feat: improve existing languages support (#283)

* improve existing languages support

* address comments

Author: asurkov

src/main/kotlin/app/extractors/CExtractor.kt

@@ -9,7 +9,7 @@ import app.model.DiffFile
 
 class CExtractor : ExtractorInterface {
     companion object {
-        const val LANGUAGE_NAME = "c"
+        const val LANGUAGE_NAME = Lang.C
         val evaluator by lazy {
             ExtractorInterface.getLibraryClassifier(LANGUAGE_NAME)
         }

src/main/kotlin/app/extractors/CSharpExtractor.kt

@@ -9,7 +9,7 @@ import app.model.DiffFile
 
 class CSharpExtractor : ExtractorInterface {
     companion object {
-        val LANGUAGE_NAME = "csharp"
+        const val LANGUAGE_NAME = Lang.CSharp
         val LIBRARIES = ExtractorInterface.getLibraries("cs")
         val evaluator by lazy {
             ExtractorInterface.getLibraryClassifier(LANGUAGE_NAME)

src/main/kotlin/app/extractors/CppExtractor.kt

@@ -9,7 +9,7 @@ import app.model.DiffFile
 
 class CppExtractor : ExtractorInterface {
     companion object {
-        val LANGUAGE_NAME = "cpp"
+        const val LANGUAGE_NAME = Lang.CPlusPlus
         val evaluator by lazy {
             ExtractorInterface.getLibraryClassifier(LANGUAGE_NAME)
         }

src/main/kotlin/app/extractors/CssExtractor.kt

@@ -8,7 +8,7 @@ import app.model.DiffFile
 
 class CssExtractor : ExtractorInterface {
     companion object {
-        val LANGUAGE_NAME = "css"
+        const val LANGUAGE_NAME = Lang.CSS
         val FILE_EXTS = listOf("css", "scss", "less", "sass")
     }
 

src/main/kotlin/app/extractors/FSharpExtractor.kt

@@ -9,7 +9,7 @@ import app.model.DiffFile
 
 class FSharpExtractor : ExtractorInterface {
     companion object {
-        val LANGUAGE_NAME = "fsharp"
+        const val LANGUAGE_NAME = Lang.FSharp
         // The behaviour of csharp library classifier is the same as for csharp.
         val LIBRARIES = ExtractorInterface.getLibraries("cs")
         val evaluator by lazy {

src/main/kotlin/app/extractors/GoExtractor.kt

@@ -9,7 +9,7 @@ import app.model.DiffFile
 
 class GoExtractor : ExtractorInterface {
     companion object {
-        val LANGUAGE_NAME = "go"
+        const val LANGUAGE_NAME = Lang.Go
         val evaluator by lazy {
             ExtractorInterface.getLibraryClassifier(LANGUAGE_NAME)
         }