using System.Text.Encodings.Web;
using System.Text.Json;

namespace NucleicProtocol.Interop;

/// Small typed constructors for the renderer's first intents. Swift remains the decoder and
/// source of truth; these helpers only keep hand-written UI JSON out of call sites.
public static class ClientIntents
{
    public static string ListSessions() => TagOnly("listSessions");
    public static string ListDashboard() => TagOnly("listDashboard");
    public static string ListPeers() => TagOnly("listPeers");
    public static string Ping() => TagOnly("ping");

    public static string Subscribe(string sessionId, ulong? sinceSequence = null, string verbosity = "full") =>
        Write(writer =>
        {
            writer.WriteString("sessionID", sessionId);
            if (sinceSequence is { } sequence) writer.WriteNumber("sinceSeq", sequence);
            writer.WriteString("t", "subscribe");
            writer.WriteString("verbosity", verbosity);
        });

    public static string Unsubscribe(string sessionId) => Write(writer =>
    {
        writer.WriteString("sessionID", sessionId);
        writer.WriteString("t", "unsubscribe");
    });

    public static string ApprovalRespond(
        string approvalId, string decisionType, JsonElement? updatedInput = null) =>
        Write(writer =>
        {
            writer.WriteString("approvalID", approvalId);
            writer.WritePropertyName("decision");
            writer.WriteStartObject();
            writer.WriteString("type", decisionType);
            if (updatedInput is { } input)
            {
                writer.WritePropertyName("updatedInput");
                input.WriteTo(writer);
            }
            writer.WriteEndObject();
            writer.WriteString("t", "approvalRespond");
        });

    public static string SendInput(string sessionId, string text) => Write(writer =>
    {
        writer.WritePropertyName("input");
        writer.WriteStartObject();
        writer.WritePropertyName("parts");
        writer.WriteStartArray();
        writer.WriteStartObject();
        writer.WriteString("text", text);
        writer.WriteString("type", "text");
        writer.WriteEndObject();
        writer.WriteEndArray();
        writer.WriteEndObject();
        writer.WriteString("sessionID", sessionId);
        writer.WriteString("t", "sendInput");
    });

    private static string TagOnly(string tag) => JsonSerializer.Serialize(
        new TagOnlyIntent(tag), ProtocolJsonContext.Default.TagOnlyIntent);

    private static string Write(Action<Utf8JsonWriter> body)
    {
        using var stream = new MemoryStream();
        using (var writer = new Utf8JsonWriter(stream, new JsonWriterOptions
        {
            Encoder = JavaScriptEncoder.UnsafeRelaxedJsonEscaping,
        }))
        {
            writer.WriteStartObject();
            body(writer);
            writer.WriteEndObject();
        }
        return System.Text.Encoding.UTF8.GetString(stream.GetBuffer(), 0, checked((int)stream.Length));
    }
}