Add detekt - static code analysis tool for Kotlin.

Signed-off-by: Yahor Berdnikau <egorr.berd@gmail.com>

build.gradle

@@ -4,18 +4,27 @@ buildscript {
 
     repositories {
         jcenter()
-        maven {
+        maven { url "https://plugins.gradle.org/m2/" }
-            url "https://plugins.gradle.org/m2/"
-        }
     }
     dependencies {
         classpath gradlePlugins.androidTools
         classpath gradlePlugins.kotlin
         classpath gradlePlugins.ktlintGradle
+        classpath(gradlePlugins.detekt) {
+            exclude module: 'kotlin-compiler-embeddable'
+            exclude module: 'kotlin-stdlib'
+        }
     }
 }
 
 allprojects {
+    // Buildscript here is required by detekt
+    buildscript {
+        repositories {
+            jcenter()
+        }
+    }
+
     repositories {
         jcenter()
     }

dependencies.gradle

@@ -7,6 +7,7 @@ ext.versions = [
         androidTools         : "2.3.3",
         ktlint               : "0.9.0",
         ktlintGradle         : "2.1.0",
+        detekt               : "1.0.0.M13.2",
 
         androidSupport       : "22.2.1",
 
@@ -26,6 +27,7 @@ ext.gradlePlugins = [
         androidTools : "com.android.tools.build:gradle:$versions.androidTools",
         kotlin       : "org.jetbrains.kotlin:kotlin-gradle-plugin:$versions.kotlin",
         ktlintGradle : "gradle.plugin.org.jlleitschuh.gradle:ktlint-gradle:$versions.ktlintGradle",
+        detekt       : "io.gitlab.arturbosch.detekt:detekt-gradle-plugin:$versions.detekt",
 ]
 
 ext.androidSupport = [

detekt-config.yml

@@ -0,0 +1,111 @@
+autoCorrect: true
+failFast: false
+
+build:
+  warningThreshold: 0
+  failThreshold: 0
+  weights:
+    complexity: 2
+    formatting: 1
+    LongParameterList: 1
+    comments: 1
+
+potential-bugs:
+  active: true
+  DuplicateCaseInWhenExpression:
+    active: true
+  EqualsWithHashCodeExist:
+    active: true
+  ExplicitGarbageCollectionCall:
+    active: true
+  LateinitUsage:
+    active: false
+  UnsafeCallOnNullableType:
+    active: false
+  UnsafeCast:
+    active: false
+
+performance:
+  active: true
+  ForEachOnRange:
+    active: true
+  SpreadOperator:
+    active: true
+
+exceptions:
+  active: true
+
+empty-blocks:
+  active: true
+
+complexity:
+  active: true
+  LongMethod:
+    threshold: 20
+  LongParameterList:
+    threshold: 5
+  LargeClass:
+    threshold: 150
+  ComplexMethod:
+    threshold: 10
+  TooManyFunctions:
+    threshold: 10
+  ComplexCondition:
+    threshold: 3
+  LabeledExpression:
+    active: false
+
+code-smell:
+  active: true
+  FeatureEnvy:
+    threshold: 0.5
+    weight: 0.45
+    base: 0.5
+
+formatting:
+  active: false
+
+style:
+  active: true
+  NewLineAtEndOfFile:
+    active: true
+  ForbiddenComment:
+    active: true
+    values: 'TODO:,FIXME:,STOPSHIP:'
+  WildcardImport:
+    active: true
+  MaxLineLength:
+    active: true
+    maxLineLength: 120
+    excludePackageStatements: false
+    excludeImportStatements: false
+  NamingConventionViolation:
+    active: true
+    variablePattern: '^(_)?[a-z$][a-zA-Z$0-9]*$'
+    constantPattern: '^([A-Z_]*|serialVersionUID)$'
+    methodPattern: '^[a-z\s`$][a-zA-Z\s$0-9`]*$'
+    classPattern: '[A-Z$][a-zA-Z$]*'
+    enumEntryPattern: '^[A-Z$][a-zA-Z_$0-9]*$'
+
+comments:
+  active: true
+  CommentOverPrivateMethod:
+    active: true
+  CommentOverPrivateProperty:
+    active: true
+  UndocumentedPublicClass:
+    active: false
+    searchInNestedClass: true
+    searchInInnerClass: true
+    searchInInnerInterface: true
+  UndocumentedPublicFunction:
+    active: false
+
+# *experimental feature*
+# Migration rules can be defined in the same config file or a new one
+migration:
+  active: false
+  imports:
+    # your.package.Class: new.package.or.Class
+    # for example:
+    # io.gitlab.arturbosch.detekt.api.Rule: io.gitlab.arturbosch.detekt.rule.Rule

gradle_scripts/code_quality.gradle

@@ -1,6 +1,7 @@
 // Applies code quality plugins when -Pqc is passed to the gradle
 def isCodeQualityEnabled = project.hasProperty('qc')
 
+// KtLint
 if (isCodeQualityEnabled) {
     apply plugin: "org.jlleitschuh.gradle.ktlint"
 
@@ -8,3 +9,20 @@ if (isCodeQualityEnabled) {
         version = versions.ktlint
     }
 }
+
+// Detekt
+if (isCodeQualityEnabled) {
+    if (!project.rootProject.plugins.hasPlugin("io.gitlab.arturbosch.detekt")) {
+        Project rootProject = project.rootProject
+        rootProject.apply {
+            apply plugin: "io.gitlab.arturbosch.detekt"
+
+            detekt {
+                version = versions.detekt
+                profile("main") {
+                    config = "${rootProject.projectDir}/detekt-config.yml"
+                }
+            }
+        }
+    }
+}