// Copyright 2024 Matthew Rich <matthewrich.conf@gmail.com>. All rights reserved.

package fs

import (
	"io/fs"
	"log/slog"
	"path/filepath"
	"fmt"
)

type DirEntry fs.DirEntry
type FS fs.FS
type Selector[Item comparable] func(r Item) bool
 
type WalkFunc func(fsys FS, path string, file DirEntry) (err error)

type WalkDir struct {
	root *WorkingDir
	subDirsStack []*WorkingDir `yaml:"-" json:"-"`
	fn WalkFunc
}

type WorkingDir struct {
	path string
	fsys FS
}

func NewWalkDir(fsys FS, path string, fn WalkFunc) *WalkDir {
	w := &WalkDir{
		subDirsStack: make([]*WorkingDir, 0, 100),
		fn: fn,
	}
	
	w.root = &WorkingDir{ path: path, fsys: fsys }
	w.subDirsStack = append(w.subDirsStack, w.root)
	return w
}

func (w *WalkDir) WalkDirectory(fsys FS, path string, filter Selector[DirEntry]) (err error) {
	var files []fs.DirEntry

	if files, err = fs.ReadDir(fsys, "."); err == nil {
		for _,file := range files {
			if filter != nil && filter(file) {
				continue
			}
			slog.Info("fs.WalkDir.WalkDirectory()", "file", file, "path", path, "file", file.Name())
			entryPath := filepath.Join(path, file.Name())
			if err = w.fn(fsys, entryPath, file); err != nil {
				slog.Info("fs.WalkDir.WalkDirectory() ERROR", "file", entryPath, "error", err)
				return
			}
			if file.IsDir() {
				var dir FS
				if dir, err = fs.Sub(fsys, file.Name()); err != nil {
					slog.Info("fs.WalkDir.WalkDirectory() SubDir ERROR", "dir", dir, "error", err)
					return
				} else {
					w.subDirsStack = append(w.subDirsStack, &WorkingDir{ path: entryPath, fsys: dir })
				}
			}
		}
	} else {
		err = fmt.Errorf("fs.ReadDir failed on path %s: %w", path, err)
	}
	return
}

func (w *WalkDir) Walk(filter Selector[DirEntry]) (err error) {
	for len(w.subDirsStack) != 0 {
		var dirPath *WorkingDir
		dirPath, w.subDirsStack = w.subDirsStack[len(w.subDirsStack) - 1], w.subDirsStack[:len(w.subDirsStack) - 1]
		if err = w.WalkDirectory(dirPath.fsys, dirPath.path, filter); err != nil {
			return
		}
	}
	return
}