package executor

import (
	"encoding/json"
	"errors"
	"fmt"
	"io"
	"log"
	"net/http"
	"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         `json:"status"`
	GasUsed         uint64        `json:"gas_used"`
	SyscallCount    int64         `json:"syscall_count"`
	ExecDur         time.Duration `json:"exec_dur"`
	PagesBeforeExec int           `json:"pages_before_exec"`
	PagesUsed       int           `json:"pages_used"`
	StartTime       time.Time     `json:"start_time"`
}

func (r Result) StatsJSONFile() txtar.File {
	data, err := json.MarshalIndent(r, "", "  ")
	if err != nil /* unlikely */ {
		panic(err)
	}

	return txtar.File{
		Name: "vmstats.json",
		Data: data,
	}
}

func (r Result) StatsFile() 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))
	table.AddRow("Page Delta", fmt.Sprint(r.PagesUsed-r.PagesBeforeExec))

	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)
	p.HC.Transport = WasmcloudBrandingTransport(c.Name, p.HC.Transport)

	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
	}

	pagesBefore := len(vm.Memory) / 65536
	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,
		PagesBeforeExec: pagesBefore,
		PagesUsed:       len(vm.Memory) / 65536,
		StartTime:       begin,
	}, nil
}

func WasmcloudBrandingTransport(handlerName string, rt http.RoundTripper) http.RoundTripper {
	return wasmcloudBrandingTransport{
		rt:          rt,
		handlerName: handlerName,
	}
}

type wasmcloudBrandingTransport struct {
	rt          http.RoundTripper
	handlerName string
}

func (w wasmcloudBrandingTransport) RoundTrip(r *http.Request) (*http.Response, error) {
	r.Header.Set("User-Agent", r.Header.Get("User-Agent")+" wasmcloud/"+w.handlerName)
	return w.rt.RoundTrip(r)
}