package ledis

import (
	"encoding/binary"
	"errors"
	"github.com/siddontang/go-leveldb/leveldb"
)

type FVPair struct {
	Field []byte
	Value []byte
}

var errHashKey = errors.New("invalid hash key")
var errHSizeKey = errors.New("invalid hsize key")

const (
	hashStartSep byte = ':'
	hashStopSep  byte = hashStartSep + 1
)

func encode_hsize_key(key []byte) []byte {
	buf := make([]byte, len(key)+1)
	buf[0] = hSizeType

	copy(buf[1:], key)
	return buf
}

func decode_hsize_key(ek []byte) ([]byte, error) {
	if len(ek) == 0 || ek[0] != hSizeType {
		return nil, errHSizeKey
	}

	return ek[1:], nil
}

func encode_hash_key(key []byte, field []byte) []byte {
	buf := make([]byte, len(key)+len(field)+1+4+1)

	pos := 0
	buf[pos] = hashType
	pos++
	binary.BigEndian.PutUint32(buf[pos:], uint32(len(key)))
	pos += 4

	copy(buf[pos:], key)
	pos += len(key)

	buf[pos] = hashStartSep
	pos++
	copy(buf[pos:], field)

	return buf
}

func encode_hash_start_key(key []byte) []byte {
	k := encode_hash_key(key, nil)
	return k
}

func encode_hash_stop_key(key []byte) []byte {
	k := encode_hash_key(key, nil)

	k[len(k)-1] = hashStopSep

	return k
}

func decode_hash_key(ek []byte) ([]byte, []byte, error) {
	if len(ek) < 6 || ek[0] != hashType {
		return nil, nil, errHashKey
	}

	pos := 1
	keyLen := int(binary.BigEndian.Uint32(ek[pos:]))
	pos += 4

	if keyLen+6 > len(ek) {
		return nil, nil, errHashKey
	}

	key := ek[pos : pos+keyLen]
	pos += keyLen

	if ek[pos] != hashStartSep {
		return nil, nil, errHashKey
	}

	pos++
	field := ek[pos:]
	return key, field, nil
}

func (db *DB) HLen(key []byte) (int64, error) {
	return Int64(db.db.Get(encode_hsize_key(key)))
}

func (db *DB) hSetItem(key []byte, field []byte, value []byte) (int64, error) {
	t := db.hashTx

	ek := encode_hash_key(key, field)

	var n int64 = 1
	if v, _ := db.db.Get(ek); v != nil {
		n = 0
	} else {
		if _, err := db.hIncrSize(key, 1); err != nil {
			return 0, err
		}
	}

	t.Put(ek, value)
	return n, nil
}

func (db *DB) HSet(key []byte, field []byte, value []byte) (int64, error) {
	t := db.hashTx
	t.Lock()
	defer t.Unlock()

	n, err := db.hSetItem(key, field, value)
	if err != nil {
		return 0, err
	}

	//todo add binlog

	err = t.Commit()
	return n, err
}

func (db *DB) HGet(key []byte, field []byte) ([]byte, error) {
	return db.db.Get(encode_hash_key(key, field))
}

func (db *DB) HMset(key []byte, args ...FVPair) error {
	t := db.hashTx
	t.Lock()
	defer t.Unlock()

	var num int64 = 0
	for i := 0; i < len(args); i++ {
		ek := encode_hash_key(key, args[i].Field)
		if v, _ := db.db.Get(ek); v == nil {
			num++
		}

		t.Put(ek, args[i].Value)
	}

	if _, err := db.hIncrSize(key, num); err != nil {
		return err
	}

	//todo add binglog
	err := t.Commit()
	return err
}

func (db *DB) HMget(key []byte, args [][]byte) ([]interface{}, error) {
	r := make([]interface{}, len(args))
	for i := 0; i < len(args); i++ {
		v, err := db.db.Get(encode_hash_key(key, args[i]))
		if err != nil {
			return nil, err
		}

		r[i] = v
	}

	return r, nil
}

func (db *DB) HDel(key []byte, args [][]byte) (int64, error) {
	t := db.hashTx
	t.Lock()
	defer t.Unlock()

	var num int64 = 0
	for i := 0; i < len(args); i++ {
		ek := encode_hash_key(key, args[i])
		if v, err := db.db.Get(ek); err != nil {
			return 0, err
		} else if v == nil {
			continue
		} else {
			num++
			t.Delete(ek)
		}
	}

	if _, err := db.hIncrSize(key, -num); err != nil {
		return 0, err
	}

	err := t.Commit()

	return num, err
}

func (db *DB) hIncrSize(key []byte, delta int64) (int64, error) {
	t := db.hashTx
	sk := encode_hsize_key(key)
	size, err := Int64(db.db.Get(sk))
	if err != nil {
		return 0, err
	} else {
		size += delta
		if size <= 0 {
			size = 0
			t.Delete(sk)
		} else {
			t.Put(sk, PutInt64(size))
		}
	}

	return size, nil
}

func (db *DB) HIncrBy(key []byte, field []byte, delta int64) (int64, error) {
	t := db.hashTx
	t.Lock()
	defer t.Unlock()

	ek := encode_hash_key(key, field)

	var n int64 = 0
	n, err := StrInt64(db.db.Get(ek))
	if err != nil {
		return 0, err
	}

	n += delta

	_, err = db.hSetItem(key, field, StrPutInt64(n))
	if err != nil {
		return 0, err
	}

	err = t.Commit()

	return n, err
}

func (db *DB) HGetAll(key []byte) ([]interface{}, error) {
	start := encode_hash_start_key(key)
	stop := encode_hash_stop_key(key)

	v := make([]interface{}, 0, 16)

	it := db.db.Iterator(start, stop, leveldb.RangeROpen, 0, -1)
	for ; it.Valid(); it.Next() {
		_, k, err := decode_hash_key(it.Key())
		if err != nil {
			return nil, err
		}
		v = append(v, k)
		v = append(v, it.Value())
	}

	it.Close()

	return v, nil
}

func (db *DB) HKeys(key []byte) ([]interface{}, error) {
	start := encode_hash_start_key(key)
	stop := encode_hash_stop_key(key)

	v := make([]interface{}, 0, 16)

	it := db.db.Iterator(start, stop, leveldb.RangeROpen, 0, -1)
	for ; it.Valid(); it.Next() {
		_, k, err := decode_hash_key(it.Key())
		if err != nil {
			return nil, err
		}
		v = append(v, k)
	}

	it.Close()

	return v, nil
}

func (db *DB) HValues(key []byte) ([]interface{}, error) {
	start := encode_hash_start_key(key)
	stop := encode_hash_stop_key(key)

	v := make([]interface{}, 0, 16)

	it := db.db.Iterator(start, stop, leveldb.RangeROpen, 0, -1)
	for ; it.Valid(); it.Next() {
		v = append(v, it.Value())
	}

	it.Close()

	return v, nil
}

func (db *DB) HClear(key []byte) (int64, error) {
	sk := encode_hsize_key(key)

	t := db.hashTx
	t.Lock()
	defer t.Unlock()

	start := encode_hash_start_key(key)
	stop := encode_hash_stop_key(key)

	var num int64 = 0
	it := db.db.Iterator(start, stop, leveldb.RangeROpen, 0, -1)
	for ; it.Valid(); it.Next() {
		t.Delete(it.Key())
		num++
	}

	it.Close()

	t.Delete(sk)

	err := t.Commit()
	return num, err
}