package main

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

	shell "github.com/ipfs/go-ipfs-api"
	"github.com/perlin-network/life/compiler"
	"github.com/perlin-network/life/exec"
	"github.com/rogpeppe/go-internal/txtar"
	"tulpa.dev/within/wasmcloud/cmd/internal"
	"within.website/olin/abi/cwa"
)

var (
	ipfsURL     = flag.String("ipfs-host", "localhost:5001", "IPFS host (must have pubsub experiment enabled)")
	workerCount = flag.Int("worker-count", 1, "number of wasm executor workers")
)

func main() {
	log.SetFlags(log.LstdFlags | log.Lshortfile)

	sh := shell.NewShell(*ipfsURL)
	subsc, err := sh.PubSubSubscribe(internal.TopicName)
	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()
	}()

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

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

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

func waitForNewWASM(ctx context.Context, wg *sync.WaitGroup, sh *shell.Shell, subsc *shell.PubSubSubscription) {
	defer wg.Done()

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

		msg, err := subsc.Next()
		if err != nil {
			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)
		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
		}

		p := cwa.NewProcess(er.WASMCID, nil, er.Env)
		p.Stdin = stdin
		p.Stdout = stdout
		p.Stderr = stdout
		p.Logger = log.New(io.MultiWriter(logBuf, os.Stdout), er.WASMCID+" ", log.LstdFlags)

		gp := &compiler.SimpleGasPolicy{GasPerInstruction: 1}
		vm, err := exec.NewVirtualMachine(wasmBin, exec.VMConfig{}, p, gp)
		if err != nil {
			p.Logger.Printf("[SYSTEM] can't create VM: %v", err)
			continue
		}

		main, ok := vm.GetFunctionExport("cwa_main")
		if !ok {
			p.Logger.Printf("[SYSTEM] can't get main function")
			continue
		}

		begin := time.Now()
		ret, err := vm.Run(main)
		if err != nil {
			p.Logger.Printf("error running main: %v", err)
			continue
		}
		dur := time.Since(begin)

		p.Logger.Printf("[SYSTEM] return status: %v", ret)

		arc := txtar.Archive{
			Comment: []byte(fmt.Sprintf("%s: execution of %s at %s", er.UUID, er.WASMCID, begin.Format(time.RFC3339))),
			Files: []txtar.File{
				{
					Name: "vmstats.txt",
					Data: []byte(fmt.Sprintf("execution time: %s\ngas used: %v\nsyscall count: %v", dur, vm.Gas, p.SyscallCount())),
				},
				{
					Name: "stdout.txt",
					Data: stdout.Bytes(),
				},
				{
					Name: "logs.txt",
					Data: logBuf.Bytes(),
				},
			},
		}

		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)
		sh.PubSubPublish(er.UUID, string(repMsg))
	}
}