package main

import (
	"context"
	"errors"
	"fmt"
	"log/slog"
	"os"
	"os/signal"
	"strconv"
	"strings"

	tgbotapi "github.com/go-telegram-bot-api/telegram-bot-api/v5"
	"github.com/joho/godotenv"
	"github.com/openai/openai-go/v3"
	"github.com/openai/openai-go/v3/option"
	"github.com/openai/openai-go/v3/responses"
	"github.com/openai/openai-go/v3/shared"
)

type OpenAIPrompter struct {
	cli openai.Client
	cfg *Config
}

func (p *OpenAIPrompter) Prompt(ctx context.Context, question string) (*HighlyTrustedResponse, error) {
	resp, err := p.cli.Responses.New(ctx, responses.ResponseNewParams{
		Instructions: openai.String(p.cfg.SystemPrompt),
		Input: responses.ResponseNewParamsInputUnion{
			OfString: openai.String(question),
		},
		Reasoning: shared.ReasoningParam{
			Effort: shared.ReasoningEffortXhigh,
		},
	})
	if err != nil {
		return nil, err
	}

	return &HighlyTrustedResponse{
		Text: resp.OutputText(),
	}, nil
}

func NewOpenAIProoooompter(cfg *Config) *OpenAIPrompter {
	return &OpenAIPrompter{
		cli: openai.NewClient(
			option.WithBaseURL(cfg.OpenAIBaseURL),
		),
		cfg: cfg,
	}
}

type HighlyTrustedResponse struct {
	Text string
}

type Proompter interface {
	Prompt(ctx context.Context, question string) (*HighlyTrustedResponse, error)
}

type App struct {
	log       *slog.Logger
	bot       *tgbotapi.BotAPI
	proompter Proompter
	sema      chan struct{}
	config    *Config
}

func (a *App) handleMessage(ctx context.Context, msg *tgbotapi.Message) error {
	if msg.Chat == nil {
		return nil
	}

	chatID := msg.Chat.ID
	if chatID != a.config.ChatID || !strings.HasPrefix(msg.Text, "@grok") {
		return nil
	}

	question := msg.Text[len("@grok"):]

	select {
	case a.sema <- struct{}{}:
	default:
		a.log.Info("concurrency limit hit", "msg", msg)
		return nil
	}
	defer func() { <-a.sema }()

	a.log.Info(
		"message passed all guards",
		"og_text", msg.Text,
		"transformed_text", question,
	)

	response, err := a.proompter.Prompt(ctx, question)
	if err != nil {
		return fmt.Errorf("prompting: %w", err)
	}

	_, err = a.bot.Send(tgbotapi.MessageConfig{
		BaseChat: tgbotapi.BaseChat{
			ChatID:           chatID,
			ReplyToMessageID: msg.MessageID,
		},
		Text: response.Text,
	})
	if err != nil {
		return fmt.Errorf("responding: %w", err)
	}

	return nil
}

func (a *App) HandleUpdates(ctx context.Context) error {
	upds := a.bot.GetUpdatesChan(tgbotapi.UpdateConfig{})
	for {
		select {
		case upd, ok := <-upds:
			if !ok {
				return errors.New("channel closed")
			}

			if upd.Message != nil {
				a.log.Info("new message", "chat", upd.Message.Chat)
				go func() {
					if err := a.handleMessage(ctx, upd.Message); err != nil {
						a.log.Error("handling message", "msg", upd.Message, "err", err)
					}
				}()
			}

		case <-ctx.Done():
			return ctx.Err()
		}
	}

}

func NewApp(cfg *Config, prompter Proompter) (*App, error) {
	var app App
	var err error

	app.proompter = prompter

	app.log = slog.New(slog.NewTextHandler(os.Stdout, &slog.HandlerOptions{}))

	app.bot, err = tgbotapi.NewBotAPI(cfg.BotToken)
	if err != nil {
		return nil, err
	}

	if cfg.MaxConcurrentRequests == 0 {
		return nil, errors.New("concurrency limit not set")
	}
	app.sema = make(chan struct{}, cfg.MaxConcurrentRequests)

	app.config = cfg

	return &app, nil
}

type Config struct {
	SystemPrompt          string
	OpenAIBaseURL         string
	BotToken              string
	MaxConcurrentRequests uint
	ChatID                int64
}

func LoadConfig(cfg *Config) error {
	if err := godotenv.Load(".env"); err != nil {
		return err
	}

	cfg.OpenAIBaseURL = os.Getenv("OPENAI_BASE_URL")
	if cfg.OpenAIBaseURL == "" {
		return errors.New("openai base url not set")
	}

	cfg.BotToken = os.Getenv("BOT_TOKEN")
	mcg, err := strconv.ParseUint(
		os.Getenv("MAX_CONCURRENT_REQUESTS"),
		10, 64,
	)
	if err != nil {
		return err
	}
	cfg.MaxConcurrentRequests = uint(mcg)
	chatID, err := strconv.ParseInt(os.Getenv("CHAT_ID"), 10, 64)
	if err != nil {
		return err
	}
	if chatID == 0 {
		return errors.New("non-zero chat id is unsafe")
	}

	cfg.ChatID = chatID

	cfg.SystemPrompt = os.Getenv("SYSTEM_PROMPT")

	return nil
}

func main() {
	ctx, cancel := signal.NotifyContext(context.Background(), os.Interrupt)
	defer cancel()

	log := slog.New(slog.NewTextHandler(os.Stdout, &slog.HandlerOptions{}))
	log.Info("Starting GROK")

	var cfg Config
	if err := LoadConfig(&cfg); err != nil {
		log.Error("loading config", "err", err)
		os.Exit(1)
	}

	prompter := NewOpenAIProoooompter(&cfg)

	app, err := NewApp(&cfg, prompter)
	if err != nil {
		log.Error("initializing app", "err", err)
		os.Exit(1)
	}

	go func() {
		if err := app.HandleUpdates(ctx); err != nil {
			log.Error("handleUpdates exited", "err", err)
		}
		cancel()
	}()

	<-ctx.Done()
}