Add observer (#8)

Author: juandahurt

Sources/Pepe/Log.swift

@@ -7,12 +7,12 @@
 
 import Foundation
 
-struct Log {
+public struct Log {
     /// Message to be logged.
-    var message: String
+    public var message: String
 
     /// How importante the log is.
-    let level: LogLevel
+    public let level: LogLevel
 
     /// The time when the message is logged.
     let date: Date

Sources/Pepe/LogModifier.swift

@@ -38,7 +38,7 @@ public class LogModifier: Equatable {
     }
 }
 
-// MARK: - Hi modifier
+// MARK: - Default modifier
 public class PepeModifier: LogModifier {
     override func modify(_ log: inout Log) {
         log.message = "🐸: \(log.message)"

Sources/Pepe/PepeLogger.swift

@@ -21,6 +21,10 @@ public struct PepeLogger {
     /// How the log operation will be executed.
     public var executionType: ExecutionType
 
+    /// It allows you to observe the logger. Note that the `executionType` is attatched not only to the
+    /// logging itself but also to this observer.
+    public var observer: LoggerObserver?
+    
     /// Internal property to allow syncronous execution.
     private let _lock = NSRecursiveLock()
 
@@ -55,6 +59,15 @@ public struct PepeLogger {
         modifiers.reversed().forEach {
             $0.modify(&log)
         }
+        observer?.willLog(log: log)
         writer.write(message: log.message)
     }
 }
+
+
+/// This protocol allows you to observe the logger.
+public protocol LoggerObserver {
+    /// It notifies the observer that a message is about to be logged.
+    /// - Parameter log: Object that contains the log itself.
+    func willLog(log: Log)
+}

Tests/PepeTests/PepeLoggerTests.swift

@@ -32,4 +32,23 @@ final class PepeLoggerTests: XCTestCase {
         let interval = end.timeIntervalSinceReferenceDate - start.timeIntervalSinceReferenceDate
         XCTAssertTrue(interval < reasonableTime)
     }
+    
+    func testLogging_withObserver_logCountShouldBeEqualToExpected() {
+        var logger = Pepe.loggerPlease()
+        let mockObserver = MockObserver()
+        logger.observer = mockObserver
+        logger.log("Hello")
+        logger.log("World!")
+        XCTAssertEqual(mockObserver.logCount, 2)
+    }
+}
+
+
+// MARK: Helpers
+internal class MockObserver: LoggerObserver {
+    var logCount = 0
+    
+    func willLog(log: Log) {
+        logCount += 1
+    }
 }