Agent runtime: majordomo in-process, Ollama Cloud config, chat endpoint (#56) (#70)

Co-authored-by: Steve Dudenhoeffer <[email protected]>

internal/api/agent.go

@@ -0,0 +1,189 @@
+package api
+
+import (
+	"context"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"io"
+	"log/slog"
+	"net/http"
+
+	mdagent "gitea.stevedudenhoeffer.com/steve/majordomo/agent"
+	"gitea.stevedudenhoeffer.com/steve/majordomo/llm"
+	"github.com/gin-gonic/gin"
+
+	"gitea.stevedudenhoeffer.com/steve/pansy/internal/agent"
+	"gitea.stevedudenhoeffer.com/steve/pansy/internal/domain"
+)
+
+// The garden assistant's chat surface (#56).
+//
+// Streaming, because a turn that clears a bed and replants it makes a dozen tool
+// calls over tens of seconds. Without streaming that is a long silence followed
+// by everything at once, which reads as a hang — and the whole design rests on
+// watching the canvas change as it happens.
+
+// chatRequest is the body of POST /agent/chat.
+type chatRequest struct {
+	GardenID int64  `json:"gardenId" binding:"required"`
+	Message  string `json:"message" binding:"required"`
+}
+
+// chatEvent is one server-sent event. Exactly one field is set.
+type chatEvent struct {
+	// Step reports a completed model round trip: which tools it called.
+	Step *stepEvent `json:"step,omitempty"`
+	// Done carries the finished turn.
+	Done *agent.Turn `json:"done,omitempty"`
+	// Error is a turn that failed, in words meant for a person.
+	Error string `json:"error,omitempty"`
+	// Warning rides alongside Done: the turn worked, but something adjacent to it
+	// didn't, and saying nothing would be the quieter lie.
+	Warning string `json:"warning,omitempty"`
+}
+
+type stepEvent struct {
+	Index int      `json:"index"`
+	Tools []string `json:"tools"`
+}
+
+func (h *handlers) agentChat(c *gin.Context) {
+	var req chatRequest
+	if err := c.ShouldBindJSON(&req); err != nil {
+		writeAPIError(c, http.StatusBadRequest, "INVALID_INPUT", "a gardenId and a message are required")
+		return
+	}
+	actor := mustActor(c)
+
+	history, err := h.svc.AgentHistory(c.Request.Context(), actor.ID, req.GardenID)
+	if err != nil {
+		writeServiceError(c, err)
+		return
+	}
+
+	send := openEventStream(c)
+
+	turn, err := h.agent.Run(c.Request.Context(), actor.ID, req.GardenID, req.Message,
+		replayHistory(history),
+		func(s mdagent.Step) {
+			send(chatEvent{Step: &stepEvent{Index: s.Index, Tools: toolNames(s)}})
+		})
+	if err != nil {
+		// The stream is already open, so an error is an event rather than a
+		// status code — the client has committed to reading a stream by now.
+		send(chatEvent{Error: chatErrorMessage(err)})
+		return
+	}
+
+	// The turn itself succeeded — the garden really did change — so Done goes out
+	// regardless. But if the transcript couldn't be saved, say so: a clean "done"
+	// followed by a conversation that has forgotten the exchange after a reload is
+	// exactly the kind of quiet inconsistency that makes a tool feel unreliable.
+	//
+	// Detached from the request context, because the commonest reason this fails
+	// is the client having gone away — and the exchange is worth keeping either
+	// way, since the change set it produced certainly is.
+	if _, err := h.svc.RecordAgentExchange(context.WithoutCancel(c.Request.Context()), actor.ID, req.GardenID,
+		req.Message, turn.Reply, turn.ChangeSetID); err != nil {
+		slog.Error("api: record agent exchange", "error", err, "garden", req.GardenID)
+		send(chatEvent{Done: turn, Warning: "I couldn't save this exchange, so it won't be here after a reload. Anything I changed is still on the canvas, and in History."})
+		return
+	}
+	send(chatEvent{Done: turn})
+}
+
+// openEventStream puts the response into SSE mode and returns a sender.
+//
+// Headers go out before the first write and the stream is flushed immediately,
+// so a proxy holding the response until it looks complete can't reintroduce
+// exactly the silence streaming exists to remove.
+func openEventStream(c *gin.Context) func(chatEvent) {
+	c.Header("Content-Type", "text/event-stream")
+	c.Header("Cache-Control", "no-cache")
+	c.Header("X-Accel-Buffering", "no")
+	c.Writer.Flush()
+
+	return func(ev chatEvent) {
+		b, err := json.Marshal(ev)
+		if err != nil {
+			slog.Error("api: encode chat event", "error", err)
+			return
+		}
+		_, _ = fmt.Fprintf(c.Writer, "data: %s\n\n", b)
+		c.Writer.Flush()
+	}
+}
+
+// getAgentHistory returns the actor's thread for a garden.
+func (h *handlers) getAgentHistory(c *gin.Context) {
+	gardenID, ok := parseIDParam(c, "id")
+	if !ok {
+		return
+	}
+	msgs, err := h.svc.AgentHistory(c.Request.Context(), mustActor(c).ID, gardenID)
+	if err != nil {
+		writeServiceError(c, err)
+		return
+	}
+	c.JSON(http.StatusOK, gin.H{"messages": msgs})
+}
+
+// deleteAgentHistory is the "start over" escape hatch.
+func (h *handlers) deleteAgentHistory(c *gin.Context) {
+	gardenID, ok := parseIDParam(c, "id")
+	if !ok {
+		return
+	}
+	if err := h.svc.ClearAgentHistory(c.Request.Context(), mustActor(c).ID, gardenID); err != nil {
+		writeServiceError(c, err)
+		return
+	}
+	c.Status(http.StatusNoContent)
+}
+
+// replayHistory turns stored text into model messages.
+//
+// Only the text is replayed — no stored tool calls. Continuity needs what was
+// said and what came back; replaying a tool call would be replaying a decision
+// made against a garden that has since moved on.
+func replayHistory(msgs []domain.AgentMessage) []llm.Message {
+	out := make([]llm.Message, 0, len(msgs))
+	for _, m := range msgs {
+		if m.Role == domain.AgentRoleUser {
+			out = append(out, llm.UserText(m.Body))
+		} else {
+			out = append(out, llm.AssistantText(m.Body))
+		}
+	}
+	return out
+}
+
+func toolNames(s mdagent.Step) []string {
+	names := make([]string, 0, len(s.Results))
+	for _, r := range s.Results {
+		names = append(names, r.Name)
+	}
+	return names
+}
+
+// chatErrorMessage turns a failure into something worth reading. Permission
+// errors in particular get named: "the agent broke" and "you can only view this
+// garden" want very different reactions.
+func chatErrorMessage(err error) string {
+	switch {
+	case errors.Is(err, domain.ErrForbidden):
+		return "You can only view this garden, so I can't change anything in it."
+	case errors.Is(err, domain.ErrNotFound):
+		return "I can't find that garden."
+	case errors.Is(err, domain.ErrInvalidInput):
+		return "I didn't get a message to work from."
+	case errors.Is(err, io.EOF), errors.Is(err, context.Canceled):
+		return "The connection dropped partway through. Anything I'd already changed is on the canvas, and in History."
+	case errors.Is(err, context.DeadlineExceeded):
+		return "That took too long and I stopped. Anything I'd already changed is on the canvas, and in History."
+	default:
+		slog.Error("api: agent run failed", "error", err)
+		return "Something went wrong talking to the model. Anything I'd already changed is on the canvas, and in History."
+	}
+}