feat: add rust extractor (#285)

* feat - add rust extractor

* address comments

Author: asurkov

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

@@ -0,0 +1,51 @@
+// Copyright 2018 Sourcerer Inc. All Rights Reserved.
+// Author: Alexander Surkov ([email protected])
+
+package app.extractors
+
+import app.model.CommitStats
+import app.model.DiffFile
+
+class RustExtractor : ExtractorInterface {
+    companion object {
+        const val LANGUAGE_NAME = Lang.Rust
+        val evaluator by lazy {
+            ExtractorInterface.getLibraryClassifier(LANGUAGE_NAME)
+        }
+        val importRegex = Regex("""^extern crate \w+;$""")
+        val commentRegex = Regex("(//.+$)|(/[*].*?[*]/)")
+        val extractImportRegex = Regex("""^extern crate (\w+);$""")
+    }
+
+    override fun extract(files: List<DiffFile>): List<CommitStats> {
+        files.map { file -> file.language = LANGUAGE_NAME }
+        return super.extract(files)
+    }
+
+    override fun extractImports(fileContent: List<String>): List<String> {
+        val imports = mutableSetOf<String>()
+
+        fileContent.forEach {
+            val res = extractImportRegex.find(it)
+            if (res != null) {
+                val lineLib = res.groupValues[1]
+                imports.add(lineLib)
+            }
+        }
+
+        return imports.toList()
+    }
+
+    override fun tokenize(line: String): List<String> {
+        var newLine = importRegex.replace(line, "")
+        newLine = commentRegex.replace(newLine, "")
+        return super.tokenize(newLine)
+    }
+
+    override fun getLineLibraries(line: String,
+                                  fileLibraries: List<String>): List<String> {
+
+        return super.getLineLibraries(line, fileLibraries, evaluator,
+            LANGUAGE_NAME)
+    }
+}

src/test/kotlin/test/tests/extractors/ExtractorTest.kt

@@ -278,4 +278,22 @@ class ExtractorTest : Spek({
         }
     }
 
+    // Rust
+    given("Rust") {
+        it("Rust imports") {
+            var lines = listOf(
+                "extern crate foo;",
+                "extern crate boo;"
+            )
+            var actualLineImports = RustExtractor().extractImports(lines)
+            assertEquals(actualLineImports, listOf("foo", "boo"))
+
+            lines = listOf(
+                "// extern crate foo;",
+                "/* extern crate boo; */"
+            )
+            actualLineImports = RustExtractor().extractImports(lines)
+            assertTrue(actualLineImports.isEmpty())
+        }
+    }
 })