internal/pkg: improve artifact interface

This moves all cache I/O code to Cache. Artifact now only contains methods for constructing their actual contents.

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

internal/pkg/tar_test.go

@@ -79,7 +79,7 @@ func TestTar(t *testing.T) {
 				return pkg.ID(h.Sum(nil))
 			}()
 
-			a, err := c.NewHTTPGetTar(
+			a, err := pkg.NewHTTPGetTar(
 				t.Context(),
 				&client,
 				"file:///testdata",
@@ -89,27 +89,27 @@ func TestTar(t *testing.T) {
 
 			if err != nil {
 				t.Fatalf("NewHTTPGetTar: error = %v", err)
-			} else if id := a.ID(); id != wantIdent {
-				t.Fatalf("ID: %s, want %s", pkg.Encode(id), pkg.Encode(wantIdent))
+			} else if id := pkg.Ident(a); id != wantIdent {
+				t.Fatalf("Ident: %s, want %s", pkg.Encode(id), pkg.Encode(wantIdent))
 			}
 
-			var pathname *check.Absolute
+			var (
+				pathname *check.Absolute
+				checksum pkg.Checksum
+			)
 			wantPathname := base.Append(
 				"identifier",
 				pkg.Encode(wantIdent),
 			)
-			if pathname, err = a.Pathname(); err != nil {
-				t.Fatalf("Pathname: error = %v", err)
+			wantChecksum := pkg.MustDecode(
+				"yJlSb2A3jxaMLuKqwp1GwHOguAHddS9MjygF9ICEeegKfRvgLPdPmNh8mva47f8o",
+			)
+			if pathname, checksum, err = c.Cure(a); err != nil {
+				t.Fatalf("Cure: error = %v", err)
 			} else if !pathname.Is(wantPathname) {
-				t.Fatalf("Pathname: %q, want %q", pathname, wantPathname)
-			}
-
-			var checksum pkg.Checksum
-			wantChecksum := pkg.MustDecode("yJlSb2A3jxaMLuKqwp1GwHOguAHddS9MjygF9ICEeegKfRvgLPdPmNh8mva47f8o")
-			if checksum, err = a.Hash(); err != nil {
-				t.Fatalf("Hash: error = %v", err)
+				t.Fatalf("Cure: %q, want %q", pathname, wantPathname)
 			} else if checksum != wantChecksum {
-				t.Fatalf("Hash: %v", &pkg.ChecksumMismatchError{
+				t.Fatalf("Cure: %v", &pkg.ChecksumMismatchError{
 					Got:  checksum,
 					Want: wantChecksum,
 				})