package files

import (
	"fmt"
	"hash/fnv"
	"io"
	"mime"
	"os"
	"path/filepath"
	"strings"

	"gitlab.com/tozd/go/errors"
	"go.alanpearce.eu/website/internal/storage"
)

type File struct {
	storage.File
}

var encodings = map[string]string{
	"br":   ".br",
	"gzip": ".gz",
}

func (r *Reader) OpenFile(path string, filename string) (*File, error) {
	f, err := os.Open(filename)
	if err != nil {
		return nil, errors.WithMessage(err, "could not open file for reading")
	}
	stat, err := f.Stat()
	if err != nil {
		return nil, errors.WithMessage(err, "could not stat file")
	}

	etag, err := etag(f)
	if err != nil {
		return nil, errors.WithMessage(err, "could not calculate etag")
	}

	file := &File{
		File: storage.File{
			Path:         path,
			ContentType:  mime.TypeByExtension(filepath.Ext(filename)),
			LastModified: stat.ModTime(),
			Etag:         etag,
			Encodings: map[string]io.ReadSeekCloser{
				"identity": f,
			},
		},
	}

	for enc, suffix := range encodings {
		_, err := os.Stat(filename + suffix)
		if err != nil {
			if errors.Is(err, os.ErrNotExist) {
				continue
			}

			return nil, errors.WithMessagef(err, "could not stat file %s", filename+suffix)
		}
		file.Encodings[enc], err = os.Open(filename + suffix)
		if err != nil {
			return nil, errors.WithMessagef(err, "could not read file %s", filename+suffix)
		}
	}

	return file, nil
}

func etag(f io.Reader) (string, error) {
	hash := fnv.New64a()
	if _, err := io.Copy(hash, f); err != nil {
		return "", errors.WithMessage(err, "could not hash file")
	}

	return fmt.Sprintf(`W/"%x"`, hash.Sum(nil)), nil
}

func (f *File) Close() error {
	var errs []error
	for _, enc := range f.Encodings {
		if err := enc.Close(); err != nil {
			errs = append(errs, err)
		}
	}

	return errors.Join(errs...)
}

func pathNameToFileName(pathname string) string {
	if strings.HasSuffix(pathname, "/") {
		pathname = pathname + "index.html"
	}

	return pathname
}

func fileNameToPathName(filename string) string {
	pathname, _ := strings.CutSuffix(filename, "index.html")

	return pathname
}