internal/pkg: standardise artifact IR

This should hopefully provide good separation between the artifact curing backend implementation and the (still work in progress) language. Making the IR parseable also guarantees uniqueness of the representation.

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

internal/pkg/file.go

@@ -25,6 +25,12 @@ var _ KnownChecksum = new(fileArtifactNamed)
 // String returns the caller-supplied reporting name.
 func (a *fileArtifactNamed) String() string { return a.name }
 
+// Params writes the caller-supplied reporting name and the file body.
+func (a *fileArtifactNamed) Params(ctx *IContext) {
+	ctx.WriteString(a.name)
+	ctx.Write(a.fileArtifact)
+}
+
 // NewFile returns a [FileArtifact] that cures into a caller-supplied byte slice.
 //
 // Caller must not modify data after NewFile returns.
@@ -39,8 +45,22 @@ func NewFile(name string, data []byte) FileArtifact {
 // Kind returns the hardcoded [Kind] constant.
 func (*fileArtifact) Kind() Kind { return KindFile }
 
-// Params writes the result of Cure.
-func (a *fileArtifact) Params(ctx *IContext) { ctx.GetHash().Write(*a) }
+// Params writes an empty string and the file body.
+func (a *fileArtifact) Params(ctx *IContext) {
+	ctx.WriteString("")
+	ctx.Write(*a)
+}
+
+func init() {
+	register(KindFile, func(r *IRReader) Artifact {
+		name := r.ReadString()
+		data := r.ReadStringBytes()
+		if _, ok := r.Finalise(); !ok {
+			panic(ErrExpectedChecksum)
+		}
+		return NewFile(name, data)
+	})
+}
 
 // Dependencies returns a nil slice.
 func (*fileArtifact) Dependencies() []Artifact { return nil }