Add go-llm v2: redesigned API for simpler LLM abstraction

v2 is a new Go module (v2/) with a dramatically simpler API:
- Unified Message type (no more Input marker interface)
- Define[T] for ergonomic tool creation with standard context.Context
- Chat session with automatic tool-call loop (agent loop)
- Streaming via pull-based StreamReader
- MCP one-call connect (MCPStdioServer, MCPHTTPServer, MCPSSEServer)
- Middleware support (logging, retry, timeout, usage tracking)
- Decoupled JSON Schema (map[string]any, no provider coupling)
- Sample tools: WebSearch, Browser, Exec, ReadFile, WriteFile, HTTP
- Providers: OpenAI, Anthropic, Google (all with streaming)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

v2/stream.go

@@ -0,0 +1,163 @@
+package llm
+
+import (
+	"context"
+	"fmt"
+	"io"
+
+	"gitea.stevedudenhoeffer.com/steve/go-llm/v2/provider"
+)
+
+// StreamEventType identifies the kind of stream event.
+type StreamEventType = provider.StreamEventType
+
+const (
+	StreamEventText      = provider.StreamEventText
+	StreamEventToolStart = provider.StreamEventToolStart
+	StreamEventToolDelta = provider.StreamEventToolDelta
+	StreamEventToolEnd   = provider.StreamEventToolEnd
+	StreamEventDone      = provider.StreamEventDone
+	StreamEventError     = provider.StreamEventError
+)
+
+// StreamEvent represents a single event in a streaming response.
+type StreamEvent struct {
+	Type StreamEventType
+
+	// Text is set for StreamEventText — the text delta.
+	Text string
+
+	// ToolCall is set for StreamEventToolStart/ToolDelta/ToolEnd.
+	ToolCall *ToolCall
+
+	// ToolIndex identifies which tool call is being updated.
+	ToolIndex int
+
+	// Error is set for StreamEventError.
+	Error error
+
+	// Response is set for StreamEventDone — the complete, aggregated response.
+	Response *Response
+}
+
+// StreamReader reads streaming events from an LLM response.
+// Must be closed when done.
+type StreamReader struct {
+	events <-chan StreamEvent
+	cancel context.CancelFunc
+	done   bool
+}
+
+func newStreamReader(ctx context.Context, p provider.Provider, req provider.Request) (*StreamReader, error) {
+	ctx, cancel := context.WithCancel(ctx)
+	providerEvents := make(chan provider.StreamEvent, 32)
+
+	publicEvents := make(chan StreamEvent, 32)
+
+	go func() {
+		defer close(publicEvents)
+		for pev := range providerEvents {
+			ev := convertStreamEvent(pev)
+			select {
+			case publicEvents <- ev:
+			case <-ctx.Done():
+				return
+			}
+		}
+	}()
+
+	go func() {
+		defer close(providerEvents)
+		if err := p.Stream(ctx, req, providerEvents); err != nil {
+			select {
+			case providerEvents <- provider.StreamEvent{Type: provider.StreamEventError, Error: err}:
+			default:
+			}
+		}
+	}()
+
+	return &StreamReader{
+		events: publicEvents,
+		cancel: cancel,
+	}, nil
+}
+
+func convertStreamEvent(pev provider.StreamEvent) StreamEvent {
+	ev := StreamEvent{
+		Type:      pev.Type,
+		Text:      pev.Text,
+		ToolIndex: pev.ToolIndex,
+	}
+	if pev.Error != nil {
+		ev.Error = pev.Error
+	}
+	if pev.ToolCall != nil {
+		tc := ToolCall{
+			ID:        pev.ToolCall.ID,
+			Name:      pev.ToolCall.Name,
+			Arguments: pev.ToolCall.Arguments,
+		}
+		ev.ToolCall = &tc
+	}
+	if pev.Response != nil {
+		resp := convertProviderResponse(*pev.Response)
+		ev.Response = &resp
+	}
+	return ev
+}
+
+// Next returns the next event from the stream.
+// Returns io.EOF when the stream is complete.
+func (sr *StreamReader) Next() (StreamEvent, error) {
+	if sr.done {
+		return StreamEvent{}, io.EOF
+	}
+	ev, ok := <-sr.events
+	if !ok {
+		sr.done = true
+		return StreamEvent{}, io.EOF
+	}
+	if ev.Type == StreamEventError {
+		return ev, ev.Error
+	}
+	if ev.Type == StreamEventDone {
+		sr.done = true
+	}
+	return ev, nil
+}
+
+// Close closes the stream reader and releases resources.
+func (sr *StreamReader) Close() error {
+	sr.cancel()
+	return nil
+}
+
+// Collect reads all events and returns the final aggregated Response.
+func (sr *StreamReader) Collect() (Response, error) {
+	var lastResp *Response
+	for {
+		ev, err := sr.Next()
+		if err == io.EOF {
+			break
+		}
+		if err != nil {
+			return Response{}, err
+		}
+		if ev.Type == StreamEventDone && ev.Response != nil {
+			lastResp = ev.Response
+		}
+	}
+	if lastResp == nil {
+		return Response{}, fmt.Errorf("stream completed without final response")
+	}
+	return *lastResp, nil
+}
+
+// Text is a convenience that collects the stream and returns just the text.
+func (sr *StreamReader) Text() (string, error) {
+	resp, err := sr.Collect()
+	if err != nil {
+		return "", err
+	}
+	return resp.Text, nil
+}