using System.Text.Json;
using System.Text.Json.Serialization;
using MeterVault.Infrastructure.Security;

namespace MeterVault.Infrastructure.Ingestion;

/// <summary>
/// The parsed <see cref="Core.Domain.IngestionEndpoint.Config"/> JSON for a Home Assistant
/// connection (SDD §6.2). The long-lived token is never held here as plaintext (SDD §6.4): either
/// <see cref="TokenEnv"/> names an environment variable resolved at runtime, or
/// <see cref="TokenEnc"/> holds it encrypted under the app's data-protection key ring.
/// </summary>
public sealed record HaEndpointConfig
{
    private static readonly JsonSerializerOptions Options = new()
    {
        PropertyNameCaseInsensitive = true,
        DefaultIgnoreCondition = JsonIgnoreCondition.WhenWritingNull,
    };

    /// <summary>Base URL of the Home Assistant instance, e.g. <c>http://homeassistant.local:8123</c>.</summary>
    public string? BaseUrl { get; init; }

    /// <summary>Name of the environment variable holding the long-lived access token.</summary>
    public string? TokenEnv { get; init; }

    /// <summary>
    /// The long-lived access token, encrypted by <see cref="Security.SecretProtector"/>. Set when
    /// the operator typed the token into the admin UI instead of naming an environment variable.
    /// </summary>
    public string? TokenEnc { get; init; }

    /// <summary>
    /// When true, a persistent WebSocket subscription pushes state changes in real time
    /// (<see cref="HomeAssistantWebSocketWorker"/>); when false (default) the REST poll worker
    /// samples on each source's interval. An endpoint is handled by exactly one of the two.
    /// </summary>
    public bool UseWebSocket { get; init; }

    public static HaEndpointConfig Parse(string? json)
    {
        if (string.IsNullOrWhiteSpace(json))
        {
            return new HaEndpointConfig();
        }

        try
        {
            return JsonSerializer.Deserialize<HaEndpointConfig>(json, Options) ?? new HaEndpointConfig();
        }
        catch (JsonException)
        {
            return new HaEndpointConfig();
        }
    }

    public string ToJson() => JsonSerializer.Serialize(this, Options);

    /// <summary>
    /// Resolves the token: the encrypted value when one was entered directly, otherwise the
    /// referenced environment variable. Null when neither yields anything.
    /// </summary>
    public string? ResolveToken(SecretProtector? protector = null) =>
        EndpointSecret.Resolve(TokenEnc, TokenEnv, protector);
}