using System.Text.Json;

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

public sealed record Ib43Reading(double? Value, DateTimeOffset ReceivedAt, string Source);

public sealed class Ib43Report
{
    public bool Accepted { get; internal set; }
    public string Raw { get; init; }
    public DateTimeOffset ReceivedAt { get; init; }
    public List<string> Issues { get; } = [];
    public Dictionary<string, Ib43Reading> Readings { get; } = new(StringComparer.Ordinal);
    public Dictionary<string, JsonElement> Fields { get; } = new(StringComparer.Ordinal);
    public HashSet<string> Kinds { get; } = [];
}

/// <summary>只解析协议事实；不产生控制、健康告警或睡眠分期。</summary>
public sealed class Ib43Parser
{
    public Ib43Report Parse(string topic, string payload, Ib43Binding binding, DateTimeOffset receivedAt)
    {
        var r = new Ib43Report { Raw = payload, ReceivedAt = receivedAt };
        if (topic != binding.PostTopic) return Reject(r, "topic-mismatch");
        try
        {
            using var document = JsonDocument.Parse(payload);
            var root = document.RootElement;
            if (HasDuplicates(root)) return Reject(r, "duplicate-json-key");
            if (root.ValueKind != JsonValueKind.Object ||
                !root.TryGetProperty("method", out var method) || method.ValueKind != JsonValueKind.String ||
                method.GetString() != "thing.property.post" ||
                !root.TryGetProperty("params", out var p) || p.ValueKind != JsonValueKind.Object)
                return Reject(r, "invalid-envelope");
            if (!p.TryGetProperty("deviceName", out var sn) || sn.ValueKind != JsonValueKind.String ||
                sn.GetString() != binding.SerialNumber ||
                (p.TryGetProperty("productKey", out var pk) &&
                 (pk.ValueKind != JsonValueKind.String || pk.GetString() != binding.ProductKey)))
                return Reject(r, "identity-mismatch");
            if (root.TryGetProperty("version", out var version) &&
                (version.ValueKind != JsonValueKind.String || version.GetString() != "1.0"))
                return Reject(r, "unsupported-version");
            r.Accepted = true;
            foreach (var key in new[] { "firmwareVer", "characteristic", "deviceMode" })
            {
                if (!p.TryGetProperty(key, out var value)) continue;
                r.Kinds.Add("startup");
                var valid = key switch
                {
                    "firmwareVer" => value.ValueKind == JsonValueKind.String,
                    "characteristic" => value.ValueKind == JsonValueKind.Object,
                    _ => value.ValueKind == JsonValueKind.Number && value.TryGetInt32(out _)
                };
                if (valid) r.Fields[key] = value.Clone(); else r.Issues.Add(key + ":invalid-type");
            }
            if (p.TryGetProperty("HR", out var hr))
            {
                r.Kinds.Add("periodic");
                if (Numbers(hr, 6, "HR", r) is { } values)
                {
                    Vitals(r, "left", values[0], values[1], values[2], "HR");
                    Vitals(r, "right", values[3], values[4], values[5], "HR");
                }
            }
            if (p.TryGetProperty("airbagsPerson", out var person))
            {
                r.Kinds.Add("periodic");
                if (Numbers(person, 2, "airbagsPerson", r) is { } values)
                {
                    if (values.All(v => v is 0 or 1))
                    {
                        r.Fields["airbagsPerson"] = person.Clone();
                        if (binding.PersonLeftIndex is int index)
                        {
                            Add(r, "left.presence", values[index], "airbagsPerson");
                            Add(r, "right.presence", values[1 - index], "airbagsPerson");
                        }
                    }
                    else r.Issues.Add("airbagsPerson:invalid-enum");
                }
            }
            foreach (var (key, length) in new[] { ("airbagsPressure", 8), ("motorHeight", 2),
                         ("motorStatus", 4), ("motorMode", 2), ("snoreStatus", 2),
                         ("LeftRegularTime", 10), ("RightRegularTime", 10) })
            {
                if (!p.TryGetProperty(key, out var value)) continue;
                r.Kinds.Add("periodic");
                if (Numbers(value, length, key, r) is not { } numbers) continue;
                if (key == "motorStatus" && numbers.Any(n => n is not (0 or 1 or 2)))
                    r.Issues.Add("motorStatus:invalid-enum");
                else r.Fields[key] = value.Clone();
            }
            if (p.TryGetProperty("adaptive", out var adaptive))
            {
                r.Kinds.Add("periodic");
                if (adaptive.ValueKind == JsonValueKind.Array && adaptive.GetArrayLength() == 2 &&
                    adaptive.EnumerateArray().All(a => a.ValueKind == JsonValueKind.Object))
                    r.Fields["adaptive"] = adaptive.Clone();
                else r.Issues.Add("adaptive:invalid-shape");
            }
            var sleep = Alias(p, "SleepReportNew", r);
            if (sleep is { } s)
            {
                r.Kinds.Add("event");
                if (s.ValueKind != JsonValueKind.Object) r.Issues.Add("SleepReportNew:invalid-type");
                else if (Alias(s, "ibNew", r) is { } ib && Numbers(ib, 12, "ibNew", r) is { } values)
                {
                    Presence(r, "left", values[0], "ibNew");
                    Presence(r, "right", values[6], "ibNew");
                    Vitals(r, "left", values[4], values[3], values[1], "ibNew");
                    Vitals(r, "right", values[10], values[9], values[7], "ibNew");
                }
                else r.Issues.Add("ibNew:missing-or-invalid");
            }
            if (r.Kinds.Count == 0) r.Issues.Add("unrecognized-report");
        }
        catch (JsonException) { return Reject(r, "invalid-json"); }
        return r;
    }

    private static Ib43Report Reject(Ib43Report r, string issue)
    { r.Accepted = false; r.Issues.Add(issue); return r; }

    private static bool HasDuplicates(JsonElement node) => node.ValueKind switch
    {
        JsonValueKind.Object => node.EnumerateObject().GroupBy(p => p.Name, StringComparer.Ordinal).Any(g => g.Count() > 1) ||
                                node.EnumerateObject().Any(p => HasDuplicates(p.Value)),
        JsonValueKind.Array => node.EnumerateArray().Any(HasDuplicates),
        _ => false
    };

    private static JsonElement? Alias(JsonElement p, string key, Ib43Report r)
    {
        var plain = p.TryGetProperty(key, out var a);
        var spaced = p.TryGetProperty(" " + key, out var b);
        // 双键即使内容相同也拒绝该字段，避免依赖 JSON 文本格式决定覆盖顺序。
        if (plain && spaced) { r.Issues.Add(key + ":ambiguous-alias"); return null; }
        if (spaced) { r.Fields["alias." + key] = JsonSerializer.SerializeToElement(" " + key); return b; }
        return plain ? a : null;
    }

    private static double[] Numbers(JsonElement value, int length, string key, Ib43Report r)
    {
        if (value.ValueKind != JsonValueKind.Array || value.GetArrayLength() != length)
        { r.Issues.Add(key + ":invalid-length"); return null; }
        var numbers = new double[length];
        var i = 0;
        foreach (var item in value.EnumerateArray())
        {
            if (item.ValueKind != JsonValueKind.Number || !item.TryGetDouble(out var number) || !double.IsFinite(number))
            { r.Issues.Add(key + ":invalid-number"); return null; }
            numbers[i++] = number;
        }
        return numbers;
    }

    private static void Add(Ib43Report r, string key, double? value, string source)
        => r.Readings[key] = new(value, r.ReceivedAt, source);

    private static void Presence(Ib43Report r, string side, double value, string source)
    {
        if (value is 0 or 1) Add(r, side + ".presence", value, source);
        else r.Issues.Add(side + ".presence:invalid-enum");
    }

    private static void Vitals(Ib43Report r, string side, double hr, double respiration, double snore, string source)
    {
        if (hr >= 0) Add(r, side + ".heartRate", hr == 0 ? null : hr, source);
        else r.Issues.Add(side + ".heartRate:negative");
        if (respiration >= 0) Add(r, side + ".respiration", respiration == 0 ? null : respiration, source);
        else r.Issues.Add(side + ".respiration:negative");
        if (snore is 0 or 1) Add(r, side + ".snoring", snore, source);
        else r.Issues.Add(side + ".snoring:invalid-enum");
    }
}