// Filesystem storage backend for Nixery.
package storage

import (
	"fmt"
	"io"
	"net/http"
	"os"
	"path"

	log "github.com/sirupsen/logrus"
)

type FSBackend struct {
	path string
}

func NewFSBackend(p string) (*FSBackend, error) {
	p = path.Clean(p)
	err := os.MkdirAll(p, 0755)
	if err != nil {
		return nil, fmt.Errorf("failed to create storage dir: %s", err)
	}

	return &FSBackend{p}, nil
}

func (b *FSBackend) Name() string {
	return fmt.Sprintf("Filesystem (%s)", b.path)
}

func (b *FSBackend) Persist(key string, f func(io.Writer) (string, int64, error)) (string, int64, error) {
	full := path.Join(b.path, key)
	dir := path.Dir(full)
	err := os.MkdirAll(dir, 0755)
	if err != nil {
		log.WithError(err).WithField("path", dir).Error("failed to create storage directory")
		return "", 0, err
	}

	file, err := os.OpenFile(full, os.O_RDWR|os.O_CREATE|os.O_TRUNC, 0644)
	if err != nil {
		log.WithError(err).WithField("file", full).Error("failed to write file")
		return "", 0, err
	}
	defer file.Close()

	return f(file)
}

func (b *FSBackend) Fetch(key string) (io.ReadCloser, error) {
	full := path.Join(b.path, key)
	return os.Open(full)
}

func (b *FSBackend) Move(old, new string) error {
	return os.Rename(path.Join(b.path, old), path.Join(b.path, new))
}

func (b *FSBackend) ServeLayer(digest string, w http.ResponseWriter) error {
	// http.Serve* functions attempt to be a lot more clever than
	// I want, but I also would prefer to avoid implementing error
	// translation myself - thus a fake request is created here.
	req := http.Request{Method: "GET"}
	http.ServeFile(w, &req, path.Join(b.path, "sha256:"+digest))

	return nil
}