using System.Text.Json;
using System.Text.Json.Serialization;
using ScadaLink.Commons.Types.DataConnections;

namespace ScadaLink.Commons.Serialization;

/// <summary>
/// Serializes <see cref="OpcUaEndpointConfig"/> to/from the typed nested JSON
/// shape stored in <c>DataConnection.PrimaryConfiguration</c> / <c>BackupConfiguration</c>.
/// On read, falls back to the legacy flat string-dict shape for pre-refactor rows
/// and returns IsLegacy=true so the form can prompt the user to re-save.
/// </summary>
public static class OpcUaEndpointConfigSerializer
{
    private static readonly JsonSerializerOptions JsonOpts = new()
    {
        PropertyNamingPolicy = JsonNamingPolicy.CamelCase,
        WriteIndented = false,
        Converters = { new JsonStringEnumConverter(JsonNamingPolicy.CamelCase) }
    };

    public static string Serialize(OpcUaEndpointConfig config)
        => JsonSerializer.Serialize(config, JsonOpts);

    public static (OpcUaEndpointConfig Config, bool IsLegacy) Deserialize(string? json)
    {
        if (string.IsNullOrWhiteSpace(json))
            return (new OpcUaEndpointConfig(), false);

        try
        {
            using var doc = JsonDocument.Parse(json);
            if (doc.RootElement.ValueKind == JsonValueKind.Object
                && doc.RootElement.TryGetProperty("endpointUrl", out _))
            {
                var typed = JsonSerializer.Deserialize<OpcUaEndpointConfig>(json, JsonOpts);
                if (typed != null)
                    return (typed, false);
            }
        }
        catch (JsonException) { /* fall through to legacy */ }

        try
        {
            return (LoadLegacy(json!), IsLegacy: true);
        }
        catch (JsonException)
        {
            return (new OpcUaEndpointConfig(), IsLegacy: true);
        }
    }

    /// <summary>
    /// Flattens the typed config to the IDictionary&lt;string,string&gt; shape that
    /// IDataConnection.ConnectAsync expects. Keys match the historical convention
    /// used by OpcUaDataConnection so the adapter can keep that interface.
    /// </summary>
    public static IDictionary<string, string> ToFlatDict(OpcUaEndpointConfig config)
    {
        var dict = new Dictionary<string, string>
        {
            ["endpoint"] = config.EndpointUrl,
            ["SecurityMode"] = config.SecurityMode.ToString(),
            ["AutoAcceptUntrustedCerts"] = config.AutoAcceptUntrustedCerts.ToString(),
            ["SessionTimeoutMs"] = config.SessionTimeoutMs.ToString(),
            ["OperationTimeoutMs"] = config.OperationTimeoutMs.ToString(),
            ["PublishingIntervalMs"] = config.PublishingIntervalMs.ToString(),
            ["SamplingIntervalMs"] = config.SamplingIntervalMs.ToString(),
            ["QueueSize"] = config.QueueSize.ToString(),
            ["KeepAliveCount"] = config.KeepAliveCount.ToString(),
            ["LifetimeCount"] = config.LifetimeCount.ToString(),
            ["MaxNotificationsPerPublish"] = config.MaxNotificationsPerPublish.ToString(),
        };
        if (config.Heartbeat is { } hb)
        {
            dict["HeartbeatTagPath"] = hb.TagPath;
            dict["HeartbeatMaxSilence"] = hb.MaxSilenceSeconds.ToString();
        }
        return dict;
    }

    public static OpcUaEndpointConfig FromFlatDict(IDictionary<string, string> dict)
    {
        var c = new OpcUaEndpointConfig();

        if (dict.TryGetValue("endpoint", out var ep) && !string.IsNullOrWhiteSpace(ep))
            c.EndpointUrl = ep;
        else if (dict.TryGetValue("EndpointUrl", out var ep2) && !string.IsNullOrWhiteSpace(ep2))
            c.EndpointUrl = ep2;

        if (dict.TryGetValue("SecurityMode", out var smStr)
            && Enum.TryParse<OpcUaSecurityMode>(smStr, ignoreCase: true, out var sm))
            c.SecurityMode = sm;

        if (dict.TryGetValue("AutoAcceptUntrustedCerts", out var aacStr)
            && bool.TryParse(aacStr, out var aac))
            c.AutoAcceptUntrustedCerts = aac;

        TryAssignInt(dict, "SessionTimeoutMs", v => c.SessionTimeoutMs = v);
        TryAssignInt(dict, "OperationTimeoutMs", v => c.OperationTimeoutMs = v);
        TryAssignInt(dict, "PublishingIntervalMs", v => c.PublishingIntervalMs = v);
        TryAssignInt(dict, "SamplingIntervalMs", v => c.SamplingIntervalMs = v);
        TryAssignInt(dict, "QueueSize", v => c.QueueSize = v);
        TryAssignInt(dict, "KeepAliveCount", v => c.KeepAliveCount = v);
        TryAssignInt(dict, "LifetimeCount", v => c.LifetimeCount = v);
        TryAssignInt(dict, "MaxNotificationsPerPublish", v => c.MaxNotificationsPerPublish = v);

        if (dict.TryGetValue("HeartbeatTagPath", out var hbPath)
            && !string.IsNullOrWhiteSpace(hbPath))
        {
            var hb = new OpcUaHeartbeatConfig { TagPath = hbPath };
            TryAssignInt(dict, "HeartbeatMaxSilence", v => hb.MaxSilenceSeconds = v);
            c.Heartbeat = hb;
        }

        return c;
    }

    private static OpcUaEndpointConfig LoadLegacy(string json)
    {
        var dict = JsonSerializer.Deserialize<Dictionary<string, string>>(json)
                   ?? new Dictionary<string, string>();
        return FromFlatDict(dict);
    }

    private static void TryAssignInt(IDictionary<string, string> dict, string key, Action<int> assign)
    {
        if (dict.TryGetValue(key, out var s) && int.TryParse(s, out var v))
            assign(v);
    }
}