package com.ftptool.sync.service;

import com.ftptool.sync.entity.ProdPullAckRecord;
import com.ftptool.sync.model.ProdPullAckStatus;
import com.ftptool.sync.model.ProdPullResult;
import com.ftptool.sync.repository.ProdPullAckRecordRepository;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Transactional;
import org.springframework.util.StringUtils;

import java.time.LocalDateTime;
import java.util.ArrayList;
import java.util.Collection;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;

/**
 * Stores pullConfig ack states and retry plans.
 */
@Service
public class ProdPullAckService {

    private static final int RETRY_DELAY_BASE_SECONDS = 30;

    private final ProdPullAckRecordRepository prodPullAckRecordRepository;

    public ProdPullAckService(ProdPullAckRecordRepository prodPullAckRecordRepository) {
        this.prodPullAckRecordRepository = prodPullAckRecordRepository;
    }

    @Transactional(readOnly = true)
    public PendingAckSummary getPendingAckSummary() {
        List<String> successIds = toRemoteIds(
                prodPullAckRecordRepository.findByAckStatusAndReportedFalseOrderByUpdatedAtAsc(ProdPullAckStatus.SUCCESS)
        );
        List<String> failedIds = toRemoteIds(
                prodPullAckRecordRepository.findByAckStatusAndReportedFalseOrderByUpdatedAtAsc(ProdPullAckStatus.FAILED)
        );
        return new PendingAckSummary(successIds, failedIds);
    }

    @Transactional
    public void recordAckSuccess(Collection<ProdPullResult.PulledConfigRef> pulledConfigs) {
        if (pulledConfigs == null) {
            return;
        }

        for (ProdPullResult.PulledConfigRef pulledConfig : pulledConfigs) {
            if (!hasRemoteId(pulledConfig)) {
                continue;
            }

            ProdPullAckRecord record = prodPullAckRecordRepository.findByRemoteConfigId(pulledConfig.getRemoteConfigId())
                    .orElseGet(ProdPullAckRecord::new);
            record.setRemoteConfigId(pulledConfig.getRemoteConfigId());
            record.setAckStatus(ProdPullAckStatus.SUCCESS);
            record.setReported(Boolean.FALSE);
            applyPullMetadata(record, pulledConfig);
            record.setRetryCount(0);
            record.setNextRetryAt(null);
            record.setLastErrorMsg(null);
            prodPullAckRecordRepository.save(record);
        }
    }

    @Transactional
    public void recordPullFailure(
            Collection<ProdPullResult.PulledConfigRef> pulledConfigs,
            String errorMsg,
            boolean retryAttempt
    ) {
        if (pulledConfigs == null) {
            return;
        }

        for (ProdPullResult.PulledConfigRef pulledConfig : pulledConfigs) {
            if (!hasRemoteId(pulledConfig)) {
                continue;
            }

            ProdPullAckRecord record = prodPullAckRecordRepository.findByRemoteConfigId(pulledConfig.getRemoteConfigId())
                    .orElseGet(ProdPullAckRecord::new);
            record.setRemoteConfigId(pulledConfig.getRemoteConfigId());
            record.setAckStatus(ProdPullAckStatus.FAILED);
            record.setReported(Boolean.FALSE);
            applyPullMetadata(record, pulledConfig);
            record.setLastErrorMsg(errorMsg);
            if (retryAttempt) {
                int retryCount = safeRetryCount(record) + 1;
                record.setRetryCount(retryCount);
                record.setNextRetryAt(calculateNextRetryAt(retryCount));
            } else {
                record.setRetryCount(0);
                record.setNextRetryAt(LocalDateTime.now());
            }
            prodPullAckRecordRepository.save(record);
        }
    }

    @Transactional
    public void markRetryAttemptFailed(RetryPullRequest retryPullRequest, String errorMsg) {
        if (retryPullRequest == null || retryPullRequest.getRemoteConfigIds().isEmpty()) {
            return;
        }

        for (String remoteConfigId : retryPullRequest.getRemoteConfigIds()) {
            prodPullAckRecordRepository.findByRemoteConfigId(remoteConfigId).ifPresent(record -> {
                int retryCount = safeRetryCount(record) + 1;
                record.setRetryCount(retryCount);
                record.setNextRetryAt(calculateNextRetryAt(retryCount));
                record.setLastErrorMsg(errorMsg);
                record.setAckStatus(ProdPullAckStatus.FAILED);
                prodPullAckRecordRepository.save(record);
            });
        }
    }

    @Transactional(readOnly = true)
    public List<RetryPullRequest> getRetryPullRequests(int maxRetryCount) {
        List<ProdPullAckRecord> failedRecords = prodPullAckRecordRepository.findByAckStatusOrderByUpdatedAtAsc(ProdPullAckStatus.FAILED);
        LocalDateTime now = LocalDateTime.now();
        Map<String, RetryPullRequest> retryPullRequests = new LinkedHashMap<String, RetryPullRequest>();

        for (ProdPullAckRecord failedRecord : failedRecords) {
            if (!hasRetryMetadata(failedRecord)) {
                continue;
            }
            if (safeRetryCount(failedRecord) >= maxRetryCount) {
                continue;
            }
            if (failedRecord.getNextRetryAt() != null && failedRecord.getNextRetryAt().isAfter(now)) {
                continue;
            }

            String groupKey = buildRetryGroupKey(failedRecord);
            RetryPullRequest retryPullRequest = retryPullRequests.get(groupKey);
            if (retryPullRequest == null) {
                retryPullRequest = new RetryPullRequest(
                        failedRecord.getSourceVersion(),
                        failedRecord.getAirportId(),
                        failedRecord.getAppName(),
                        failedRecord.getFileName()
                );
                retryPullRequests.put(groupKey, retryPullRequest);
            }
            retryPullRequest.addRemoteConfigId(failedRecord.getRemoteConfigId());
        }

        return new ArrayList<RetryPullRequest>(retryPullRequests.values());
    }

    @Transactional
    public void markPendingAsReported() {
        List<ProdPullAckRecord> records = prodPullAckRecordRepository.findByReportedFalseOrderByUpdatedAtAsc();
        for (ProdPullAckRecord record : records) {
            record.setReported(Boolean.TRUE);
            prodPullAckRecordRepository.save(record);
        }
    }

    private void applyPullMetadata(ProdPullAckRecord record, ProdPullResult.PulledConfigRef pulledConfig) {
        if (pulledConfig == null) {
            return;
        }
        if (StringUtils.hasText(pulledConfig.getConfigVersion())) {
            record.setSourceVersion(pulledConfig.getConfigVersion().trim());
        }
        if (StringUtils.hasText(pulledConfig.getAirportId())) {
            record.setAirportId(pulledConfig.getAirportId().trim());
        }
        if (StringUtils.hasText(pulledConfig.getAppName())) {
            record.setAppName(pulledConfig.getAppName().trim());
        }
        if (StringUtils.hasText(pulledConfig.getFileName())) {
            record.setFileName(pulledConfig.getFileName().trim());
        }
    }

    private boolean hasRemoteId(ProdPullResult.PulledConfigRef pulledConfig) {
        return pulledConfig != null && StringUtils.hasText(pulledConfig.getRemoteConfigId());
    }

    private boolean hasRetryMetadata(ProdPullAckRecord failedRecord) {
        return StringUtils.hasText(failedRecord.getSourceVersion())
                && StringUtils.hasText(failedRecord.getAirportId())
                && StringUtils.hasText(failedRecord.getAppName())
                && StringUtils.hasText(failedRecord.getFileName());
    }

    private int safeRetryCount(ProdPullAckRecord record) {
        return record.getRetryCount() == null ? 0 : record.getRetryCount().intValue();
    }

    private LocalDateTime calculateNextRetryAt(int retryCount) {
        long delaySeconds = RETRY_DELAY_BASE_SECONDS * (1L << Math.max(0, retryCount - 1));
        return LocalDateTime.now().plusSeconds(delaySeconds);
    }

    private String buildRetryGroupKey(ProdPullAckRecord failedRecord) {
        return failedRecord.getSourceVersion() + "|"
                + failedRecord.getAirportId() + "|"
                + failedRecord.getAppName() + "|"
                + failedRecord.getFileName();
    }

    private List<String> toRemoteIds(List<ProdPullAckRecord> records) {
        List<String> ids = new ArrayList<String>();
        for (ProdPullAckRecord record : records) {
            ids.add(record.getRemoteConfigId());
        }
        return ids;
    }

    public static class PendingAckSummary {

        private final List<String> ackSucIds;
        private final List<String> ackFailIds;

        public PendingAckSummary(List<String> ackSucIds, List<String> ackFailIds) {
            this.ackSucIds = ackSucIds;
            this.ackFailIds = ackFailIds;
        }

        public List<String> getAckSucIds() {
            return ackSucIds;
        }

        public List<String> getAckFailIds() {
            return ackFailIds;
        }

        public boolean hasPendingAck() {
            return !(ackSucIds == null || ackSucIds.isEmpty()) || !(ackFailIds == null || ackFailIds.isEmpty());
        }
    }

    public static class RetryPullRequest {

        private final String sourceVersion;
        private final String airportId;
        private final String appName;
        private final String fileName;
        private final List<String> remoteConfigIds = new ArrayList<String>();

        public RetryPullRequest(String sourceVersion, String airportId, String appName, String fileName) {
            this.sourceVersion = sourceVersion;
            this.airportId = airportId;
            this.appName = appName;
            this.fileName = fileName;
        }

        public String getSourceVersion() {
            return sourceVersion;
        }

        public String getAirportId() {
            return airportId;
        }

        public String getAppName() {
            return appName;
        }

        public String getFileName() {
            return fileName;
        }

        public List<String> getRemoteConfigIds() {
            return remoteConfigIds;
        }

        private void addRemoteConfigId(String remoteConfigId) {
            this.remoteConfigIds.add(remoteConfigId);
        }
    }
}