package main

import (
	"bytes"
	"context"
	"encoding/json"
	"flag"
	"fmt"
	"io/ioutil"
	"log"
	"os"
	"os/signal"
	"sync"
	"syscall"
	"time"

	"github.com/facebookgo/flagenv"
	shell "github.com/ipfs/go-ipfs-api"
	nats "github.com/nats-io/nats.go"
	"github.com/perlin-network/life/exec"
	"github.com/rogpeppe/go-internal/txtar"
	"tulpa.dev/within/wasmcloud/cmd/internal"
	"tulpa.dev/within/wasmcloud/executor"
)

var (
	natsURL       = flag.String("nats-url", nats.DefaultURL, "nats URL")
	ipfsURL       = flag.String("ipfs-host", "localhost:5001", "IPFS host")
	workerCount   = flag.Int("worker-count", 1, "number of wasm executor workers")
	gasLimit      = flag.Int("gas-limit", 1048576, "number of wasm instructions per execution")
	ramLimit      = flag.Int("ram-limit", 128, "number of wasm pages that can be used")
	loopTimeout   = flag.Duration("loop-timeout", 30*time.Second, "idle time per loop")
	cwaEntrypoint = flag.String("cwa-entrypoint", "_start", "entrypoint into CWA programs")
)

func main() {
	flagenv.Parse()
	flag.Parse()
	log.SetFlags(log.LstdFlags | log.Lshortfile)

	sh := shell.NewShell(*ipfsURL)

	nc, err := nats.Connect(*natsURL)
	if err != nil {
		log.Fatal(err)
	}

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

	c := make(chan os.Signal, 2)
	signal.Notify(c, os.Interrupt, syscall.SIGTERM)
	go func() {
		<-c
		cancel()
		log.Println("press ^C again to kill all of this")
		<-c
		os.Exit(0)
	}()

	var wg sync.WaitGroup
	wg.Add(*workerCount)

	for range make([]struct{}, *workerCount) {
		go waitForNewWASM(ctx, &wg, sh, nc)
	}

	log.Printf("waiting for work on %s", internal.TopicName)
	wg.Wait()
}

func waitForNewWASM(ctx context.Context, wg *sync.WaitGroup, sh *shell.Shell, nc *nats.Conn) {
	defer wg.Done()
	subsc, err := nc.QueueSubscribeSync(internal.TopicName, "workers")
	if err != nil {
		return
	}

	for {
		select {
		case <-ctx.Done():
			return
		default:
		}

		msg, err := subsc.NextMsg(*loopTimeout)
		if err != nil {
			if err == nats.ErrTimeout {
				continue
			}

			log.Printf("error getting message: %v", err)
			return
		}

		data := msg.Data
		var er internal.ExecRequest
		err = json.Unmarshal(data, &er)
		if err != nil {
			log.Printf("invalid message %s: %v", string(data), err)
			continue
		}

		stdin := bytes.NewBuffer(er.Data)
		stdout := bytes.NewBuffer(nil)
		stderr := bytes.NewBuffer(nil)
		logBuf := bytes.NewBuffer(nil)

		bin, err := sh.Cat(er.WASMCID)
		if err != nil {
			log.Printf("can't get wasm: %v", err)
			continue
		}

		wasmBin, err := ioutil.ReadAll(bin)
		bin.Close()
		if err != nil {
			log.Printf("can't get wasm binary %s: %v", er.WASMCID, err)
			continue
		}

		c := executor.Config{
			VMConfig: exec.VMConfig{
				GasLimit:                 uint64(*gasLimit),
				ReturnOnGasLimitExceeded: true,
				MaxMemoryPages:           *ramLimit,
			},

			Name:     er.Name,
			FuncName: *cwaEntrypoint,
			Env:      er.Env,
			Binary:   wasmBin,
			Stdin:    stdin,
			Stdout:   stdout,
			Stderr:   stderr,
			LogSink:  logBuf,
		}

		result, err := executor.Run(c)
		if err != nil {
			log.Printf("can't run binary: %v", err)
		}

		arc := txtar.Archive{
			Comment: []byte(fmt.Sprintf("%s: execution of %s at %s", er.UUID, er.Name, result.StartTime.Format(time.RFC3339))),
			Files: []txtar.File{
				{
					Name: "logs.txt",
					Data: logBuf.Bytes(),
				},
				{
					Name: "stdout.txt",
					Data: stdout.Bytes(),
				},
				{
					Name: "stderr.txt",
					Data: stderr.Bytes(),
				},
				result.StatsFile(),
				{
					Name: "wasm.cid",
					Data: []byte(er.WASMCID),
				},
			},
		}

		interm := bytes.NewBuffer(txtar.Format(&arc))
		cid, err := sh.Add(interm)
		if err != nil {
			log.Printf("can't save execution results: %v", err)
			continue
		}

		log.Printf("wasm module %s execution finished, logs at %s", er.WASMCID, cid)
		resp := internal.ExecResponse{
			WASMCID:      er.WASMCID,
			LogBundleCID: cid,
			Logs:         arc,
			UUID:         er.UUID,
		}
		repMsg, _ := json.Marshal(resp)
		msg.Respond(repMsg)
	}
}