package executor

import (
	"errors"
	"fmt"
	"io"
	"log"
	"os"
	"time"

	"github.com/gosuri/uitable"
	"github.com/perlin-network/life/compiler"
	"github.com/perlin-network/life/exec"
	"github.com/rogpeppe/go-internal/txtar"
	"within.website/olin/abi/cwa"
)

var (
	ErrNoCWAMain = errors.New("executor: no cwa_main function defined")
)

type Config struct {
	exec.VMConfig

	Name           string
	FuncName       string
	Env            map[string]string
	Binary         []byte
	Stdin          io.Reader
	Stdout, Stderr io.Writer
	LogSink        io.Writer
}

type Result struct {
	Status       int64
	GasUsed      uint64
	SyscallCount int64
	ExecDur      time.Duration
	PagesUsed    int
	StartTime    time.Time
}

func (r Result) ToFile() txtar.File {
	table := uitable.New()

	table.AddRow("Status", fmt.Sprint(r.Status))
	table.AddRow("Gas Used", fmt.Sprint(r.GasUsed))
	table.AddRow("Syscall Count", fmt.Sprint(r.SyscallCount))
	table.AddRow("Exec Duration", r.ExecDur.String())
	table.AddRow("Pages Used", fmt.Sprint(r.PagesUsed))

	return txtar.File{
		Name: "vmstats.txt",
		Data: []byte(table.String()),
	}
}

func Run(c Config) (*Result, error) {
	p := cwa.NewProcess(c.Name, nil, c.Env)
	p.Stdin = c.Stdin
	p.Stdout = c.Stdout
	p.Stderr = c.Stderr
	p.Logger = log.New(io.MultiWriter(c.LogSink, os.Stdout), c.Name+" ", log.LstdFlags)

	gp := &compiler.SimpleGasPolicy{GasPerInstruction: 1}
	vm, err := exec.NewVirtualMachine(c.Binary, c.VMConfig, p, gp)
	if err != nil {
		return nil, err
	}

	main, ok := vm.GetFunctionExport(c.FuncName)
	if !ok {
		return nil, ErrNoCWAMain
	}

	begin := time.Now()
	ret, err := vm.Run(main)
	if err != nil {
		return nil, err
	}
	dur := time.Since(begin)

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

	return &Result{
		Status:       ret,
		GasUsed:      vm.Gas,
		SyscallCount: p.SyscallCount(),
		ExecDur:      dur,
		PagesUsed:    len(vm.Memory) / 65536,
		StartTime:    begin,
	}, nil
}