package main

import (
	"bufio"
	"context"
	"fmt"
	"github.com/jackc/pgx/v5/pgxpool"
	"github.com/riverqueue/river"
	"github.com/riverqueue/river/riverdriver/riverpgxv5"
	"log/slog"
	// "math/rand"
	"os"
	"time"
	"go.opentelemetry.io/otel"
	"go.opentelemetry.io/otel/exporters/otlp/otlptrace/otlptracegrpc"
	"go.opentelemetry.io/otel/exporters/otlp/otlpmetric/otlpmetricgrpc"
	"go.opentelemetry.io/otel/sdk/resource"
	"go.opentelemetry.io/otel/sdk/trace"
	"go.opentelemetry.io/otel/sdk/metric"
	semconv "go.opentelemetry.io/otel/semconv/v1.21.0"
	"net/http"
	"google.golang.org/grpc"
	"google.golang.org/grpc/credentials/insecure"
)

// River Worker

type MessageArgs struct {
	Message string `json:"string"`
}

func (MessageArgs) Kind() string {
	return "message"
}

type MessageWorker struct {
	dbPool *pgxpool.Pool
	river.WorkerDefaults[MessageArgs]
}

func InitWorkers(pool *pgxpool.Pool) (*river.Workers, error) {
	slog.Info("Initializing River workers")
	workers := river.NewWorkers()
	// need to specify generic type
	err := river.AddWorkerSafely[MessageArgs](workers, &MessageWorker{dbPool: pool})
	if err != nil {
		slog.Error("Failed to add workers")
	}
	return workers, err
}

// Old function that does use transactions so when the worker SIGKILL it lost track of itself
//func (w *MessageWorker) Work(ctx context.Context, job *river.Job[MessageArgs]) error {
//	randTime := rand.Intn(10)
//	fileName := fmt.Sprintf("./data/msg-%d.txt", time.Now().Unix())
//	slog.Info("Sleeping to simulate some work", "sleep", randTime)
//	time.Sleep(time.Second * time.Duration(randTime))

//	err := os.WriteFile(fileName, []byte(job.Args.Message), 0777)
//	if err != nil {
//		slog.Error("Failed to save file")
//	}
//	slog.Info("Saved message!", "filename", fileName)
//	return err
//}

func (w *MessageWorker) Work(ctx context.Context, job *river.Job[MessageArgs]) error {
	//https://riverqueue.com/docs/reliable-workers#idempotency-with-transactions
	tx, err := w.dbPool.Begin(ctx)
	if err != nil {
		return err
	}
	defer tx.Rollback(ctx)

	// our logic
	//randTime := rand.Intn(10)
	randTime := 10
	fileName := fmt.Sprintf("./data/msg-%d.txt", time.Now().Unix())
	slog.Info("Sleeping to simulate some work", "sleep", randTime)
	time.Sleep(time.Second * time.Duration(randTime))

	err = os.WriteFile(fileName, []byte(job.Args.Message), 0777)
	if err != nil {
		slog.Error("Failed to save file")
	}
	slog.Info("Saved message!", "filename", fileName)

	_, err = river.JobCompleteTx[*riverpgxv5.Driver](ctx, tx, job)
	if err != nil {
		return err
	}

	return tx.Commit(ctx)
}

func (w *MessageWorker) Timeout(job *river.Job[MessageArgs]) time.Duration {
	return time.Second * 30
}

func setupOTel() (func(context.Context) error, error) {
	// OTLP gRPC exporters for traces and metrics
	traceExp, err := otlptracegrpc.New(context.Background(),
		otlptracegrpc.WithEndpoint("localhost:4317"),
		otlptracegrpc.WithDialOption(grpc.WithTransportCredentials(insecure.NewCredentials())),
	)
	if err != nil {
		return nil, err
	}

	metricExp, err := otlpmetricgrpc.New(context.Background(),
		otlpmetricgrpc.WithEndpoint("localhost:4317"),
		otlpmetricgrpc.WithDialOption(grpc.WithTransportCredentials(insecure.NewCredentials())),
	)
	if err != nil {
		return nil, err
	}

	res, err := resource.New(context.Background(),
		resource.WithAttributes(
			semconv.ServiceName("go-background-jobs"),
		),
	)
	if err != nil {
		return nil, err
	}

	// Tracer provider
	tp := trace.NewTracerProvider(
		trace.WithBatcher(traceExp),
		trace.WithResource(res),
	)
	otel.SetTracerProvider(tp)

	// Meter provider
	mp := metric.NewMeterProvider(
		metric.WithReader(metric.NewPeriodicReader(metricExp)),
		metric.WithResource(res),
	)
	otel.SetMeterProvider(mp)

	return tp.Shutdown, nil
}

func main() {
	ctx := context.Background()

	shutdown, err := setupOTel()
	if err != nil {
		panic(err)
	}
	defer shutdown(ctx)

	dbPool, err := pgxpool.New(ctx, os.Getenv("PG_URI"))
	if err != nil {
		slog.Error("Error setting up db", "error", err.Error())
		panic(err.Error())
	}
	defer dbPool.Close()

	workers, err := InitWorkers(dbPool)
	if err != nil {
		// abort!
		panic(err.Error())
	}

	// create a River client
	rc, err := river.NewClient(riverpgxv5.New(dbPool), &river.Config{
		RescueStuckJobsAfter: 1 * time.Minute,
		Queues: map[string]river.QueueConfig{
			river.QueueDefault: {MaxWorkers: 100},
		},
		Workers: workers,
	})
	if err != nil {
		slog.Error("Failed to setup river client", "error", err.Error())
		panic(err.Error())
	}

	// In K8s you could separate our the worker process from a HTTP/gRPC service
	// by using rc.Enqueue in the server, and rc.Start in the worker
	go func() {
		slog.Info("Starting river background worker process")
		err = rc.Start(ctx)
		if err != nil {
			slog.Error("Failed to start river background workers", "error", err.Error())
			panic(err.Error())
		}
	}()

	// enter the loop
	for {
		inputReader := bufio.NewReader(os.Stdin)
		fmt.Println("Type in a message and I will save it to ./data:")
		msg, err := inputReader.ReadString('\n')
		if err != nil {
			slog.Error("Failed to read message. Try again", "error", err.Error())
		}

		// TODO use rc.InsertTx. See https://riverqueue.com/docs/transactional-enqueueing
		_, err = rc.Insert(ctx, MessageArgs{Message: msg}, nil)
		if err != nil {
			slog.Error("Failed to enqueue message. Sorry", "error", err.Error())
			continue
		}
		slog.Info("Submitted message for processing", "msg", msg)
	}
}