using Microsoft.Extensions.Options;
using System.Text.Json;

namespace Evergreen.Health.Application.Health.Integrations.Ib43;

public sealed record Ib43Field(JsonElement Value, DateTimeOffset ReceivedAt);
public sealed record Ib43Snapshot(string ProductKey, string SerialNumber, bool Simulation,
    string Transport, string Freshness, DateTimeOffset? LastTelemetryAt,
    IReadOnlyDictionary<string, Ib43Reading> Readings, IReadOnlyDictionary<string, Ib43Field> Fields);
public sealed record Ib43Diagnostic(string Topic, DateTimeOffset ReceivedAt, string Raw, string[] Issues);

/// <summary>进程内有界缓存。没有设备遗嘱，不能将数据超时等同于已确认设备离线。</summary>
public sealed class Ib43StateStore(IOptions<Ib43Options> options, Ib43Parser parser, TimeProvider clock)
{
    public const int MaxPayloadBytes = 65536;
    private readonly object _gate = new();
    private readonly Dictionary<string, DeviceState> _states = new(StringComparer.Ordinal);
    private readonly Queue<Ib43Diagnostic> _diagnostics = new();
    private string _transport = options.Value.Enabled ? "disconnected" : "disabled";

    private sealed class DeviceState
    {
        public DateTimeOffset? LastTelemetryAt;
        public Dictionary<string, Ib43Reading> Readings { get; } = new(StringComparer.Ordinal);
        public Dictionary<string, Ib43Field> Fields { get; } = new(StringComparer.Ordinal);
    }

    public void SetTransport(string state) { lock (_gate) _transport = state; }

    public void RejectOversized(string topic)
    {
        lock (_gate)
        {
            _diagnostics.Enqueue(new(topic, clock.GetUtcNow(), "", ["payload-too-large:body-not-retained"]));
            while (_diagnostics.Count > 32) _diagnostics.Dequeue();
        }
    }

    public Ib43Report Receive(string topic, string payload, bool retained = false)
    {
        lock (_gate)
        {
            var now = clock.GetUtcNow();
            var binding = options.Value.Devices.FirstOrDefault(d => d.PostTopic == topic);
            Ib43Report report;
            if (binding == null || retained || System.Text.Encoding.UTF8.GetByteCount(payload) > MaxPayloadBytes)
            {
                report = new() { Raw = payload.Length > 4096 ? payload[..4096] : payload, ReceivedAt = now };
                report.Issues.Add(binding == null ? "unbound-topic" : retained ? "retained-not-live" : "payload-too-large");
            }
            else report = parser.Parse(topic, payload, binding, now);

            _diagnostics.Enqueue(new(topic, now, report.Raw, report.Issues.ToArray()));
            while (_diagnostics.Count > 32) _diagnostics.Dequeue();
            if (!report.Accepted) return report;
            if (!_states.TryGetValue(topic, out var state)) _states[topic] = state = new();
            foreach (var (key, value) in report.Readings) state.Readings[key] = value;
            foreach (var (key, value) in report.Fields) state.Fields[key] = new(value, now);
            // 只有有效实时字段刷新活跃性；能力包、未知包和坏包不能掩盖实时数据停止。
            if (report.Readings.Count > 0 || report.Fields.Keys.Any(k => k is "airbagsPerson" or
                "airbagsPressure" or "motorHeight" or "motorStatus" or "snoreStatus"))
                state.LastTelemetryAt = now;
            return report;
        }
    }

    public Ib43Snapshot[] Snapshot()
    {
        lock (_gate)
        {
            var now = clock.GetUtcNow();
            return options.Value.Devices.Select(binding =>
            {
                _states.TryGetValue(binding.PostTopic, out var state);
                var last = state?.LastTelemetryAt;
                var freshness = last == null ? "unknown" :
                    now - last.Value > TimeSpan.FromSeconds(options.Value.StaleAfterSeconds) ? "stale" : "recent";
                return new Ib43Snapshot(binding.ProductKey, binding.SerialNumber, binding.Simulation,
                    _transport, freshness, last,
                    state == null ? new Dictionary<string, Ib43Reading>() : new(state.Readings),
                    state == null ? new Dictionary<string, Ib43Field>() : new(state.Fields));
            }).ToArray();
        }
    }

    // 不通过公共 H5 API 暴露原始健康数据；后续持久化需绑定用户权限与保留期限。
    public Ib43Diagnostic[] Diagnostics() { lock (_gate) return _diagnostics.ToArray(); }
}