add plain text parser with paragraph-based chapter splitting

VorleserKit/Sources/BookParser/PlainTextParser.swift

@@ -0,0 +1,21 @@
+import Foundation
+
+public struct PlainTextParser {
+	public static func parse(text: String, title: String, author: String? = nil) -> Book {
+		let paragraphs = text.components(separatedBy: "\n\n")
+			.map { $0.trimmingCharacters(in: .whitespacesAndNewlines) }
+			.filter { !$0.isEmpty }
+
+		let chapters = paragraphs.enumerated().map { index, text in
+			Chapter(index: index, title: "Section \(index + 1)", text: text)
+		}
+
+		return Book(title: title, author: author, chapters: chapters)
+	}
+
+	public static func parse(url: URL) throws -> Book {
+		let text = try String(contentsOf: url, encoding: .utf8)
+		let title = url.deletingPathExtension().lastPathComponent
+		return parse(text: text, title: title)
+	}
+}

VorleserKit/Tests/BookParserTests/PlainTextParserTests.swift

@@ -0,0 +1,36 @@
+import Testing
+import Foundation
+@testable import BookParser
+
+@Suite("PlainTextParser")
+struct PlainTextParserTests {
+	@Test func parsesMultipleChapters() throws {
+		let text = "First chapter content.\n\nSecond chapter content.\n\nThird chapter."
+		let book = PlainTextParser.parse(text: text, title: "Test Book")
+		#expect(book.chapters.count == 3)
+		#expect(book.chapters[0].text == "First chapter content.")
+		#expect(book.chapters[1].text == "Second chapter content.")
+	}
+
+	@Test func parsesSingleParagraphAsOneChapter() {
+		let text = "Just a single paragraph with no double newlines."
+		let book = PlainTextParser.parse(text: text, title: "Test")
+		#expect(book.chapters.count == 1)
+		#expect(book.chapters[0].text == text)
+	}
+
+	@Test func setsTitle() {
+		let book = PlainTextParser.parse(text: "Hello", title: "My Book")
+		#expect(book.title == "My Book")
+	}
+
+	@Test func parsesFromFile() throws {
+		let tmpFile = URL(fileURLWithPath: NSTemporaryDirectory()).appendingPathComponent("test.txt")
+		try "Line one.\n\nLine two.".write(to: tmpFile, atomically: true, encoding: .utf8)
+		defer { try? FileManager.default.removeItem(at: tmpFile) }
+
+		let book = try PlainTextParser.parse(url: tmpFile)
+		#expect(book.chapters.count == 2)
+		#expect(book.title == "test")
+	}
+}