use registration system and test the dispatching of this system

Sources/Parsers/ColorsFileParser.swift

@@ -26,42 +26,41 @@ public enum ColorsParserError: Error, CustomStringConvertible {
 }
 
 protocol ColorsFileTypeParser: class {
+  static var extensions: [String] { get }
+
+  init()
   func parseFile(at path: Path) throws -> [String: UInt32]
 }
 
 public final class ColorsFileParser {
-  enum Extension: String {
-    case clr
-    case json
-    case txt
-    case xml
-  }
-
+  private var parsers = [String: ColorsFileTypeParser.Type]()
   var colors = [String: UInt32]()
 
-  public init() {}
+  public init() {
+    register(parser: ColorsCLRFileParser.self)
+    register(parser: ColorsJSONFileParser.self)
+    register(parser: ColorsTextFileParser.self)
+    register(parser: ColorsXMLFileParser.self)
+  }
 
   public func parseFile(at path: Path) throws {
-    guard let ext = Extension(rawValue: path.extension ?? "") else {
+    guard let parserType = parsers[path.extension?.lowercased() ?? ""] else {
       throw ColorsParserError.unsupportedFileType
     }
 
-    let colors: [String: UInt32]
-    switch ext {
-    case .clr:
-      colors = try ColorsCLRFileParser().parseFile(at: path)
-    case .json:
-      colors = try ColorsJSONFileParser().parseFile(at: path)
-    case .txt:
-      colors = try ColorsTextFileParser().parseFile(at: path)
-    case .xml:
-      colors = try ColorsXMLFileParser().parseFile(at: path)
-    }
+    let parser = parserType.init()
+    let colors = try parser.parseFile(at: path)
 
     for (name, value) in colors {
       self.colors[name] = value
     }
   }
+
+  func register(parser: ColorsFileTypeParser.Type) {
+    for ext in parser.extensions {
+      parsers[ext] = parser
+    }
+  }
 }
 
 // MARK: - Private Helpers

Sources/Parsers/ColorsFileParsers/ColorsCLRFileParser.swift

@@ -8,6 +8,8 @@ import Foundation
 import PathKit
 
 final class ColorsCLRFileParser: ColorsFileTypeParser {
+  static var extensions = ["clr"]
+
   private enum Keys {
     static let userColors = "UserColors"
   }

Sources/Parsers/ColorsFileParsers/ColorsJSONFileParser.swift

@@ -8,6 +8,8 @@ import Foundation
 import PathKit
 
 final class ColorsJSONFileParser: ColorsFileTypeParser {
+  static var extensions = ["json"]
+
   func parseFile(at path: Path) throws -> [String: UInt32] {
     do {
       let json = try JSONSerialization.jsonObject(with: try path.read(), options: [])

Sources/Parsers/ColorsFileParsers/ColorsTXTFileParser.swift

@@ -8,6 +8,8 @@ import Foundation
 import PathKit
 
 final class ColorsTextFileParser: ColorsFileTypeParser {
+  static var extensions = ["txt"]
+
   private var colors = [String: UInt32]()
 
   private func addColor(named name: String, value: String) throws {

Sources/Parsers/ColorsFileParsers/ColorsXMLFileParser.swift

@@ -9,6 +9,8 @@ import Kanna
 import PathKit
 
 final class ColorsXMLFileParser: ColorsFileTypeParser {
+  static var extensions = ["xml"]
+
   private enum XML {
     static let colorXPath = "/resources/color"
     static let nameAttribute = "name"

Tests/SwiftGenKitTests/ColorsTests.swift

@@ -4,9 +4,24 @@
 // MIT Licence
 //
 
+import PathKit
 import XCTest
 @testable import SwiftGenKit
 
+final class TestFileParser1: ColorsFileTypeParser {
+  static var extensions = ["test1"]
+  func parseFile(at path: Path) throws -> [String: UInt32] {
+    return ["test1": 1]
+  }
+}
+
+final class TestFileParser2: ColorsFileTypeParser {
+  static var extensions = ["test2"]
+  func parseFile(at path: Path) throws -> [String: UInt32] {
+    return ["test2": 1]
+  }
+}
+
 class ColorParserTests: XCTestCase {
   func testEmpty() {
     let parser = ColorsFileParser()
@@ -15,6 +30,33 @@ class ColorParserTests: XCTestCase {
     XCTDiffContexts(result, expected: "empty.plist", sub: .colors)
   }
 
+  // MARK: - Dispatch
+
+  func testDispatchKnowExtension() throws {
+    let parser = ColorsFileParser()
+    parser.register(parser: TestFileParser1.self)
+    parser.register(parser: TestFileParser2.self)
+
+    try parser.parseFile(at: "someFile.test1")
+    XCTAssertEqual(parser.colors["test1"], 1)
+    XCTAssertNil(parser.colors["test2"])
+  }
+
+  func testDispatchUnknownExtension() {
+    let parser = ColorsFileParser()
+    parser.register(parser: TestFileParser1.self)
+    parser.register(parser: TestFileParser2.self)
+
+    do {
+      try parser.parseFile(at: "someFile.unknown")
+      XCTFail("Code did succeed while it was expected to fail for unknown extension")
+    } catch ColorsParserError.unsupportedFileType {
+      // That's the expected exception we want to happen
+    } catch let error {
+      XCTFail("Unexpected error occured while parsing: \(error)")
+    }
+  }
+
   // MARK: - String parsing
 
   func testStringNoPrefix() throws {