[#1347] Clean up the code

diktat-rules/src/main/kotlin/org/cqfn/diktat/ruleset/rules/chapter3/files/IndentationError.kt

@@ -0,0 +1,7 @@
+package org.cqfn.diktat.ruleset.rules.chapter3.files
+
+/**
+ * @property expected expected indentation as a number of spaces
+ * @property actual actual indentation as a number of spaces
+ */
+internal data class IndentationError(val expected: Int, val actual: Int)

diktat-rules/src/main/kotlin/org/cqfn/diktat/ruleset/utils/StringUtils.kt

@@ -6,6 +6,12 @@ package org.cqfn.diktat.ruleset.utils
 
 import org.jetbrains.kotlin.lexer.KtTokens
 
+internal const val NEWLINE = '\n'
+
+internal const val SPACE = ' '
+
+internal const val TAB = '\t'
+
 @Suppress("VARIABLE_NAME_INCORRECT_FORMAT")
 val JAVA = arrayOf("abstract", "assert", "boolean",
     "break", "byte", "case", "catch", "char", "class", "const",
@@ -97,3 +103,15 @@ fun String.removePrefix(): String {
     }
     return this
 }
+
+/**
+ * @return the indentation of the last line of this string.
+ */
+internal fun String.lastIndent() = substringAfterLast(NEWLINE).count(::isSpaceCharacter)
+
+/**
+ * @param ch the character to examine.
+ * @return `true` if [ch] is a [SPACE], `false` otherwise.
+ */
+internal fun isSpaceCharacter(ch: Char): Boolean =
+    ch == SPACE

diktat-rules/src/main/kotlin/org/cqfn/diktat/ruleset/utils/indentation/Checkers.kt

@@ -5,8 +5,8 @@
 package org.cqfn.diktat.ruleset.utils.indentation
 
 import org.cqfn.diktat.ruleset.rules.chapter3.files.IndentationError
-import org.cqfn.diktat.ruleset.rules.chapter3.files.lastIndent
 import org.cqfn.diktat.ruleset.utils.hasParent
+import org.cqfn.diktat.ruleset.utils.lastIndent
 
 import com.pinterest.ktlint.core.ast.ElementType.ARROW
 import com.pinterest.ktlint.core.ast.ElementType.AS_KEYWORD

diktat-rules/src/main/kotlin/org/cqfn/diktat/ruleset/utils/indentation/IndentationConfig.kt

@@ -37,5 +37,5 @@ internal class IndentationConfig(config: Map<String, String>) : RuleConfiguratio
     /**
      * The indentation size for each file
      */
-    val indentationSize = config["indentationSize"]?.toInt() ?: IndentationRule.INDENT_SIZE
+    val indentationSize = config["indentationSize"]?.toInt() ?: IndentationRule.DEFAULT_INDENT_SIZE
 }

diktat-rules/src/test/kotlin/org/cqfn/diktat/ruleset/chapter3/spaces/IndentationRuleFixTest.kt

@@ -241,7 +241,7 @@ class IndentationRuleFixTest : FixTestBase("test/paragraph3/indentation",
 
                 if (!lintResult.isSuccessful) {
                     softly.assertThat(lintResult.actualContent)
-                        .describedAs("lint result for \"$actual\"")
+                        .describedAs("lint result for ${actual.describe()}")
                         .isEqualTo(lintResult.expectedContent)
                 }
             }

diktat-rules/src/test/kotlin/org/cqfn/diktat/ruleset/chapter3/spaces/IndentationRuleTestMixin.kt

@@ -284,6 +284,26 @@ internal interface IndentationRuleTestMixin {
             }
         }
 
+    /**
+     * @return a brief description of this code fragment.
+     */
+    fun String.describe(): String {
+        val lines = splitToSequence('\n')
+
+        var first: String? = null
+
+        val count = lines.onEachIndexed { index, line ->
+            if (index == 0) {
+                first = line
+            }
+        }.count()
+
+        return when (count) {
+            1 -> "\"$this\""
+            else -> "\"$first\u2026\" ($count line(s))"
+        }
+    }
+
     /**
      * @return `true` if known-to-fail unit tests can be muted on the CI server.
      */

diktat-rules/src/test/kotlin/org/cqfn/diktat/ruleset/chapter3/spaces/IndentationRuleWarnTest.kt

@@ -757,7 +757,7 @@ class IndentationRuleWarnTest : LintTestBase(::IndentationRule), IndentationRule
         assertSoftly { softly ->
             expressionBodyFunctionsSingleIndent.forEach { code ->
                 softly.assertThat(lintResult(code, customConfig.asRulesConfigList()))
-                    .describedAs("lint result for \"$code\"")
+                    .describedAs("lint result for ${code.describe()}")
                     .isNotEmpty
                     .hasSizeBetween(1, 3).allSatisfy(Consumer { lintError ->
                         assertThat(lintError.ruleId).describedAs("ruleId").isEqualTo(ruleId)
@@ -782,7 +782,7 @@ class IndentationRuleWarnTest : LintTestBase(::IndentationRule), IndentationRule
         assertSoftly { softly ->
             expressionBodyFunctionsContinuationIndent.forEach { code ->
                 softly.assertThat(lintResult(code, customConfig.asRulesConfigList()))
-                    .describedAs("lint result for \"$code\"")
+                    .describedAs("lint result for ${code.describe()}")
                     .isNotEmpty
                     .hasSizeBetween(1, 3).allSatisfy(Consumer { lintError ->
                         assertThat(lintError.ruleId).describedAs("ruleId").isEqualTo(ruleId)

diktat-rules/src/test/kotlin/org/cqfn/diktat/util/DiktatRuleSetProvider4Test.kt

@@ -13,6 +13,7 @@ import org.cqfn.diktat.ruleset.rules.DiktatRuleSetProvider
 import com.pinterest.ktlint.core.Rule
 import com.pinterest.ktlint.core.RuleSet
 import com.pinterest.ktlint.core.RuleSetProvider
+import org.assertj.core.api.Assertions.assertThat
 import org.jetbrains.kotlin.com.intellij.lang.ASTNode
 import org.junit.jupiter.api.Assertions
 import org.junit.jupiter.api.Test
@@ -43,6 +44,7 @@ class DiktatRuleSetProviderTest {
             .map { it.nameWithoutExtension }
             .filterNot { it in ignoreFile }
         val rulesName = DiktatRuleSetProvider().get()
+            .asSequence()
             .onEachIndexed { index, rule ->
                 if (index != 0) {
                     Assertions.assertTrue(
@@ -53,8 +55,9 @@ class DiktatRuleSetProviderTest {
             }
             .map { (it as? DiktatRuleSetProvider.OrderedRule)?.rule ?: it }
             .map { it::class.simpleName!! }
-            .filter { it != "DummyWarning" }
-        Assertions.assertEquals(filesName.sorted().toList(), rulesName.sorted())
+            .filterNot { it == "DummyWarning" }
+            .toList()
+        assertThat(rulesName.sorted()).containsExactlyElementsOf(filesName.sorted().toList())
     }
 
     @Test
@@ -122,6 +125,9 @@ class DiktatRuleSetProviderTest {
     }
 
     companion object {
-        private val ignoreFile = listOf("DiktatRuleSetProvider", "DiktatRule")
+        private val ignoreFile = listOf(
+            "DiktatRuleSetProvider",
+            "DiktatRule",
+            "IndentationError")
     }
 }