split wasm filter (#186)

* split wasm filter

* fix int and unit tests

* rename public_types => common and move common code there

* rename

* fix int test

crates/common/src/stats.rs

@@ -0,0 +1,103 @@
+use log::error;
+use proxy_wasm::hostcalls;
+use proxy_wasm::types::*;
+
+#[allow(unused)]
+pub trait Metric {
+    fn id(&self) -> u32;
+    fn value(&self) -> Result<u64, String> {
+        match hostcalls::get_metric(self.id()) {
+            Ok(value) => Ok(value),
+            Err(Status::NotFound) => Err(format!("metric not found: {}", self.id())),
+            Err(err) => Err(format!("unexpected status: {:?}", err)),
+        }
+    }
+}
+
+#[allow(unused)]
+pub trait IncrementingMetric: Metric {
+    fn increment(&self, offset: i64) {
+        match hostcalls::increment_metric(self.id(), offset) {
+            Ok(_) => (),
+            Err(err) => error!("error incrementing metric: {:?}", err),
+        }
+    }
+}
+
+#[allow(unused)]
+pub trait RecordingMetric: Metric {
+    fn record(&self, value: u64) {
+        match hostcalls::record_metric(self.id(), value) {
+            Ok(_) => (),
+            Err(err) => error!("error recording metric: {:?}", err),
+        }
+    }
+}
+
+#[derive(Copy, Clone, Debug)]
+pub struct Counter {
+    id: u32,
+}
+
+#[allow(unused)]
+impl Counter {
+    pub fn new(name: String) -> Counter {
+        let returned_id = hostcalls::define_metric(MetricType::Counter, &name)
+            .expect("failed to define counter '{}', name");
+        Counter { id: returned_id }
+    }
+}
+
+impl Metric for Counter {
+    fn id(&self) -> u32 {
+        self.id
+    }
+}
+
+impl IncrementingMetric for Counter {}
+
+#[derive(Copy, Clone, Debug)]
+pub struct Gauge {
+    id: u32,
+}
+
+impl Gauge {
+    pub fn new(name: String) -> Gauge {
+        let returned_id = hostcalls::define_metric(MetricType::Gauge, &name)
+            .expect("failed to define gauge '{}', name");
+        Gauge { id: returned_id }
+    }
+}
+
+impl Metric for Gauge {
+    fn id(&self) -> u32 {
+        self.id
+    }
+}
+
+/// For state of the world updates
+impl RecordingMetric for Gauge {}
+/// For offset deltas
+impl IncrementingMetric for Gauge {}
+
+#[derive(Copy, Clone)]
+pub struct Histogram {
+    id: u32,
+}
+
+#[allow(unused)]
+impl Histogram {
+    pub fn new(name: String) -> Histogram {
+        let returned_id = hostcalls::define_metric(MetricType::Histogram, &name)
+            .expect("failed to define histogram '{}', name");
+        Histogram { id: returned_id }
+    }
+}
+
+impl Metric for Histogram {
+    fn id(&self) -> u32 {
+        self.id
+    }
+}
+
+impl RecordingMetric for Histogram {}