add BookParser facade with format detection, Book character addressing tests

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

VorleserKit/Sources/BookParser/BookParser.swift

@@ -0,0 +1,24 @@
+import Foundation
+
+public enum BookParserError: Error, CustomStringConvertible {
+	case unsupportedFormat(String)
+
+	public var description: String {
+		switch self {
+		case .unsupportedFormat(let ext): "unsupported file format: \(ext)"
+		}
+	}
+}
+
+public struct BookParser {
+	public static func parse(url: URL) throws -> Book {
+		switch url.pathExtension.lowercased() {
+		case "epub":
+			return try EPUBParser.parse(url: url)
+		case "txt", "text":
+			return try PlainTextParser.parse(url: url)
+		default:
+			throw BookParserError.unsupportedFormat(url.pathExtension)
+		}
+	}
+}

VorleserKit/Tests/BookParserTests/BookTests.swift

@@ -0,0 +1,57 @@
+import Testing
+import Foundation
+@testable import BookParser
+@testable import VorleserKit
+
+@Suite("BookParser")
+struct BookParserFacadeTests {
+	@Test func detectsEPUBByExtension() throws {
+		let url = Bundle.module.url(forResource: "test", withExtension: "epub", subdirectory: "Fixtures")!
+		let book = try BookParser.parse(url: url)
+		#expect(book.chapters.count == 2)
+	}
+
+	@Test func detectsTextByExtension() throws {
+		let tmpFile = URL(fileURLWithPath: NSTemporaryDirectory()).appendingPathComponent("test.txt")
+		try "Paragraph one.\n\nParagraph two.".write(to: tmpFile, atomically: true, encoding: .utf8)
+		defer { try? FileManager.default.removeItem(at: tmpFile) }
+
+		let book = try BookParser.parse(url: tmpFile)
+		#expect(book.chapters.count == 2)
+	}
+}
+
+@Suite("Book character addressing")
+struct BookCharacterAddressingTests {
+	let book = Book(
+		title: "Test",
+		author: nil,
+		chapters: [
+			Chapter(index: 0, title: "Ch 1", text: "Hello world."),
+			Chapter(index: 1, title: "Ch 2", text: "Second chapter."),
+		]
+	)
+
+	@Test func totalCharacters() {
+		#expect(book.totalCharacters == 27)
+	}
+
+	@Test func chapterAndLocalOffset() {
+		let first = book.chapterAndLocalOffset(for: 0)
+		#expect(first?.chapterIndex == 0)
+		#expect(first?.localOffset == 0)
+
+		let second = book.chapterAndLocalOffset(for: 12)
+		#expect(second?.chapterIndex == 1)
+		#expect(second?.localOffset == 0)
+	}
+
+	@Test func sentenceIndex() {
+		let idx = book.sentenceIndex(containing: 0)
+		#expect(idx != nil)
+	}
+
+	@Test func outOfRangeReturnsNil() {
+		#expect(book.chapterAndLocalOffset(for: 9999) == nil)
+	}
+}