go-receipt-tracker/workers/gemini.go

package workers

import (
	"context"
	"fmt"
	"log/slog"
	"regexp"
	"sync/atomic"

	"git.savin.nyc/alex/go-receipt-tracker/bus"
	"git.savin.nyc/alex/go-receipt-tracker/config"
	"git.savin.nyc/alex/go-receipt-tracker/utils"
	"github.com/google/generative-ai-go/genai"
	"google.golang.org/api/option"
)

type Gemini struct {
	id            string
	model         string
	opts          *config.Parser
	client        *genai.Client
	subscriptions map[string]chan bus.Event //
	bus           *bus.Bus
	log           *slog.Logger
	cancel        context.CancelFunc //
	end           uint32             // ensure the close methods are only called once
}

func NewGemini(cfg *config.Parser, b *bus.Bus) *Gemini {
	ai := &Gemini{
		id:            cfg.Type,  // "gemini",
		model:         cfg.Model, // [ "gemini-1.5-flash", "gemini-2.0-flash-preview-02-05" ]
		opts:          cfg,
		subscriptions: make(map[string]chan bus.Event),
		bus:           b,
	}
	// model := client.GenerativeModel("gemini-1.5-flash")

	return ai
}

func (ai *Gemini) ID() string {
	return ai.id
}

func (ai *Gemini) Type() string {
	return "parser"
}

func (ai *Gemini) Init(log *slog.Logger) error {
	ai.log = log

	ctx := context.Background()
	client, err := genai.NewClient(ctx, option.WithAPIKey(ai.opts.ApiKey))
	if err != nil {
		log.Error("cannot", "error", err)
	}
	ai.client = client

	return nil
}

func (ai *Gemini) Serve() {
	if atomic.LoadUint32(&ai.end) == 1 {
		return
	}

	ai.subscribe("parser:" + ai.ID())
	// ai.subscribe("parser:*")

	ctx, cancel := context.WithCancel(context.Background())
	ai.cancel = cancel

	go ai.eventLoop(ctx)
}

func (ai *Gemini) OneTime() error {
	return nil
}

func (ai *Gemini) Stop() {
	ai.client.Close()
}

func (ai *Gemini) Close() {
}

func (ai *Gemini) subscribe(chn string) error {
	s, err := ai.bus.Subscribe(chn, ai.Type()+":"+ai.ID())
	if err != nil {
		ai.log.Error("couldn't subscribe to a channel", "channel", chn, "error", err.Error())
		return err
	}
	ai.subscriptions[chn] = s

	return nil
}

// eventLoop loops forever
func (ai *Gemini) eventLoop(ctx context.Context) {
	ai.log.Debug(ai.ID() + " communication event loop started")
	defer ai.log.Debug(ai.ID() + " communication event loop halted")

	for {
		for chn, ch := range ai.subscriptions {
			select {
			case event := <-ch:
				switch event.Payload.(type) {
				case *bus.Message:
					ai.log.Debug("got a new message to a channel", "channel", chn, "worker type", ai.Type(), "worker id", ai.ID())

					msg := event.Payload.(*bus.Message)
					res, err := ai.recognize(event.Payload.(*bus.Message).Image.Filename)
					if err != nil {
						ai.log.Error("got an error from parser ("+ai.ID()+")", "error", err)
					}

					msg.Image.Parsed[ai.ID()] = res
					err = ai.bus.Publish("processor:receipt_add", msg)
					if err != nil {
						ai.log.Error("couldn't publish to a channel", "channel", "processor:receipt_add", "error", err.Error())
					}
				}
			case <-ctx.Done():
				ai.log.Info("stopping " + ai.ID() + " communication event loop")
				return
			}
		}
	}
}

func (ai *Gemini) recognize(img string) (res string, err error) {
	ctx := context.Background()

	r := regexp.MustCompile(`^\x60{3}(?:json)\n([\s\S]*?)\n*\x60{3}\n*$`)

	file, err := ai.client.UploadFileFromPath(ctx, img, nil)
	if err != nil {
		ai.log.Error("cannot upload a receipt file", "Messages error: %v\n", err)
		return "", err
	}
	defer ai.client.DeleteFile(ctx, file.Name)

	gotFile, err := ai.client.GetFile(ctx, file.Name)
	if err != nil {
		ai.log.Error("cannot get uploaded file name", "error", err)
	}
	ai.log.Debug("successfully uploaded file", "filename", gotFile.Name)

	model := ai.client.GenerativeModel("gemini-1.5-flash")
	resp, err := model.GenerateContent(ctx,
		genai.FileData{URI: file.URI},
		genai.Text(config.Request))
	if err != nil {
		ai.log.Error("cannot recognize a receipt", "Messages error: %v\n", err)
	}

	for _, cand := range resp.Candidates {
		if cand.Content != nil {
			for _, part := range cand.Content.Parts {
				res += fmt.Sprint(part)
			}
		}
	}

	if r.MatchString(res) {
		res = r.FindStringSubmatch(res)[1]
	}

	if !utils.IsJSON(res) {
		ai.log.Error("Gemini returned not valid JSON", "%+v", res)
		return "", err
	}

	ai.log.Debug("recognition result", "worker", ai.ID(), "output", res)

	return res, nil
}