<?php

const DBHOST = 'localhost';
CONST DBPORT = '3306';
const DBNAME = 'test';
const DBUSER = 'root';
const DBPASS = '';


withDb(function($db) {
    $total = 0;
    foreach (uidGenerator(1000) as $uid) {
        migrateUser($uid);
        $total++;
    }
    echo "Total users migrated：$total\n";
});

function uidGenerator($limit) {
    $uids = [];
    $lastId = 0;

    while (true) {
        $uids = [];

        withDb(function($db) use (&$uids, $lastId, $limit) {
            $selectUsers = $db->prepare('SELECT uid from tbl_member WHERE uid > :lastId AND col1 > 0 ORDER BY uid ASC LIMIT :limit');
            $selectUsers->bindParam(':lastId', $lastId, PDO::PARAM_INT);
            $selectUsers->bindParam(':limit', $limit, PDO::PARAM_INT);
            $selectUsers->execute();
            foreach($selectUsers->fetchAll() as $user) {
                $uids []= $user['uid'];
            }
            $selectUsers->closeCursor();
        });

        if (! $uids) {
            break;
        }

        foreach ($uids as $uid) {
            yield $uid;
        }

        $lastId = end($uids);
    }
}

function migrateUser($uid) {
    echo "Migrating user: $uid \n";

    withTransaction(function(PDO $db) use ($uid) {
        $selectMember = $db->prepare('SELECT col1 FROM tbl_member WHERE uid = :uid FOR UPDATE');
        $updateMember = $db->prepare('UPDATE tbl_member SET col1 = :col1 WHERE uid = :uid');
        $insertLog = $db->prepare('INSERT INTO tbl_member_log (uid, oldCol1, newCol1) VALUES (:uid, :oldCol1, newCol1)');

        $selectMember->execute([':uid' => $uid]);
        $member = $selectMember->fetch();

        $newCol1 = bcadd($member['col1'], 100, 2);

        $updateMember->execute([
            ':uid' => $uid,
            ':col1' => $newCol1,
        ]);

        $insertLog->execute([
            ':uid' => $uid,
            ':oldCol1' => $member['col1'],
            ':newCol1' => $newCol1,
        ]);

        $selectMember->closeCursor();
        $updateMember->closeCursor();
        $insertLog->closeCursor();
    });
}

function withTransaction($func) {
    withDb(function(PDO $db) use ($func) {
        try {
            $db->beginTransaction();
            $func($db);
            $db->commit();
        } catch (Exception $e) {
            $db->rollBack();
            throw $e;
        }
    });
}

function withDb($func) {
    static $dbh = null;
    try {
        if ($dbh === null) {
            $dbh = new PDO(sprintf('mysql:host=%s;dbname=%s;charset=UTF8;port=%s', DBHOST, DBNAME, DBPORT), DBUSER, DBPASS);
            if (! $dbh) {
                throw new \Exception('Can not connect to database!');
            }
        }

        $dbh->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);

        $func($dbh);
    } catch (PDOException $e) {
        print "Error!: " . $e->getMessage() . PHP_EOL;
        die();
    }
}