package persistence

import (
	"database/sql"
	"fmt"
	"time"

	"github.com/status-im/go-waku/waku/v2/protocol/pb"
	"github.com/status-im/go-waku/waku/v2/utils"
	"go.uber.org/zap"
)

type MessageProvider interface {
	GetAll() ([]StoredMessage, error)
	Put(cursor *pb.Index, pubsubTopic string, message *pb.WakuMessage) error
	Stop()
}

// DBStore is a MessageProvider that has a *sql.DB connection
type DBStore struct {
	MessageProvider
	db  *sql.DB
	log *zap.SugaredLogger

	maxMessages int
	maxDuration time.Duration
}

type StoredMessage struct {
	ID           []byte
	PubsubTopic  string
	ReceiverTime int64
	Message      *pb.WakuMessage
}

// DBOption is an optional setting that can be used to configure the DBStore
type DBOption func(*DBStore) error

// WithDB is a DBOption that lets you use any custom *sql.DB with a DBStore.
func WithDB(db *sql.DB) DBOption {
	return func(d *DBStore) error {
		d.db = db
		return nil
	}
}

// WithDriver is a DBOption that will open a *sql.DB connection
func WithDriver(driverName string, datasourceName string) DBOption {
	return func(d *DBStore) error {
		db, err := sql.Open(driverName, datasourceName)
		if err != nil {
			return err
		}
		d.db = db
		return nil
	}
}

func WithRetentionPolicy(maxMessages int, maxDuration time.Duration) DBOption {
	return func(d *DBStore) error {
		d.maxDuration = maxDuration
		d.maxMessages = maxMessages
		return nil
	}
}

// Creates a new DB store using the db specified via options.
// It will create a messages table if it does not exist and
// clean up records according to the retention policy used
func NewDBStore(log *zap.SugaredLogger, options ...DBOption) (*DBStore, error) {
	result := new(DBStore)
	result.log = log.Named("dbstore")

	for _, opt := range options {
		err := opt(result)
		if err != nil {
			return nil, err
		}
	}

	err := result.createTable()
	if err != nil {
		return nil, err
	}

	err = result.cleanOlderRecords()
	if err != nil {
		return nil, err
	}

	return result, nil
}

func (d *DBStore) createTable() error {
	sqlStmt := `CREATE TABLE IF NOT EXISTS message (
		id BLOB,
		receiverTimestamp INTEGER NOT NULL,
		senderTimestamp INTEGER NOT NULL,
		contentTopic BLOB NOT NULL,
		pubsubTopic BLOB NOT NULL,
		payload BLOB,
		version INTEGER NOT NULL DEFAULT 0,
		CONSTRAINT messageIndex PRIMARY KEY (senderTimestamp, id, pubsubTopic)
	) WITHOUT ROWID;
	
	CREATE INDEX IF NOT EXISTS message_senderTimestamp ON message(senderTimestamp);
	CREATE INDEX IF NOT EXISTS message_receiverTimestamp ON message(receiverTimestamp);`
	_, err := d.db.Exec(sqlStmt)
	if err != nil {
		return err
	}
	return nil
}

func (d *DBStore) cleanOlderRecords() error {
	// Delete older messages
	if d.maxDuration > 0 {
		sqlStmt := `DELETE FROM message WHERE receiverTimestamp < ?`
		_, err := d.db.Exec(sqlStmt, utils.GetUnixEpochFrom(time.Now().Add(-d.maxDuration)))
		if err != nil {
			return err
		}
	}

	// Limit number of records to a max N
	if d.maxMessages > 0 {
		sqlStmt := `DELETE FROM message WHERE id IN (SELECT id FROM message ORDER BY receiverTimestamp DESC LIMIT -1 OFFSET ?)`
		_, err := d.db.Exec(sqlStmt, d.maxMessages)
		if err != nil {
			return err
		}
	}

	// reduce the size of the DB file after the delete operation. See: https://www.sqlite.org/lang_vacuum.html
	_, err := d.db.Exec("VACUUM")
	if err != nil {
		return err
	}

	return nil
}

// Closes a DB connection
func (d *DBStore) Stop() {
	d.db.Close()
}

// Inserts a WakuMessage into the DB
func (d *DBStore) Put(cursor *pb.Index, pubsubTopic string, message *pb.WakuMessage) error {
	stmt, err := d.db.Prepare("INSERT INTO message (id, receiverTimestamp, senderTimestamp, contentTopic, pubsubTopic, payload, version) VALUES (?, ?, ?, ?, ?, ?, ?)")
	if err != nil {
		return err
	}
	_, err = stmt.Exec(cursor.Digest, cursor.ReceiverTime, message.Timestamp, message.ContentTopic, pubsubTopic, message.Payload, message.Version)
	if err != nil {
		return err
	}

	return nil
}

// Returns all the stored WakuMessages
func (d *DBStore) GetAll() ([]StoredMessage, error) {
	start := time.Now()
	defer func() {
		elapsed := time.Since(start)
		d.log.Info(fmt.Sprintf("Loading records from the DB took %s", elapsed))
	}()

	rows, err := d.db.Query("SELECT id, receiverTimestamp, senderTimestamp, contentTopic, pubsubTopic, payload, version FROM message ORDER BY senderTimestamp ASC")
	if err != nil {
		return nil, err
	}

	var result []StoredMessage

	defer rows.Close()

	for rows.Next() {
		var id []byte
		var receiverTimestamp int64
		var senderTimestamp int64
		var contentTopic string
		var payload []byte
		var version uint32
		var pubsubTopic string

		err = rows.Scan(&id, &receiverTimestamp, &senderTimestamp, &contentTopic, &pubsubTopic, &payload, &version)
		if err != nil {
			d.log.Fatal(err)
		}

		msg := new(pb.WakuMessage)
		msg.ContentTopic = contentTopic
		msg.Payload = payload
		msg.Timestamp = senderTimestamp
		msg.Version = version

		record := StoredMessage{
			ID:           id,
			PubsubTopic:  pubsubTopic,
			ReceiverTime: receiverTimestamp,
			Message:      msg,
		}

		result = append(result, record)
	}

	d.log.Info(fmt.Sprintf("DB returned %d records", len(result)))

	err = rows.Err()
	if err != nil {
		return nil, err
	}

	return result, nil
}