// Copyright 2014 by Sascha L. Teichmann
// Use of this source code is governed by the MIT license
// that can be found in the LICENSE file.

package main

import (
	"database/sql"
	"os"

	"bitbucket.org/s_l_teichmann/mtredisalize/common"

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

const (
	fetchSql = "SELECT pos, data FROM blocks"
)

type SQLiteBlockProducer struct {
	db       *sql.DB
	rows     *sql.Rows
	splitter common.KeySplitter
}

func NewSQLiteBlockProducer(path string, splitter common.KeySplitter) (sbp *SQLiteBlockProducer, err error) {

	// check if we can stat it -> exists.
	if _, err = os.Stat(path); err != nil {
		return
	}

	var db *sql.DB
	if db, err = sql.Open("sqlite3", path); err != nil {
		return
	}

	var rows *sql.Rows
	if rows, err = db.Query(fetchSql); err != nil {
		db.Close()
		return
	}

	sbp = &SQLiteBlockProducer{
		db:       db,
		rows:     rows,
		splitter: splitter}

	return
}

func (sbp *SQLiteBlockProducer) Next(block *Block) (err error) {
	if sbp.rows == nil {
		err = NoMoreBlocksErr
		return
	}
	if sbp.rows.Next() {
		var key int64
		if err = sbp.rows.Scan(&key, &block.Data); err == nil {
			block.Coord = sbp.splitter(key)
		}
	} else {
		sbp.rows.Close()
		sbp.rows = nil
		err = NoMoreBlocksErr
	}
	return
}

func (sbp *SQLiteBlockProducer) Close() error {
	if sbp.rows != nil {
		sbp.rows.Close()
	}
	return sbp.db.Close()
}