Extract repl state as a separate object

compiler/cli/cli-common/src/org/jetbrains/kotlin/cli/common/repl/AggregatedReplState.kt

@@ -0,0 +1,79 @@
+/*
+ * Copyright 2010-2017 JetBrains s.r.o.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.jetbrains.kotlin.cli.common.repl
+
+import java.util.concurrent.locks.ReentrantReadWriteLock
+import kotlin.concurrent.read
+import kotlin.concurrent.write
+
+open class AggregatedReplStateHistory<T1, T2>(val history1: IReplStageHistory<T1>, val history2: IReplStageHistory<T2>, override val lock: ReentrantReadWriteLock = ReentrantReadWriteLock())
+    : IReplStageHistory<Pair<T1, T2>>, AbstractList<ReplHistoryRecord<Pair<T1, T2>>>()
+{
+    override val size: Int
+        get() = minOf(history1.size, history2.size)
+
+    override fun push(id: ILineId, item: Pair<T1, T2>) {
+        lock.write {
+            assertSameSize()
+            history1.push(id, item.first)
+            history2.push(id, item.second)
+        }
+    }
+
+    override fun get(index: Int): ReplHistoryRecord<Pair<T1, T2>> = lock.read {
+        assertSameSize()
+        val r1 = history1[index]
+        val r2 = history2[index]
+        assertSameId(r1, r2)
+        ReplHistoryRecord(r1.id, r1.item to r2.item)
+    }
+
+    override fun pop(): ReplHistoryRecord<Pair<T1, T2>>? = lock.write {
+        assertSameSize()
+        val r1 = history1.pop()
+        val r2 = history2.pop()
+        if (r1 == null && r2 == null) return null
+        if (r1 == null || r2 == null) throw IllegalStateException("Aggregated history mismatch: $r1 vs $r2")
+        assertSameId(r1, r2)
+        ReplHistoryRecord(r1.id, r1.item to r2.item)
+    }
+
+    override fun resetTo(id: ILineId): Iterable<ILineId> = lock.write {
+        assertSameSize()
+        val i1 = history1.resetTo(id).toList()
+        val i2 = history2.resetTo(id).toList()
+        if (i1 != i2) throw IllegalStateException("Aggregated history resetted lines mismatch: $i1 != $i2")
+        i1
+    }
+
+    private fun assertSameSize() {
+        if (history1.size != history2.size) throw IllegalStateException("Aggregated history sizes mismatch: ${history1.size} != ${history2.size}")
+    }
+
+    private fun assertSameId(r1: ReplHistoryRecord<T1>, r2: ReplHistoryRecord<T2>) {
+        if (r1.id != r2.id) throw IllegalStateException("Aggregated history mismatch: ${r1.id} != ${r2.id}")
+    }
+}
+
+open class AggregatedReplStageState<T1, T2>(val state1: IReplStageState<T1>, val state2: IReplStageState<T2>, override val lock: ReentrantReadWriteLock = ReentrantReadWriteLock())
+    : IReplStageState<Pair<T1, T2>>
+{
+    override val history: IReplStageHistory<Pair<T1, T2>> = AggregatedReplStateHistory(state1.history, state2.history, lock)
+
+    override fun <StateT : IReplStageState<*>> asState(): StateT = (state1 as? StateT) ?: (state2 as StateT) ?: super.asState()
+}
+

compiler/cli/cli-common/src/org/jetbrains/kotlin/cli/common/repl/BasicReplState.kt

@@ -0,0 +1,69 @@
+/*
+ * Copyright 2010-2017 JetBrains s.r.o.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.jetbrains.kotlin.cli.common.repl
+
+import java.io.Serializable
+import java.util.*
+import java.util.concurrent.locks.ReentrantReadWriteLock
+import kotlin.concurrent.write
+
+data class LineId(override val no: Int, private val codeHash: Int) : ILineId, Serializable {
+
+    constructor(no: Int, code: String): this(no, code.hashCode())
+    constructor(codeLine: ReplCodeLine): this(codeLine.no, codeLine.code.hashCode())
+
+    override fun compareTo(other: ILineId): Int = (other as? LineId)?.let {
+        val c = no.compareTo(it.no)
+        if (c == 0) codeHash.compareTo(it.codeHash)
+        else c
+    } ?: -1 // TODO: check if it doesn't break something
+
+    companion object {
+        private val serialVersionUID: Long = 8328353000L
+    }
+}
+
+open class BasicReplStageHistory<T>(override val lock: ReentrantReadWriteLock = ReentrantReadWriteLock()) : IReplStageHistory<T>, ArrayList<ReplHistoryRecord<T>>() {
+
+    override fun push(id: ILineId, item: T) {
+        lock.write {
+            add(ReplHistoryRecord(id, item))
+        }
+    }
+
+    override fun pop(): ReplHistoryRecord<T>? = lock.write { if (isEmpty()) null else removeAt(lastIndex) }
+
+    override fun resetTo(id: ILineId): Iterable<ILineId> {
+        lock.write {
+            val idx = indexOfFirst { it.id == id }
+            if (idx < 0) throw java.util.NoSuchElementException("Cannot rest to inexistent line ${id.no}")
+            if (idx < lastIndex) {
+                val removed = asSequence().drop(idx + 1).map { it.id }.toList()
+                removeRange(idx + 1, lastIndex)
+                return removed
+            }
+            else return emptyList()
+        }
+    }
+}
+
+class BasicReplStageState<HistoryItemT>: IReplStageState<HistoryItemT> {
+
+    override val lock = ReentrantReadWriteLock()
+
+    override val history: BasicReplStageHistory<HistoryItemT> = BasicReplStageHistory(lock)
+}

compiler/cli/cli-common/src/org/jetbrains/kotlin/cli/common/repl/GenericEvaluatorState.kt

@@ -0,0 +1,38 @@
+/*
+ * Copyright 2010-2017 JetBrains s.r.o.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.jetbrains.kotlin.cli.common.repl
+
+import java.io.File
+import java.net.URLClassLoader
+import java.util.concurrent.locks.ReentrantReadWriteLock
+import kotlin.concurrent.read
+
+open class GenericReplEvaluatorState(baseClasspath: Iterable<File>, baseClassloader: ClassLoader?, override val lock: ReentrantReadWriteLock = ReentrantReadWriteLock())
+    : IReplStageState<EvalClassWithInstanceAndLoader>
+{
+    override val history: IReplStageHistory<EvalClassWithInstanceAndLoader> = BasicReplStageHistory(lock)
+
+    val topClassLoader: ReplClassLoader = makeReplClassLoader(baseClassloader, baseClasspath)
+
+    val currentClasspath: List<File> get() = lock.read {
+        history.peek()?.item?.classLoader?.listAllUrlsAsFiles()
+        ?: topClassLoader.listAllUrlsAsFiles()
+    }
+}
+
+internal fun makeReplClassLoader(baseClassloader: ClassLoader?, baseClasspath: Iterable<File>) =
+        ReplClassLoader(URLClassLoader(baseClasspath.map { it.toURI().toURL() }.toTypedArray(), baseClassloader))

compiler/cli/cli-common/src/org/jetbrains/kotlin/cli/common/repl/GenericReplCompilingEvaluator.kt

@@ -22,27 +22,36 @@ import kotlin.concurrent.write
 
 class GenericReplCompilingEvaluator(val compiler: ReplCompiler,
                                     baseClasspath: Iterable<File>,
-                                    baseClassloader: ClassLoader?,
-                                    protected val fallbackScriptArgs: ScriptArgsWithTypes? = null,
-                                    repeatingMode: ReplRepeatingMode = ReplRepeatingMode.REPEAT_ONLY_MOST_RECENT,
-                                    protected val stateLock: ReentrantReadWriteLock = ReentrantReadWriteLock()
+                                    baseClassloader: ClassLoader? = Thread.currentThread().contextClassLoader,
+                                    private val fallbackScriptArgs: ScriptArgsWithTypes? = null,
+                                    repeatingMode: ReplRepeatingMode = ReplRepeatingMode.REPEAT_ONLY_MOST_RECENT
 ) : ReplFullEvaluator {
-    val evaluator = GenericReplEvaluator(baseClasspath, baseClassloader, fallbackScriptArgs, repeatingMode, stateLock)
+    val evaluator = GenericReplEvaluator(baseClasspath, baseClassloader, fallbackScriptArgs, repeatingMode)
 
-    override fun compileAndEval(codeLine: ReplCodeLine, scriptArgs: ScriptArgsWithTypes?, verifyHistory: List<ReplCodeLine>?, invokeWrapper: InvokeWrapper?): ReplEvalResult {
-        return stateLock.write {
-            val compiled = compiler.compile(codeLine, verifyHistory)
+    override fun createState(lock: ReentrantReadWriteLock): IReplStageState<*> = AggregatedReplStageState(compiler.createState(lock), evaluator.createState(lock), lock)
+
+    override fun compileAndEval(state: IReplStageState<*>, codeLine: ReplCodeLine, scriptArgs: ScriptArgsWithTypes?, invokeWrapper: InvokeWrapper?): ReplEvalResult {
+        return state.lock.write {
+            val aggregatedState = state.asState<AggregatedReplStageState<*, *>>()
+            val compiled = compiler.compile(state, codeLine)
             when (compiled) {
-                is ReplCompileResult.Error -> ReplEvalResult.Error.CompileTime(compiled.compiledHistory, compiled.message, compiled.location)
-                is ReplCompileResult.HistoryMismatch -> ReplEvalResult.HistoryMismatch(compiled.compiledHistory, compiled.lineNo)
-                is ReplCompileResult.Incomplete -> ReplEvalResult.Incomplete(compiled.compiledHistory)
+                is ReplCompileResult.Error -> ReplEvalResult.Error.CompileTime(compiled.message, compiled.location)
+                is ReplCompileResult.HistoryMismatch -> ReplEvalResult.HistoryMismatch(compiled.lineNo)
+                is ReplCompileResult.Incomplete -> ReplEvalResult.Incomplete()
                 is ReplCompileResult.CompiledClasses -> {
-                    val result = eval(compiled, scriptArgs, invokeWrapper)
+                    val result = eval(state, compiled, scriptArgs, invokeWrapper)
                     when (result) {
                         is ReplEvalResult.Error,
                         is ReplEvalResult.HistoryMismatch,
                         is ReplEvalResult.Incomplete -> {
-                            result.completedEvalHistory.lastOrNull()?.let { compiler.resetToLine(it) }
+                            aggregatedState.apply {
+                                lock.write {
+                                    if (state1.history.size > state2.history.size) {
+                                        state2.history.peek()?.let { state1.history.resetTo(it.id) }
+                                        assert(state1.history.size == state2.history.size)
+                                    }
+                                }
+                            }
                             result
                         }
                         is ReplEvalResult.ValueResult,
@@ -56,49 +65,25 @@ class GenericReplCompilingEvaluator(val compiler: ReplCompiler,
         }
     }
 
-    override fun resetToLine(lineNumber: Int): List<ReplCodeLine> {
-        stateLock.write {
-            val removedCompiledLines = compiler.resetToLine(lineNumber)
-            val removedEvaluatorLines = evaluator.resetToLine(lineNumber)
+    override fun eval(state: IReplStageState<*>, compileResult: ReplCompileResult.CompiledClasses, scriptArgs: ScriptArgsWithTypes?, invokeWrapper: InvokeWrapper?): ReplEvalResult =
+            evaluator.eval(state, compileResult, scriptArgs, invokeWrapper)
 
-            removedCompiledLines.zip(removedEvaluatorLines).forEach {
-                if (it.first != it.second) {
-                    throw IllegalStateException("History mismatch when resetting lines")
-                }
-            }
+    override fun check(state: IReplStageState<*>, codeLine: ReplCodeLine): ReplCheckResult = compiler.check(state, codeLine)
 
-            return removedCompiledLines
-        }
-    }
-
-    override fun resetToLine(line: ReplCodeLine): List<ReplCodeLine> = resetToLine(line.no)
-
-    override val lastEvaluatedScripts: List<EvalHistoryType> get() = evaluator.lastEvaluatedScripts
-    override val history: List<ReplCodeLine> get() = evaluator.history
-    override val currentClasspath: List<File> get() = evaluator.currentClasspath
-
-    override val compiledHistory: List<ReplCodeLine> get() = compiler.history
-    override val evaluatedHistory: List<ReplCodeLine> get() = evaluator.history
-
-    override fun eval(compileResult: ReplCompileResult.CompiledClasses, scriptArgs: ScriptArgsWithTypes?, invokeWrapper: InvokeWrapper?): ReplEvalResult =
-            evaluator.eval(compileResult, scriptArgs, invokeWrapper)
-
-    override fun check(codeLine: ReplCodeLine): ReplCheckResult = compiler.check(codeLine)
-
-    override fun compileToEvaluable(codeLine: ReplCodeLine, defaultScriptArgs: ScriptArgsWithTypes?, verifyHistory: List<ReplCodeLine>?): Pair<ReplCompileResult, Evaluable?> {
-        val compiled = compiler.compile(codeLine, verifyHistory)
+    override fun compileToEvaluable(state: IReplStageState<*>, codeLine: ReplCodeLine, defaultScriptArgs: ScriptArgsWithTypes?): Pair<ReplCompileResult, Evaluable?> {
+        val compiled = compiler.compile(state, codeLine)
         return when (compiled) {
-            is ReplCompileResult.CompiledClasses -> Pair(compiled, DelayedEvaluation(compiled, stateLock, evaluator, defaultScriptArgs ?: fallbackScriptArgs))
+            // TODO: seems usafe when delayed evaluation may happen after some more compileAndEval calls on the same state; check and fix or protect
+            is ReplCompileResult.CompiledClasses -> Pair(compiled, DelayedEvaluation(state, compiled, evaluator, defaultScriptArgs ?: fallbackScriptArgs))
             else -> Pair(compiled, null)
         }
     }
 
-    class DelayedEvaluation(override val compiledCode: ReplCompileResult.CompiledClasses,
-                            private val stateLock: ReentrantReadWriteLock,
+    class DelayedEvaluation(private val state: IReplStageState<*>,
+                            override val compiledCode: ReplCompileResult.CompiledClasses,
                             private val evaluator: ReplEvaluator,
                             private val defaultScriptArgs: ScriptArgsWithTypes?) : Evaluable {
-        override fun eval(scriptArgs: ScriptArgsWithTypes?, invokeWrapper: InvokeWrapper?): ReplEvalResult {
-            return stateLock.write { evaluator.eval(compiledCode, scriptArgs ?: defaultScriptArgs, invokeWrapper) }
-        }
+        override fun eval(scriptArgs: ScriptArgsWithTypes?, invokeWrapper: InvokeWrapper?): ReplEvalResult =
+                evaluator.eval(state, compiledCode, scriptArgs ?: defaultScriptArgs, invokeWrapper)
     }
-}
+}

compiler/cli/cli-common/src/org/jetbrains/kotlin/cli/common/repl/GenericReplEvaluator.kt

@@ -18,144 +18,111 @@ package org.jetbrains.kotlin.cli.common.repl
 
 import org.jetbrains.kotlin.resolve.jvm.JvmClassName
 import java.io.File
-import java.net.URLClassLoader
 import java.util.concurrent.locks.ReentrantReadWriteLock
-import kotlin.concurrent.read
 import kotlin.concurrent.write
 
-open class GenericReplEvaluator(baseClasspath: Iterable<File>,
-                                baseClassloader: ClassLoader?,
+open class GenericReplEvaluator(val baseClasspath: Iterable<File>,
+                                val baseClassloader: ClassLoader? = Thread.currentThread().contextClassLoader,
                                 protected val fallbackScriptArgs: ScriptArgsWithTypes? = null,
-                                protected val repeatingMode: ReplRepeatingMode = ReplRepeatingMode.REPEAT_ONLY_MOST_RECENT,
-                                protected val stateLock: ReentrantReadWriteLock = ReentrantReadWriteLock()
+                                protected val repeatingMode: ReplRepeatingMode = ReplRepeatingMode.REPEAT_ONLY_MOST_RECENT
 ) : ReplEvaluator {
 
-    private val topClassLoader: ReplClassLoader = makeReplClassLoader(baseClassloader, baseClasspath)
+//    private val evaluatedHistory = ReplHistory<EvalClassWithInstanceAndLoader>()
 
-    private val evaluatedHistory = ReplHistory<EvalClassWithInstanceAndLoader>()
+//    override val history: List<ReplCodeLine> get() = stateLock.read { evaluatedHistory.copySources() }
 
-    override fun resetToLine(lineNumber: Int): List<ReplCodeLine> {
-        return stateLock.write {
-            evaluatedHistory.resetToLine(lineNumber)
-        }.map { it.first }
-    }
+//    private class HistoryActions(
+//            val effectiveHistory: List<EvalClassWithInstanceAndLoader>,
+//                                 val verify: (compareHistory: SourceList?) -> Int?,
+//                                 val addPlaceholder: (line: CompiledReplCodeLine, value: EvalClassWithInstanceAndLoader) -> Unit,
+//                                 val removePlaceholder: (line: CompiledReplCodeLine) -> Boolean,
+//                                 val addFinal: (line: CompiledReplCodeLine, value: EvalClassWithInstanceAndLoader) -> Unit,
+//                                 val processClasses: (compileResult: ReplCompileResult.CompiledClasses) -> Pair<ClassLoader, Class<out Any>>
+//    )
 
-    override val history: List<ReplCodeLine> get() = stateLock.read { evaluatedHistory.copySources() }
+    override fun createState(lock: ReentrantReadWriteLock): IReplStageState<*> = GenericReplEvaluatorState(baseClasspath, baseClassloader, lock)
 
-    override val currentClasspath: List<File> get() = stateLock.read {
-        evaluatedHistory.copyValues().lastOrNull()?.classLoader?.listAllUrlsAsFiles()
-        ?: topClassLoader.listAllUrlsAsFiles()
-    }
-
-    private class HistoryActions(val effectiveHistory: List<EvalClassWithInstanceAndLoader>,
-                                 val verify: (compareHistory: SourceList?) -> Int?,
-                                 val addPlaceholder: (line: CompiledReplCodeLine, value: EvalClassWithInstanceAndLoader) -> Unit,
-                                 val removePlaceholder: (line: CompiledReplCodeLine) -> Boolean,
-                                 val addFinal: (line: CompiledReplCodeLine, value: EvalClassWithInstanceAndLoader) -> Unit,
-                                 val processClasses: (compileResult: ReplCompileResult.CompiledClasses) -> Pair<ClassLoader, Class<out Any>>)
-
-    private fun prependClassLoaderWithNewClasses(effectiveHistory: List<EvalClassWithInstanceAndLoader>, compileResult: ReplCompileResult.CompiledClasses): Pair<ClassLoader, Class<out Any>> {
-        return stateLock.write {
-            var mainLineClassName: String? = null
-            val classLoader = makeReplClassLoader(effectiveHistory.lastOrNull()?.classLoader ?: topClassLoader, compileResult.classpathAddendum)
-            fun classNameFromPath(path: String) = JvmClassName.byInternalName(path.removeSuffix(".class"))
-            fun compiledClassesNames() = compileResult.classes.map { classNameFromPath(it.path).internalName.replace('/', '.') }
-            val expectedClassName = compileResult.generatedClassname
-            compileResult.classes.filter { it.path.endsWith(".class") }
-                    .forEach {
-                        val className = classNameFromPath(it.path)
-                        if (className.internalName == expectedClassName || className.internalName.endsWith("/$expectedClassName")) {
-                            mainLineClassName = className.internalName.replace('/', '.')
-                        }
-                        classLoader.addClass(className, it.bytes)
-                    }
-
-            val scriptClass = try {
-                classLoader.loadClass(mainLineClassName!!)
-            }
-            catch (t: Throwable) {
-                throw Exception("Error loading class $mainLineClassName: known classes: ${compiledClassesNames()}", t)
-            }
-            Pair(classLoader, scriptClass)
-        }
-    }
-
-    override fun eval(compileResult: ReplCompileResult.CompiledClasses,
+    override fun eval(state: IReplStageState<*>,
+                      compileResult: ReplCompileResult.CompiledClasses,
                       scriptArgs: ScriptArgsWithTypes?,
                       invokeWrapper: InvokeWrapper?): ReplEvalResult {
-        stateLock.write {
-            val verifyHistory = compileResult.compiledHistory.dropLast(1)
-            val defaultHistoryActor = HistoryActions(
-                    effectiveHistory = evaluatedHistory.copyValues(),
-                    verify = { line -> evaluatedHistory.firstMismatchingHistory(line) },
-                    addPlaceholder = { line, value -> evaluatedHistory.add(line, value) },
-                    removePlaceholder = { line -> evaluatedHistory.removeLast(line) },
-                    addFinal = { line, value -> evaluatedHistory.add(line, value) },
-                    processClasses = { compiled ->
-                        prependClassLoaderWithNewClasses(evaluatedHistory.copyValues(), compiled)
-                    })
+        state.lock.write {
+            val evalState = state.asState<GenericReplEvaluatorState>()
+//            val verifyHistory = compileResult.state.dropLast(1)
+//            val defaultHistoryActor = HistoryActions(
+//                    effectiveHistory = evalState.history.map { it.item },
+//                    verify = { line -> evalState.history.firstMismatchingHistory(line) },
+//                    addPlaceholder = { line, value -> evalState.history.add(line, value) },
+//                    removePlaceholder = { line -> evalState.history.removeLast(line) },
+//                    addFinal = { line, value -> evalState.history.add(line, value) },
+//                    processClasses = { compiled ->
+//                        prependClassLoaderWithNewClasses(evalState.history.copyValues(), compiled, )
+//                    })
 
-            val historyActor: HistoryActions = when (repeatingMode) {
-                ReplRepeatingMode.NONE -> defaultHistoryActor
+            val historyActor = when (repeatingMode) {
+                ReplRepeatingMode.NONE -> HistoryActionsForNoRepeat(evalState)
                 ReplRepeatingMode.REPEAT_ONLY_MOST_RECENT -> {
-                    val lastItem = evaluatedHistory.lastItem()
-                    if (lastItem == null || lastItem.first.source != compileResult.compiledCodeLine.source) {
-                        defaultHistoryActor
+                    val lastItem = evalState.history.peek()
+                    if (lastItem == null || lastItem.id != compileResult.lineId) {
+                        HistoryActionsForNoRepeat(evalState)
                     }
                     else {
-                        val trimmedHistory = ReplHistory(evaluatedHistory.copyAll().dropLast(1))
-                        HistoryActions(
-                                effectiveHistory = trimmedHistory.copyValues(),
-                                verify = { trimmedHistory.firstMismatchingHistory(it) },
-                                addPlaceholder = { _, _ -> NO_ACTION() },
-                                removePlaceholder = { NO_ACTION_THAT_RETURNS(true) },
-                                addFinal = { line, value ->
-                                    evaluatedHistory.removeLast(line)
-                                    evaluatedHistory.add(line, value)
-                                },
-                                processClasses = { _ ->
-                                    Pair(lastItem.second.classLoader, lastItem.second.klass.java)
-                                })
+                        HistoryActionsForRepeatRecentOnly(evalState)
+//                        val trimmedHistory = ReplHistory(evalState.history.copyAll().dropLast(1))
+//                        HistoryActions
+//                                effectiveHistory = trimmedHistory.copyValues(),
+//                                verify = { trimmedHistory.firstMismatchingHistory(it) },
+//                                addPlaceholder = { _, _ -> NO_ACTION() },
+//                                removePlaceholder = { NO_ACTION_THAT_RETURNS(true) },
+//                                addFinal = { line, value ->
+//                                    evalState.history.removeLast(line)
+//                                    evalState.history.add(line, value)
+//                                },
+//                                processClasses = { _ ->
+//                                    Pair(lastItem.second.classLoader, lastItem.second.klass.java)
+//                                })
                     }
                 }
                 ReplRepeatingMode.REPEAT_ANY_PREVIOUS -> {
-                    if (evaluatedHistory.isEmpty() || !evaluatedHistory.contains(compileResult.compiledCodeLine.source)) {
-                        defaultHistoryActor
+                    val matchingItem = evalState.history.firstOrNull { it.id == compileResult.lineId }
+                    if (matchingItem == null) {
+                        HistoryActionsForNoRepeat(evalState)
                     }
                     else {
-                        val historyCopy = evaluatedHistory.copyAll()
-                        val matchingItem = historyCopy.first { it.first.source == compileResult.compiledCodeLine.source }
-                        val trimmedHistory = ReplHistory(evaluatedHistory.copyAll().takeWhile { it != matchingItem })
-                        HistoryActions(
-                                effectiveHistory = trimmedHistory.copyValues(),
-                                verify = { trimmedHistory.firstMismatchingHistory(it) },
-                                addPlaceholder = { _, _ -> NO_ACTION() },
-                                removePlaceholder = { NO_ACTION_THAT_RETURNS(true) },
-                                addFinal = { line, value ->
-                                    val extraLines = evaluatedHistory.resetToLine(line)
-                                    evaluatedHistory.removeLast(line)
-                                    evaluatedHistory.add(line, value)
-                                    extraLines.forEach {
-                                        evaluatedHistory.add(it.first, it.second)
-                                    }
-                                },
-                                processClasses = { _ ->
-                                    Pair(matchingItem.second.classLoader, matchingItem.second.klass.java)
-                                })
+                        HistoryActionsForRepeatAny(evalState, matchingItem)
+//                        val historyCopy = evalState.history.copyAll()
+//                        val matchingItem = historyCopy.first { it.first.source == compileResult.compiledCodeLine.source }
+//                        val trimmedHistory = ReplHistory(evalState.history.copyAll().takeWhile { it != matchingItem })
+//                        HistoryActions(
+//                                effectiveHistory = trimmedHistory.copyValues(),
+//                                verify = { trimmedHistory.firstMismatchingHistory(it) },
+//                                addPlaceholder = { _, _ -> NO_ACTION() },
+//                                removePlaceholder = { NO_ACTION_THAT_RETURNS(true) },
+//                                addFinal = { line, value ->
+//                                    val extraLines = evalState.history.resetToLine(line)
+//                                    evalState.history.removeLast(line)
+//                                    evalState.history.add(line, value)
+//                                    extraLines.forEach {
+//                                        evalState.history.add(it.first, it.second)
+//                                    }
+//                                },
+//                                processClasses = { _ ->
+//                                    Pair(matchingItem.second.classLoader, matchingItem.second.klass.java)
+//                                })
                     }
                 }
             }
 
-            val firstMismatch = historyActor.verify(verifyHistory)
-            if (firstMismatch != null) {
-                return@eval ReplEvalResult.HistoryMismatch(evaluatedHistory.copySources(), firstMismatch)
-            }
+//            val firstMismatch = historyActor.firstMismatch(verifyHistory)
+//            if (firstMismatch != null) {
+//                return@eval ReplEvalResult.HistoryMismatch(firstMismatch)
+//            }
 
             val (classLoader, scriptClass) = try {
                 historyActor.processClasses(compileResult)
             }
             catch (e: Exception) {
-                return@eval ReplEvalResult.Error.Runtime(evaluatedHistory.copySources(), e.message ?: "unknown", e)
+                return@eval ReplEvalResult.Error.Runtime(e.message ?: "unknown", e)
             }
 
             val currentScriptArgs = scriptArgs ?: fallbackScriptArgs
@@ -170,7 +137,7 @@ open class GenericReplEvaluator(baseClasspath: Iterable<File>,
             // TODO: try/catch ?
             val scriptInstanceConstructor = scriptClass.getConstructor(*constructorParams)
 
-            historyActor.addPlaceholder(compileResult.compiledCodeLine, EvalClassWithInstanceAndLoader(scriptClass.kotlin, null, classLoader, invokeWrapper))
+            historyActor.addPlaceholder(compileResult.lineId, EvalClassWithInstanceAndLoader(scriptClass.kotlin, null, classLoader, invokeWrapper))
 
             val scriptInstance =
                     try {
@@ -178,33 +145,113 @@ open class GenericReplEvaluator(baseClasspath: Iterable<File>,
                         else scriptInstanceConstructor.newInstance(*constructorArgs)
                     }
                     catch (e: Throwable) {
-                        historyActor.removePlaceholder(compileResult.compiledCodeLine)
+                        historyActor.removePlaceholder(compileResult.lineId)
 
                         // ignore everything in the stack trace until this constructor call
-                        return@eval ReplEvalResult.Error.Runtime(evaluatedHistory.copySources(),
-                                                                 renderReplStackTrace(e.cause!!, startFromMethodName = "${scriptClass.name}.<init>"), e as? Exception)
+                        return@eval ReplEvalResult.Error.Runtime(renderReplStackTrace(e.cause!!, startFromMethodName = "${scriptClass.name}.<init>"), e as? Exception)
                     }
 
-            historyActor.removePlaceholder(compileResult.compiledCodeLine)
-            historyActor.addFinal(compileResult.compiledCodeLine, EvalClassWithInstanceAndLoader(scriptClass.kotlin, scriptInstance, classLoader, invokeWrapper))
+            historyActor.removePlaceholder(compileResult.lineId)
+            historyActor.addFinal(compileResult.lineId, EvalClassWithInstanceAndLoader(scriptClass.kotlin, scriptInstance, classLoader, invokeWrapper))
 
             val resultField = scriptClass.getDeclaredField(SCRIPT_RESULT_FIELD_NAME).apply { isAccessible = true }
             val resultValue: Any? = resultField.get(scriptInstance)
 
-            return if (compileResult.hasResult) ReplEvalResult.ValueResult(evaluatedHistory.copySources(), resultValue)
-            else ReplEvalResult.UnitResult(evaluatedHistory.copySources())
+            return if (compileResult.hasResult) ReplEvalResult.ValueResult(resultValue)
+            else ReplEvalResult.UnitResult()
         }
     }
 
-    override val lastEvaluatedScripts: List<EvalHistoryType> get() {
-        return stateLock.read { evaluatedHistory.copyAll() }
-    }
-
     companion object {
         private val SCRIPT_RESULT_FIELD_NAME = "\$\$result"
     }
 
-    private fun makeReplClassLoader(baseClassloader: ClassLoader?, baseClasspath: Iterable<File>) =
-            ReplClassLoader(URLClassLoader(baseClasspath.map { it.toURI().toURL() }.toTypedArray(), baseClassloader))
 }
 
+private open class HistoryActionsForNoRepeat(val state: GenericReplEvaluatorState) {
+
+    open val effectiveHistory: List<EvalClassWithInstanceAndLoader> get() = state.history.map { it.item }
+
+    open fun<OtherT> firstMismatch(other: IReplStageHistory<OtherT>): Pair<ReplHistoryRecord<EvalClassWithInstanceAndLoader>?, ReplHistoryRecord<OtherT>?>? = state.history.firstMismatch(other)
+
+    open fun addPlaceholder(lineId: ILineId, value: EvalClassWithInstanceAndLoader) { state.history.push(lineId, value) }
+
+    open fun removePlaceholder(lineId: ILineId): Boolean = state.history.verifiedPop(lineId) != null
+
+    open fun addFinal(lineId: ILineId, value: EvalClassWithInstanceAndLoader) { state.history.push(lineId, value) }
+
+    open fun processClasses(compileResult: ReplCompileResult.CompiledClasses): Pair<ClassLoader, Class<out Any>> = prependClassLoaderWithNewClasses(effectiveHistory, compileResult)
+
+    private fun prependClassLoaderWithNewClasses(effectiveHistory: List<EvalClassWithInstanceAndLoader>,
+                                                 compileResult: ReplCompileResult.CompiledClasses
+    ): Pair<ClassLoader, Class<out Any>> {
+        var mainLineClassName: String? = null
+        val classLoader = makeReplClassLoader(effectiveHistory.lastOrNull()?.classLoader ?: state.topClassLoader, compileResult.classpathAddendum)
+        fun classNameFromPath(path: String) = JvmClassName.byInternalName(path.removeSuffix(".class"))
+        fun compiledClassesNames() = compileResult.classes.map { classNameFromPath(it.path).internalName.replace('/', '.') }
+        val expectedClassName = compileResult.mainClassName
+        compileResult.classes.filter { it.path.endsWith(".class") }
+                .forEach {
+                    val className = classNameFromPath(it.path)
+                    if (className.internalName == expectedClassName || className.internalName.endsWith("/$expectedClassName")) {
+                        mainLineClassName = className.internalName.replace('/', '.')
+                    }
+                    classLoader.addClass(className, it.bytes)
+                }
+
+        val scriptClass = try {
+            classLoader.loadClass(mainLineClassName!!)
+        }
+        catch (t: Throwable) {
+            throw Exception("Error loading class $mainLineClassName: known classes: ${compiledClassesNames()}", t)
+        }
+        return Pair(classLoader, scriptClass)
+    }
+}
+
+private open class HistoryActionsForRepeatRecentOnly(state: GenericReplEvaluatorState) : HistoryActionsForNoRepeat(state) {
+
+    val currentLast = state.history.peek()!!
+
+    override val effectiveHistory: List<EvalClassWithInstanceAndLoader> get() = super.effectiveHistory.dropLast(1)
+
+    override fun<OtherT> firstMismatch(other: IReplStageHistory<OtherT>): Pair<ReplHistoryRecord<EvalClassWithInstanceAndLoader>?, ReplHistoryRecord<OtherT>?>? =
+            state.history.firstMismatchFiltered(other) { it.id != currentLast.id }
+
+    override fun addPlaceholder(lineId: ILineId, value: EvalClassWithInstanceAndLoader) {}
+
+    override fun removePlaceholder(lineId: ILineId): Boolean = true
+
+    override fun addFinal(lineId: ILineId, value: EvalClassWithInstanceAndLoader) {
+        state.history.pop()
+        state.history.push(lineId, value)
+    }
+
+    override fun processClasses(compileResult: ReplCompileResult.CompiledClasses): Pair<ClassLoader, Class<out Any>> =
+            currentLast.item.classLoader to currentLast.item.klass.java
+}
+
+private open class HistoryActionsForRepeatAny(state: GenericReplEvaluatorState, val matchingLine: ReplHistoryRecord<EvalClassWithInstanceAndLoader>): HistoryActionsForNoRepeat(state) {
+
+    override val effectiveHistory: List<EvalClassWithInstanceAndLoader> get() = state.history.takeWhile { it.id != matchingLine.id }.map { it.item }
+
+    override fun<OtherT> firstMismatch(other: IReplStageHistory<OtherT>): Pair<ReplHistoryRecord<EvalClassWithInstanceAndLoader>?, ReplHistoryRecord<OtherT>?>? =
+            state.history.firstMismatchWhile(other) { it.id != matchingLine.id }
+
+    override fun addPlaceholder(lineId: ILineId, value: EvalClassWithInstanceAndLoader) {}
+
+    override fun removePlaceholder(lineId: ILineId): Boolean = true
+
+    override fun addFinal(lineId: ILineId, value: EvalClassWithInstanceAndLoader) {
+        val extraLines = state.history.takeLastWhile { it.id == matchingLine.id }
+        state.history.resetTo(lineId)
+        state.history.pop()
+        state.history.push(lineId, value)
+        extraLines.forEach {
+            state.history.push(it.id, it.item)
+        }
+    }
+
+    override fun processClasses(compileResult: ReplCompileResult.CompiledClasses): Pair<ClassLoader, Class<out Any>> =
+            matchingLine.item.classLoader to matchingLine.item.klass.java
+}

compiler/cli/cli-common/src/org/jetbrains/kotlin/cli/common/repl/KotlinJsr223JvmScriptEngineBase.kt

@@ -19,16 +19,17 @@ package org.jetbrains.kotlin.cli.common.repl
 import org.jetbrains.kotlin.cli.common.messages.CompilerMessageLocation
 import java.io.Reader
 import java.util.concurrent.atomic.AtomicInteger
+import java.util.concurrent.locks.ReentrantReadWriteLock
 import javax.script.*
 
-val KOTLIN_SCRIPT_HISTORY_BINDINGS_KEY = "kotlin.script.history"
+val KOTLIN_SCRIPT_STATE_BINDINGS_KEY = "kotlin.script.state"
 val KOTLIN_SCRIPT_LINE_NUMBER_BINDINGS_KEY = "kotlin.script.line.number"
 
 // TODO consider additional error handling
-var Bindings.kotlinScriptHistory: MutableList<ReplCodeLine>
+var Bindings.kotlinScriptState: IReplStageState<*>
     @Suppress("UNCHECKED_CAST")
-    get() = getOrPut(KOTLIN_SCRIPT_HISTORY_BINDINGS_KEY, { arrayListOf<ReplCodeLine>() }) as MutableList<ReplCodeLine>
-    set(v) { put(KOTLIN_SCRIPT_HISTORY_BINDINGS_KEY, v) }
+    get() = get(KOTLIN_SCRIPT_STATE_BINDINGS_KEY) as IReplStageState<*>
+    set(v) { put(KOTLIN_SCRIPT_STATE_BINDINGS_KEY, v) }
 
 val Bindings.kotlinScriptLineNumber: AtomicInteger
     @Suppress("UNCHECKED_CAST")
@@ -36,8 +37,8 @@ val Bindings.kotlinScriptLineNumber: AtomicInteger
 
 abstract class KotlinJsr223JvmScriptEngineBase(protected val myFactory: ScriptEngineFactory) : AbstractScriptEngine(), ScriptEngine, Compilable {
 
-    protected abstract val replCompiler: ReplCompileAction
-    protected abstract val replScriptEvaluator: ReplFullEvaluator
+    protected abstract val replCompiler: ReplCompiler
+    protected abstract val replEvaluator: ReplFullEvaluator
 
     override fun eval(script: String, context: ScriptContext): Any? = compileAndEval(script, context)
 
@@ -52,20 +53,18 @@ abstract class KotlinJsr223JvmScriptEngineBase(protected val myFactory: ScriptEn
     override fun getFactory(): ScriptEngineFactory = myFactory
 
     // the parameter could be used in the future when we decide to keep state completely in the context and solve appropriate problems (now e.g. replCompiler keeps separate state)
-    fun nextCodeLine(@Suppress("UNUSED_PARAMETER") context: ScriptContext, code: String) = ReplCodeLine(this.context.getBindings(ScriptContext.ENGINE_SCOPE).kotlinScriptLineNumber.incrementAndGet(), code)
+    fun nextCodeLine(context: ScriptContext, code: String) = ReplCodeLine(context.getBindings(ScriptContext.ENGINE_SCOPE).kotlinScriptLineNumber.incrementAndGet(), code)
 
-    private fun getCurrentHistory(@Suppress("UNUSED_PARAMETER") context: ScriptContext) = this.context.getBindings(ScriptContext.ENGINE_SCOPE).kotlinScriptHistory
+    protected open fun createState(lock: ReentrantReadWriteLock = ReentrantReadWriteLock()): IReplStageState<*> = AggregatedReplStageState(replCompiler.createState(lock), replEvaluator.createState(lock), lock)
 
-    private fun setContextHistory(@Suppress("UNUSED_PARAMETER") context: ScriptContext, history: ArrayList<ReplCodeLine>) {
-        this.context.getBindings(ScriptContext.ENGINE_SCOPE).kotlinScriptHistory = history
-    }
+    private fun getCurrentState(context: ScriptContext) = context.getBindings(ScriptContext.ENGINE_SCOPE).getOrPut(KOTLIN_SCRIPT_STATE_BINDINGS_KEY, { replEvaluator.createState() }) as IReplStageState<*>
 
     open fun overrideScriptArgs(context: ScriptContext): ScriptArgsWithTypes? = null
 
     open fun compileAndEval(script: String, context: ScriptContext): Any? {
         val codeLine = nextCodeLine(context, script)
-        val history = getCurrentHistory(context)
-        val result = replScriptEvaluator.compileAndEval(codeLine, scriptArgs = overrideScriptArgs(context), verifyHistory = history)
+        val state = getCurrentState(context)
+        val result = replEvaluator.compileAndEval(state, codeLine, scriptArgs = overrideScriptArgs(context))
         val ret = when (result) {
             is ReplEvalResult.ValueResult -> result.value
             is ReplEvalResult.UnitResult -> null
@@ -73,29 +72,27 @@ abstract class KotlinJsr223JvmScriptEngineBase(protected val myFactory: ScriptEn
             is ReplEvalResult.Incomplete -> throw ScriptException("error: incomplete code")
             is ReplEvalResult.HistoryMismatch -> throw ScriptException("Repl history mismatch at line: ${result.lineNo}")
         }
-        setContextHistory(context, ArrayList(result.completedEvalHistory))
         return ret
     }
 
     open fun compile(script: String, context: ScriptContext): CompiledScript {
         val codeLine = nextCodeLine(context, script)
-        val history = getCurrentHistory(context)
+        val state = getCurrentState(context)
 
-        val result = replCompiler.compile(codeLine, history)
+        val result = replCompiler.compile(state, codeLine)
         val compiled = when (result) {
             is ReplCompileResult.Error -> throw ScriptException("Error${result.locationString()}: ${result.message}")
             is ReplCompileResult.Incomplete -> throw ScriptException("error: incomplete code")
             is ReplCompileResult.HistoryMismatch -> throw ScriptException("Repl history mismatch at line: ${result.lineNo}")
             is ReplCompileResult.CompiledClasses -> result
         }
-        // TODO: check if it is ok to keep compiled history in the same place as compiledEval one
-        setContextHistory(context, ArrayList(result.compiledHistory))
         return CompiledKotlinScript(this, codeLine, compiled)
     }
 
     open fun eval(compiledScript: CompiledKotlinScript, context: ScriptContext): Any? {
+        val state = getCurrentState(context)
         val result = try {
-            replScriptEvaluator.eval(compiledScript.compiledData, scriptArgs = overrideScriptArgs(context))
+            replEvaluator.eval(state, compiledScript.compiledData, scriptArgs = overrideScriptArgs(context))
         }
         catch (e: Exception) {
             throw ScriptException(e)
@@ -108,7 +105,6 @@ abstract class KotlinJsr223JvmScriptEngineBase(protected val myFactory: ScriptEn
             is ReplEvalResult.Incomplete -> throw ScriptException("error: incomplete code")
             is ReplEvalResult.HistoryMismatch -> throw ScriptException("Repl history mismatch at line: ${result.lineNo}")
         }
-        setContextHistory(context, ArrayList(result.completedEvalHistory))
         return ret
     }
 

compiler/cli/cli-common/src/org/jetbrains/kotlin/cli/common/repl/ReplApi.kt

@@ -20,6 +20,7 @@ import org.jetbrains.kotlin.cli.common.messages.CompilerMessageLocation
 import java.io.File
 import java.io.Serializable
 import java.util.*
+import java.util.concurrent.locks.ReentrantReadWriteLock
 import kotlin.reflect.KClass
 
 data class ReplCodeLine(val no: Int, val code: String) : Serializable {
@@ -43,9 +44,14 @@ data class CompiledClassData(val path: String, val bytes: ByteArray) : Serializa
     }
 }
 
+interface CreateReplStageStateAction {
+    fun createState(lock: ReentrantReadWriteLock = ReentrantReadWriteLock()): IReplStageState<*>
+}
+
+// --- check
 
 interface ReplCheckAction {
-    fun check(codeLine: ReplCodeLine): ReplCheckResult
+    fun check(state: IReplStageState<*>, codeLine: ReplCodeLine): ReplCheckResult
 }
 
 sealed class ReplCheckResult : Serializable {
@@ -63,40 +69,25 @@ sealed class ReplCheckResult : Serializable {
     }
 }
 
-interface ReplResettableCodeLine {
-    fun resetToLine(lineNumber: Int): List<ReplCodeLine>
-
-    fun resetToLine(line: ReplCodeLine): List<ReplCodeLine> = resetToLine(line.no)
-}
-
-interface ReplCodeLineHistory {
-    val history: List<ReplCodeLine>
-}
-
-interface ReplCombinedHistory {
-    val compiledHistory: List<ReplCodeLine>
-    val evaluatedHistory: List<ReplCodeLine>
-}
+// --- compile
 
 interface ReplCompileAction {
-    fun compile(codeLine: ReplCodeLine, verifyHistory: List<ReplCodeLine>? = null): ReplCompileResult
+    fun compile(state: IReplStageState<*>, codeLine: ReplCodeLine): ReplCompileResult
 }
 
-sealed class ReplCompileResult(val compiledHistory: List<ReplCodeLine>) : Serializable {
-    class CompiledClasses(compiledHistory: List<ReplCodeLine>,
-                          val compiledCodeLine: CompiledReplCodeLine,
-                          val generatedClassname: String,
+sealed class ReplCompileResult : Serializable {
+    class CompiledClasses(val lineId: LineId,
+                          val mainClassName: String,
                           val classes: List<CompiledClassData>,
                           val hasResult: Boolean,
-                          val classpathAddendum: List<File>) : ReplCompileResult(compiledHistory)
+                          val classpathAddendum: List<File>) : ReplCompileResult()
 
-    class Incomplete(compiledHistory: List<ReplCodeLine>) : ReplCompileResult(compiledHistory)
+    class Incomplete : ReplCompileResult()
 
-    class HistoryMismatch(compiledHistory: List<ReplCodeLine>, val lineNo: Int) : ReplCompileResult(compiledHistory)
+    class HistoryMismatch(val lineNo: Int) : ReplCompileResult()
 
-    class Error(compiledHistory: List<ReplCodeLine>,
-                val message: String,
-                val location: CompilerMessageLocation = CompilerMessageLocation.NO_LOCATION) : ReplCompileResult(compiledHistory) {
+    class Error(val message: String,
+                val location: CompilerMessageLocation = CompilerMessageLocation.NO_LOCATION) : ReplCompileResult() {
         override fun toString(): String = "Error(message = \"$message\""
     }
 
@@ -105,43 +96,35 @@ sealed class ReplCompileResult(val compiledHistory: List<ReplCodeLine>) : Serial
     }
 }
 
-interface ReplCompiler : ReplResettableCodeLine, ReplCodeLineHistory, ReplCompileAction, ReplCheckAction
+interface ReplCompiler : ReplCompileAction, ReplCheckAction, CreateReplStageStateAction
 
-typealias EvalHistoryType = Pair<CompiledReplCodeLine, EvalClassWithInstanceAndLoader>
-
-interface ReplEvaluatorExposedInternalHistory {
-    val lastEvaluatedScripts: List<EvalHistoryType>
-}
-
-interface ReplClasspath {
-    val currentClasspath: List<File>
-}
+// --- eval
 
 data class EvalClassWithInstanceAndLoader(val klass: KClass<*>, val instance: Any?, val classLoader: ClassLoader, val invokeWrapper: InvokeWrapper?)
 
 interface ReplEvalAction {
-    fun eval(compileResult: ReplCompileResult.CompiledClasses,
+    fun eval(state: IReplStageState<*>,
+             compileResult: ReplCompileResult.CompiledClasses,
              scriptArgs: ScriptArgsWithTypes? = null,
              invokeWrapper: InvokeWrapper? = null): ReplEvalResult
 }
 
-sealed class ReplEvalResult(val completedEvalHistory: List<ReplCodeLine>) : Serializable {
-    class ValueResult(completedEvalHistory: List<ReplCodeLine>, val value: Any?) : ReplEvalResult(completedEvalHistory) {
+sealed class ReplEvalResult : Serializable {
+    class ValueResult(val value: Any?) : ReplEvalResult() {
         override fun toString(): String = "Result: $value"
     }
 
-    class UnitResult(completedEvalHistory: List<ReplCodeLine>) : ReplEvalResult(completedEvalHistory)
+    class UnitResult : ReplEvalResult()
 
-    class Incomplete(completedEvalHistory: List<ReplCodeLine>) : ReplEvalResult(completedEvalHistory)
+    class Incomplete : ReplEvalResult()
 
-    class HistoryMismatch(completedEvalHistory: List<ReplCodeLine>, val lineNo: Int) : ReplEvalResult(completedEvalHistory)
+    class HistoryMismatch(val lineNo: Int) : ReplEvalResult()
 
-    sealed class Error(completedEvalHistory: List<ReplCodeLine>, val message: String) : ReplEvalResult(completedEvalHistory) {
-        class Runtime(completedEvalHistory: List<ReplCodeLine>, message: String, val cause: Exception? = null) : Error(completedEvalHistory, message)
+    sealed class Error(val message: String) : ReplEvalResult() {
+        class Runtime(message: String, val cause: Exception? = null) : Error(message)
 
-        class CompileTime(completedEvalHistory: List<ReplCodeLine>,
-                          message: String,
-                          val location: CompilerMessageLocation = CompilerMessageLocation.NO_LOCATION) : Error(completedEvalHistory, message)
+        class CompileTime(message: String,
+                          val location: CompilerMessageLocation = CompilerMessageLocation.NO_LOCATION) : Error(message)
 
         override fun toString(): String = "${this::class.simpleName}Error(message = \"$message\""
     }
@@ -151,43 +134,44 @@ sealed class ReplEvalResult(val completedEvalHistory: List<ReplCodeLine>) : Seri
     }
 }
 
-interface ReplEvaluator : ReplResettableCodeLine, ReplCodeLineHistory, ReplEvaluatorExposedInternalHistory, ReplEvalAction, ReplClasspath
+interface ReplEvaluator : ReplEvalAction, CreateReplStageStateAction
+
+// --- compileAdnEval
 
 interface ReplAtomicEvalAction {
-    fun compileAndEval(codeLine: ReplCodeLine,
+    fun compileAndEval(state: IReplStageState<*>,
+                       codeLine: ReplCodeLine,
                        scriptArgs: ScriptArgsWithTypes? = null,
-                       verifyHistory: List<ReplCodeLine>? = null,
                        invokeWrapper: InvokeWrapper? = null): ReplEvalResult
 }
 
-interface ReplAtomicEvaluator : ReplResettableCodeLine, ReplCombinedHistory, ReplEvaluatorExposedInternalHistory, ReplAtomicEvalAction, ReplCheckAction, ReplClasspath
+interface ReplAtomicEvaluator : ReplAtomicEvalAction, ReplCheckAction
 
 interface ReplDelayedEvalAction {
-    fun compileToEvaluable(codeLine: ReplCodeLine, defaultScriptArgs: ScriptArgsWithTypes? = null, verifyHistory: List<ReplCodeLine>?): Pair<ReplCompileResult, Evaluable?>
+    fun compileToEvaluable(state: IReplStageState<*>,
+                           codeLine: ReplCodeLine,
+                           defaultScriptArgs: ScriptArgsWithTypes? = null): Pair<ReplCompileResult, Evaluable?>
 }
 
+// other
+
 interface Evaluable {
     val compiledCode: ReplCompileResult.CompiledClasses
     fun eval(scriptArgs: ScriptArgsWithTypes? = null, invokeWrapper: InvokeWrapper? = null): ReplEvalResult
 }
 
-interface ReplFullEvaluator : ReplEvaluator, ReplAtomicEvaluator, ReplDelayedEvalAction, ReplCombinedHistory
+interface ReplFullEvaluator : ReplEvaluator, ReplAtomicEvaluator, ReplDelayedEvalAction
 
 /**
  * Keep args and arg types together, so as a whole they are present or absent
  */
 class ScriptArgsWithTypes(val scriptArgs: Array<out Any?>, val scriptArgsTypes: Array<out KClass<out Any>>) : Serializable {
+    init { assert(scriptArgs.size == scriptArgsTypes.size) }
     companion object {
         private val serialVersionUID: Long = 8529357500L
     }
 }
 
-interface ScriptTemplateEmptyArgsProvider {
-    val defaultEmptyArgs: ScriptArgsWithTypes?
-}
-
-class SimpleScriptTemplateEmptyArgsProvider(override val defaultEmptyArgs: ScriptArgsWithTypes? = null) : ScriptTemplateEmptyArgsProvider
-
 enum class ReplRepeatingMode {
     NONE,
     REPEAT_ONLY_MOST_RECENT,

compiler/cli/cli-common/src/org/jetbrains/kotlin/cli/common/repl/ReplState.kt

@@ -0,0 +1,83 @@
+/*
+ * Copyright 2010-2017 JetBrains s.r.o.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.jetbrains.kotlin.cli.common.repl
+
+import java.util.concurrent.locks.ReentrantReadWriteLock
+import kotlin.concurrent.read
+import kotlin.concurrent.write
+
+
+interface ILineId : Comparable<ILineId> {
+    val no: Int
+}
+
+data class ReplHistoryRecord<out T> (val id: ILineId, val item: T)
+
+interface IReplStageHistory<T> : List<ReplHistoryRecord<T>> {
+
+    fun backwardIterator(): Iterator<ReplHistoryRecord<T>> = lock.read { asReversed().iterator() } // TODO: check perf
+
+    fun peek(): ReplHistoryRecord<T>? = lock.read { lastOrNull() }
+
+    fun push(id: ILineId, item: T)
+
+    fun pop(): ReplHistoryRecord<T>?
+
+    fun verifiedPop(id: ILineId): ReplHistoryRecord<T>? = lock.write {
+        if (lastOrNull()?.id == id) pop()
+        else null
+    }
+
+    fun resetTo(id: ILineId): Iterable<ILineId>
+
+    fun <OtherT> firstMismatch(other: IReplStageHistory<OtherT>): Pair<ReplHistoryRecord<T>?, ReplHistoryRecord<OtherT>?>? =
+            lock.read { other.lock.read {
+                iterator().asSequence().zip(other.asSequence()).firstOrNull { it.first.id != it.second.id }?.let { it.first to it.second }
+            } }
+
+    fun<OtherT> firstMismatchFiltered(other: IReplStageHistory<OtherT>, predicate: (ReplHistoryRecord<T>) -> Boolean): Pair<ReplHistoryRecord<T>?, ReplHistoryRecord<OtherT>?>? =
+            lock.read { other.lock.read {
+                iterator().asSequence().filter(predicate).zip(other.asSequence()).firstOrNull { it.first.id != it.second.id }?.let { it.first to it.second }
+            } }
+
+    fun<OtherT> firstMismatchWhile(other: IReplStageHistory<OtherT>, predicate: (ReplHistoryRecord<T>) -> Boolean): Pair<ReplHistoryRecord<T>?, ReplHistoryRecord<OtherT>?>? =
+            lock.read { other.lock.read {
+                iterator().asSequence().takeWhile(predicate).zip(other.asSequence()).firstOrNull { it.first.id != it.second.id }?.let { it.first to it.second }
+            } }
+
+    fun <OtherT> matches(other: IReplStageHistory<OtherT>): Boolean =
+            lock.read { other.lock.read {
+                size == other.size && firstMismatch(other) == null
+            } }
+
+    fun <OtherT> isProperPrefix(other: IReplStageHistory<OtherT>): Boolean =
+            lock.read { other.lock.read {
+                size == other.size - 1 && firstMismatch(other) == null
+            } }
+
+    val lock: ReentrantReadWriteLock
+}
+
+interface IReplStageState<T> {
+    val history: IReplStageHistory<T>
+
+    val lock: ReentrantReadWriteLock
+
+    fun <StateT : IReplStageState<*>> asState(): StateT = (this as? StateT) ?: throw IllegalArgumentException("$this is not an expected instance of IReplStageState")
+}
+
+