2 files changed, 82 insertions, 13 deletions

diff --git a/internal/readings/offline.go b/internal/readings/offline.go
index 59a03fa..c2c276b 100644
--- a/internal/readings/offline.go
+++ b/internal/readings/offline.go
@@ -8,6 +8,7 @@ import (
 	"github.com/lukaszkasprzak/lectio/internal/caldata"
 	"github.com/lukaszkasprzak/lectio/internal/calendar"
 	"github.com/lukaszkasprzak/lectio/internal/config"
+	"github.com/lukaszkasprzak/lectio/internal/i18n"
 	"github.com/lukaszkasprzak/lectio/internal/liturgy"
 	"github.com/lukaszkasprzak/lectio/internal/naming"
 )
@@ -60,24 +61,47 @@ var ofPart = map[string]struct{ id, heading string }{
 	"gospel":      {"ewangelia", "Ewangelia"},
 }
 
-// efPartHeading gives the traditional (1962) section's heading per UI language;
-// the EF has only an epistle/lesson and a gospel. Unlike the OF headings these
-// are not translated downstream, so they are set in the target language here.
+// efPartHeading gives the traditional (1962) section's ID and heading per UI
+// language; the EF has only an epistle/lesson and a gospel. The label words are
+// i18n data, like the modern ones. Unlike the OF headings these are not
+// translated downstream (render.LocalizeHeading only handles modern IDs), so
+// they are resolved in the target language here.
 func efPartHeading(part, lang string) (id, heading string) {
-	pl := lang == "pl"
 	switch part {
 	case "first":
-		if pl {
-			return "epistola", "Lekcja"
-		}
-		return "epistola", "Lesson"
+		id = "epistola"
 	case "gospel":
-		if pl {
-			return "evangelium", "Ewangelia"
-		}
-		return "evangelium", "Gospel"
+		id = "evangelium"
+	default:
+		return "", ""
+	}
+	heading = i18n.Get(lang).PartLabel[id]
+	if heading == "" {
+		heading = id
+	}
+	return id, heading
+}
+
+// ofPartOrder and efPartOrder are the display orders of each lectionary's
+// sections. They are the single source of truth for which part IDs exist.
+var (
+	ofPartOrder = []string{"pierwsze_czytanie", "psalm", "drugie_czytanie", "aklamacja", "ewangelia"}
+	efPartOrder = []string{"epistola", "evangelium"}
+)
+
+// PartIDs returns the part IDs the given lectionary can emit, in display order.
+// lect takes config.Config.Lectionary's values: "new" or "traditional". An
+// unknown lectionary returns nil. Callers that build per-part UI (the dlectio
+// app's reading filters) must derive their list from this rather than
+// hardcoding IDs.
+func PartIDs(lect string) []string {
+	switch lect {
+	case "new":
+		return append([]string(nil), ofPartOrder...)
+	case "traditional":
+		return append([]string(nil), efPartOrder...)
 	}
-	return "", ""
+	return nil
 }
 
 // sectionsFor turns computed readings into render-ready sections, tagging each
diff --git a/internal/readings/partids_test.go b/internal/readings/partids_test.go
index 68f5ec0..1ba9373 100644
--- a/internal/readings/partids_test.go
+++ b/internal/readings/partids_test.go
@@ -4,6 +4,7 @@ import (
 	"testing"
 
 	"github.com/lukaszkasprzak/lectio/internal/config"
+	"github.com/lukaszkasprzak/lectio/internal/i18n"
 )
 
 // The day header must carry the rank, not just name and colour: the app's
@@ -28,3 +29,47 @@ func TestDayInfoCarriesRank(t *testing.T) {
 		}
 	}
 }
+
+// PartIDs must list exactly the IDs the engine can emit, in display order.
+// The app derives its "show readings" checkboxes from this; when it hardcoded
+// them instead, seven of the nine 1962 IDs were wrong and the epistle's
+// checkbox did nothing.
+func TestPartIDs(t *testing.T) {
+	wantNew := []string{"pierwsze_czytanie", "psalm", "drugie_czytanie", "aklamacja", "ewangelia"}
+	wantOld := []string{"epistola", "evangelium"}
+	if got := PartIDs("new"); !equalSlice(got, wantNew) {
+		t.Errorf("PartIDs(new) = %v, want %v", got, wantNew)
+	}
+	if got := PartIDs("traditional"); !equalSlice(got, wantOld) {
+		t.Errorf("PartIDs(traditional) = %v, want %v", got, wantOld)
+	}
+	if got := PartIDs("nonsense"); len(got) != 0 {
+		t.Errorf("PartIDs(nonsense) = %v, want empty", got)
+	}
+}
+
+// Every ID PartIDs lists must have a label in every shipped language,
+// otherwise a checkbox would render a raw ID like "epistola".
+func TestEveryPartIDHasLabels(t *testing.T) {
+	for _, lect := range []string{"new", "traditional"} {
+		for _, id := range PartIDs(lect) {
+			for _, lang := range []string{"en", "pl"} {
+				if i18n.Get(lang).PartLabel[id] == "" {
+					t.Errorf("%s/%s: no label for %q", lect, lang, id)
+				}
+			}
+		}
+	}
+}
+
+func equalSlice(a, b []string) bool {
+	if len(a) != len(b) {
+		return false
+	}
+	for i := range a {
+		if a[i] != b[i] {
+			return false
+		}
+	}
+	return true
+}