internal/pkg: compute http identifier from url

The previous implementation exposes arbitrary user input to the cache as an identifier, which is highly error-prone and can cause the cache to enter an inconsistent state if the user is not careful. This change replaces the implementation to compute identifier late, using url string as params.

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

internal/pkg/net.go

@@ -11,10 +11,14 @@ import (
 	"hakurei.app/container/check"
 )
 
-// An httpArtifact is an [Artifact] backed by an [http] request.
+// An httpArtifact is an [Artifact] backed by a [http] url string. The method is
+// hardcoded as [http.MethodGet]. Request body is not allowed because it cannot
+// be deterministically represented by Params.
 type httpArtifact struct {
-	// Caller-supplied request.
-	req *http.Request
+	// Caller-supplied context.
+	ctx context.Context
+	// Caller-supplied url string.
+	url string
 
 	// Caller-supplied checksum of the response body. This is validated during
 	// curing and the first call to Data.
@@ -30,15 +34,6 @@ type httpArtifact struct {
 	mu sync.Mutex
 }
 
-// NewHTTP returns a new [File] backed by the supplied client and request. If
-// c is nil, [http.DefaultClient] is used instead.
-func NewHTTP(c *http.Client, req *http.Request, checksum Checksum) File {
-	if c == nil {
-		c = http.DefaultClient
-	}
-	return &httpArtifact{req: req, checksum: checksum, doFunc: c.Do}
-}
-
 // NewHTTPGet returns a new [File] backed by the supplied client. A GET request
 // is set up for url. If c is nil, [http.DefaultClient] is used instead.
 func NewHTTPGet(
@@ -46,24 +41,22 @@ func NewHTTPGet(
 	c *http.Client,
 	url string,
 	checksum Checksum,
-) (File, error) {
-	req, err := http.NewRequestWithContext(ctx, http.MethodGet, url, nil)
-	if err != nil {
-		return nil, err
+) File {
+	if ctx == nil {
+		ctx = context.Background()
 	}
-	return NewHTTP(c, req, checksum), nil
+	if c == nil {
+		c = http.DefaultClient
+	}
+	return &httpArtifact{ctx: ctx, url: url, checksum: checksum, doFunc: c.Do}
 }
 
 // Kind returns the hardcoded [Kind] constant.
-func (a *httpArtifact) Kind() Kind { return KindHTTP }
+func (a *httpArtifact) Kind() Kind { return KindHTTPGet }
 
-// ID returns the caller-supplied hash of the response body.
-func (a *httpArtifact) ID() ID { return a.checksum }
-
-// Params is unreachable.
-func (a *httpArtifact) Params() []byte {
-	panic("not implemented")
-}
+// Params returns the backing url string. Context is not represented as it does
+// not affect [Cache.Cure] outcome.
+func (a *httpArtifact) Params() []byte { return []byte(a.url) }
 
 // Dependencies returns a nil slice.
 func (a *httpArtifact) Dependencies() []Artifact { return nil }
@@ -82,8 +75,14 @@ func (e ResponseStatusError) Error() string {
 // do sends the caller-supplied request on the caller-supplied [http.Client]
 // and reads its response body to EOF and returns the resulting bytes.
 func (a *httpArtifact) do() (data []byte, err error) {
+	var req *http.Request
+	req, err = http.NewRequestWithContext(a.ctx, http.MethodGet, a.url, nil)
+	if err != nil {
+		return
+	}
+
 	var resp *http.Response
-	if resp, err = a.doFunc(a.req); err != nil {
+	if resp, err = a.doFunc(req); err != nil {
 		return
 	}