// godlighty -- highly-customizable HTTP, HTTP/2, HTTPS server
// Copyright (C) 2021-2024 Sergey Matveev <stargrave@stargrave.org>
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, version 3 of the License.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program.  If not, see <http://www.gnu.org/licenses/>.

package godlighty

import (
	_ "embed"
	"html/template"
	"io/fs"
	"os"
	"path"
	"sort"
	"time"

	"github.com/dustin/go-humanize"
)

const MTimeFmt = "2006-01-02 15:04:05Z"

var (
	//go:embed dirlist.tmpl
	DirListTmplRaw string
	DirListTmpl    = template.Must(template.New("dirlist").Parse(DirListTmplRaw))
)

type ByName []fs.DirEntry

func (a ByName) Len() int {
	return len(a)
}

func (a ByName) Swap(i, j int) {
	a[i], a[j] = a[j], a[i]
}

func (a ByName) Less(i, j int) bool {
	return a[i].Name() < a[j].Name()
}

type DirListFile struct {
	Idx     int
	Name    string
	Size    string
	IsDir   bool
	Type    string
	ModTime string
	Symlink string
}

func dirList(
	cfg *HostCfg,
	dir, pth string,
	entries []os.DirEntry,
	readme string,
) (*os.File, error) {
	sort.Sort(ByName(entries))
	files := make([]DirListFile, 0, len(entries))
	for i, entry := range entries {
		fi, err := entry.Info()
		if err != nil {
			return nil, err
		}
		file := DirListFile{
			Idx:     i,
			Name:    fi.Name(),
			Size:    humanize.IBytes(uint64(fi.Size())),
			ModTime: fi.ModTime().UTC().Truncate(time.Second).Format(MTimeFmt),
		}
		if fi.IsDir() {
			file.IsDir = true
		} else {
			file.Type = mediaType(file.Name, cfg.MIMEs)
		}
		if (entry.Type() & fs.ModeSymlink) > 0 {
			file.Symlink, _ = os.Readlink(path.Join(pth, fi.Name()))
		}
		files = append(files, file)
	}
	fd, err := os.CreateTemp("", "godlist-dirlist-")
	if err != nil {
		return nil, err
	}
	os.Remove(fd.Name())
	var root string
	if dir == "/" {
		dir = ""
		root = "/"
	}
	err = DirListTmpl.Execute(fd, struct {
		Root   string
		Dir    string
		Files  []DirListFile
		Readme string
	}{
		Root:   root,
		Dir:    dir,
		Files:  files,
		Readme: readme,
	})
	if err != nil {
		fd.Close()
		return nil, err
	}
	return fd, err
}