Content Filters Pipeline

sequenceDiagram participant Browser participant Middleware participant Controller participant LangResolver as LanguageResolver participant Resource participant Pipeline as FilterPipeline participant Segmenter as HtmlSegmenter participant GCache as GlossaryConceptCache participant DB as MySQL Browser->>Middleware: GET /api/v1/courses/{id}/lessons/{id}/pages/{id} Middleware->>Controller: Authenticated + throttle passes note over Controller: Injected: FilterPipelineInterface + LanguageResolver Controller->>Controller: lessonService.showPage(dto) Controller->>Resource: new LessonPageResource(page) Controller->>Resource: withPluginfileResolution(resolver, courseId) note over Resource: @@PLUGINFILE@@ tokens resolved to real URLs Controller->>Resource: withFilters(pipeline, languageResolver, courseId) Controller->>Resource: toResponse(request) Resource->>Resource: toArray(request) — applyFilters(contents, format, req) Resource->>LangResolver: resolve(moodleUser) LangResolver-->>Resource: "en" via 3-step chain Resource->>Resource: new FilterContext(courseId, userId, "en", TextFormat::Html) Resource->>Pipeline: process(html, context) Pipeline->>Pipeline: MultilangFilter.apply — strip non-matching lang spans Pipeline->>Segmenter: walk(html, urlToLink transform) Segmenter-->>Pipeline: URL-linked text (skips inside a, .nolink) Pipeline->>Segmenter: walk(html, emoticon transform) Segmenter-->>Pipeline: emoticon span placeholders Pipeline->>Pipeline: MediapluginFilter.apply — a href mp4 to video tag Pipeline->>Pipeline: DisplayH5pFilter.apply — H5P URL to div placeholder Pipeline->>GCache: forCourse(courseId) GCache->>DB: SELECT glossary_entries (if cache miss, TTL 300s) DB-->>GCache: concept rows GCache-->>Pipeline: Collection of GlossaryConceptDTO Pipeline->>Segmenter: walk(html, glossary link transform) Segmenter-->>Pipeline: auto-linked glossary terms Pipeline->>Pipeline: AlgebraFilter.apply — @@expr@@ to LaTeX Pipeline->>Pipeline: TexFilter.apply — normalise TeX delimiters Pipeline->>Segmenter: walk(html, mathjax wrap transform) Segmenter-->>Pipeline: span.filter_mathjax_equation wrapped Pipeline-->>Resource: filtered HTML string Resource-->>Controller: array with filtered fields Controller-->>Browser: 200 JSON with filtered contents

flowchart TD A([HTTP Request]) --> B{Auth middleware} B -- 401 --> ERR1([401 Unauthorized]) B -- passes --> C[Controller method] C --> D[Service: fetch Moodle data from DB] D -- not found --> ERR2([404 Not Found]) D -- found --> E[Build Resource object] E --> F[withPluginfileResolution called first] F --> G[Resolve all PLUGINFILE tokens to real URLs] G --> H{withFilters called?} H -- No --> SKIP[Return raw field value as-is] SKIP --> RESP H -- Yes --> I[applyFilters in toArray] I --> J{text null or empty?} J -- Yes --> SKIP2[Return null or empty] J -- No --> K[Build FilterContext: courseId userId language format] K --> L[FilterPipeline::process] L --> M[MultilangFilter: strip non-matching lang spans] M --> N[UrlToLinkFilter via HtmlSegmenter: wrap bare URLs in anchor] N --> O[EmoticonFilter via HtmlSegmenter: replace codes with span] O --> P[MediapluginFilter: convert audio/video anchors to HTML5 tags] P --> Q[DisplayH5pFilter: convert H5P URL to div placeholder] Q --> R{GlossaryConceptCache: forCourse} R -- cache hit --> S[GlossaryFilter via HtmlSegmenter: auto-link terms] R -- cache miss --> T[DB: load approved glossary entries and aliases] T --> U[Cache result for TTL seconds] U --> S S --> V[AlgebraFilter: normalise algebra syntax to LaTeX] V --> W[TexFilter: normalise all TeX delimiters to standard form] W --> X[MathjaxFilter via HtmlSegmenter: wrap LaTeX in span] X --> RESP RESP([filtered HTML returned to resource]) --> JSON([200 JSON Response]) style ERR1 fill:#ef4444,color:#fff,stroke:none style ERR2 fill:#ef4444,color:#fff,stroke:none style SKIP fill:#1a1d27,color:#64748b,stroke:#2a2d3e style SKIP2 fill:#1a1d27,color:#64748b,stroke:#2a2d3e style JSON fill:#10b981,color:#fff,stroke:none