From 62b3a098bdbe71ecd33194677e58801195b73682 Mon Sep 17 00:00:00 2001
From: hrj <harshad.rj@gmail.com>
Date: Sun, 5 Jul 2020 00:50:05 +0530
Subject: [PATCH] synchronise access to database statements

---
 src/main/scala/lc/Main.scala | 64 ++++++++++++++++++++++--------------
 1 file changed, 40 insertions(+), 24 deletions(-)

diff --git a/src/main/scala/lc/Main.scala b/src/main/scala/lc/Main.scala
index 61eaa87..8496f2f 100644
--- a/src/main/scala/lc/Main.scala
+++ b/src/main/scala/lc/Main.scala
@@ -5,12 +5,15 @@ import java.io.ByteArrayInputStream
 import java.util.concurrent._
 import java.util.UUID
 import java.sql.{Blob, ResultSet}
+import java.util.concurrent.atomic.AtomicInteger
 
 case class Size(height: Int, width: Int)
 case class Parameters(level: String, media: String, input_type: String, size: Option[Size])
 case class Id(id: String)
 case class Answer(answer: String, id: String)
 
+case class ProviderSecret(provider: String, secret: String)
+
 class Captcha(throttle: Int) extends DBConn {
 
   val stmt = getConn()
@@ -55,20 +58,25 @@ class Captcha(throttle: Int) extends DBConn {
     }
   }
 
+  private val uniqueIntCount = new AtomicInteger()
+
   def generateChallenge(param: Parameters): String = {
   	//TODO: eval params to choose a provider
   	val providerMap = getProvider()
   	val provider = providers(providerMap)
     val challenge = provider.returnChallenge()
     val blob = new ByteArrayInputStream(challenge.content)
-    val token = scala.util.Random.nextInt(10000).toString
-    insertPstmt.setString(1, token)
-    insertPstmt.setString(2, provider.getId)
-    insertPstmt.setString(3, challenge.secret)
-    insertPstmt.setString(4, providerMap)
-    insertPstmt.setString(5, challenge.contentType)
-    insertPstmt.setBlob(6, blob)
-    insertPstmt.executeUpdate()
+    // val token = scala.util.Random.nextInt(100000).toString
+    val token = uniqueIntCount.incrementAndGet().toString
+    insertPstmt.synchronized {
+      insertPstmt.setString(1, token)
+      insertPstmt.setString(2, provider.getId)
+      insertPstmt.setString(3, challenge.secret)
+      insertPstmt.setString(4, providerMap)
+      insertPstmt.setString(5, challenge.contentType)
+      insertPstmt.setBlob(6, blob)
+      insertPstmt.executeUpdate()
+    }
     token
   }
 
@@ -91,34 +99,42 @@ class Captcha(throttle: Int) extends DBConn {
   }
 
   def getChallenge(param: Parameters): Id = {
-    val rs = stmt.executeQuery("SELECT token FROM challenge WHERE solved=FALSE ORDER BY RAND() LIMIT 1")
-    val id = if(rs.next()){
-      rs.getString("token")
-    } else {
-      generateChallenge(param)
+    val idOpt = stmt.synchronized {
+      val rs = stmt.executeQuery("SELECT token FROM challenge WHERE solved=FALSE ORDER BY RAND() LIMIT 1")
+      if(rs.next()) {
+        Some(rs.getString("token"))
+      } else {
+        None
+      }
     }
+    val id = idOpt.getOrElse(generateChallenge(param))
     val uuid = getUUID(id)
     Id(uuid)
   }
 
   def getUUID(id: String): String = {
     val uuid = UUID.randomUUID().toString
-    mapPstmt.setString(1,uuid)
-    mapPstmt.setString(2,id)
-    mapPstmt.executeUpdate()
+    mapPstmt.synchronized {
+      mapPstmt.setString(1,uuid)
+      mapPstmt.setString(2,id)
+      mapPstmt.executeUpdate()
+    }
     uuid
   }
 
   def checkAnswer(answer: Answer): Boolean = {
-    selectPstmt.setString(1, answer.id)
-    val rs: ResultSet = selectPstmt.executeQuery()
-    if (rs.first()) {
-      val secret = rs.getString("secret")
-      val provider = rs.getString("provider")
-      providers(provider).checkAnswer(secret, answer.answer)
-    } else {
-      false
+    val psOpt:Option[ProviderSecret] = selectPstmt.synchronized {
+      selectPstmt.setString(1, answer.id)
+      val rs: ResultSet = selectPstmt.executeQuery()
+      if (rs.first()) {
+        val secret = rs.getString("secret")
+        val provider = rs.getString("provider")
+        Some(ProviderSecret(provider, secret))
+      } else {
+        None
+      }
     }
+    psOpt.map(ps => providers(ps.provider).checkAnswer(ps.secret, answer.answer)).getOrElse(false)
   }
 
   def getHash(email: String): Int = {