internal/rosa: wrap per-arch values

This is cleaner syntax in some specific cases.

Signed-off-by: Ophestra <cat@gensokyo.uk>

internal/rosa/rosa.go

@@ -69,6 +69,18 @@ func triplet() string {
 	return linuxArch() + "-rosa-linux-musl"
 }
 
+// perArch is a value that differs per architecture.
+type perArch[T any] map[string]T
+
+// unwrap returns the value for the current architecture.
+func (p perArch[T]) unwrap() T {
+	v, ok := p[runtime.GOARCH]
+	if !ok {
+		panic("unsupported target " + runtime.GOARCH)
+	}
+	return v
+}
+
 const (
 	// EnvTriplet holds the return value of triplet.
 	EnvTriplet = "ROSA_TRIPLE"

internal/rosa/stage0.go

@@ -1,7 +1,6 @@
 package rosa
 
 import (
-	"runtime"
 	"sync"
 
 	"hakurei.app/internal/pkg"
@@ -61,23 +60,14 @@ var (
 // NewStage0 returns a stage0 distribution created from curing [Stage0].
 func NewStage0() pkg.Artifact {
 	stage0Once.Do(func() {
-		var seed string
-		switch runtime.GOARCH {
-		case "amd64":
-			seed = "tqM1Li15BJ-uFG8zU-XjgFxoN_kuzh1VxrSDVUVa0vGmo-NeWapSftH739sY8EAg"
-		case "arm64":
-			seed = "CJj3ZSnRyLmFHlWIQtTPQD9oikOZY4cD_mI3v_-LIYc2hhg-cq_CZFBLzQBAkFIn"
-		case "riscv64":
-			seed = "FcszJjcVWdKAnn-bt8qmUn5GUUTjv_xQjXOWkUpOplRkG3Ckob3StUoAi5KQ5-QF"
-
-		default:
-			panic("unsupported target " + runtime.GOARCH)
-		}
-
 		stage0 = pkg.NewHTTPGetTar(
 			nil, "https://hakurei.app/seed/20260210/"+
 				"stage0-"+triplet()+".tar.bz2",
-			mustDecode(seed),
+			mustDecode(perArch[string]{
+				"amd64":   "tqM1Li15BJ-uFG8zU-XjgFxoN_kuzh1VxrSDVUVa0vGmo-NeWapSftH739sY8EAg",
+				"arm64":   "CJj3ZSnRyLmFHlWIQtTPQD9oikOZY4cD_mI3v_-LIYc2hhg-cq_CZFBLzQBAkFIn",
+				"riscv64": "FcszJjcVWdKAnn-bt8qmUn5GUUTjv_xQjXOWkUpOplRkG3Ckob3StUoAi5KQ5-QF",
+			}.unwrap()),
 			pkg.TarBzip2,
 		)
 	})