resolves #50: badge url

Implements serving of an SVG badge at the url /badge/JOB.svg which
prettily shows the job's current status

UserManual.md

@@ -542,6 +542,18 @@ This directory is also a good place to add any extra assets needed for this cust
 
 ---
 
+# Badges
+
+Laminar will serve a job's current status as a pretty badge at the url `/badge/JOBNAME.svg`. This can be used as a link to your server instance from your Github README.md file or cat blog:
+
+```
+<a href="https://my-example-laminar-server.com/jobs/my-project">
+  <img src="https://my-example-laminar-server.com/badge/my-project.svg">
+</a>
+```
+
+---
+
 # Reference
 
 ## Service configuration file

src/interface.h

@@ -135,6 +135,11 @@ struct LaminarInterface {
     // proper web server which handles this url.
     virtual kj::Own<MappedFile> getArtefact(std::string path) = 0;
 
+    // Given the name of a job, populate the provided string reference with
+    // SVG content describing the last known state of the job. Returns false
+    // if the job is unknown.
+    virtual bool handleBadgeRequest(std::string job, std::string& badge) = 0;
+
     // Fetches the content of $LAMINAR_HOME/custom/style.css or an empty
     // string. Ideally, this would instead be served by a proper web server
     // which handles this url.

src/laminar.cpp

@@ -924,6 +924,48 @@ kj::Own<MappedFile> Laminar::getArtefact(std::string path) {
     return kj::heap<MappedFileImpl>(fs::path(fs::path(homeDir)/"archive"/path).c_str());
 }
 
+bool Laminar::handleBadgeRequest(std::string job, std::string &badge) {
+    RunState rs = RunState::UNKNOWN;
+    db->stmt("SELECT result FROM builds WHERE name = ? ORDER BY number DESC LIMIT 1")
+            .bind(job)
+            .fetch<int>([&](int result){
+        rs = (RunState) result;
+    });
+    if(rs == RunState::UNKNOWN)
+        return false;
+
+    std::string status = to_string(rs);
+    // Empirical approximation of pixel width. Not particularly stable.
+    const int jobNameWidth = job.size() * 7 + 10;
+    const int statusWidth = status.size() * 7 + 10;
+    const char* gradient1 = (rs == RunState::SUCCESS) ? "#2aff4d" : "#ff2a2a";
+    const char* gradient2 = (rs == RunState::SUCCESS) ? "#24b43c" : "#b42424";
+    char* svg = NULL;
+    asprintf(&svg,
+R"x(
+<svg xmlns="http://www.w3.org/2000/svg">
+  <clipPath id="clip">
+    <rect width="%d" height="20" rx="4"/>
+  </clipPath>
+  <linearGradient id="job" x1="0" x2="0" y1="0" y2="1">
+    <stop offset="0" stop-color="#666" />
+    <stop offset="1" stop-color="#333" />
+  </linearGradient>
+  <linearGradient id="status" x1="0" x2="0" y1="0" y2="1">
+    <stop offset="0" stop-color="%s" />
+    <stop offset="1" stop-color="%s" />
+  </linearGradient>
+  <g clip-path="url(#clip)" font-family="DejaVu Sans,Verdana,sans-serif" font-size="12" text-anchor="middle">
+    <rect width="%d" height="20" fill="url(#job)"/>
+    <text x="%d" y="14" fill="#fff">%s</text>
+    <rect x="%d" width="%d" height="20" fill="url(#status)"/>
+    <text x="%d" y="14" fill="#000">%s</text>
+  </g>
+</svg>)x", jobNameWidth+statusWidth, gradient1, gradient2, jobNameWidth, jobNameWidth/2+1, job.data(), jobNameWidth, statusWidth, jobNameWidth+statusWidth/2, status.data());
+    badge = svg;
+    return true;
+}
+
 std::string Laminar::getCustomCss() {
     MappedFileImpl cssFile(fs::path(fs::path(homeDir)/"custom"/"style.css").c_str());
     if(cssFile.address()) {

src/laminar.h

@@ -56,6 +56,7 @@ public:
     void sendStatus(LaminarClient* client) override;
     bool setParam(std::string job, uint buildNum, std::string param, std::string value) override;
     kj::Own<MappedFile> getArtefact(std::string path) override;
+    bool handleBadgeRequest(std::string job, std::string& badge) override;
     std::string getCustomCss() override;
     void abortAll() override;
     void notifyConfigChanged() override;

src/server.cpp

@@ -311,6 +311,7 @@ private:
         } else {
             // handle regular HTTP request
             const char* start, *end, *content_type;
+            std::string badge;
             responseHeaders.clear();
             if(resource.compare(0, strlen("/archive/"), "/archive/") == 0) {
                 kj::Own<MappedFile> file = laminar.getArtefact(resource.substr(strlen("/archive/")));
@@ -331,6 +332,11 @@ private:
                 responseHeaders.add("Content-Transfer-Encoding", "binary");
                 auto stream = response.send(200, "OK", responseHeaders, end-start);
                 return stream->write(start, end-start).attach(kj::mv(stream));
+            } else if(url.startsWith("/badge/") && url.endsWith(".svg") && laminar.handleBadgeRequest(resource.substr(7,resource.length()-11), badge)) {
+                responseHeaders.set(kj::HttpHeaderId::CONTENT_TYPE, "image/svg+xml");
+                responseHeaders.add("Cache-Control", "no-cache");
+                auto stream = response.send(200, "OK", responseHeaders, badge.size());
+                return stream->write(badge.data(), badge.size()).attach(kj::mv(badge)).attach(kj::mv(stream));
             }
             return response.sendError(404, "Not Found", responseHeaders);
         }

test/test-server.cpp

@@ -65,6 +65,7 @@ public:
     MOCK_METHOD1(sendStatus, void(LaminarClient* client));
     MOCK_METHOD4(setParam, bool(std::string job, uint buildNum, std::string param, std::string value));
     MOCK_METHOD0(getCustomCss, std::string());
+    MOCK_METHOD2(handleBadgeRequest, bool(std::string, std::string&));
     MOCK_METHOD0(abortAll, void());
     MOCK_METHOD0(notifyConfigChanged, void());
 };