1 files changed, 137 insertions, 0 deletions
diff --git a/src/Controllers/Metrics/MetricsEngine.php b/src/Controllers/Metrics/MetricsEngine.php
new file mode 100644
index 00000000..eeb47d8a
--- /dev/null
+++ b/src/Controllers/Metrics/MetricsEngine.php
@@ -0,0 +1,137 @@
+<?php
+
+namespace Engelsystem\Controllers\Metrics;
+
+use Engelsystem\Renderer\EngineInterface;
+
+class MetricsEngine implements EngineInterface
+{
+    /**
+     * Render metrics
+     *
+     * @example $data = ['foo' => [['labels' => ['foo'=>'bar'], 'value'=>42]], 'bar'=>123]
+     *
+     * @param string  $path
+     * @param mixed[] $data
+     * @return string
+     */
+    public function get($path, $data = []): string
+    {
+        $return = [];
+        foreach ($data as $name => $list) {
+            if (is_int($name)) {
+                $return[] = '# ' . $this->escape($list);
+                continue;
+            }
+
+            $list = is_array($list) ? $list : [$list];
+            $name = 'engelsystem_' . $name;
+
+            if (isset($list['help'])) {
+                $return[] = sprintf('# HELP %s %s', $name, $this->escape($list['help']));
+                unset($list['help']);
+            }
+
+            if (isset($list['type'])) {
+                $return[] = sprintf('# TYPE %s %s', $name, $list['type']);
+                unset($list['type']);
+            }
+
+            $list = (!isset($list['value']) || !isset($list['labels'])) ? $list : [$list];
+            foreach ($list as $row) {
+                $row = is_array($row) ? $row : [$row];
+
+                $return[] = $this->formatData($name, $row);
+            }
+        }
+
+        return implode("\n", $return);
+    }
+
+    /**
+     * @param string $path
+     * @return bool
+     */
+    public function canRender($path): bool
+    {
+        return $path == '/metrics';
+    }
+
+    /**
+     * @param string      $name
+     * @param array|mixed $row
+     * @see https://prometheus.io/docs/instrumenting/exposition_formats/
+     * @return string
+     */
+    protected function formatData($name, $row): string
+    {
+        return sprintf(
+            '%s%s %s',
+            $name,
+            $this->renderLabels($row),
+            $this->renderValue($row));
+    }
+
+    /**
+     * @param array|mixed $row
+     * @return mixed
+     */
+    protected function renderLabels($row): string
+    {
+        $labels = [];
+        if (!is_array($row) || empty($row['labels'])) {
+            return '';
+        }
+
+        foreach ($row['labels'] as $type => $value) {
+            $labels[$type] = $type . '="' . $this->formatValue($value) . '"';
+        }
+
+        return '{' . implode(',', $labels) . '}';
+    }
+
+    /**
+     * @param array|mixed $row
+     * @return mixed
+     */
+    protected function renderValue($row)
+    {
+        if (isset($row['value'])) {
+            return $this->formatValue($row['value']);
+        }
+
+        return $this->formatValue(array_pop($row));
+    }
+
+    /**
+     * @param mixed $value
+     * @return mixed
+     */
+    protected function formatValue($value)
+    {
+        if (is_bool($value)) {
+            return (int)$value;
+        }
+
+        return $this->escape($value);
+    }
+
+    /**
+     * @param mixed $value
+     * @return mixed
+     */
+    protected function escape($value)
+    {
+        $replace = [
+            '\\' => '\\\\',
+            '"'  => '\\"',
+            "\n" => '\\n',
+        ];
+
+        return str_replace(
+            array_keys($replace),
+            array_values($replace),
+            $value
+        );
+    }
+}