Add walking over a playlist (#5)

README.md

@@ -106,7 +106,7 @@ The [Swift Package Manager](https://swift.org/package-manager/) is a tool for ma
 
 ```swift
 dependencies: [
-    .package(url: "https://github.com/omaralbeik/M3UKit.git", from: "0.4.0")
+    .package(url: "https://github.com/omaralbeik/M3UKit.git", from: "0.5.0")
 ]
 ```
 
@@ -121,15 +121,15 @@ $ swift build
 To integrate M3UKit into your Xcode project using [CocoaPods](https://cocoapods.org), specify it in your Podfile:
 
 ```rb
-pod 'M3UKit', :git => 'https://github.com/omaralbeik/M3UKit.git', :tag => '0.4.0'
+pod 'M3UKit', :git => 'https://github.com/omaralbeik/M3UKit.git', :tag => '0.5.0'
 ```
 
 ### Carthage
 
 To integrate M3UKit into your Xcode project using [Carthage](https://github.com/Carthage/Carthage), specify it in your Cartfile:
 
 ```
-github "omaralbeik/M3UKit" ~> 0.4.0
+github "omaralbeik/M3UKit" ~> 0.5.0
 ```
 
 ### Manually

Sources/M3UKit/Parsers/PlaylistParser.swift

@@ -40,13 +40,7 @@ public final class PlaylistParser: Parser {
   /// - Parameter input: source.
   /// - Returns: playlist.
   public func parse(_ input: PlaylistSource) throws -> Playlist {
-    guard let rawString = input.rawString else {
-      throw ParsingError.invalidSource
-    }
-
-    guard rawString.starts(with: "#EXTM3U") else {
-      throw ParsingError.invalidSource
-    }
+		let rawString = try extractRawString(from: input)
 
     var channels: [Playlist.Channel] = []
 
@@ -85,6 +79,48 @@ public final class PlaylistParser: Parser {
     return Playlist(channels: channels)
   }
 
+	/// Walk over a playlist and return its channels one-by-one.
+	/// - Parameters:
+	///   - input: source.
+	///   - handler: Handler to be called with the parsed channel.
+	public func walk(
+		_ input: PlaylistSource,
+		handler: @escaping (Playlist.Channel) -> Void
+	) throws {
+		let rawString = try extractRawString(from: input)
+
+		let metadataParser = ChannelMetadataParser()
+		var lastMetadataLine: String?
+		var lastURL: URL?
+		var channelMetadataParsingError: Error?
+		var lineNumber = 0
+
+		rawString.enumerateLines { line, stop in
+			if metadataParser.isInfoLine(line) {
+				lastMetadataLine = line
+			} else if let url = URL(string: line) {
+				lastURL = url
+			}
+
+			if let metadataLine = lastMetadataLine, let url = lastURL {
+				do {
+					let metadata = try metadataParser.parse((lineNumber, metadataLine))
+					handler(.init(metadata: metadata, url: url))
+					lastMetadataLine = nil
+					lastURL = nil
+				} catch {
+					channelMetadataParsingError = error
+					stop = true
+				}
+			}
+			lineNumber += 1
+		}
+
+		if let error = channelMetadataParsingError {
+			throw error
+		}
+	}
+
   /// Parse a playlist on a queue with a completion handler.
   /// - Parameters:
   ///   - input: source.
@@ -118,4 +154,18 @@ public final class PlaylistParser: Parser {
       }
     }
   }
+
+	// MARK: - Helpers
+
+	private func extractRawString(from input: PlaylistSource) throws -> String {
+		guard let rawString = input.rawString else {
+			throw ParsingError.invalidSource
+		}
+
+		guard rawString.starts(with: "#EXTM3U") else {
+			throw ParsingError.invalidSource
+		}
+
+		return rawString
+	}
 }

Tests/M3UKitTests/PlaylistTests.swift

@@ -42,6 +42,32 @@ final class PlaylistTests: XCTestCase {
     XCTAssertThrowsError(try parser.parse(InvalidSource()))
   }
 
+	func testWalking() throws {
+		let parser = PlaylistParser()
+		var channels: [Playlist.Channel] = []
+
+		let exp = expectation(description: "Walking succeeded")
+		let validURL = Bundle.module.url(forResource: "valid", withExtension: "m3u")!
+		try parser.walk(validURL) { channel in
+			channels.append(channel)
+			if channels.count == 105 {
+				exp.fulfill()
+			}
+		}
+
+		waitForExpectations(timeout: 1)
+		XCTAssertEqual(channels.count, 105)
+	}
+
+	func testWalkingInvalidSource() {
+		let parser = PlaylistParser()
+		XCTAssertThrowsError(try parser.walk("") { _ in })
+
+		let invalidURL = Bundle.module.url(forResource: "invalid", withExtension: "m3u")!
+		XCTAssertThrowsError(try parser.walk(invalidURL) { _ in })
+	}
+
+
   func testErrorDescription() {
     let error = PlaylistParser.ParsingError.invalidSource
     XCTAssertEqual(error.errorDescription, "The playlist is invalid")