package utils

import (
	"database/sql"
	"os"
	"time"

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

const (
	DbDriver    = "sqlite3"
	TableCreate = `
                create table IF NOT EXISTS telegram (
                    [tele_id] INTEGER PRIMARY KEY AUTOINCREMENT,
                    [tele_recv_time] TIMESTAMP NOT NULL DEFAULT (datetime('now', 'localtime')),
                    [tele_processed] int(1) NOT NULL DEFAULT 0,
                    [tele_text] TEXT NOT NULL    
                )
`
	InsertNew = "insert into telegram (tele_text) values (?)"
	InsertOld = "insert into telegram (tele_text, tele_processed) values (?, 1)"

	count  = "select count(*) from telegram where tele_processed=0"
	load   = "select tele_id, tele_text from telegram where tele_processed=0 Limit 100"
	update = "update telegram set tele_processed = 1 where tele_id=?"
)

type telegram struct {
	id   int64
	text string
}

var (
	dbFile      string
	initTable   bool
	initialized bool
	isWriting   bool
)

func getDb() *sql.DB {
	//log.Println("init database ", initTable)
	if initTable && !initialized {
		Log.Info("remove database file ", dbFile)
		os.Remove(dbFile)
	}
	db, err := sql.Open(DbDriver, dbFile)
	if err != nil {
		Log.Fatal("error in open database ", err)
	}
	return db
}

func InitDb(file string, init bool) error {
	dbFile = file
	initTable = init
	var dbErr error
	db := getDb()
	defer db.Close()
	_, dbErr = db.Exec(TableCreate)
	checkDbErr(dbErr, "error in create table")
	Log.Infof("database %s initialized", dbFile)
	initialized = true
	return nil
}

func InsertTelegram(teleString string) {
	getWriteLock()
	db := getDb()
	defer db.Close()
	var insertSQL string
	if ClientReady && WriteToClient(teleString) == nil {
		insertSQL = InsertOld
	} else {
		insertSQL = InsertNew
	}
	stmt, _ := db.Prepare(insertSQL)

	defer stmt.Close()
	result, err := stmt.Exec(teleString)
	id, _ := result.LastInsertId()
	checkDbErr(err, "error in insert telegram ")
	isWriting = false
	if insertSQL == InsertOld {
		Log.Infof("telegram [%d] processed ", id)
	} else {
		Log.Infof("telegram [%d] saved ", id)
	}
}

func LoadUnprocessed() {
	Log.Info("loading telegram")
	db := getDb()
	defer db.Close()
	for {
		telegrams := getTelegram(db)
		if len(telegrams) < 1 {
			break
		}
		for _, t := range telegrams {
			if WriteToClient(t.text) == nil {
				processed(db, t)
			}
		}
	}
	ClientReady = true
	Log.Info("client is ready for new telegram")
}

func getTelegram(db *sql.DB) []telegram {
	var telegrams []telegram
	num := countTelegram()
	Log.Infof("%n telegram unprocessed ", num)
	if num < 1 {
		return telegrams
	}
	Log.Info("try to load unprocessed telegram ")
	rows, err := db.Query(load)
	checkDbErr(err, "error in query telegram")
	defer rows.Close()
	for rows.Next() {
		var t telegram
		err := rows.Scan(&t.id, &t.text)
		checkDbErr(err, "error in scan telegram")
		telegrams = append(telegrams, t)
	}
	return telegrams
}

func processed(db *sql.DB, t telegram) {
	getWriteLock()
	tx, err := db.Begin()
	checkDbErr(err, "error in begin update")
	stmt, err := db.Prepare(update)
	defer stmt.Close()
	checkDbErr(err, "error in create update statement")
	result, err := stmt.Exec(t.id)
	checkDbErr(err, "error in update telegram status")
	id, _ := result.RowsAffected()
	Log.Infof("[%d] telegram update : %t", id, id > 0)
	isWriting = false
	Log.Info("release lock")
	tx.Commit()
}

func countTelegram() int64 {
	db := getDb()
	var countErr error
	stmt, _ := db.Prepare(count)
	defer stmt.Close()
	var num int64
	countErr = stmt.QueryRow().Scan(&num)
	checkDbErr(countErr, "error in count telegram")
	return num
}

func getWriteLock() {
	count := 0
	Log.Debugf("write lock : %t", isWriting)
	for isWriting && count < 10 {
		Log.Info("waiting for write ")
		time.Sleep(5 * time.Second)
		count++
	}
	if count >= 10 {
		Log.Fatal("database locked")
	}
	isWriting = true
}

func checkDbErr(err error, msg string) {
	if err != nil {
		Log.Fatal(msg, err)
	}
}