package com.ruoyi.device.simulator;

import java.math.BigDecimal;
import java.time.Instant;
import java.time.LocalDateTime;
import java.time.ZoneId;
import java.time.format.DateTimeFormatter;
import java.time.format.DateTimeParseException;
import java.time.temporal.ChronoUnit;
import java.util.ArrayList;
import java.util.Comparator;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;
import java.util.Set;
import com.ruoyi.device.simulator.BtsSimulatorStateStore.CollectorChannelState;
import com.ruoyi.device.simulator.BtsSimulatorStateStore.CollectorHistoryFaults;
import com.ruoyi.device.simulator.BtsSimulatorStateStore.CollectorMeasurementRecord;
import com.ruoyi.device.simulator.BtsSimulatorStateStore.CollectorMetricState;
import com.ruoyi.device.simulator.BtsSimulatorStateStore.CollectorRealtimeMeasurement;
import com.ruoyi.device.simulator.BtsSimulatorStateStore.CollectorState;

/** 实现第一版开发采集器的独立采样与故障注入合同。 */
public final class DevelopmentCollectorSimulation
{
    public static final int DEFAULT_SAMPLE_INTERVAL_MS = 1000;
    public static final int MIN_SAMPLE_INTERVAL_MS = 100;
    public static final int MAX_SAMPLE_INTERVAL_MS = 60000;
    public static final int MAX_HISTORY_PAGE_SIZE = 1000;
    private static final int MAX_SAMPLES_PER_ADVANCE = 1000;
    private static final ZoneId DEVICE_ZONE = ZoneId.of("Asia/Hong_Kong");
    private static final DateTimeFormatter DEVICE_TIME_FORMATTER =
            DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss.SSS");

    private DevelopmentCollectorSimulation() { }

    /** 创建带稳定 S 通道和三项固定演示指标的采集器状态。 */
    public static List<CollectorChannelState> defaultChannels(int channelCount)
    {
        List<CollectorChannelState> channels = new ArrayList<>(channelCount);
        for (int index = 1; index <= channelCount; index++)
        {
            channels.add(new CollectorChannelState(channelCode(index), List.of(
                    new CollectorMetricState("temperature", new BigDecimal("25.0")
                            .add(BigDecimal.valueOf(index, 1)), "℃"),
                    new CollectorMetricState("positive_potential", new BigDecimal("3.700"), "V"),
                    new CollectorMetricState("negative_potential", new BigDecimal("-0.100"), "V"))));
        }
        return List.copyOf(channels);
    }

    /** 调整通道数时保留已有通道配置，并为新增通道生成稳定默认配置。 */
    public static CollectorState resize(CollectorState current, String ip, int channelCount, boolean online,
            Instant changedAt)
    {
        List<CollectorChannelState> defaults = defaultChannels(channelCount);
        List<CollectorChannelState> channels = new ArrayList<>(channelCount);
        for (int index = 0; index < channelCount; index++)
            channels.add(index < current.channels().size() ? current.channels().get(index) : defaults.get(index));
        Instant lastSampledAt = online == current.online() ? current.lastSampledAt() : changedAt;
        List<CollectorRealtimeMeasurement> latestMeasurements = retainConfiguredMeasurements(
                current.latestMeasurements(), channels);
        return copy(current, ip, channelCount, online, current.sampleIntervalMs(), current.nextSequence(),
                lastSampledAt, channels, latestMeasurements, current.historyRecordCount(), current.historyFaults());
    }

    /** 更新采样频率和历史下载故障；测量原始历史保持只追加。 */
    public static CollectorState configureSampling(CollectorState current, int sampleIntervalMs,
            CollectorHistoryFaults historyFaults)
    {
        validateSampleInterval(sampleIntervalMs);
        validateFaults(historyFaults);
        return copy(current, current.ip(), current.channelCount(), current.online(), sampleIntervalMs,
                current.nextSequence(), current.lastSampledAt(), current.channels(), current.latestMeasurements(),
                current.historyRecordCount(), historyFaults);
    }

    /** 替换一个演示通道的指标配置；动态添加项与固定指标共用指标编码合同。 */
    public static CollectorState configureChannel(CollectorState current, String channelCode,
            List<CollectorMetricState> metrics)
    {
        validateMetrics(metrics);
        int channelIndex = parseChannelIndex(channelCode, current.channelCount());
        List<CollectorChannelState> channels = new ArrayList<>(current.channels());
        channels.set(channelIndex, new CollectorChannelState(channelCode(channelIndex + 1), metrics));
        List<CollectorRealtimeMeasurement> latestMeasurements = retainConfiguredMeasurements(
                current.latestMeasurements(), channels);
        return copy(current, current.ip(), current.channelCount(), current.online(), current.sampleIntervalMs(),
                current.nextSequence(), current.lastSampledAt(), channels, latestMeasurements,
                current.historyRecordCount(), current.historyFaults());
    }

    /** 按采集器自身频率推进采样；离线期间不生成记录，恢复后从下一序号继续。 */
    public static CollectorAdvance advance(CollectorState current, Instant now)
    {
        if (!current.online()) return new CollectorAdvance(current, List.of());
        Instant sampleAt = current.lastSampledAt() == null
                ? now
                : current.lastSampledAt().plusMillis(current.sampleIntervalMs());
        if (sampleAt.isAfter(now)) return new CollectorAdvance(current, List.of());

        List<CollectorMeasurementRecord> appendedRecords = new ArrayList<>();
        Map<String, CollectorRealtimeMeasurement> latest = new LinkedHashMap<>();
        for (CollectorRealtimeMeasurement measurement : current.latestMeasurements())
            latest.put(measurementKey(measurement.channelCode(), measurement.metricCode()), measurement);
        long sequence = current.nextSequence();
        int generated = 0;
        Instant lastSampledAt = current.lastSampledAt();
        while (!sampleAt.isAfter(now) && generated < MAX_SAMPLES_PER_ADVANCE)
        {
            for (CollectorChannelState channel : current.channels())
            {
                for (CollectorMetricState metric : channel.metrics())
                {
                    CollectorMeasurementRecord record = new CollectorMeasurementRecord("dev-sim", current.deviceCode(),
                            channel.channelCode(), sequence, sampleAt,
                            DEVICE_TIME_FORMATTER.format(sampleAt.atZone(DEVICE_ZONE)), now,
                            metric.metricCode(), metric.value(), metric.unit());
                    appendedRecords.add(record);
                    latest.put(measurementKey(record.channelCode(), record.metricCode()),
                            new CollectorRealtimeMeasurement(record.adapterCode(), record.collectorCode(),
                                    record.channelCode(), record.sequenceId(), record.deviceTime(),
                                    record.deviceTimeRaw(), record.serverReceivedAt(), record.metricCode(),
                                    record.value(), record.unit()));
                }
            }
            lastSampledAt = sampleAt;
            sequence++;
            generated++;
            sampleAt = sampleAt.plusMillis(current.sampleIntervalMs());
        }
        CollectorState next = copy(current, current.ip(), current.channelCount(), current.online(),
                current.sampleIntervalMs(),
                sequence, lastSampledAt, current.channels(), List.copyOf(latest.values()),
                current.historyRecordCount() + appendedRecords.size(),
                current.historyFaults());
        return new CollectorAdvance(next, appendedRecords);
    }

    /** 返回独立保存的最新实时快照，不从原始历史反推当前状态。 */
    public static CollectorRealtimeSnapshot realtime(CollectorState current)
    {
        return new CollectorRealtimeSnapshot(current.deviceCode(), current.online(), current.sampleIntervalMs(),
                current.latestMeasurements());
    }

    /** 对只追加原始模拟历史应用可重复的下载故障视图，再按偏移量分页。 */
    public static CollectorHistoryPage history(CollectorState current, List<CollectorMeasurementRecord> rawHistory,
            long offset, int limit)
    {
        if (offset < 0) throw new IllegalArgumentException("offset must not be negative");
        if (limit < 1 || limit > MAX_HISTORY_PAGE_SIZE)
            throw new IllegalArgumentException("limit must be between 1 and " + MAX_HISTORY_PAGE_SIZE);

        List<CollectorMeasurementRecord> download = faultedHistory(current, rawHistory);
        int from = (int) Math.min(offset, download.size());
        int to = Math.min(from + limit, download.size());
        return new CollectorHistoryPage(current.deviceCode(), offset, to, to < download.size(),
                download.size(), download.subList(from, to));
    }

    /** 校验 Redis 恢复的采集器采样状态，拒绝损坏状态被静默替换。 */
    public static void validate(CollectorState state, List<CollectorMeasurementRecord> rawHistory)
    {
        validateSampleInterval(state.sampleIntervalMs());
        if (state.nextSequence() < 1 || state.channels().size() != state.channelCount())
            throw new IllegalStateException("Invalid collector sampling state in Redis");
        for (int index = 0; index < state.channels().size(); index++)
        {
            CollectorChannelState channel = state.channels().get(index);
            if (!channelCode(index + 1).equals(channel.channelCode()))
                throw new IllegalStateException("Invalid collector channel identity in Redis");
            validateMetrics(channel.metrics());
        }
        validateLatestMeasurements(state);
        validateHistory(state, rawHistory);
        validateFaults(state.historyFaults());
    }

    private static void validateLatestMeasurements(CollectorState state)
    {
        Set<String> configured = configuredMeasurementKeys(state.channels());
        Set<String> identities = new java.util.HashSet<>();
        for (CollectorRealtimeMeasurement measurement : state.latestMeasurements())
        {
            String key = measurementKey(measurement.channelCode(), measurement.metricCode());
            if (!validMeasurement(state, measurement.adapterCode(), measurement.collectorCode(),
                    measurement.channelCode(), measurement.sequenceId(), measurement.deviceTime(),
                    measurement.deviceTimeRaw(), measurement.serverReceivedAt(), measurement.metricCode(),
                    measurement.value(), measurement.unit()) || !configured.contains(key) || !identities.add(key)
                    || measurement.sequenceId() >= state.nextSequence())
                throw new IllegalStateException("Invalid collector realtime state in Redis");
        }
    }

    private static void validateHistory(CollectorState state, List<CollectorMeasurementRecord> rawHistory)
    {
        long maximumSequence = 0;
        long previousSequence = 0;
        Set<String> identities = new java.util.HashSet<>();
        for (CollectorMeasurementRecord record : rawHistory)
        {
            String identity = record.sequenceId() + "\u0000" + record.channelCode() + "\u0000" + record.metricCode();
            if (!validMeasurement(state, record.adapterCode(), record.collectorCode(), record.channelCode(),
                    record.sequenceId(), record.deviceTime(), record.deviceTimeRaw(), record.serverReceivedAt(),
                    record.metricCode(), record.value(), record.unit()) || !identities.add(identity)
                    || record.sequenceId() < previousSequence)
                throw new IllegalStateException("Invalid collector history state in Redis");
            maximumSequence = Math.max(maximumSequence, record.sequenceId());
            previousSequence = record.sequenceId();
        }
        if (state.nextSequence() <= maximumSequence)
            throw new IllegalStateException("Invalid collector history sequence in Redis");
        if (state.historyRecordCount() != rawHistory.size())
            throw new IllegalStateException("Invalid collector history count in Redis");
    }

    private static boolean validMeasurement(CollectorState state, String adapterCode, String collectorCode,
            String channelCode, long sequenceId, Instant deviceTime, String deviceTimeRaw,
            Instant serverReceivedAt, String metricCode, BigDecimal value, String unit)
    {
        return "dev-sim".equals(adapterCode) && state.deviceCode().equals(collectorCode)
                && validHistoricalChannelCode(channelCode)
                && sequenceId > 0 && deviceTime != null && deviceTimeRaw != null && !deviceTimeRaw.isBlank()
                && validDeviceTime(deviceTime, deviceTimeRaw) && serverReceivedAt != null
                && !serverReceivedAt.isBefore(deviceTime) && metricCode != null && !metricCode.isBlank()
                && metricCode.equals(metricCode.trim()) && value != null && unit != null && !unit.isBlank()
                && unit.equals(unit.trim());
    }

    private static boolean validHistoricalChannelCode(String channelCode)
    {
        if (channelCode == null || !channelCode.matches("S-\\d{2}")) return false;
        int index = Integer.parseInt(channelCode.substring(2));
        return index >= 1 && channelCode(index).equals(channelCode);
    }

    private static boolean validDeviceTime(Instant deviceTime, String deviceTimeRaw)
    {
        try
        {
            Instant parsed = LocalDateTime.parse(deviceTimeRaw, DEVICE_TIME_FORMATTER)
                    .atZone(DEVICE_ZONE).toInstant();
            return parsed.equals(deviceTime.truncatedTo(ChronoUnit.MILLIS));
        }
        catch (DateTimeParseException exception)
        {
            return false;
        }
    }

    private static List<CollectorRealtimeMeasurement> retainConfiguredMeasurements(
            List<CollectorRealtimeMeasurement> measurements, List<CollectorChannelState> channels)
    {
        Set<String> configured = configuredMeasurementKeys(channels);
        return measurements.stream()
                .filter(item -> configured.contains(measurementKey(item.channelCode(), item.metricCode())))
                .toList();
    }

    private static Set<String> configuredMeasurementKeys(List<CollectorChannelState> channels)
    {
        Set<String> configured = new java.util.HashSet<>();
        for (CollectorChannelState channel : channels)
            for (CollectorMetricState metric : channel.metrics())
                configured.add(measurementKey(channel.channelCode(), metric.metricCode()));
        return configured;
    }

    private static String measurementKey(String channelCode, String metricCode)
    {
        return channelCode + "\u0000" + metricCode;
    }

    private static List<CollectorMeasurementRecord> faultedHistory(CollectorState current,
            List<CollectorMeasurementRecord> rawHistory)
    {
        CollectorHistoryFaults faults = current.historyFaults();
        Set<Long> missing = Set.copyOf(faults.missingSequences());
        List<CollectorMeasurementRecord> records = new ArrayList<>();
        for (CollectorMeasurementRecord record : rawHistory)
        {
            if (missing.contains(record.sequenceId())) continue;
            records.add(record);
            if (Long.valueOf(record.sequenceId()).equals(faults.duplicateSequence())) records.add(record);
            if (Long.valueOf(record.sequenceId()).equals(faults.conflictingSequence()))
                records.add(new CollectorMeasurementRecord(record.adapterCode(), record.collectorCode(),
                        record.channelCode(), record.sequenceId(), record.deviceTime(), record.deviceTimeRaw(),
                        record.serverReceivedAt(), record.metricCode(),
                        record.value().add(new BigDecimal("0.001")), record.unit()));
        }
        if (faults.outOfOrder())
            records.sort(Comparator.comparingLong(CollectorMeasurementRecord::sequenceId).reversed()
                    .thenComparing(CollectorMeasurementRecord::channelCode)
                    .thenComparing(CollectorMeasurementRecord::metricCode));
        return records;
    }

    private static CollectorState copy(CollectorState current, String ip, int channelCount, boolean online,
            int sampleIntervalMs, long nextSequence, Instant lastSampledAt,
            List<CollectorChannelState> channels, List<CollectorRealtimeMeasurement> latestMeasurements,
            long historyRecordCount,
            CollectorHistoryFaults faults)
    {
        return new CollectorState(current.collectorId(), current.deviceCode(), ip.trim(), current.mac(),
                current.name(), current.manufacturer(), current.model(), channelCount, online, sampleIntervalMs,
                nextSequence, lastSampledAt, channels, latestMeasurements, historyRecordCount, faults);
    }

    private static void validateSampleInterval(int sampleIntervalMs)
    {
        if (sampleIntervalMs < MIN_SAMPLE_INTERVAL_MS || sampleIntervalMs > MAX_SAMPLE_INTERVAL_MS)
            throw new IllegalArgumentException("sampleIntervalMs must be between " + MIN_SAMPLE_INTERVAL_MS
                    + " and " + MAX_SAMPLE_INTERVAL_MS);
    }

    private static void validateMetrics(List<CollectorMetricState> metrics)
    {
        if (metrics == null || metrics.isEmpty())
            throw new IllegalArgumentException("Collector channel must contain at least one metric");
        java.util.HashSet<String> codes = new java.util.HashSet<>();
        for (CollectorMetricState metric : metrics)
        {
            if (metric.metricCode() == null || metric.metricCode().isBlank() || metric.value() == null
                    || !metric.metricCode().equals(metric.metricCode().trim())
                    || metric.unit() == null || metric.unit().isBlank()
                    || !metric.unit().equals(metric.unit().trim()) || !codes.add(metric.metricCode()))
                throw new IllegalArgumentException("Collector metric code, value and unit must be valid and unique");
        }
    }

    private static void validateFaults(CollectorHistoryFaults faults)
    {
        if (faults == null) throw new IllegalArgumentException("historyFaults must not be null");
        if (faults.missingSequences().stream().anyMatch(sequence -> sequence == null || sequence < 1)
                || faults.duplicateSequence() != null && faults.duplicateSequence() < 1
                || faults.conflictingSequence() != null && faults.conflictingSequence() < 1)
            throw new IllegalArgumentException("History fault sequences must be positive");
    }

    private static int parseChannelIndex(String value, int channelCount)
    {
        if (value == null || !value.matches("S-\\d{2}"))
            throw new IllegalArgumentException("Collector channel must use S-01...S-N identity");
        int index = Integer.parseInt(value.substring(2)) - 1;
        if (index < 0 || index >= channelCount || !channelCode(index + 1).equals(value))
            throw new IllegalArgumentException("Unknown collector channel: " + value);
        return index;
    }

    private static String channelCode(int index)
    {
        return String.format("S-%02d", index);
    }

    public record CollectorRealtimeSnapshot(String collectorCode, boolean online, int sampleIntervalMs,
            List<CollectorRealtimeMeasurement> measurements)
    {
        public CollectorRealtimeSnapshot { measurements = List.copyOf(measurements); }
    }

    public record CollectorAdvance(CollectorState state, List<CollectorMeasurementRecord> appendedRecords)
    {
        public CollectorAdvance { appendedRecords = List.copyOf(appendedRecords); }
    }

    public record CollectorHistoryPage(String collectorCode, long offset, long nextOffset, boolean hasMore,
            long total, List<CollectorMeasurementRecord> records)
    {
        public CollectorHistoryPage { records = List.copyOf(records); }
    }
}