One image request type instead of five (closes #307)

The new package internal/imagerequest holds the request type, its two
parts Source and Transform, the Format and Fit types, the dimension and
fit checks, the /v1/image/ path parsing and the variant key; it imports
no other package of pixa. imgcache.ParsedURL, imgcache.ImageRequest,
signature.Request, imageprocessor.Request, the second Size, format and
fit types and the conversions between them are gone. The image
processor takes a Transform only. encurl keeps a private struct with the
token's CBOR field names, so tokens made before still decode. VariantKey
moves with the function that makes it. Tests follow the moved and
renamed code; the tests of the removed conversions go with them.

Model: opus-5-5

internal/handlers/imageenc.go

@@ -14,6 +14,7 @@ import (
 	"sneak.berlin/go/pixa/internal/encurl"
 	"sneak.berlin/go/pixa/internal/httpfetcher"
 	"sneak.berlin/go/pixa/internal/imageprocessor"
+	"sneak.berlin/go/pixa/internal/imagerequest"
 	"sneak.berlin/go/pixa/internal/imgcache"
 	"sneak.berlin/go/pixa/internal/magic"
 )
@@ -37,10 +38,11 @@ func (s *Handlers) HandleImageEnc() http.HandlerFunc {
 
 		// Log the request
 		s.log.Debug("encrypted image request",
-			"host", req.SourceHost,
-			"path", req.SourcePath,
-			"dimensions", fmt.Sprintf("%dx%d", req.Size.Width, req.Size.Height),
-			"format", req.Format,
+			"host", req.Source.Host,
+			"path", req.Source.Path,
+			"dimensions", fmt.Sprintf("%dx%d",
+				req.Transform.Size.Width, req.Transform.Size.Height),
+			"format", req.Transform.Format,
 		)
 
 		// Fetch and process the image (no signature validation
@@ -88,10 +90,10 @@ func (s *Handlers) HandleImageEnc() http.HandlerFunc {
 		duration := time.Since(start)
 		s.log.Info("image served",
 			"request_id", middleware.GetReqID(ctx),
-			"cache_key", imgcache.CacheKey(req),
-			"host", req.SourceHost,
-			"path", req.SourcePath,
-			"format", req.Format,
+			"cache_key", imagerequest.CacheKey(req),
+			"host", req.Source.Host,
+			"path", req.Source.Path,
+			"format", req.Transform.Format,
 			"cache_status", resp.CacheStatus,
 			"served_bytes", written,
 			"duration_ms", duration.Milliseconds(),
@@ -100,12 +102,12 @@ func (s *Handlers) HandleImageEnc() http.HandlerFunc {
 }
 
 // parseImageEncRequest decrypts the token of an encrypted image URL into an
-// ImageRequest and checks it. On a token that is missing, does not decrypt,
+// image request and checks it. On a token that is missing, does not decrypt,
 // has expired or asks for something not valid, it writes an error response
 // and returns false.
 func (s *Handlers) parseImageEncRequest(
 	w http.ResponseWriter, r *http.Request,
-) (*imgcache.ImageRequest, bool) {
+) (*imagerequest.Request, bool) {
 	// Extract token from URL
 	token := chi.URLParam(r, "token")
 	if token == "" {
@@ -115,7 +117,7 @@ func (s *Handlers) parseImageEncRequest(
 	}
 
 	// Decrypt and validate the payload
-	payload, err := s.encGen.Parse(token)
+	req, err := s.encGen.Parse(token)
 	if err != nil {
 		if errors.Is(err, encurl.ErrExpired) {
 			s.log.Debug("encrypted URL expired", "error", err)
@@ -130,14 +132,11 @@ func (s *Handlers) parseImageEncRequest(
 		return nil, false
 	}
 
-	// Convert payload to ImageRequest
-	req := payload.ToImageRequest()
-
 	// Apply the same dimension and fit-mode bounds as the plain image
 	// route: a sealed payload is trusted for its origin, not for staying
 	// within limits, so an over-limit size or unknown fit mode is a 400
 	// here rather than an out-of-memory or a 500 from the processor.
-	err = imgcache.ValidateImageRequest(req)
+	err = imagerequest.ValidateImageRequest(req)
 	if err != nil {
 		s.log.Debug("encrypted URL failed validation", "error", err)
 		s.respondError(w, "invalid encrypted URL: "+err.Error(),