/*
Copyright 2016 The Fission Authors.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/

package controller

import (
	"errors"
	"github.com/coreos/etcd/client"
	"github.com/satori/go.uuid"
	"golang.org/x/net/context"
	"reflect"
)

type (
	resource interface {
		key() string
	}

	serializer interface {
		serialize(r resource) ([]byte, error)
		deserialize(buf []byte, r resource) error
	}

	resourceStore struct {
		*fileStore
		client.KeysAPI
		serializer
	}
)

func makeResourceStore(fs *fileStore, ks client.KeysAPI, s serializer) *resourceStore {
	return &resourceStore{fileStore: fs, KeysAPI: ks, serializer: s}
}

func getTypeName(r resource) (string, error) {
	typ := reflect.TypeOf(r)
	if typ.Kind().String() == "ptr" {
		typ = typ.Elem()
	}
	typName := typ.Name()
	if len(typName) == 0 {
		return "", errors.New("Failed to get type")
	}
	return typName, nil
}

func getKey(r resource) (string, error) {
	typName, err := getTypeName(r)
	if err != nil {
		return "", err
	}
	rkey := r.key()
	return (typName + "/" + rkey), nil
}

func (rs *resourceStore) create(r resource) error {
	key, err := getKey(r)
	if err != nil {
		return err
	}

	serialized, err := rs.serializer.serialize(r)
	if err != nil {
		return err
	}

	_, err = rs.KeysAPI.Set(context.Background(), key, string(serialized),
		&client.SetOptions{PrevExist: client.PrevNoExist})
	return err
}

func (rs *resourceStore) read(rkey string, res resource) error {
	typName, err := getTypeName(res)
	if err != nil {
		return err
	}
	key := typName + "/" + rkey

	resp, err := rs.KeysAPI.Get(context.Background(), key, nil)
	if err != nil {
		return err
	}
	return rs.serializer.deserialize([]byte(resp.Node.Value), res)
}

func (rs *resourceStore) update(r resource) error {
	key, err := getKey(r)
	if err != nil {
		return err
	}

	serialized, err := rs.serializer.serialize(r)
	if err != nil {
		return err
	}

	_, err = rs.KeysAPI.Set(context.Background(), key, string(serialized),
		&client.SetOptions{PrevExist: client.PrevExist})
	return err
}

func (rs *resourceStore) delete(typename, rkey string) error {
	key := typename + "/" + rkey
	_, err := rs.KeysAPI.Delete(context.Background(), key, nil) // ignore response
	return err
}

func (rs *resourceStore) getAll(key string) ([]string, error) {
	resp, err := rs.KeysAPI.Get(context.Background(), key, &client.GetOptions{Recursive: true})
	if err != nil {
		return nil, err
	}

	res := make([]string, 0, len(resp.Node.Nodes))
	for _, n := range resp.Node.Nodes {
		res = append(res, n.Value)
	}
	return res, nil
}

func (rs *resourceStore) writeFile(parentKey string, contents []byte) (string, string, error) {
	uid := uuid.NewV4().String()

	err := rs.fileStore.write(uid, contents)
	if err != nil {
		return "", "", err
	}

	resp, err := rs.KeysAPI.CreateInOrder(context.Background(), parentKey, uid, nil)
	if err != nil {
		_ = rs.fileStore.delete(uid)
		return "", "", err
	}

	return resp.Node.Key, uid, nil
}

func (rs *resourceStore) readFile(key string, uid *string) ([]byte, error) {
	resp, err := rs.KeysAPI.Get(context.Background(), key, &client.GetOptions{Sort: true})
	if err != nil {
		return nil, err
	}

	if uid == nil {
		// get latest
		n := resp.Node.Nodes
		uid = &n[len(n)-1].Value
	} else {
		// validate uid is in the list
		found := false
		for _, u := range resp.Node.Nodes {
			if *uid == u.Value {
				found = true
				break
			}
		}
		if !found {
			return nil, errors.New("Invalid UUID")
		}
	}

	contents, err := rs.fileStore.read(*uid)
	return contents, err
}

func (rs *resourceStore) deleteFile(key string, uid string) error {
	resp, err := rs.KeysAPI.Get(context.Background(), key, &client.GetOptions{Sort: true})
	if err != nil {
		return err
	}
	for _, u := range resp.Node.Nodes {
		if u.Value == uid {
			err = rs.fileStore.delete(u.Value)
			return err
		}
	}
	return errors.New("won't delete unreferenced file")
}