package content

import (
	"bytes"
	"encoding/binary"
	"fmt"
	"git.gammaspectra.live/S.O.N.G/FinalCommander/utilities"
	"github.com/ipfs/go-cid"
	"github.com/multiformats/go-multihash"
	"time"
)

// HashIdentifier Main identifier
type HashIdentifier multihash.DecodedMultihash

func (i *HashIdentifier) IsKey() bool {
	return i.Code == multihash.SHA2_256
}
func (i *HashIdentifier) Encode() []byte {
	b, _ := multihash.Encode(i.Digest, i.Code)
	return b
}
func (i *HashIdentifier) CID() cid.Cid {
	return cid.NewCidV1(cid.Raw, i.Hash())
}
func (i *HashIdentifier) Hash() multihash.Multihash {
	return i.Encode()
}
func (i *HashIdentifier) Equals(o *HashIdentifier) bool {
	return i.Code == o.Code && bytes.Compare(i.Digest, o.Digest) == 0
}

func NewHashIdentifierFromMultihash(mh multihash.Multihash) *HashIdentifier {
	d, err := multihash.Decode(mh)
	if err != nil {
		return nil
	}
	i := HashIdentifier(*d)
	return &i
}

type Entry struct {
	Key     HashIdentifier
	Version uint64
	// CheckTime indicates relative unix time entry was accessed
	AccessTime int64
	// CheckTime indicates next unix time a check shall be made
	CheckTime   int64
	InvalidList []int
}

type Alias struct {
	Key        HashIdentifier
	Identifier HashIdentifier
}

func (e *Alias) Encode() []byte {
	return e.Identifier.Encode()
}

func DecodeAlias(key HashIdentifier, message []byte) *Alias {
	buffer := bytes.NewBuffer(message)
	read, mh, err := multihash.MHFromBytes(buffer.Bytes())
	if err != nil {
		return nil
	}
	buffer.Next(read)

	if buffer.Len() != 0 { //Unknown extra data
		return nil
	}

	return &Alias{
		Key:        key,
		Identifier: *NewHashIdentifierFromMultihash(mh),
	}
}

func (e *Entry) Encode() ([]byte, error) {
	if !e.Valid() {
		return nil, fmt.Errorf("invalid Entry")
	}

	message := &bytes.Buffer{}

	buf := make([]byte, binary.MaxVarintLen64)

	n := binary.PutUvarint(buf, e.Version)
	_, _ = message.Write(buf[:n])

	if e.Version == 0 {
		n := binary.PutVarint(buf, e.AccessTime)
		_, _ = message.Write(buf[:n])
		n = binary.PutVarint(buf, e.CheckTime)
		_, _ = message.Write(buf[:n])
		message.Write(utilities.EncodeIntegerList(e.InvalidList))
	}

	return message.Bytes(), nil
}

func DecodeEntry(key HashIdentifier, message []byte) *Entry {
	entry := Entry{
		Key: key,
	}
	var err error
	buffer := bytes.NewBuffer(message)

	entry.Version, err = binary.ReadUvarint(buffer)
	if err != nil {
		return nil
	}

	if entry.Version == 0 {
		entry.AccessTime, err = binary.ReadVarint(buffer)
		if err != nil {
			return nil
		}
		entry.CheckTime, err = binary.ReadVarint(buffer)
		if err != nil {
			return nil
		}
		entry.InvalidList = utilities.DecodeIntegerList(buffer.Bytes())

		return &entry
	}

	return nil
}

func (e *Entry) UpdateAccessTime(db *Database) {
	now := time.Now().UTC().Unix()

	diff := e.AccessTime - now
	e.AccessTime = now

	if diff < 0 {
		diff = -diff
	}

	if diff > 3600*24 { //Update max every day
		_ = db.SetEntry(e)
	}
}

func (e *Entry) InInvalidList(i int) bool {
	for _, v := range e.InvalidList {
		if i == v {
			return true
		}
	}
	return false
}

func (e *Entry) NeedsCheck() bool {
	return e.CheckTime < time.Now().UTC().Unix()
}

func (e *Entry) Valid() bool {
	return e.Key.IsKey() && e.AccessTime != 0 && e.CheckTime != 0
}

func (e *Entry) Multihash() multihash.Multihash {
	return e.Key.Hash()
}

func (e *Entry) CID() cid.Cid {
	return e.Key.CID()
}