| 1 | # frozen_string_literal: true |
| 2 | |
| 3 | # Serves the Open Graph share-card PNGs referenced by the OG/Twitter meta tags. |
| 4 | # |
| 5 | # Cards are cached by content hash (OgImageService never runs on the hot path |
| 6 | # when a cached card exists) and answered with a long-lived, public, ETag'd |
| 7 | # response so crawlers and CDNs only fetch bytes once. Private repositories are |
| 8 | # never rendered — the endpoint 404s so no preview can leak. |
| 9 | class OgImagesController < ApplicationController |
| 10 | CACHE_TTL = 7.days |
| 11 | FALLBACK_IMAGE = "favicon/web-app-manifest-512x512.png" |
| 12 | FALLBACK_CACHE_TTL = 5.minutes |
| 13 | |
| 14 | # GET /og/:username/:repository.png |
| 15 | def show |
| 16 | repository = public_repository |
| 17 | return head :not_found unless repository |
| 18 | |
| 19 | serve_card("#{OgImageService::TEMPLATE_VERSION}-#{repository.og_version}") do |
| 20 | OgImageService.render(repository: repository) |
| 21 | end |
| 22 | end |
| 23 | |
| 24 | # GET /og.png — the generic sitewide card (default og:image). |
| 25 | def default |
| 26 | serve_card("#{OgImageService::TEMPLATE_VERSION}-default") do |
| 27 | OgImageService.render_default |
| 28 | end |
| 29 | end |
| 30 | |
| 31 | private |
| 32 | |
| 33 | def public_repository |
| 34 | owner = User.find_by(username: params[:username]) |
| 35 | return nil unless owner |
| 36 | |
| 37 | repository = owner.repositories.find_by(name: params[:repository]) |
| 38 | return nil if repository.nil? || repository.is_private |
| 39 | |
| 40 | repository |
| 41 | end |
| 42 | |
| 43 | # Conditional-GET + cache wrapper. Yields the PNG bytes only on a cache miss; |
| 44 | # on any rendering failure (e.g. libvips missing) falls back to a static image |
| 45 | # with a short TTL so the failure self-heals. |
| 46 | def serve_card(version) |
| 47 | return unless stale?(etag: version, public: true) |
| 48 | |
| 49 | png = Rails.cache.fetch([ "og", version ], expires_in: CACHE_TTL) { yield } |
| 50 | expires_in CACHE_TTL, public: true |
| 51 | send_data png, type: "image/png", disposition: "inline" |
| 52 | rescue StandardError => e |
| 53 | Rails.logger.warn("[OG] falling back to static card: #{e.class}: #{e.message}") |
| 54 | expires_in FALLBACK_CACHE_TTL, public: true |
| 55 | send_file Rails.public_path.join(FALLBACK_IMAGE), type: "image/png", disposition: "inline" |
| 56 | end |
| 57 | end |