package tplCmd

import (
	`bytes`
	`os`
	`os/exec`
	`text/template`
)

// ToCmd returns an (os/)exec.Cmd from a TemplateCmd. t should be a tunnelbroker.FetchedTunnel, generally.
func (c *TemplateCmd) ToCmd(t any) (cmd *exec.Cmd, err error) {

	var progName string
	var envs []string
	var tpl *template.Template
	var args []string
	var buf *bytes.Buffer = new(bytes.Buffer)

	buf.Reset()
	if tpl, err = template.New("").Parse(c.Program); err != nil {
		return
	}
	if err = tpl.Execute(buf, t); err != nil {
		return
	}
	progName = buf.String()

	if c.Args != nil && len(c.Args) > 0 {
		args = make([]string, len(c.Args))
		for idx, arg := range c.Args {
			buf.Reset()
			if tpl, err = template.New("").Parse(arg); err != nil {
				return
			}
			if err = tpl.Execute(buf, t); err != nil {
				return
			}
			args[idx] = buf.String()
		}

	}

	if c.EnvVars != nil && len(c.EnvVars) > 0 {
		envs = make([]string, len(c.EnvVars))
		for idx, env := range c.EnvVars {
			buf.Reset()
			if tpl, err = template.New("").Parse(env); err != nil {
				return
			}
			if err = tpl.Execute(buf, t); err != nil {
				return
			}
			envs[idx] = buf.String()
		}
	}
	if !c.IsolateEnv {
		if envs != nil && len(envs) > 0 {
			envs = append(os.Environ(), envs...)
		} else {
			envs = os.Environ()
		}
	}

	if args != nil && len(args) > 0 {
		cmd = exec.Command(progName, args...)
	} else {
		cmd = exec.Command(progName)
	}

	cmd.Env = envs

	return
}