// Copyright 2025 Google LLC
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
// This sample demonstrates how to use sessions to maintain state across
// multiple requests. It implements a shopping cart where items persist
// between calls using the session API.
//
// To run:
//
// go run .
//
// In another terminal, test (items persist across requests):
//
// curl -X POST http://localhost:8080/manageCart \
// -H "Content-Type: application/json" \
// -d '{"data": "Add apples and bananas to my cart"}'
//
// curl -X POST http://localhost:8080/manageCart \
// -H "Content-Type: application/json" \
// -d '{"data": "What is in my cart?"}'
package main
import (
"context"
"fmt"
"log"
"net/http"
"github.com/firebase/genkit/go/ai"
"github.com/firebase/genkit/go/core/x/session"
"github.com/firebase/genkit/go/genkit"
"github.com/firebase/genkit/go/plugins/googlegenai"
"github.com/firebase/genkit/go/plugins/server"
"google.golang.org/genai"
)
// CartState holds the shopping cart items.
type CartState struct {
Items []string `json:"items"`
}
func main() {
ctx := context.Background()
g := genkit.Init(ctx, genkit.WithPlugins(&googlegenai.GoogleAI{}))
// Create in-memory store (shared across requests).
store := session.NewInMemoryStore[CartState]()
// Fixed session ID for simplicity.
const sessionID = "shopping-session"
// Define addToCart tool - adds an item to the cart stored in session state.
addToCartTool := genkit.DefineTool(g, "addToCart",
"Adds items to the shopping cart",
func(ctx *ai.ToolContext, input struct{ Items []string }) ([]string, error) {
sess := session.FromContext[CartState](ctx.Context)
if sess == nil {
return nil, fmt.Errorf("no session in context")
}
state := sess.State()
state.Items = append(state.Items, input.Items...)
if err := sess.UpdateState(ctx.Context, state); err != nil {
return nil, err
}
return state.Items, nil
},
)
// Define getCart tool - returns all items currently in the cart.
getCartTool := genkit.DefineTool(g, "getCart",
"Returns all items currently in the shopping cart",
func(ctx *ai.ToolContext, input struct{}) ([]string, error) {
sess := session.FromContext[CartState](ctx.Context)
if sess == nil {
return nil, fmt.Errorf("no session in context")
}
return sess.State().Items, nil
},
)
// Define flow that uses session to maintain cart state across requests.
genkit.DefineFlow(g, "manageCart", func(ctx context.Context, input string) (string, error) {
// Load existing session or create new one.
sess, err := session.Load(ctx, store, sessionID)
if err != nil {
// Session doesn't exist, create it.
sess, err = session.New(ctx,
session.WithID[CartState](sessionID),
session.WithStore(store),
session.WithInitialState(CartState{Items: []string{}}),
)
if err != nil {
return "", err
}
}
// Attach session to context for tools.
ctx = session.NewContext(ctx, sess)
return genkit.GenerateText(ctx, g,
ai.WithModel(googlegenai.ModelRef("gemini-2.5-flash", &genai.GenerateContentConfig{
ThinkingConfig: &genai.ThinkingConfig{
ThinkingBudget: genai.Ptr[int32](0),
},
})),
ai.WithSystem("You are a helpful shopping assistant. Use the provided tools to manage the user's cart."),
ai.WithTools(addToCartTool, getCartTool),
ai.WithPrompt(input),
)
})
// Start server.
mux := http.NewServeMux()
for _, a := range genkit.ListFlows(g) {
mux.HandleFunc("POST /"+a.Name(), genkit.Handler(a))
}
log.Fatal(server.Start(ctx, "127.0.0.1:8080", mux))
}
