package kvstore

import (
	"database/sql"
	"sync"
	"time"

	_ "github.com/mattn/go-sqlite3"
)

type KV struct {
	primary bool
	dbPath  string

	db *sql.DB

	maxSeqNumStmt  *sql.Stmt
	logIterateStmt *sql.Stmt

	w *writer

	onStore  func(string, uint64, []byte)
	onDelete func(string, uint64)

	closeLock sync.Mutex
	recvLock  sync.Mutex
}

func newKV(
	dir string,
	primary bool,
	onStore func(string, uint64, []byte),
	onDelete func(string, uint64),
) *KV {
	kv := &KV{
		dbPath:   dbPath(dir),
		primary:  primary,
		onStore:  onStore,
		onDelete: onDelete,
	}

	opts := `?_journal=WAL`
	db, err := sql.Open("sqlite3", kv.dbPath+opts)
	must(err)

	_, err = db.Exec(sqlSchema)
	must(err)

	kv.maxSeqNumStmt, err = db.Prepare(sqlMaxSeqNumGet)
	must(err)
	kv.logIterateStmt, err = db.Prepare(sqlLogIterate)
	must(err)

	_, err = db.Exec(sqlSchema)
	must(err)

	kv.db = db

	if kv.primary {
		kv.w = newWriter(kv.db)
		kv.w.Start(kv.MaxSeqNum())
	}
	return kv
}

func NewPrimary(dir string) *KV {
	return newKV(dir, true, nil, nil)
}

func NewSecondary(
	dir string,
	onStore func(collection string, id uint64, data []byte),
	onDelete func(collection string, id uint64),
) *KV {
	return newKV(dir, false, onStore, onDelete)
}

func (kv *KV) Primary() bool {
	return kv.primary
}

func (kv *KV) MaxSeqNum() (seqNum uint64) {
	must(kv.maxSeqNumStmt.QueryRow().Scan(&seqNum))
	return seqNum
}

func (kv *KV) Iterate(collection string, each func(id uint64, data []byte)) {
	rows, err := kv.db.Query(sqlKVIterate, collection)
	must(err)
	defer rows.Close()

	var (
		id   uint64
		data []byte
	)

	for rows.Next() {
		must(rows.Scan(&id, &data))
		each(id, data)
	}
}

func (kv *KV) Close() {
	kv.closeLock.Lock()
	defer kv.closeLock.Unlock()

	if kv.w != nil {
		kv.w.Stop()
	}

	if kv.db != nil {
		kv.db.Close()
		kv.db = nil
	}
}

func (kv *KV) Store(collection string, id uint64, data []byte) {
	kv.w.Store(collection, id, data)
}

func (kv *KV) Delete(collection string, id uint64) {
	kv.w.Delete(collection, id)
}

func (kv *KV) CleanBefore(seconds int64) {
	_, err := kv.db.Exec(sqlCleanQuery, time.Now().Unix()-seconds)
	must(err)
}