max()/minI() supported

idea/src/org/jetbrains/kotlin/idea/intentions/loopToCallChain/matchAndConvert.kt

@@ -45,6 +45,7 @@ object MatcherRegistrar {
             FindTransformationMatcher,
             AddToCollectionTransformation.Matcher,
             CountTransformation.Matcher,
+            MaxOrMinTransformation.Matcher,
             IntroduceIndexMatcher,
             FilterTransformation.Matcher,
             MapTransformation.Matcher,

idea/src/org/jetbrains/kotlin/idea/intentions/loopToCallChain/result/MaxOrMinTransformation.kt

@@ -0,0 +1,86 @@
+/*
+ * Copyright 2010-2016 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.idea.intentions.loopToCallChain.result
+
+import org.jetbrains.kotlin.idea.intentions.loopToCallChain.*
+import org.jetbrains.kotlin.lexer.KtTokens
+import org.jetbrains.kotlin.psi.*
+import org.jetbrains.kotlin.psi.psiUtil.blockExpressionsOrSingle
+
+class MaxOrMinTransformation(
+        loop: KtForExpression,
+        private val inputVariable: KtCallableDeclaration,
+        initialization: VariableInitialization,
+        private val isMax: Boolean
+) : AssignToVariableResultTransformation(loop, initialization) {
+
+    override val presentation: String
+        get() = if (isMax) "max()" else "min()"
+
+    override fun generateCode(chainedCallGenerator: ChainedCallGenerator): KtExpression {
+        val call = chainedCallGenerator.generate(presentation)
+        return KtPsiFactory(call).createExpressionByPattern("$0\n ?: $1", call, initialization.initializer)
+    }
+
+    /**
+     * Matches:
+     *     val variable = <initial>
+     *     for (...) {
+     *         ...
+     *         if (variable > <input variable>) { // or '<' or operands swapped
+     *             variable = <input variable>
+     *         }
+     *     }
+     */
+    object Matcher : TransformationMatcher {
+        override val indexVariableAllowed: Boolean
+            get() = false
+
+        override fun match(state: MatchingState): TransformationMatch.Result? {
+            val ifExpression = state.statements.singleOrNull() as? KtIfExpression ?: return null
+            if (ifExpression.`else` != null) return null
+
+            val condition = ifExpression.condition as? KtBinaryExpression ?: return null
+            val comparison = condition.operationToken
+            if (comparison !in setOf(KtTokens.GT, KtTokens.LT)) return null
+            val left = condition.left as? KtNameReferenceExpression ?: return null
+            val right = condition.right as? KtNameReferenceExpression ?: return null
+            val otherHand = if (left.isVariableReference(state.inputVariable)) {
+                right
+            }
+            else if (right.isVariableReference(state.inputVariable)) {
+                left
+            }
+            else {
+                return null
+            }
+
+            val variableInitialization = (otherHand.isVariableInitializedBeforeLoop(state.outerLoop, checkNoOtherUsagesInLoop = false)
+                                          ?: return null)
+
+            val then = ifExpression.then ?: return null
+            val statement = then.blockExpressionsOrSingle().singleOrNull() as? KtBinaryExpression ?: return null
+            if (statement.operationToken != KtTokens.EQ) return null
+            if (!statement.left.isVariableReference(variableInitialization.variable)) return null
+            if (!statement.right.isVariableReference(state.inputVariable)) return null
+
+            val isMax = (comparison == KtTokens.GT) xor (otherHand == left)
+            val transformation = MaxOrMinTransformation(state.outerLoop, state.inputVariable, variableInitialization, isMax)
+            return TransformationMatch.Result(transformation)
+        }
+    }
+}