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3eaa21229d
The ETag was the pixel hash of the original image, so a CoverArtQuality or EnableWebPEncoding change altered the resized bytes without changing the ETag — revalidating clients got a spurious 304 and kept the old encoding. Resized responses now carry a representation ETag (hash + size + square + encode settings) used for the ETag header and If-None-Match, while the immutable decision stays on the pixel hash (URLs remain pixel-identity per the spec, so hash-suffixed clients keep zero-request caching). Full-size originals fall back to the pixel hash as before.
69 lines
2.3 KiB
Go
69 lines
2.3 KiB
Go
// Package imghttp holds the shared HTTP caching contract for artwork responses, so the
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// subsonic, public, and jellyfin image handlers apply identical headers without importing
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// each other.
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package imghttp
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import (
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"net/http"
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"strings"
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"github.com/navidrome/navidrome/core/artwork"
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)
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// WriteImageHeaders applies the artwork caching contract and reports whether a 304 was written
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// (in which case the caller must not write a body). requestedHash is the hash the client asserted
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// (id suffix / JWT payload / jellyfin tag param), or "" when the request carried no hash.
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func WriteImageHeaders(w http.ResponseWriter, r *http.Request, img *artwork.Image, requestedHash string) (wrote304 bool) {
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h := w.Header()
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// Placeholders are transient stand-ins for not-yet-resolved art: never cached, no validators.
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if img.Placeholder {
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h.Set("Cache-Control", "no-store")
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return false
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}
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// The validator identifies the served representation (resized/re-encoded bytes version it via
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// ETag), so a CoverArtQuality/EnableWebPEncoding change invalidates a revalidating client's
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// cache. Falls back to the pixel hash for full-size originals (bytes == the hash).
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etag := img.ETag
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if etag == "" {
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etag = img.Hash
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}
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h.Set("ETag", `"`+etag+`"`)
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if !img.LastUpdated.IsZero() {
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h.Set("Last-Modified", img.LastUpdated.UTC().Format(http.TimeFormat))
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}
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// Immutable only when the client asked for the exact current pixel hash; bare/legacy/mismatched
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// requests get cheap ETag revalidation instead, which fixes stale art after re-resolution.
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if requestedHash != "" && requestedHash == img.Hash {
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h.Set("Cache-Control", "public, max-age=31536000, immutable")
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} else {
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h.Set("Cache-Control", "public, no-cache")
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}
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if ifNoneMatch(r.Header.Get("If-None-Match"), etag) {
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w.WriteHeader(http.StatusNotModified)
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return true
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}
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return false
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}
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// ifNoneMatch reports whether the If-None-Match header asserts the given hash, using weak
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// comparison (RFC 9110): "*" matches any current representation and W/ prefixes are ignored.
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func ifNoneMatch(header, hash string) bool {
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header = strings.TrimSpace(header)
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if header == "" {
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return false
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}
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if header == "*" {
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return true
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}
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for _, tag := range strings.Split(header, ",") {
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tag = strings.TrimSpace(tag)
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tag = strings.TrimPrefix(tag, "W/")
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if strings.Trim(tag, `"`) == hash {
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return true
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}
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}
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return false
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}
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