Add cooldown support for RubyGems

Filter versions from the compact index (/info/{name}) by fetching
timestamps from the versions API (/api/v1/versions/{name}.json).
Both requests run concurrently to minimize latency. If the versions
API is unavailable, the compact index is proxied unfiltered.

Handles platform-specific versions (e.g. 1.0.0-java) by matching
the compact index format.

Author: andrew

README.md

@@ -28,7 +28,7 @@ Currently works with npm, PyPI, pub.dev, Composer, and Cargo, which all include
 |----------|-------------------|:--------:|:---------:|
 | npm | JavaScript | Yes | ✓ |
 | Cargo | Rust | Yes | ✓ |
-| RubyGems | Ruby | | ✓ |
+| RubyGems | Ruby | Yes | ✓ |
 | Go proxy | Go | | ✓ |
 | Hex | Elixir | | ✓ |
 | pub.dev | Dart | Yes | ✓ |

docs/configuration.md

@@ -209,7 +209,7 @@ Durations support days (`7d`), hours (`48h`), and minutes (`30m`). Set to `0` to
 
 Resolution order: package override, then ecosystem override, then global default. This lets you set a conservative default while exempting trusted packages.
 
-Currently supported for npm, PyPI, pub.dev, Composer, Cargo, NuGet, and Conda. These ecosystems include publish timestamps in their metadata.
+Currently supported for npm, PyPI, pub.dev, Composer, Cargo, NuGet, Conda, and RubyGems. These ecosystems include publish timestamps in their metadata.
 
 ## Docker
 

internal/handler/gem.go

@@ -1,10 +1,15 @@
 package handler
 
 import (
+	"bufio"
+	"encoding/json"
 	"fmt"
 	"io"
 	"net/http"
 	"strings"
+	"time"
+
+	"github.com/git-pkgs/purl"
 )
 
 const (
@@ -41,7 +46,7 @@ func (h *GemHandler) Routes() http.Handler {
 
 	// Compact index (bundler 2.x+)
 	mux.HandleFunc("GET /versions", h.proxyUpstream)
-	mux.HandleFunc("GET /info/{name}", h.proxyUpstream)
+	mux.HandleFunc("GET /info/{name}", h.handleCompactIndex)
 
 	// Quick index
 	mux.HandleFunc("GET /quick/Marshal.4.8/{filename}", h.proxyUpstream)
@@ -98,6 +103,191 @@ func (h *GemHandler) parseGemFilename(filename string) (name, version string) {
 	return "", ""
 }
 
+// handleCompactIndex serves the compact index for a gem, filtering versions
+// based on cooldown when enabled.
+func (h *GemHandler) handleCompactIndex(w http.ResponseWriter, r *http.Request) {
+	if h.proxy.Cooldown == nil || !h.proxy.Cooldown.Enabled() {
+		h.proxyUpstream(w, r)
+		return
+	}
+
+	name := r.PathValue("name")
+	if name == "" {
+		http.Error(w, "invalid gem name", http.StatusBadRequest)
+		return
+	}
+
+	h.proxy.Logger.Info("gem compact index request with cooldown", "name", name)
+
+	indexResp, filteredVersions, err := h.fetchIndexAndVersions(r, name)
+	if err != nil {
+		h.proxy.Logger.Error("upstream compact index request failed", "error", err)
+		http.Error(w, "upstream request failed", http.StatusBadGateway)
+		return
+	}
+	defer func() { _ = indexResp.Body.Close() }()
+
+	if indexResp.StatusCode != http.StatusOK {
+		copyResponseHeaders(w, indexResp.Header)
+		w.WriteHeader(indexResp.StatusCode)
+		_, _ = io.Copy(w, indexResp.Body)
+		return
+	}
+
+	if filteredVersions == nil {
+		h.proxy.Logger.Warn("failed to fetch version timestamps, proxying unfiltered", "name", name)
+		copyResponseHeaders(w, indexResp.Header)
+		w.WriteHeader(http.StatusOK)
+		_, _ = io.Copy(w, indexResp.Body)
+		return
+	}
+
+	h.writeFilteredIndex(w, indexResp, name, filteredVersions)
+}
+
+// fetchIndexAndVersions fetches the compact index and versions API concurrently.
+// Returns the index response, a set of versions to filter (nil if versions API failed),
+// and an error if the index fetch itself failed.
+func (h *GemHandler) fetchIndexAndVersions(r *http.Request, name string) (*http.Response, map[string]bool, error) {
+	type versionsResult struct {
+		filtered map[string]bool
+		err      error
+	}
+
+	versionsCh := make(chan versionsResult, 1)
+	go func() {
+		filtered, err := h.fetchFilteredVersions(r, name)
+		versionsCh <- versionsResult{filtered: filtered, err: err}
+	}()
+
+	indexResp, err := h.fetchCompactIndex(r, name)
+
+	versionsRes := <-versionsCh
+
+	if err != nil {
+		return nil, nil, err
+	}
+
+	if versionsRes.err != nil {
+		return indexResp, nil, nil
+	}
+
+	return indexResp, versionsRes.filtered, nil
+}
+
+// fetchCompactIndex fetches the compact index from upstream.
+func (h *GemHandler) fetchCompactIndex(r *http.Request, name string) (*http.Response, error) {
+	indexURL := h.upstreamURL + "/info/" + name
+	req, err := http.NewRequestWithContext(r.Context(), http.MethodGet, indexURL, nil)
+	if err != nil {
+		return nil, err
+	}
+	for _, hdr := range []string{"Accept", "Accept-Encoding", "If-None-Match", "If-Modified-Since"} {
+		if v := r.Header.Get(hdr); v != "" {
+			req.Header.Set(hdr, v)
+		}
+	}
+	return h.proxy.HTTPClient.Do(req)
+}
+
+// writeFilteredIndex writes the compact index response with cooldown-filtered versions removed.
+func (h *GemHandler) writeFilteredIndex(w http.ResponseWriter, resp *http.Response, name string, filtered map[string]bool) {
+	for k, vv := range resp.Header {
+		if strings.EqualFold(k, "Content-Length") {
+			continue // length will change after filtering
+		}
+		for _, v := range vv {
+			w.Header().Add(k, v)
+		}
+	}
+	w.WriteHeader(http.StatusOK)
+
+	scanner := bufio.NewScanner(resp.Body)
+	for scanner.Scan() {
+		line := scanner.Text()
+
+		if line == "---" {
+			_, _ = fmt.Fprintln(w, line)
+			continue
+		}
+
+		version := line
+		if spaceIdx := strings.IndexByte(line, ' '); spaceIdx > 0 {
+			version = line[:spaceIdx]
+		}
+
+		if filtered[version] {
+			h.proxy.Logger.Info("cooldown: filtering gem version",
+				"gem", name, "version", version)
+			continue
+		}
+
+		_, _ = fmt.Fprintln(w, line)
+	}
+}
+
+// copyResponseHeaders copies HTTP headers from a response to a writer.
+func copyResponseHeaders(w http.ResponseWriter, headers http.Header) {
+	for k, vv := range headers {
+		for _, v := range vv {
+			w.Header().Add(k, v)
+		}
+	}
+}
+
+// gemVersion represents a version entry from the RubyGems versions API.
+type gemVersion struct {
+	Number    string `json:"number"`
+	Platform  string `json:"platform"`
+	CreatedAt string `json:"created_at"`
+}
+
+// fetchFilteredVersions fetches the versions API and returns a set of version
+// strings that should be filtered out by cooldown.
+func (h *GemHandler) fetchFilteredVersions(r *http.Request, name string) (map[string]bool, error) {
+	versionsURL := fmt.Sprintf("%s/api/v1/versions/%s.json", h.upstreamURL, name)
+	req, err := http.NewRequestWithContext(r.Context(), http.MethodGet, versionsURL, nil)
+	if err != nil {
+		return nil, err
+	}
+
+	resp, err := h.proxy.HTTPClient.Do(req)
+	if err != nil {
+		return nil, err
+	}
+	defer func() { _ = resp.Body.Close() }()
+
+	if resp.StatusCode != http.StatusOK {
+		return nil, fmt.Errorf("versions API returned %d", resp.StatusCode)
+	}
+
+	var versions []gemVersion
+	if err := json.NewDecoder(resp.Body).Decode(&versions); err != nil {
+		return nil, err
+	}
+
+	packagePURL := purl.MakePURLString("gem", name, "")
+	filtered := make(map[string]bool)
+
+	for _, v := range versions {
+		createdAt, err := time.Parse(time.RFC3339, v.CreatedAt)
+		if err != nil {
+			continue
+		}
+
+		if !h.proxy.Cooldown.IsAllowed("gem", packagePURL, createdAt) {
+			// Build version string matching compact index format
+			versionStr := v.Number
+			if v.Platform != "" && v.Platform != "ruby" {
+				versionStr = v.Number + "-" + v.Platform
+			}
+			filtered[versionStr] = true
+		}
+	}
+
+	return filtered, nil
+}
+
 // proxyUpstream forwards a request to rubygems.org without caching.
 func (h *GemHandler) proxyUpstream(w http.ResponseWriter, r *http.Request) {
 	upstreamURL := h.upstreamURL + r.URL.Path