AI Chat

<thinking>
Considering the user's question about Blazor...
</thinking>

<search>
https://learn.microsoft.com/en-us/aspnet/core/blazor
https://docs.fluentui-blazor.net
</search>

<text>
**Blazor** is a .NET framework for building interactive web UIs. It supports both Server and WebAssembly hosting.
</text>

public interface IChatService
{
    IAsyncEnumerable<string> RunStreamingAsync(
        string prompt,
        CancellationToken cancellationToken = default);
}

public interface IStreamResponseParser
{
    void AppendChunk(string chunk);
}

public interface IStreamResponseParserService
{
    IStreamResponseParser CreateStream(IList<MessageComponent> components);
}

using System.Runtime.CompilerServices;

public class OpenAiChatService : IChatService
{
    private readonly HttpClient _http;

    public OpenAiChatService(HttpClient http) => _http = http;

    public async IAsyncEnumerable<string> RunStreamingAsync(
        string prompt,
        [EnumeratorCancellation] CancellationToken ct = default)
    {
        var request = new { model = "gpt-4", messages = new[] { new { role = "user", content = prompt } } };
        using var res = await _http.PostAsJsonAsync("https://api.openai.com/v1/chat/completions", request, ct);
        res.EnsureSuccessStatusCode();
        await using var stream = await res.Content.ReadAsStreamAsync(ct);

        await foreach (var chunk in ReadStreamAsChunks(stream, ct))
            yield return chunk;
    }

    private static async IAsyncEnumerable<string> ReadStreamAsChunks(Stream stream, [EnumeratorCancellation] CancellationToken ct)
    {
        using var reader = new StreamReader(stream);
        var buffer = new char[256];
        int read;
        while ((read = await reader.ReadAsync(buffer, ct)) > 0)
            yield return new string(buffer, 0, read);
    }
}

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

// Option A: Convert JSON to tag format, yield as one chunk
public class JsonToTagChatService : IChatService
{
    private readonly HttpClient _http;

    public async IAsyncEnumerable<string> RunStreamingAsync(string prompt, CancellationToken ct = default)
    {
        var json = await _http.GetStringAsync($"/api/chat?q={Uri.EscapeDataString(prompt)}", ct);
        var doc = JsonSerializer.Deserialize<ApiResponse>(json)!;

        var sb = new StringBuilder();
        if (!string.IsNullOrEmpty(doc.Thinking)) sb.Append($"<thinking>{doc.Thinking}</thinking>");
        if (doc.Sources?.Count > 0) sb.Append("<search>\n").AppendJoin('\n', doc.Sources).Append("\n</search>");
        if (!string.IsNullOrEmpty(doc.Text)) sb.Append($"<text>{doc.Text}</text>");

        yield return sb.ToString();
    }

    private record ApiResponse(string? Thinking, List<string>? Sources, string? Text);
}

// Option B: Custom parser for JSON (register via IStreamResponseParserService)
// Use when the API returns the full JSON in one chunk.
public class JsonStreamResponseParser : IStreamResponseParser
{
    private readonly IList<MessageComponent> _components;
    private string _buffer = string.Empty;
    private bool _parsed;

    public JsonStreamResponseParser(IList<MessageComponent> components) => _components = components;

    public void AppendChunk(string chunk)
    {
        if (_parsed) return;
        _buffer += chunk;
        var doc = JsonSerializer.Deserialize<ApiResponse>(_buffer);
        if (doc == null) return;

        _parsed = true;
        if (!string.IsNullOrEmpty(doc.Thinking)) _components.Add(new ThinkingMessageComponent { Content = doc.Thinking });
        if (doc.Sources?.Count > 0) _components.Add(new WebSearchMessageComponent { Content = string.Join("\n", doc.Sources) });
        if (!string.IsNullOrEmpty(doc.Text)) _components.Add(new TextMessageComponent { Content = doc.Text });
    }

    private record ApiResponse(string? Thinking, List<string>? Sources, string? Text);
}