Fork tasks from snapshots; snapshot only when text follows tool calls

internal/agents/fork.go

@@ -0,0 +1,102 @@
+package agents
+
+import (
+	"context"
+	"fmt"
+	"time"
+
+	"g.fc.run/misc/byre/internal/api"
+)
+
+func (m *Manager) Fork(ctx context.Context, src api.Task, project api.Project, n int, creator api.User) (api.Task, error) {
+	if creator.GitName == "" || creator.GitEmail == "" {
+		return api.Task{}, ErrNoGitIdentity
+	}
+	if src.Status != api.TaskStatusActive {
+		return api.Task{}, fmt.Errorf("%w: task %s is %s", ErrConflict, src.Id, src.Status)
+	}
+
+	snap, err := m.store.GetSnapshot(ctx, src.Id, n)
+	if err != nil {
+		return api.Task{}, err
+	}
+	srcSess, err := m.store.GetSession(ctx, snap.AgentSessionId)
+	if err != nil {
+		return api.Task{}, err
+	}
+	events, err := m.store.TaskEvents(ctx, src.Id, 0, -1)
+	if err != nil {
+		return api.Task{}, err
+	}
+	at := forkPoint(events, snap.AgentSessionId, snap.EventSeq)
+	if at == "" {
+		return api.Task{}, fmt.Errorf("%w: snapshot %d of task %s has no recorded agent message at or before it to fork the conversation from", ErrConflict, n, src.Id)
+	}
+
+	t, err := m.createTask(ctx, project, api.Task{
+		Title:      fmt.Sprintf("%s (fork of #%d)", src.Title, n),
+		MergeTitle: src.MergeTitle,
+		CreatedBy:  creator.Login,
+		TodoItem:   src.TodoItem,
+		ForkedFrom: &src.Id,
+		ForkedAt:   &n,
+	}, snap.CommitSha, creator.Login)
+	if err != nil {
+		return api.Task{}, err
+	}
+
+	id := newUUID()
+	err = m.store.CreateSession(ctx, api.AgentSession{
+		Id:              id,
+		TaskId:          t.Id,
+		Vendor:          srcSess.Vendor,
+		Model:           srcSess.Model,
+		VendorSessionId: id,
+		State:           api.AgentSessionStateIdle,
+		Role:            api.Implementer,
+		CreatedBy:       creator.Login,
+		CreatedAt:       time.Now().UTC(),
+		ForkedFrom:      &srcSess.VendorSessionId,
+		ForkedAt:        &at,
+	}, t.ProjectId)
+	if err != nil {
+		return api.Task{}, fmt.Errorf("task %s created, but its agent session was not: %w", t.Id, err)
+	}
+	return t, nil
+}
+
+func forkPoint(events []api.Event, sessionID string, seq int64) string {
+	at := ""
+	open := map[string]bool{}
+	for _, ev := range events {
+		if ev.AgentSessionId == nil || *ev.AgentSessionId != sessionID {
+			continue
+		}
+		uuid, _ := ev.Payload["vendor_uuid"].(string)
+		if uuid == "" {
+			continue
+		}
+		id := ""
+		switch ev.Kind {
+		case "agent.tool_call":
+			id, _ = ev.Payload["id"].(string)
+		case "agent.tool_result":
+			id, _ = ev.Payload["tool_use_id"].(string)
+		}
+		after := ev.Seq > seq
+		if after && (len(open) == 0 || id == "") {
+			break
+		}
+		switch ev.Kind {
+		case "agent.tool_call":
+			open[id] = true
+		case "agent.tool_result":
+			delete(open, id)
+		}
+		at = uuid
+		if after && len(open) == 0 {
+			break
+		}
+	}
+	return at
+}