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StreamMessageReader.cs
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StreamMessageReader.cs
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using Cysharp.IO;
using System.Runtime.CompilerServices;
using System.Text.Json;
namespace Claudia;
// parser of server-sent events
// https://developer.mozilla.org/en-US/docs/Web/API/Server-sent_events/Using_server-sent_events
internal class StreamMessageReader : IDisposable
{
readonly Utf8StreamReader reader;
readonly bool configureAwait;
MessageStreamEventKind currentEvent;
public StreamMessageReader(Stream stream, bool configureAwait)
{
this.reader = new Utf8StreamReader(stream, leaveOpen: true) { ConfigureAwait = configureAwait };
this.configureAwait = configureAwait;
}
public async IAsyncEnumerable<IMessageStreamEvent> ReadMessagesAsync([EnumeratorCancellation] CancellationToken cancellationToken)
{
while (await reader.LoadIntoBufferAsync(cancellationToken).ConfigureAwait(configureAwait))
{
while (reader.TryReadLine(out var line))
{
var streamEvent = ParseLine(line);
if (streamEvent == null) continue;
yield return streamEvent;
if (streamEvent.TypeKind == MessageStreamEventKind.MessageStop)
{
yield break;
}
}
}
}
IMessageStreamEvent? ParseLine(ReadOnlyMemory<byte> line)
{
// line is these kinds
// event: event_name
// data: json
// (empty line)
var span = line.Span;
if (span.Length == 0)
{
return null; // next.
}
else if (span[0] == 'e') // event
{
// Parse Event.
var first = span[7]; // "event: [c|m|p|e]"
if (first == 'c') // content_block_start/delta/stop
{
switch (span[23]) // event: content_block_..[]
{
case (byte)'a': // st[a]rt
currentEvent = MessageStreamEventKind.ContentBlockStart;
break;
case (byte)'o': // st[o]p
currentEvent = MessageStreamEventKind.ContentBlockStop;
break;
case (byte)'l': // de[l]ta
currentEvent = MessageStreamEventKind.ContentBlockDelta;
break;
default:
break;
}
}
else if (first == 'm') // message_start/delta/stop
{
switch (span[17]) // event: message_..[]
{
case (byte)'a': // st[a]rt
currentEvent = MessageStreamEventKind.MessageStart;
break;
case (byte)'o': // st[o]p
currentEvent = MessageStreamEventKind.MessageStop;
break;
case (byte)'l': // de[l]ta
currentEvent = MessageStreamEventKind.MessageDelta;
break;
default:
break;
}
}
else if (first == 'p')
{
currentEvent = MessageStreamEventKind.Ping;
}
else if (first == 'e')
{
currentEvent = (MessageStreamEventKind)(-1);
}
else
{
// Unknown Event, Skip.
// throw new InvalidOperationException("Unknown Event. Line:" + Encoding.UTF8.GetString(line.ToArray()));
currentEvent = (MessageStreamEventKind)(-2);
}
return null; // continue
}
else if (span[0] == 'd') // data
{
// Parse Data.
var jsonReader = new Utf8JsonReader(span.Slice(6)); // skip data:
switch (currentEvent)
{
case MessageStreamEventKind.Ping:
return JsonSerializer.Deserialize<Ping>(ref jsonReader, AnthropicJsonSerializerContext.Default.Options)!;
case MessageStreamEventKind.MessageStart:
return JsonSerializer.Deserialize<MessageStart>(ref jsonReader, AnthropicJsonSerializerContext.Default.Options)!;
case MessageStreamEventKind.MessageDelta:
return JsonSerializer.Deserialize<MessageDelta>(ref jsonReader, AnthropicJsonSerializerContext.Default.Options)!;
case MessageStreamEventKind.MessageStop:
return JsonSerializer.Deserialize<MessageStop>(ref jsonReader, AnthropicJsonSerializerContext.Default.Options)!;
case MessageStreamEventKind.ContentBlockStart:
return JsonSerializer.Deserialize<ContentBlockStart>(ref jsonReader, AnthropicJsonSerializerContext.Default.Options)!;
case MessageStreamEventKind.ContentBlockDelta:
return JsonSerializer.Deserialize<ContentBlockDelta>(ref jsonReader, AnthropicJsonSerializerContext.Default.Options)!;
case MessageStreamEventKind.ContentBlockStop:
return JsonSerializer.Deserialize<ContentBlockStop>(ref jsonReader, AnthropicJsonSerializerContext.Default.Options)!;
case (MessageStreamEventKind)(-1):
var error = JsonSerializer.Deserialize<ErrorResponseShape>(ref jsonReader, AnthropicJsonSerializerContext.Default.Options);
throw new ClaudiaException(error!.ErrorResponse.ToErrorCode(), error.ErrorResponse.Type, error.ErrorResponse.Message);
default:
// unknown event, skip
return null;
}
}
return null;
}
public void Dispose()
{
reader.Dispose();
}
}