//go:build !windows

package sshd

import (
	"errors"
	"fmt"
	"io"
	"os"
	"os/exec"

	"github.com/creack/pty"
	"golang.org/x/crypto/ssh"
)

const (
	ptySupported = true
	runSupported = true
)

// run starts the user's shell (or, for exec, runs cmd through it) and returns its exit code.
// With a pty request it gets a terminal, otherwise plain pipes.
func run(ch ssh.Channel, cmd string, p *ptyReq, win <-chan [2]uint32) int {
	shell := os.Getenv("SHELL")
	if shell == "" {
		shell = "/bin/sh"
	}
	var c *exec.Cmd
	if cmd == "" {
		c = exec.Command(shell, "-l")
	} else {
		c = exec.Command(shell, "-c", cmd)
	}
	c.Env = os.Environ()
	if p != nil {
		term := p.term
		if term == "" {
			term = "xterm"
		}
		c.Env = append(c.Env, "TERM="+term)
		return runPty(ch, c, p, win)
	}
	in, err := c.StdinPipe()
	if err != nil {
		fmt.Fprintf(ch.Stderr(), "bamboo: %v\r\n", err)
		return 255
	}
	go func() { io.Copy(in, ch); in.Close() }()
	c.Stdout = ch
	c.Stderr = ch.Stderr()
	return exitCode(c.Run(), c)
}

func runPty(ch ssh.Channel, c *exec.Cmd, p *ptyReq, win <-chan [2]uint32) int {
	f, err := pty.StartWithSize(c, &pty.Winsize{Cols: uint16(p.cols), Rows: uint16(p.rows)})
	if err != nil {
		fmt.Fprintf(ch.Stderr(), "bamboo: %v\r\n", err)
		return 255
	}
	defer f.Close()
	done := make(chan struct{})
	defer close(done)
	go func() {
		for {
			select {
			case w := <-win:
				pty.Setsize(f, &pty.Winsize{Cols: uint16(w[0]), Rows: uint16(w[1])})
			case <-done:
				return
			}
		}
	}()
	go func() { io.Copy(f, ch) }()
	io.Copy(ch, f) // ends with an error when the shell exits and the terminal closes
	return exitCode(c.Wait(), c)
}

func exitCode(err error, c *exec.Cmd) int {
	if err == nil {
		return 0
	}
	var ee *exec.ExitError
	if errors.As(err, &ee) && ee.ExitCode() >= 0 {
		return ee.ExitCode()
	}
	return 255
}