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 short CBOR field names. 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/imgcache/service.go

@@ -19,6 +19,7 @@ import (
 	"sneak.berlin/go/pixa/internal/allowlist"
 	"sneak.berlin/go/pixa/internal/httpfetcher"
 	"sneak.berlin/go/pixa/internal/imageprocessor"
+	"sneak.berlin/go/pixa/internal/imagerequest"
 	"sneak.berlin/go/pixa/internal/magic"
 	"sneak.berlin/go/pixa/internal/signature"
 )
@@ -139,7 +140,9 @@ var ErrProcessingTimedOut = errors.New(
 // While its source URL is in the negative cache, a cached variant is still
 // served and a variant not in the cache is still made from a cached source;
 // only a request that needs the source fetched is refused.
-func (s *Service) Get(ctx context.Context, req *ImageRequest) (*ImageResponse, error) {
+func (s *Service) Get(
+	ctx context.Context, req *imagerequest.Request,
+) (*ImageResponse, error) {
 	// Propagate AllowHTTP setting to the request
 	req.AllowHTTP = s.allowHTTP
 
@@ -186,7 +189,7 @@ func (s *Service) Get(ctx context.Context, req *ImageRequest) (*ImageResponse, e
 }
 
 // Warm pre-fetches and caches an image without returning it.
-func (s *Service) Warm(ctx context.Context, req *ImageRequest) error {
+func (s *Service) Warm(ctx context.Context, req *imagerequest.Request) error {
 	_, err := s.Get(ctx, req)
 
 	return err
@@ -204,7 +207,7 @@ func (s *Service) WaitForProcessing(ctx context.Context) int {
 }
 
 // ValidateRequest validates the request signature if required.
-func (s *Service) ValidateRequest(req *ImageRequest) error {
+func (s *Service) ValidateRequest(req *imagerequest.Request) error {
 	// Check if host is allowed (no signature required)
 	sourceURL := req.SourceURL()
 
@@ -227,7 +230,7 @@ func (s *Service) ValidateRequest(req *ImageRequest) error {
 	}
 
 	// Signature required for non-allowed hosts
-	return s.signer.Verify(signatureRequest(req))
+	return s.signer.Verify(req)
 }
 
 // GenerateSignedURL generates a signed URL for the given request. The URL
@@ -236,26 +239,22 @@ func (s *Service) ValidateRequest(req *ImageRequest) error {
 // set to 85 or cover, the values the route uses when a URL has no q or fit.
 func (s *Service) GenerateSignedURL(
 	baseURL string,
-	req *ImageRequest,
+	req *imagerequest.Request,
 	ttl time.Duration,
 ) (string, error) {
-	if req.Quality == 0 {
-		req.Quality = 85
+	if req.Transform.Quality == 0 {
+		req.Transform.Quality = 85
 	}
 
-	if req.FitMode == "" {
-		req.FitMode = FitCover
+	if req.Transform.FitMode == "" {
+		req.Transform.FitMode = imagerequest.FitCover
 	}
 
-	sigReq := signatureRequest(req)
-	path, sig, exp := s.signer.GenerateSignedURL(sigReq, ttl)
-
-	// Propagate the generated signature and expiration back onto the request.
-	req.Expires = sigReq.Expires
-	req.Signature = sigReq.Signature
+	// Sets the request's Expires and Signature
+	path, sig, exp := s.signer.GenerateSignedURL(req, ttl)
 
 	return fmt.Sprintf("%s%s?sig=%s&exp=%d&q=%d&fit=%s",
-		baseURL, path, sig, exp, req.Quality, req.FitMode), nil
+		baseURL, path, sig, exp, req.Transform.Quality, req.Transform.FitMode), nil
 }
 
 // errPanicked is returned when processing a variant panicked.
@@ -268,14 +267,14 @@ var errPanicked = errors.New("panic while processing image")
 // the first request's cancellation, so the others are still served if that
 // client goes away, but keeps its deadline.
 func (s *Service) processOrWait(
-	ctx context.Context, req *ImageRequest,
+	ctx context.Context, req *imagerequest.Request,
 ) (*ImageResponse, error) {
 	// A request that has already ended starts no processing
 	if ctx.Err() != nil {
 		return nil, ctx.Err()
 	}
 
-	cacheKey := CacheKey(req)
+	cacheKey := imagerequest.CacheKey(req)
 
 	// Closed when this request's own function runs, which singleflight does
 	// only when no other request is processing the variant
@@ -293,7 +292,7 @@ func (s *Service) processOrWait(
 				recovered := recover()
 				if recovered != nil {
 					s.log.Error("panic while processing image",
-						"host", req.SourceHost, "path", req.SourcePath,
+						"host", req.Source.Host, "path", req.Source.Path,
 						"panic", recovered, "stack", string(debug.Stack()))
 
 					if hub := sentry.GetHubFromContext(ctx); hub != nil {
@@ -393,8 +392,8 @@ func (s *Service) loadCachedSource(
 // if available.
 func (s *Service) processFromSourceOrFetch(
 	ctx context.Context,
-	req *ImageRequest,
-	cacheKey VariantKey,
+	req *imagerequest.Request,
+	cacheKey imagerequest.VariantKey,
 ) (*processedVariant, error) {
 	// Check if we have cached source content
 	contentHash, _, err := s.cache.LookupSource(ctx, req)
@@ -431,8 +430,8 @@ func (s *Service) processFromSourceOrFetch(
 // source URL is in the negative cache.
 func (s *Service) fetchAndProcess(
 	ctx context.Context,
-	req *ImageRequest,
-	cacheKey VariantKey,
+	req *imagerequest.Request,
+	cacheKey imagerequest.VariantKey,
 ) (*processedVariant, error) {
 	// Check negative cache - skip fetching for recently-failed URLs
 	negHit, err := s.cache.checkNegativeCache(ctx, req)
@@ -442,8 +441,8 @@ func (s *Service) fetchAndProcess(
 
 	if negHit {
 		s.log.Debug("negative cache hit",
-			"host", req.SourceHost,
-			"path", req.SourcePath,
+			"host", req.Source.Host,
+			"path", req.Source.Path,
 		)
 
 		return nil, fmt.Errorf("%w: %w", httpfetcher.ErrUpstreamError, ErrNegativeCached)
@@ -493,8 +492,8 @@ func (s *Service) fetchAndProcess(
 	// Log upstream fetch details
 	s.log.Info("upstream fetched",
 		"request_id", middleware.GetReqID(ctx),
-		"host", req.SourceHost,
-		"path", req.SourcePath,
+		"host", req.Source.Host,
+		"path", req.Source.Path,
 		"bytes", fetchBytes,
 		"fetch_ms", fetchResult.FetchDurationMs,
 		"rate", downloadRate,
@@ -510,7 +509,7 @@ func (s *Service) fetchAndProcess(
 	err = magic.ValidateMagicBytes(sourceData, fetchResult.ContentType)
 	if err != nil {
 		s.log.Warn("source refused", "request_id", middleware.GetReqID(ctx),
-			"host", req.SourceHost, "path", req.SourcePath,
+			"host", req.Source.Host, "path", req.Source.Path,
 			"content_type", fetchResult.ContentType, "error", err)
 		s.storeNegative(ctx, req, httpStatusUnsupportedMediaType, err)
 
@@ -533,12 +532,12 @@ func (s *Service) fetchAndProcess(
 // failed with err, so the source is not fetched again until the entry
 // expires. A failure to store the entry is only logged.
 func (s *Service) storeNegative(
-	ctx context.Context, req *ImageRequest, statusCode int, err error,
+	ctx context.Context, req *imagerequest.Request, statusCode int, err error,
 ) {
 	storeErr := s.cache.StoreNegative(ctx, req, statusCode, err.Error())
 	if storeErr != nil {
 		s.log.Warn("failed to store negative cache entry",
-			"host", req.SourceHost, "path", req.SourcePath, "error", storeErr)
+			"host", req.Source.Host, "path", req.Source.Path, "error", storeErr)
 	}
 }
 
@@ -554,24 +553,17 @@ type processedVariant struct {
 // result.
 func (s *Service) processAndStore(
 	ctx context.Context,
-	req *ImageRequest,
-	cacheKey VariantKey,
+	req *imagerequest.Request,
+	cacheKey imagerequest.VariantKey,
 	source io.Reader,
 	fetchBytes int64,
 ) (*processedVariant, error) {
 	// Process the image
 	processStart := time.Now()
 
-	processReq := &imageprocessor.Request{
-		Size:    imageprocessor.Size{Width: req.Size.Width, Height: req.Size.Height},
-		Format:  imageprocessor.Format(req.Format),
-		Quality: req.Quality,
-		FitMode: imageprocessor.FitMode(req.FitMode),
-	}
-
 	// ctx has the deadline of the request doing the processing, which can
 	// end while a request waiting for its image has time left
-	processResult, err := s.processor.Process(ctx, source, processReq)
+	processResult, err := s.processor.Process(ctx, source, &req.Transform)
 	if errors.Is(err, context.DeadlineExceeded) {
 		return nil, fmt.Errorf("%w: %w", ErrProcessingTimedOut, err)
 	}
@@ -604,10 +596,10 @@ func (s *Service) processAndStore(
 
 	s.log.Info("image converted",
 		"request_id", middleware.GetReqID(ctx),
-		"host", req.SourceHost,
-		"path", req.SourcePath,
+		"host", req.Source.Host,
+		"path", req.Source.Path,
 		"src_format", processResult.InputFormat,
-		"dst_format", req.Format,
+		"dst_format", req.Transform.Format,
 		"src_bytes", fetchBytes,
 		"dst_bytes", outputSize,
 		"src_dimensions", fmt.Sprintf("%dx%d",
@@ -616,8 +608,8 @@ func (s *Service) processAndStore(
 			processResult.Width, processResult.Height),
 		"size_ratio", fmt.Sprintf("%.1f%%", sizePercent),
 		"convert_ms", processDuration.Milliseconds(),
-		"quality", req.Quality,
-		"fit", req.FitMode,
+		"quality", req.Transform.Quality,
+		"fit", req.Transform.FitMode,
 	)
 
 	// Store variant to cache
@@ -636,24 +628,6 @@ func (s *Service) processAndStore(
 	}, nil
 }
 
-// signatureRequest projects an ImageRequest onto the standalone
-// signature.Request type used by the signature package. This keeps the
-// import edge one-way: imgcache depends on signature, never the reverse.
-func signatureRequest(req *ImageRequest) *signature.Request {
-	return &signature.Request{
-		SourceHost:  req.SourceHost,
-		SourcePath:  req.SourcePath,
-		SourceQuery: req.SourceQuery,
-		Width:       req.Size.Width,
-		Height:      req.Size.Height,
-		Format:      string(req.Format),
-		Quality:     req.Quality,
-		FitMode:     string(req.FitMode),
-		Signature:   req.Signature,
-		Expires:     req.Expires,
-	}
-}
-
 // HTTP status codes for error responses.
 const (
 	httpStatusBadGateway           = 502
@@ -680,7 +654,7 @@ func extractStatusCode(err error) int {
 const etagHashLength = 16
 
 // formatETag formats a VariantKey as a quoted ETag value.
-func formatETag(key VariantKey) string {
+func formatETag(key imagerequest.VariantKey) string {
 	hash := string(key)
 	// Use first 16 characters of hash for a shorter but still unique ETag
 	if len(hash) > etagHashLength {