Initial implementation of songbook toolset

Kotlin/JVM multi-module project for generating a scout songbook PDF
from ChordPro-format text files. Includes ChordPro parser, layout engine
with greedy spread packing for double-page songs, OpenPDF renderer,
CLI (Clikt), Compose Desktop GUI, and 5 sample songs.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

model/build.gradle.kts

@@ -0,0 +1,3 @@
+plugins {
+    id("songbook-conventions")
+}

model/src/main/kotlin/de/pfadfinder/songbook/model/BookConfig.kt

@@ -0,0 +1,67 @@
+package de.pfadfinder.songbook.model
+
+data class BookConfig(
+    val book: BookMeta = BookMeta(),
+    val songs: SongsConfig = SongsConfig(),
+    val fonts: FontsConfig = FontsConfig(),
+    val layout: LayoutConfig = LayoutConfig(),
+    val images: ImagesConfig = ImagesConfig(),
+    val referenceBooks: List<ReferenceBook> = emptyList(),
+    val output: OutputConfig = OutputConfig()
+)
+
+data class BookMeta(
+    val title: String = "Liederbuch",
+    val subtitle: String? = null,
+    val edition: String? = null,
+    val format: String = "A5"
+)
+
+data class SongsConfig(
+    val directory: String = "./songs",
+    val order: String = "alphabetical"  // "alphabetical" or "manual"
+)
+
+data class FontsConfig(
+    val lyrics: FontSpec = FontSpec(family = "Helvetica", size = 10f),
+    val chords: FontSpec = FontSpec(family = "Helvetica", size = 9f, color = "#333333"),
+    val title: FontSpec = FontSpec(family = "Helvetica", size = 14f),
+    val metadata: FontSpec = FontSpec(family = "Helvetica", size = 8f),
+    val toc: FontSpec = FontSpec(family = "Helvetica", size = 9f)
+)
+
+data class FontSpec(
+    val family: String = "Helvetica",
+    val file: String? = null,
+    val size: Float = 10f,
+    val color: String = "#000000"
+)
+
+data class LayoutConfig(
+    val margins: Margins = Margins(),
+    val chordLineSpacing: Float = 3f,    // mm
+    val verseSpacing: Float = 4f,         // mm
+    val pageNumberPosition: String = "bottom-outer"
+)
+
+data class Margins(
+    val top: Float = 15f,
+    val bottom: Float = 15f,
+    val inner: Float = 20f,
+    val outer: Float = 12f
+)
+
+data class ImagesConfig(
+    val directory: String = "./images"
+)
+
+data class ReferenceBook(
+    val id: String,
+    val name: String,
+    val abbreviation: String
+)
+
+data class OutputConfig(
+    val directory: String = "./output",
+    val filename: String = "liederbuch.pdf"
+)

model/src/main/kotlin/de/pfadfinder/songbook/model/BookRenderer.kt

@@ -0,0 +1,7 @@
+package de.pfadfinder.songbook.model
+
+import java.io.OutputStream
+
+interface BookRenderer {
+    fun render(layout: LayoutResult, config: BookConfig, output: OutputStream)
+}

model/src/main/kotlin/de/pfadfinder/songbook/model/FontMetrics.kt

@@ -0,0 +1,6 @@
+package de.pfadfinder.songbook.model
+
+interface FontMetrics {
+    fun measureTextWidth(text: String, font: FontSpec, size: Float): Float
+    fun measureLineHeight(font: FontSpec, size: Float): Float
+}

model/src/main/kotlin/de/pfadfinder/songbook/model/Layout.kt

@@ -0,0 +1,26 @@
+package de.pfadfinder.songbook.model
+
+data class MeasuredSong(
+    val song: Song,
+    val totalHeightMm: Float,
+    val pageCount: Int  // 1 or 2
+)
+
+sealed class PageContent {
+    data class SongPage(val song: Song, val pageIndex: Int) : PageContent()  // pageIndex 0 or 1 for 2-page songs
+    data class FillerImage(val imagePath: String) : PageContent()
+    data object BlankPage : PageContent()
+}
+
+data class LayoutResult(
+    val tocPages: Int,
+    val pages: List<PageContent>,
+    val tocEntries: List<TocEntry>
+)
+
+data class TocEntry(
+    val title: String,
+    val pageNumber: Int,
+    val isAlias: Boolean = false,
+    val references: Map<String, Int> = emptyMap()  // bookAbbrev → page
+)

model/src/main/kotlin/de/pfadfinder/songbook/model/Song.kt

@@ -0,0 +1,31 @@
+package de.pfadfinder.songbook.model
+
+data class Song(
+    val title: String,
+    val aliases: List<String> = emptyList(),
+    val lyricist: String? = null,
+    val composer: String? = null,
+    val key: String? = null,
+    val tags: List<String> = emptyList(),
+    val notes: List<String> = emptyList(),
+    val references: Map<String, Int> = emptyMap(), // bookId → page number
+    val capo: Int? = null,
+    val sections: List<SongSection> = emptyList()
+)
+
+data class SongSection(
+    val type: SectionType,
+    val label: String? = null,
+    val lines: List<SongLine> = emptyList()
+)
+
+enum class SectionType {
+    VERSE, CHORUS, BRIDGE, REPEAT
+}
+
+data class SongLine(val segments: List<LineSegment>)
+
+data class LineSegment(
+    val chord: String? = null,  // null = no chord above this segment
+    val text: String
+)