Pageview times experiment (#69)

* experiment: track pageview times

* strictly respect do not track

* oops

* asdfasdfasdf

* add blogpost

* fix typos oops

2 files changed, 54 insertions, 0 deletions

diff --git a/cmd/site/main.go b/cmd/site/main.go
index b7774b1..04d8bc4 100644
--- a/cmd/site/main.go
+++ b/cmd/site/main.go
@@ -223,6 +223,7 @@ func Build() (*Site, error) {
 		w.Header().Set("Content-Type", "application/xml")
 		_, _ = smi.WriteTo(w)
 	})))
+	s.mux.HandleFunc("/api/pageview-timer", handlePageViewTimer)
 
 	return s, nil
 }
diff --git a/cmd/site/pageview.go b/cmd/site/pageview.go
new file mode 100644
index 0000000..5154659
--- /dev/null
+++ b/cmd/site/pageview.go
@@ -0,0 +1,53 @@
+package main
+
+import (
+	"encoding/json"
+	"io/ioutil"
+	"net/http"
+	"time"
+
+	"github.com/prometheus/client_golang/prometheus"
+	"within.website/ln"
+)
+
+var (
+	readTimes = prometheus.NewHistogramVec(prometheus.HistogramOpts{
+		Name: "blogpage_read_times",
+		Help: "This tracks how much time people spend reading articles on my blog",
+	}, []string{"path"})
+)
+
+func init() {
+	_ = prometheus.Register(readTimes)
+}
+
+func handlePageViewTimer(w http.ResponseWriter, r *http.Request) {
+	if r.Header.Get("DNT") == "1" {
+		http.NotFound(w, r)
+		return
+	}
+
+	data, err := ioutil.ReadAll(r.Body)
+	if err != nil {
+		ln.Error(r.Context(), err, ln.Info("while reading data"))
+		http.Error(w, "oopsie whoopsie uwu", http.StatusInternalServerError)
+		return
+	}
+	r.Body.Close()
+
+	type metricsData struct {
+		Path      string    `json:"path"`
+		StartTime time.Time `json:"start_time"`
+		EndTime   time.Time `json:"end_time"`
+	}
+	var md metricsData
+	err = json.Unmarshal(data, &md)
+	if err != nil {
+		http.NotFound(w, r)
+		return
+	}
+
+	diff := md.EndTime.Sub(md.StartTime).Seconds()
+
+	readTimes.WithLabelValues(md.Path).Observe(float64(diff))
+}