package os

import "os"
import "io"
import "io/fs"
import "html/template"
import "git.tebibyte.media/sashakoshka/step"

var _ step.FuncProviderFor = new(Provider)

// Provider provides OS functions.
type Provider struct {
	
}

// Package fulfills the step.Provider interface.
func (this *Provider) Package () string {
	return "os"
}

// FuncMapFor fulfills the step.FuncProviderFor interface.
func (this *Provider) FuncMapFor (document *step.Document) template.FuncMap {
	stat := &state {
		document: document,
	}
	return template.FuncMap {
		"env":        stat.funcEnv,
		"exists":     stat.funcExists,
		"isFile":     stat.funcIsFile,
		"isDir":      stat.funcIsDir,
		"statFile":   stat.funcStatFile,
		"readFile":   stat.funcReadFile,
		"readDir":    stat.funcReadDir,
		"listFiles":  stat.funcListFiles,
		"writeFile":  stat.funcWriteFile,
		"appendFile": stat.funcAppendFile,
		"renameFile": stat.funcRenameFile,
		"removeFile": stat.funcRemoveFile,
	}
}

type state struct {
	document *step.Document
}

func (this *state) funcEnv (name string) string {
	return os.Getenv(name)
}

func (this *state) funcExists (name string) (bool, error) {
	name, err := this.document.Rel(name)
	if err != nil { return false, err }
	_, err = os.Stat(name)
	return err == nil, nil
}

func (this *state) funcIsFile (name string) (bool, error) {
	name, err := this.document.Rel(name)
	if err != nil { return false, err }
	info, err := os.Stat(name)
	if err != nil { return false, nil }
	return info.Mode().IsRegular(),nil
}

func (this *state) funcIsDir (name string) (bool, error) {
	name, err := this.document.Rel(name)
	if err != nil { return false, err }
	info, err := os.Stat(name)
	if err != nil { return false, nil }
	return info.IsDir(), nil
}

func (this *state) funcStatFile (name string) (fs.FileInfo, error) {
	name, err := this.document.Rel(name)
	if err != nil { return nil, err }
	return os.Stat(name)
}

func (this *state) funcReadFile (name string) (string, error) {
	name, err := this.document.Rel(name)
	if err != nil { return "", err }
	file, err := os.Open(name)
	if err != nil { return "", err  }
	defer file.Close()
	buffer, err := io.ReadAll(file)
	if err != nil { return "", err  }
	return string(buffer), nil
}

func (this *state) funcReadDir (name string) ([]fs.DirEntry, error) {
	name, err := this.document.Rel(name)
	if err != nil { return nil, err }
	return os.ReadDir(name)
}

func (this *state) funcListFiles (name string) ([]string, error) {
	name, err := this.document.Rel(name)
	if err != nil { return nil, err }
	entries, err := os.ReadDir(name)
	if err != nil { return nil, err }
	strings := make([]string, len(entries))
	for index, entry := range entries {
		strings[index] = entry.Name()
	}
	return strings, nil
}

func (this *state) funcWriteFile (name, content string) error {
	name, err := this.document.Rel(name)
	if err != nil { return err }
	file, err := os.Create(name)
	if err != nil { return err }
	_, err = io.WriteString(file, content)
	return err
}

func (this *state) funcAppendFile (name, content string) error {
	name, err := this.document.Rel(name)
	if err != nil { return err }
	file, err := os.OpenFile(name, os.O_CREATE | os.O_WRONLY | os.O_APPEND, 0644)
	if err != nil { return err }
	_, err = io.WriteString(file, content)
	return err
}

func (this *state) funcRenameFile (name, newName string) error {
	name, err := this.document.Rel(name)
	if err != nil { return err }
	return os.Rename(name, newName)
}

func (this *state) funcRemoveFile (name string) error {
	name, err := this.document.Rel(name)
	if err != nil { return err }
	return os.Remove(name)
}