feat: add /x/acpio package (#188)

Relates to coder/internal#1333

Adds /x/acpio package

Author: johnstcn

go.mod

@@ -6,6 +6,7 @@ require (
 	github.com/ActiveState/termtest/xpty v0.6.0
 	github.com/acarl005/stripansi v0.0.0-20180116102854-5a71ef0e047d
 	github.com/charmbracelet/bubbletea v1.3.4
+	github.com/coder/acp-go-sdk v0.6.3
 	github.com/coder/agentapi-sdk-go v0.0.0-20250505131810-560d1d88d225
 	github.com/coder/quartz v0.1.2
 	github.com/danielgtaylor/huma/v2 v2.32.0
@@ -15,6 +16,7 @@ require (
 	github.com/spf13/viper v1.20.1
 	github.com/stretchr/testify v1.11.1
 	github.com/tmaxmax/go-sse v0.10.0
+	go.uber.org/goleak v1.3.0
 	golang.org/x/term v0.30.0
 	golang.org/x/xerrors v0.0.0-20240903120638-7835f813f4da
 )

go.sum

@@ -163,6 +163,8 @@ github.com/ckaznocha/intrange v0.3.1 h1:j1onQyXvHUsPWujDH6WIjhyH26gkRt/txNlV7Lsp
 github.com/ckaznocha/intrange v0.3.1/go.mod h1:QVepyz1AkUoFQkpEqksSYpNpUo3c5W7nWh/s6SHIJJk=
 github.com/client9/misspell v0.3.4/go.mod h1:qj6jICC3Q7zFZvVWo7KLAzC3yx5G7kyvSDkc90ppPyw=
 github.com/cncf/udpa/go v0.0.0-20191209042840-269d4d468f6f/go.mod h1:M8M6+tZqaGXZJjfX53e64911xZQV5JYwmTeXPW+k8Sc=
+github.com/coder/acp-go-sdk v0.6.3 h1:LsXQytehdjKIYJnoVWON/nf7mqbiarnyuyE3rrjBsXQ=
+github.com/coder/acp-go-sdk v0.6.3/go.mod h1:yKzM/3R9uELp4+nBAwwtkS0aN1FOFjo11CNPy37yFko=
 github.com/coder/agentapi-sdk-go v0.0.0-20250505131810-560d1d88d225 h1:tRIViZ5JRmzdOEo5wUWngaGEFBG8OaE1o2GIHN5ujJ8=
 github.com/coder/agentapi-sdk-go v0.0.0-20250505131810-560d1d88d225/go.mod h1:rNLVpYgEVeu1Zk29K64z6Od8RBP9DwqCu9OfCzh8MR4=
 github.com/coder/paralleltestctx v0.0.1 h1:eauyehej1XYTGwgzGWMTjeRIVgOpU6XLPNVb2oi6kDs=

x/acpio/acp_conversation.go

@@ -0,0 +1,262 @@
+package acpio
+
+import (
+	"context"
+	"log/slog"
+	"slices"
+	"strings"
+	"sync"
+
+	st "github.com/coder/agentapi/lib/screentracker"
+	"github.com/coder/quartz"
+)
+
+// Compile-time assertion that ACPConversation implements st.Conversation
+var _ st.Conversation = (*ACPConversation)(nil)
+
+// ChunkableAgentIO extends AgentIO with chunk callback support for streaming responses.
+// This interface is what ACPConversation needs from its AgentIO implementation.
+type ChunkableAgentIO interface {
+	st.AgentIO
+	SetOnChunk(fn func(chunk string))
+}
+
+// ACPConversation tracks conversations with ACP-based agents.
+// Unlike PTY-based Conversation, ACP has blocking writes where the
+// response is complete when Write() returns.
+type ACPConversation struct {
+	mu                sync.Mutex
+	ctx               context.Context
+	cancel            context.CancelFunc
+	agentIO           ChunkableAgentIO
+	messages          []st.ConversationMessage
+	nextID            int  // monotonically increasing message ID
+	prompting         bool // true while agent is processing
+	streamingResponse strings.Builder
+	logger            *slog.Logger
+	emitter           st.Emitter
+	initialPrompt     []st.MessagePart
+	clock             quartz.Clock
+}
+
+// noopEmitter is a no-op implementation of Emitter for when no emitter is provided.
+type noopEmitter struct{}
+
+func (noopEmitter) EmitMessages([]st.ConversationMessage) {}
+func (noopEmitter) EmitStatus(st.ConversationStatus)      {}
+func (noopEmitter) EmitScreen(string)                     {}
+
+// NewACPConversation creates a new ACPConversation.
+// If emitter is provided, it will receive events when messages/status/screen change.
+// If clock is nil, a real clock will be used.
+func NewACPConversation(ctx context.Context, agentIO ChunkableAgentIO, logger *slog.Logger, initialPrompt []st.MessagePart, emitter st.Emitter, clock quartz.Clock) *ACPConversation {
+	if logger == nil {
+		logger = slog.Default()
+	}
+	if clock == nil {
+		clock = quartz.NewReal()
+	}
+	if emitter == nil {
+		emitter = noopEmitter{}
+	}
+	ctx, cancel := context.WithCancel(ctx)
+	c := &ACPConversation{
+		ctx:           ctx,
+		cancel:        cancel,
+		agentIO:       agentIO,
+		logger:        logger,
+		initialPrompt: initialPrompt,
+		emitter:       emitter,
+		clock:         clock,
+	}
+	return c
+}
+
+// Messages returns the conversation history.
+func (c *ACPConversation) Messages() []st.ConversationMessage {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+	return slices.Clone(c.messages)
+}
+
+// Send sends a message to the agent synchronously.
+// It blocks until the agent has finished processing and returns any error
+// from the underlying write. Returns a validation error immediately if
+// the message is invalid or another message is already being processed.
+func (c *ACPConversation) Send(messageParts ...st.MessagePart) error {
+	message := ""
+	for _, part := range messageParts {
+		message += part.String()
+	}
+
+	// Validate whitespace BEFORE trimming (match PTY behavior)
+	if message != strings.TrimSpace(message) {
+		return st.ErrMessageValidationWhitespace
+	}
+
+	if message == "" {
+		return st.ErrMessageValidationEmpty
+	}
+
+	// Check if already prompting and set state atomically
+	c.mu.Lock()
+	if c.prompting {
+		c.mu.Unlock()
+		return st.ErrMessageValidationChanging
+	}
+	c.messages = append(c.messages, st.ConversationMessage{
+		Id:      c.nextID,
+		Role:    st.ConversationRoleUser,
+		Message: message,
+		Time:    c.clock.Now(),
+	})
+	c.nextID++
+	// Add placeholder for streaming agent response
+	c.messages = append(c.messages, st.ConversationMessage{
+		Id:      c.nextID,
+		Role:    st.ConversationRoleAgent,
+		Message: "",
+		Time:    c.clock.Now(),
+	})
+	c.nextID++
+	c.streamingResponse.Reset()
+	c.prompting = true
+	status := c.statusLocked()
+	c.mu.Unlock()
+
+	// Emit status change to "running" before starting the prompt
+	c.emitter.EmitStatus(status)
+
+	c.logger.Debug("ACPConversation sending message", "message", message)
+
+	return c.executePrompt(messageParts)
+}
+
+// Start sets up chunk handling and sends the initial prompt if provided.
+func (c *ACPConversation) Start(ctx context.Context) {
+	// Wire up the chunk callback for streaming
+	c.agentIO.SetOnChunk(c.handleChunk)
+
+	// Send initial prompt if provided
+	if len(c.initialPrompt) > 0 {
+		// Run in a goroutine because Send blocks until the prompt completes,
+		// and Start must return immediately per the Conversation interface.
+		go func() {
+			err := c.Send(c.initialPrompt...)
+			if err != nil {
+				c.logger.Error("ACPConversation failed to send initial prompt", "error", err)
+			}
+		}()
+	} else {
+		// No initial prompt means we start in stable state
+		c.emitter.EmitStatus(c.Status())
+	}
+}
+
+// Status returns the current conversation status.
+func (c *ACPConversation) Status() st.ConversationStatus {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+	return c.statusLocked()
+}
+
+// statusLocked returns the status without acquiring the lock (caller must hold lock).
+func (c *ACPConversation) statusLocked() st.ConversationStatus {
+	if c.prompting {
+		return st.ConversationStatusChanging // agent is processing
+	}
+	return st.ConversationStatusStable
+}
+
+// Stop cancels any in-progress operations.
+func (c *ACPConversation) Stop() {
+	c.cancel()
+}
+
+// Text returns the current streaming response text.
+func (c *ACPConversation) Text() string {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+	return c.streamingResponse.String()
+}
+
+// handleChunk is called for each streaming chunk from the agent.
+func (c *ACPConversation) handleChunk(chunk string) {
+	c.mu.Lock()
+	// Log and discard chunks that arrive after the prompt has completed or errored.
+	// This should not happen under normal operation — if it does, it indicates a
+	// bug in the ACP SDK or a race in the connection teardown.
+	if !c.prompting {
+		c.mu.Unlock()
+		c.logger.Error("received chunk while not prompting (late/unexpected chunk discarded)",
+			"chunkLen", len(chunk))
+		return
+	}
+	c.streamingResponse.WriteString(chunk)
+	// Only update the last message if it's the agent placeholder (defense-in-depth)
+	if len(c.messages) > 0 && c.messages[len(c.messages)-1].Role == st.ConversationRoleAgent {
+		c.messages[len(c.messages)-1].Message = c.streamingResponse.String()
+	}
+	messages := slices.Clone(c.messages)
+	status := c.statusLocked()
+	screen := c.streamingResponse.String()
+	c.mu.Unlock()
+
+	c.emitter.EmitMessages(messages)
+	c.emitter.EmitStatus(status)
+	c.emitter.EmitScreen(screen)
+}
+
+// executePrompt runs the actual agent request and returns any error.
+func (c *ACPConversation) executePrompt(messageParts []st.MessagePart) error {
+	var err error
+	for _, part := range messageParts {
+		if c.ctx.Err() != nil {
+			err = c.ctx.Err()
+			break
+		}
+		if partErr := part.Do(c.agentIO); partErr != nil {
+			err = partErr
+			break
+		}
+	}
+
+	c.mu.Lock()
+	c.prompting = false
+
+	if err != nil {
+		c.logger.Error("ACPConversation message failed", "error", err)
+		// Remove the agent's streaming message on error (may be empty or partial)
+		if len(c.messages) > 0 && c.messages[len(c.messages)-1].Role == st.ConversationRoleAgent {
+			c.messages = c.messages[:len(c.messages)-1]
+		}
+		messages := slices.Clone(c.messages)
+		status := c.statusLocked()
+		screen := c.streamingResponse.String()
+		c.mu.Unlock()
+
+		c.emitter.EmitMessages(messages)
+		c.emitter.EmitStatus(status)
+		c.emitter.EmitScreen(screen)
+		return err
+	}
+
+	// Final response should already be in the last message via streaming
+	// but ensure it's finalized
+	response := c.streamingResponse.String()
+	if len(c.messages) > 0 && c.messages[len(c.messages)-1].Role == st.ConversationRoleAgent {
+		// Intentionally not trimming space here.
+		c.messages[len(c.messages)-1].Message = response
+	}
+	messages := slices.Clone(c.messages)
+	status := c.statusLocked()
+	screen := c.streamingResponse.String()
+	c.mu.Unlock()
+
+	c.emitter.EmitMessages(messages)
+	c.emitter.EmitStatus(status)
+	c.emitter.EmitScreen(screen)
+
+	c.logger.Debug("ACPConversation message complete", "responseLen", len(response))
+	return nil
+}