//  Copyright (c) 2014 Couchbase, Inc.
//  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 boltdb

import (
	indexStore "github.com/blevesearch/bleve/index/store"
	"github.com/boltdb/bolt"
)

type op struct {
	k []byte
	v []byte
}

type Batch struct {
	store         *Store
	alreadyLocked bool
	ops           []op
	merges        map[string]indexStore.AssociativeMergeChain
}

func newBatch(store *Store) *Batch {
	rv := Batch{
		store:  store,
		ops:    make([]op, 0),
		merges: make(map[string]indexStore.AssociativeMergeChain),
	}
	return &rv
}

func newBatchAlreadyLocked(store *Store) *Batch {
	rv := Batch{
		store:         store,
		alreadyLocked: true,
		ops:           make([]op, 0),
		merges:        make(map[string]indexStore.AssociativeMergeChain),
	}
	return &rv
}

func (i *Batch) Set(key, val []byte) {
	i.ops = append(i.ops, op{key, val})
}

func (i *Batch) Delete(key []byte) {
	i.ops = append(i.ops, op{key, nil})
}

func (i *Batch) Merge(key []byte, oper indexStore.AssociativeMerge) {
	opers, ok := i.merges[string(key)]
	if !ok {
		opers = make(indexStore.AssociativeMergeChain, 0, 1)
	}
	opers = append(opers, oper)
	i.merges[string(key)] = opers
}

func (i *Batch) Execute() error {
	if !i.alreadyLocked {
		i.store.writer.Lock()
		defer i.store.writer.Unlock()
	}
	return i.store.db.Update(func(tx *bolt.Tx) error {
		b := tx.Bucket([]byte(i.store.bucket))

		// first process the merges
		for k, mc := range i.merges {
			val := b.Get([]byte(k))
			var err error
			val, err = mc.Merge([]byte(k), val)
			if err != nil {
				return err
			}
			if val == nil {
				err := b.Delete([]byte(k))
				if err != nil {
					return err
				}
			} else {
				err := b.Put([]byte(k), val)
				if err != nil {
					return err
				}
			}
		}

		// now process the regular get/set ops
		for _, o := range i.ops {
			if o.v == nil {
				if err := b.Delete(o.k); err != nil {
					return err
				}
			} else {
				if err := b.Put(o.k, o.v); err != nil {
					return err
				}
			}
		}

		return nil
	})
}

func (i *Batch) Close() error {
	return nil
}