2 files changed, 29 insertions, 0 deletions
diff --git a/internal/bible/bible.go b/internal/bible/bible.go
index 0254ceb..312daeb 100644
--- a/internal/bible/bible.go
+++ b/internal/bible/bible.go
@@ -2,6 +2,7 @@ package bible
 
 import (
 	"embed"
+	"sort"
 	"strconv"
 	"strings"
 	"sync"
@@ -58,3 +59,15 @@ func load(version string) *corpus {
 func Verses(version, book string, chap int) []Verse {
 	return load(version).books[book][chap]
 }
+
+// Chapters returns the chapter numbers present for a book in a version, sorted
+// ascending (empty if the version has no such book).
+func Chapters(version, book string) []int {
+	chapMap := load(version).books[book]
+	chaps := make([]int, 0, len(chapMap))
+	for ch := range chapMap {
+		chaps = append(chaps, ch)
+	}
+	sort.Ints(chaps)
+	return chaps
+}
diff --git a/internal/bible/bible_test.go b/internal/bible/bible_test.go
index efd22d6..36223a3 100644
--- a/internal/bible/bible_test.go
+++ b/internal/bible/bible_test.go
@@ -28,3 +28,19 @@ func TestVerses(t *testing.T) {
 }
 
 func hasPrefix(s, p string) bool { return len(s) >= len(p) && s[:len(p)] == p }
+
+func TestChapters(t *testing.T) {
+	ch := Chapters("wuj", "John")
+	if len(ch) == 0 || ch[0] != 1 {
+		t.Fatalf("John chapters = %v", ch)
+	}
+	for i := 1; i < len(ch); i++ {
+		if ch[i] <= ch[i-1] {
+			t.Errorf("chapters not sorted ascending: %v", ch)
+			break
+		}
+	}
+	if got := Chapters("wuj", "Nonesuch"); len(got) != 0 {
+		t.Errorf("missing book chapters = %v want empty", got)
+	}
+}