using System.Text.Json;
using System.Text.Json.Serialization;

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 stored by reference only: <see cref="TokenEnv"/>
/// names an environment variable resolved at runtime — never the token itself (SDD §6.4).
/// </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; }

    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 from the referenced environment variable (null if unset).</summary>
    public string? ResolveToken() =>
        string.IsNullOrWhiteSpace(TokenEnv) ? null : Environment.GetEnvironmentVariable(TokenEnv);
}