// Move the latest download in ~/Downloads to the current directory.
//
// Usage: mvldown <rename_as>
// The optional argument specifies the new name of the file.
package main

import (
	"fmt"
	"io/ioutil"
	"os"
	"path"
	"sort"
)

type MostRecent []os.FileInfo

func (fs MostRecent) Len() int      { return len(fs) }
func (fs MostRecent) Swap(i, j int) { fs[i], fs[j] = fs[j], fs[i] }
func (fs MostRecent) Less(i, j int) bool {
	return fs[i].ModTime().After(fs[j].ModTime())
}

func main() {
	rename_as := ""
	args := os.Args[1:]
	if len(args) == 1 {
		rename_as = args[0]
	}

	home_dir := os.Getenv("HOME")
	if home_dir == "" {
		fmt.Println("HOME env var isn't set")
		os.Exit(1)
	}

	downloads_dir := path.Join(home_dir, "Downloads")
	if _, err := os.Stat(downloads_dir); err != nil {
		fmt.Printf("Cannot access ~/Downloads: %s\n", err)
		os.Exit(1)
	}

	files, err := ioutil.ReadDir(downloads_dir)
	if err != nil {
		fmt.Printf("Cannot access ~/Downloads: %s\n", err)
		os.Exit(1)
	}

	if len(files) == 0 {
		fmt.Printf("~/Downloads is empty\n")
		os.Exit(1)
	}

	sort.Sort(MostRecent(files))

	most_recent := files[0].Name()
	full := path.Join(downloads_dir, most_recent)

	if len(rename_as) == 0 {
		rename_as = most_recent
	}

	rename_as = path.Join(".", rename_as)

	if _, err := os.Stat(rename_as); err == nil {
		fmt.Printf("%s already exists\n", rename_as)
		os.Exit(1)
	}

	err = os.Rename(full, rename_as)
	if err != nil {
		fmt.Printf("Error renaming: %s\n", err)
	}

	fmt.Printf("moved %s to %s\n", full, rename_as)
}