package executables

import (
	"embed"
	"errors"
	"io"
	"io/fs"
	"os/exec"
	"path"
	"strings"
	"velvettear/badger/internal/log"
)

const FFPROBE = "ffprobe"
const FPCALC = "fpcalc"

var MandatoryExecutables []string
var Executables []Executable

// exported function(s)
func Initialize(mandatoryExecutables ...string) {
	if len(mandatoryExecutables) == 0 {
		MandatoryExecutables = []string{FFPROBE, FPCALC}
	} else {
		MandatoryExecutables = mandatoryExecutables
	}
	Executables = locateSystemExecutables()
}

func GetExecutable(executableName string) (Executable, error) {
	for _, executable := range Executables {
		if strings.ToLower(executable.Name) == strings.ToLower(executableName) {
			return executable, nil
		}
	}
	return Executable{}, errors.New("executable '" + executableName + "' is unavailable")
}

func GetMissingExecutables() []string {
	missingExecutables := []string{}
	for _, mandatoryExecutableName := range MandatoryExecutables {
		mandatoryExecutableName = strings.ToLower(mandatoryExecutableName)
		for _, availableExecutable := range Executables {
			availableExecutableName := strings.ToLower(availableExecutable.Name)
			if strings.Contains(availableExecutableName, mandatoryExecutableName) {
				continue
			}
		}
		missingExecutables = append(missingExecutables, mandatoryExecutableName)
	}
	return missingExecutables
}

func ExportExecutables(embeddedFS *embed.FS) {
	error := fs.WalkDir(embeddedFS, ".", func(file string, entry fs.DirEntry, error error) error {
		if entry.IsDir() || file == "." {
			return nil
		}
		executable, error := exportThirdPartyExecutable(embeddedFS, path.Base(file))
		if error != nil {
			return error
		}
		Executables = append(Executables, executable)
		return nil
	})
	if error != nil {
		log.Fatal("encountered one or more errors exporting third party executables", error.Error())
	}
}

func AreMandatoryExecutablesAvailable() bool {
	for {
		mandatoryExecutable := MandatoryExecutables[0]
		for _, availableExecutable := range Executables {
			if availableExecutable.Name != mandatoryExecutable {
				continue
			}
			MandatoryExecutables = MandatoryExecutables[1:]
			break
		}
		if len(MandatoryExecutables) == 0 {
			break
		}
	}
	return len(MandatoryExecutables) == 0
}

func (executable Executable) Spawn(arguments ...string) (string, error) {
	return spawnProcess(executable.Path, arguments...)
}

func spawnProcess(command string, arguments ...string) (string, error) {
	cmd := exec.Command(command, arguments...)
	stdout, stdoutError := cmd.StdoutPipe()
	stderr, stderrError := cmd.StderrPipe()
	cmd.Start()
	if stdoutError != nil {
		return "", stdoutError
	}
	if stderrError != nil {
		return "", stderrError
	}
	resultBytes, stdoutError := io.ReadAll(stdout)
	if stdoutError != nil {
		return "", stdoutError
	}
	errorBytes, stderrError := io.ReadAll(stderr)
	if stderrError != nil {
		return "", stderrError
	}
	cmd.Wait()
	error := strings.Trim(string(errorBytes), "\n")
	if len(error) > 0 {
		return "", errors.New(error)
	}
	return strings.Trim(string(resultBytes), "\n"), nil
}

// struct(s)
type Executable struct {
	Name string
	Path string
}