nix/coverage-html: generate badge

nix/coverage-html.nix

@@ -6,6 +6,8 @@
   cmocka,
   libllvm,
   pkg-config,
+  htmlq,
+  anybadge,
 }:
 stdenv.mkDerivation {
   pname = "where-are-my-friends-coverage-html";
@@ -25,8 +27,10 @@ stdenv.mkDerivation {
   };
 
   nativeBuildInputs = [
-    libllvm
     pkg-config
+    libllvm
+    htmlq
+    anybadge
   ];
   buildInputs = [ cmocka ];
 
@@ -55,6 +59,28 @@ stdenv.mkDerivation {
 
     llvm-cov show "''${LLVM_COV_ARGS[@]}"
 
+    TOTAL_COVERAGE="$(
+      htmlq 'td > pre' <coverage-html/index.html \
+      | sed '0,/^<pre>Totals<\/pre>$/d' \
+      | head -n 1 \
+      | sed -e 's/<pre>[[:space:]]*//' -e 's/%.*$/%/' \
+    )"
+
+    if [[ "$TOTAL_COVERAGE" == *% ]]; then
+      COVERAGE_VALUE="''${TOTAL_COVERAGE%\%}"
+      if [[ "$COVERAGE_VALUE" -ge 80 ]]; then
+        COLOR="green"
+      elif [[ "$COVERAGE_VALUE" -ge 50 ]]; then
+        COLOR="yellow"
+      else
+        COLOR="red"
+      fi
+    else
+      COLOR="lightgrey"
+    fi
+
+    anybadge --label "coverage" --value "$TOTAL_COVERAGE" --color "$COLOR" > coverage-html/coverage.svg
+
     runHook postBuild
   '';