package db

import (
	"errors"
	"sync"

	"github.com/harmony-one/harmony/utils"
)

// MemDatabase is the test memory database. It won't be used for any production.
type MemDatabase struct {
	db   map[string][]byte
	lock sync.RWMutex
}

// NewMemDatabase returns a pointer of the new creation of MemDatabase.
func NewMemDatabase() *MemDatabase {
	return &MemDatabase{
		db: make(map[string][]byte),
	}
}

// NewMemDatabaseWithCap returns a pointer of the new creation of MemDatabase with the given size.
func NewMemDatabaseWithCap(size int) *MemDatabase {
	return &MemDatabase{
		db: make(map[string][]byte, size),
	}
}

// Put puts (key, value) item into MemDatabase.
func (db *MemDatabase) Put(key []byte, value []byte) error {
	db.lock.Lock()
	defer db.lock.Unlock()

	db.db[string(key)] = utils.CopyBytes(value)
	return nil
}

// Has checks if the key is included into MemDatabase.
func (db *MemDatabase) Has(key []byte) (bool, error) {
	db.lock.RLock()
	defer db.lock.RUnlock()

	_, ok := db.db[string(key)]
	return ok, nil
}

// Get gets value of the given key.
func (db *MemDatabase) Get(key []byte) ([]byte, error) {
	db.lock.RLock()
	defer db.lock.RUnlock()

	if entry, ok := db.db[string(key)]; ok {
		return utils.CopyBytes(entry), nil
	}
	return nil, errors.New("not found")
}

// Keys returns all keys of the given MemDatabase.
func (db *MemDatabase) Keys() [][]byte {
	db.lock.RLock()
	defer db.lock.RUnlock()

	keys := [][]byte{}
	for key := range db.db {
		keys = append(keys, []byte(key))
	}
	return keys
}

// Delete deletes the given key.
func (db *MemDatabase) Delete(key []byte) error {
	db.lock.Lock()
	defer db.lock.Unlock()

	delete(db.db, string(key))
	return nil
}

// Close closes the given db.
func (db *MemDatabase) Close() {}

// NewBatch returns a batch of MemDatabase transactions.
func (db *MemDatabase) NewBatch() Batch {
	return &memBatch{db: db}
}

// Len returns the length of the given db.
func (db *MemDatabase) Len() int { return len(db.db) }

type kv struct {
	k, v []byte
	del  bool
}

type memBatch struct {
	db     *MemDatabase
	writes []kv
	size   int
}

func (b *memBatch) Put(key, value []byte) error {
	b.writes = append(b.writes, kv{utils.CopyBytes(key), utils.CopyBytes(value), false})
	b.size += len(value)
	return nil
}

func (b *memBatch) Delete(key []byte) error {
	b.writes = append(b.writes, kv{utils.CopyBytes(key), nil, true})
	b.size++
	return nil
}

func (b *memBatch) Write() error {
	b.db.lock.Lock()
	defer b.db.lock.Unlock()

	for _, kv := range b.writes {
		if kv.del {
			delete(b.db.db, string(kv.k))
			continue
		}
		b.db.db[string(kv.k)] = kv.v
	}
	return nil
}

func (b *memBatch) ValueSize() int {
	return b.size
}

func (b *memBatch) Reset() {
	b.writes = b.writes[:0]
	b.size = 0
}