package main

import (
    "fmt"
    "os"
    "time"
    ssh "golang.org/x/crypto/ssh"
)


func Signer(privateKeyFile string) (ssh.Signer, error) {
    priv, err := os.ReadFile(privateKeyFile)
    if err != nil {
        return nil, err
    }

    signer, err := ssh.ParsePrivateKey(priv)
    if err != nil {
        return nil, err
    }

    return signer, nil
}


func UnmarshalSSHPacketEnv(data []byte) (name, value string, ok bool) {
    // https://www.rfc-editor.org/rfc/rfc4254.html#section-6.4
    var packet struct {
        Name, Value string
    }
    if ssh.Unmarshal(data, &packet) != nil {
        return
    }
    return packet.Name, packet.Value, true
}


func UnmarshalSSHPacketExec(data []byte) (command string, ok bool) {
    // https://www.rfc-editor.org/rfc/rfc4254.html#section-6.5
    var packet struct {
        Command string
    }
    if ssh.Unmarshal(data, &packet) != nil {
        return
    }
    return packet.Command, true
}

func SendExitStatus(channel ssh.Channel, exitStatus int) error {
    // https://www.rfc-editor.org/rfc/rfc4254.html#section-6.10
    // https://github.com/golang/go/issues/6235#issuecomment-66084526
    data := ssh.Marshal(&struct{ExitStatus uint32}{uint32(exitStatus)})
    _, err := channel.SendRequest("exit-status", false, data)
    return err
}


func UnnecessarilyMovieLikeRejection(channel ssh.Channel, requestC <-chan *ssh.Request) {
    done := make(chan struct{}, 0)
    go func() {
        for {
            req, ok := <-requestC
            if !ok {
                return
            }

            if req.WantReply {
                go func() {
                    <-done
                    req.Reply(false, nil)
                }()
            }
        }
    }()

    for _, r := range "=== ACCESS DENIED ===" {
        fmt.Fprintf(channel.Stderr(), "%c", r)
        time.Sleep(50 * time.Millisecond)
    }
    fmt.Fprintf(channel.Stderr(), "\r\n")
    close(done)
}


// TODO This *is* `(*ssh.Request).Reply`; see: https://cs.opensource.google/go/x/crypto/+/bc19a97f:ssh/channel.go;l=96
func reply(req *ssh.Request, ok bool) {
    if req.WantReply {
        req.Reply(ok, nil)
    }
}