package main

import (
    "fmt"
    "io"
    "sort"
    "strings"

    //"io"
    "io/ioutil"
    "log"
    "os"
    //"path/filepath"
    //"strings"
)

func dirTree(out io.Writer, path string, printFiles bool) error  {
    dirTreeLevel(out, make(map[int]bool), path, printFiles)
    return nil
}


func dirTreeLevel(out io.Writer, level map[int]bool, path string, printFiles bool) error  {
    dirEntry, err := ioutil.ReadDir(path)
    if err != nil {
        log.Fatal(err)
    }
    delimiter := createDelimiter(level)
    var hasNext bool = true;
    //var idx int = -1;
    levelEntry := sortDir(dirEntry, !printFiles)
    var mapLevel = make(map[int]bool)
    for k,v := range level {
        mapLevel[k] = v
    }
    for idx, f := range  levelEntry {
        var rune = "├"
        if (idx + 1 == len(levelEntry)) {
            rune = "└"
            hasNext = false
        }
        if (f.IsDir()) {
            fmt.Fprintf(out, "%s%s───%s\n", delimiter, rune, f.Name())
        }
        if (printFiles && !f.IsDir()) {
            size := fmt.Sprintf("%db", f.Size())
            if (f.Size() == 0) {
                size = "empty"
            }
            fmt.Fprintf(out, "%s%s───%s (%s)\n", delimiter, rune, f.Name(), size)
        }
        if (f.IsDir()) {
            mapLevel[len(level)] = hasNext;
            dirTreeLevel(out, mapLevel, path + "/" + f.Name(), printFiles)
        }
    }

    return nil
}

func createDelimiter(level map[int]bool) string  {
    var delimiter string = ""
    //fmt.Printf("%v\n", level)
    for _, hasNext := range level {
        var levelDelimiter string = "#"
        if (hasNext == true) {
            levelDelimiter = "│"
        }
        delimiter = fmt.Sprintf("%s%s%s", delimiter, levelDelimiter, "\t")
    }
    return delimiter
}


func sortDir(dirEntry []os.FileInfo, dropFiles bool) (files []os.FileInfo) {
    for _,v := range dirEntry {
        if (v.IsDir()) {
            files = append(files, v)
        } else if (!dropFiles) {
            files = append(files, v)
        }
    }
    sort.Slice(files, func(i, j int) bool {
        var fnode = files[i]
        var snode = files[j]
        //if (fnode.IsDir() != snode.IsDir()) {
        //  if (fnode.IsDir()) {
        //      return true
        //  } else {
        //      return false
        //  }
        //}
        return strings.ToLower(fnode.Name()) < strings.ToLower(snode.Name())
    })
    return files
}


func main() {
    out := os.Stdout
    if !(len(os.Args) == 2 || len(os.Args) == 3) {
        panic("usage go run main.go . [-f]")
    }
    path := os.Args[1]
    printFiles := len(os.Args) == 3 && os.Args[2] == "-f"
    err := dirTree(out, path, printFiles)
    if err != nil {
        panic(err.Error())
    }
}