.dto.TrendSearchResultDto;
import com.goldenchart.dto.TrendSearchResultsResponse;
import com.goldenchart.entity.GcAppSettings;
import com.goldenchart.entity.GcTrendSearchSnapshot;
import com.goldenchart.repository.GcAppSettingsRepository;
import com.goldenchart.repository.GcTrendSearchSnapshotRepository;
import lombok.RequiredArgsConstructor;
import lombok.extern.slf4j.Slf4j;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Transactional;

import java.time.Instant;
import java.time.LocalDateTime;
import java.time.ZoneId;
import java.util.Collections;
import java.util.List;
import java.util.Optional;

@Service
@RequiredArgsConstructor
@Slf4j
public class TrendSearchSnapshotService {

    private static final TypeReference<List<TrendSearchResultDto>> RESULT_LIST_TYPE = new TypeReference<>() {};

    private final GcTrendSearchSnapshotRepository snapshotRepo;
    private final GcAppSettingsRepository appSettingsRepo;
    private final TrendSearchService trendSearchService;
    private final TrendSearchSettingsHelper settingsHelper;
    private final ObjectMapper mapper;

    @Transactional(readOnly = true)
    public TrendSearchResultsResponse getResults(Long userId, String deviceId) {
        String scopeKey = TrendSearchScope.key(userId, deviceId);
        return snapshotRepo.findById(scopeKey)
                .map(this::toResponse)
                .orElse(TrendSearchResultsResponse.empty());
    }

    @Transactional
    public List<TrendSearchResultDto> scanAndPersist(Long userId, String deviceId, TrendSearchRequest request) {
        GcAppSettings app = findAppSettings(userId, deviceId);
        TrendSearchRequest req = app != null
                ? settingsHelper.mergeRequestWithSettings(request, app)
                : (request != null ? request : new TrendSearchRequest());
        List<TrendSearchResultDto> results = trendSearchService.scan(req);
        persist(scopeKey(userId, deviceId), userId, deviceId, req, results);
        return results;
    }

    @Transactional
    public void runScheduledScan(Long userId, String deviceId) {
        String scopeKey = TrendSearchScope.key(userId, deviceId);
        GcAppSettings app = findAppSettings(userId, deviceId);
        if (app == null) return;

        TrendSearchRequest last = snapshotRepo.findById(scopeKey)
                .map(s -> settingsHelper.parseRequestJson(s.getRequestJson()))
                .orElse(null);
        TrendSearchRequest req = settingsHelper.buildRequest(app, last);
        List<TrendSearchResultDto> results = trendSearchService.scan(req);
        persist(scopeKey, userId, deviceId, req, results);
        log.debug("[TrendSearch] scheduled scan scope={} count={}", scopeKey, results.size());
    }

    private void persist(String scopeKey, Long userId, String deviceId,
                         TrendSearchRequest req, List<TrendSearchResultDto> results) {
        try {
            String resultsJson = mapper.writeValueAsString(results != null ? results : Collections.emptyList());
            String requestJson = mapper.writeValueAsString(req);
            GcTrendSearchSnapshot snap = snapshotRepo.findById(scopeKey).orElseGet(() ->
                    GcTrendSearchSnapshot.builder().scopeKey(scopeKey).build());
            snap.setUserId(userId);
            snap.setDeviceId(deviceId);
            snap.setTimeframe(req.getTimeframe() != null ? req.getTimeframe() : "1d");
            snap.setScannedAt(LocalDateTime.now());
            snap.setRequestJson(requestJson);
            snap.setResultsJson(resultsJson);
            snapshotRepo.save(snap);
        } catch (Exception e) {
            log.warn("[TrendSearch] persist failed scope={}: {}", scopeKey, e.getMessage());
        }
    }

    private TrendSearchResultsResponse toResponse(GcTrendSearchSnapshot snap) {
        List<TrendSearchResultDto> list = Collections.emptyList();
        try {
            if (snap.getResultsJson() != null && !snap.getResultsJson().isBlank()) {
                list = mapper.readValue(snap.getResultsJson(), RESULT_LIST_TYPE);
            }
        } catch (Exception e) {
            log.warn("[TrendSearch] deserialize results scope={}: {}", snap.getScopeKey(), e.getMessage());
        }
        Instant scannedAt = snap.getScannedAt() != null
                ? snap.getScannedAt().atZone(ZoneId.systemDefault()).toInstant()
                : null;
        return TrendSearchResultsResponse.builder()
                .results(list)
                .timeframe(snap.getTimeframe())
                .scannedAt(scannedAt)
                .build();
    }

    private GcAppSettings findAppSettings(Long userId, String deviceId) {
        if (userId != null) {
            return appSettingsRepo.findByUserId(userId).orElse(null);
        }
        if (deviceId != null && !deviceId.isBlank()) {
            return appSettingsRepo.findByDeviceId(deviceId).orElse(null);
        }
        return null;
    }

    private static String scopeKey(Long userId, String deviceId) {
        return TrendSearchScope.key(userId, deviceId);
    }

    /** 스케줄러: 마지막 스캔 시각 (없으면 epoch) */
    @Transactional(readOnly = true)
    public Optional<LocalDateTime> lastScannedAt(Long userId, String deviceId) {
        return snapshotRepo.findById(TrendSearchScope.key(userId, deviceId))
                .map(GcTrendSearchSnapshot::getScannedAt);
    }
}