// Package exe provides a mechanism for executing system commands.
package exe

import (
	"fmt"
	"log"
	"os"
	"os/exec"
	"strings"
)

// ExeCtx represents the context needed for program execution.
type ExeCtx struct {
	Args     []string
	Command  string
	EnvName  string
	EnvVars  []string
	Prefix   string
	Displays map[string]string
	Stderr   *os.File
	Stdout   *os.File
	Suffix   string
	Title    string
	WorkDir  string
}

func (ec *ExeCtx) Execute() error {
	var c *exec.Cmd
	var cmnd string
	var args []string

	if ec.Prefix != "" {
		prefix := strings.Split(ec.Prefix, " ")
		p, a := prefix[0], prefix[1:]
		cmnd = p
		if len(prefix) > 1 {
			args = append(args, a...)
		}
		args = append(args, ec.Command)
		args = append(args, ec.Args...)

	} else {
		cmnd = ec.Command
		args = append(args, ec.Args...)
	}

	c = exec.Command(cmnd)
	c.Args = append(c.Args, args...)
	c.Dir = ec.WorkDir
	c.Stderr = ec.Stderr
	c.Stdout = ec.Stdout
	c.Env = append(c.Env, ec.EnvVars...)
	c.Env = append(c.Env, userEnv(ec.Command)...)

	err := c.Run()
	if err != nil {
		return err
	}

	return nil
}

func QuickExe(cmnd string, args ...string) (string, error) {
	c := exec.Command(cmnd, args...)
	o, err := c.CombinedOutput()
	if err != nil {
		return "", err
	}
	return string(o), nil
}

func exePath(exeName string) (string, error) {
	path, err := exec.LookPath(exeName)
	if err != nil {
		return "", err
	}
	return path, nil
}

func GenPrefix(wineExe, winePrefix, wineArch string) error {
	wine, err := exePath("wine")
	if err == nil {
		wineExe = wine
	} else {
		log.Println("WARNING: New wine prefixes should be created with a system wine but WEM couldn't find one")
		log.Println("WARNING: Proceeding anyways with the configured WineExe but please note that there may be issues with this prefix!")
	}

	c := exec.Command(wineExe, "WEMTEST")
	devnull, err := os.Open(os.DevNull)
	if err != nil {
		return err
	}
	c.Stderr = devnull
	c.Stdout = devnull
	c.Env = append(c.Env, userEnv(wineExe)...)
	c.Env = append(c.Env,
		fmt.Sprintf("WINEPREFIX=%s", winePrefix),
		fmt.Sprintf("WINEARCH=%s", wineArch),
	)
	// This will fail, but it will first create the prefix
	_ = c.Run()
	return nil
}

// userEnv provides key variables from the user's
// environment that are needed for wine to run.
func userEnv(cmnd string) []string {
	return []string{
		"DISPLAY=" + os.Getenv("DISPLAY"),
		"HOME=" + os.Getenv("HOME"),
		"PATH=" + os.Getenv("PATH"),
		"XDG_RUNTIME_DIR=" + os.Getenv("XDG_RUNTIME_DIR"),
	}
}