package main

import (
	"bytes"
	"fmt"
	"io"
	"io/ioutil"
	"log"
	"os"
	"path/filepath"
	"strings"
)

func main() {
	log.SetFlags(log.Ldate | log.Ltime | log.Lshortfile)
	binDirs := []string{}
	for _, env := range os.Environ() {
		if strings.HasPrefix(env, "GOPATH=") {
			i := strings.Index(env, "=")
			paths := filepath.SplitList(env[i+1:])
			for _, path := range paths {
				binDirs = append(binDirs, filepath.Join(path, "bin"))
			}
		}
	}

	files := map[string]os.FileInfo{}

	for _, binDir := range binDirs {
		fi, err := os.Stat(binDir)
		if err != nil {
			log.Printf("%+v", err)
			continue
		}
		if !fi.IsDir() {
			log.Printf("%s is not a directory!", binDir)
			continue
		}
		dirInfo, err := ioutil.ReadDir(binDir)
		if err != nil {
			log.Printf("%+v", err)
			continue
		}
		for _, di := range dirInfo {
			files[filepath.Join(binDir, di.Name())] = di
		}
	}

	execs := []string{}
	buf := &bytes.Buffer{}
	for name, _ := range files {
		buf.Reset()
		if !exists(name) {
			log.Fatal("this should never happen: file we just found isn't there now")
		}
		if fi, err := os.Stat(name); fi.IsDir() {
			if err != nil {
				log.Fatal(err)
			}
			continue
		}
		fi, err := os.Open(name)
		if err != nil {
			log.Fatal(err)
		}
		lr := &io.LimitedReader{
			R: fi,
			N: 2,
		}
		_, err = io.Copy(buf, lr)
		if err != nil {
			log.Fatal(err)
		}

		execPatterns := [][]byte{
			{0x7f, 0x45},
			{0xcf, 0xfa},
		}
		for _, b := range execPatterns {
			if bytes.Equal(buf.Bytes(), b) {
				execs = append(execs, name)
			}
		}
	}

	for _, exec := range execs {
		fmt.Println(exec)
	}
}

func exists(path string) bool {
	if _, err := os.Stat(path); err != nil {
		return false
	} else if os.IsNotExist(err) {
		return false
	}
	return true
}