server: chart of humidity vs time

6 files changed, 77 insertions, 15 deletions

diff --git a/server/building.go b/server/building.go
index 8772374..e275c65 100644
--- a/server/building.go
+++ b/server/building.go
@@ -23,10 +23,10 @@ func (b Building) average() (Humidity, bool) {
 	var sum Humidity = 0
 	nRooms := 0
 	for room, record := range b {
-		c := make(chan Humidity)
+		c := make(chan Entry[Humidity])
 		record.getRecent <- c
-		if humidity, ok := <-c; ok {
-			sum += humidity
+		if e, ok := <-c; ok {
+			sum += e.v
 			nRooms++
 		} else {
 			log.Printf("Warning: no humidity for room '%s'\n", room)
diff --git a/server/chart.go b/server/chart.go
new file mode 100644
index 0000000..1f20d3c
--- /dev/null
+++ b/server/chart.go
@@ -0,0 +1,55 @@
+package main
+
+import (
+	"log"
+	"net/http"
+	"fmt"
+	"time"
+	"github.com/wcharczuk/go-chart/v2"
+)
+
+type ChartHandler struct {
+	building Building
+}
+
+func (h ChartHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
+	log.Println(r.Method, r.URL)
+
+	if r.Method != http.MethodGet {
+		w.WriteHeader(http.StatusMethodNotAllowed)
+		fmt.Fprintf(w, "invalid method: '%s'", r.Method)
+		return
+	}
+
+	var series []chart.Series
+	for room, record := range h.building {
+		var x []time.Time
+		var y []float64
+		c := make(chan Entry[Humidity])
+		record.get <- c
+		for e := range c {
+			x = append(x, e.t)
+			y = append(y, float64(e.v))
+		}
+		series = append(series, chart.TimeSeries{
+			Name: string(room),
+			XValues: x,
+			YValues: y,
+		})
+	}
+
+	graph := chart.Chart{
+		Background: chart.Style{
+			Padding: chart.Box{Top: 20, Left: 20},
+		},
+		Series: series,
+	}
+	graph.Elements = []chart.Renderable{
+		chart.Legend(&graph),
+	}
+
+	w.Header().Set("Content-Type", "image/png")
+	if err := graph.Render(chart.PNG, w); err != nil {
+		log.Println(err)
+	}
+}
diff --git a/server/dashboard.go b/server/dashboard.go
index 48a9423..1dca024 100644
--- a/server/dashboard.go
+++ b/server/dashboard.go
@@ -65,10 +65,12 @@ func (h DashboardHandler) buildDashboard() Dashboard {
 
 	rooms := make(map[RoomID]Humidity)
 	for id, record := range h.building {
-		c := make(chan Humidity)
+		c := make(chan Entry[Humidity])
 		record.getRecent <- c
-		humidity, ok := <-c
-		if !ok {
+		var humidity Humidity
+		if e, ok := <-c; ok {
+			humidity = e.v
+		} else {
 			humidity = -1
 		}
 		rooms[id] = humidity
diff --git a/server/dashboard.html b/server/dashboard.html
index 23e1d97..50ad682 100644
--- a/server/dashboard.html
+++ b/server/dashboard.html
@@ -21,6 +21,7 @@
 				unknown
 			{{- end -}}
 		</p>
+
 		<table>
 			<tr><th>Room</th><th>Humidity</th></tr>
 			{{ range $id, $humidity := .Rooms }}
@@ -37,5 +38,8 @@
 				</tr>
 			{{ end }}
 		</table>
+
+		<h4 style="text-align: center;">Humidity per Room vs. Time</h4>
+		<img src="/chart.png" alt="chart of humidity vs time"/>
 	</body>
 </html>
diff --git a/server/record.go b/server/record.go
index c2f38eb..407dcd7 100644
--- a/server/record.go
+++ b/server/record.go
@@ -6,11 +6,11 @@ import (
 
 type Record[T any] struct {
 	put       chan<- T
-	get       chan<- chan T
-	getRecent chan<- chan T
+	get       chan<- chan Entry[T]
+	getRecent chan<- chan Entry[T]
 }
 
-type entry[T any] struct {
+type Entry[T any] struct {
 	t time.Time
 	v T
 }
@@ -19,11 +19,11 @@ type entry[T any] struct {
 // If the capacity is exceeded, old entires will be discarded and new ones kept.
 func newRecord[T any](capacity int) Record[T] {
 	put := make(chan T)
-	get := make(chan chan T)
-	getRecent := make(chan chan T)
+	get := make(chan chan Entry[T])
+	getRecent := make(chan chan Entry[T])
 
 	go func() {
-		entries := make([]entry[T], 0, capacity)
+		entries := make([]Entry[T], 0, capacity)
 
 		for {
 			select {
@@ -31,7 +31,7 @@ func newRecord[T any](capacity int) Record[T] {
 				if !ok {
 					return
 				}
-				entries = append(entries, entry[T]{time.Now(), v})
+				entries = append(entries, Entry[T]{time.Now(), v})
 				if len(entries) > capacity {
 					entries = entries[1:]
 				}
@@ -40,7 +40,7 @@ func newRecord[T any](capacity int) Record[T] {
 					return
 				}
 				for _, e := range entries {
-					c <- e.v
+					c <- e
 				}
 				close(c)
 			case c, ok := <-getRecent:
@@ -48,7 +48,7 @@ func newRecord[T any](capacity int) Record[T] {
 					return
 				}
 				if len(entries) > 0 {
-					c <- entries[len(entries)-1].v
+					c <- entries[len(entries)-1]
 				}
 				close(c)
 			}
diff --git a/server/server.go b/server/server.go
index 4ef5151..8cfb1b0 100644
--- a/server/server.go
+++ b/server/server.go
@@ -33,6 +33,7 @@ func main() {
 	http.Handle("/humidity", HumidityHandler{building})
 	http.Handle("/target_humidity", TargetHumidityHandler{target})
 	http.Handle("/duty_cycle", DutyCycleHandler{dutyCycle})
+	http.Handle("/chart.png", ChartHandler{building})
 
 	fmt.Printf("Listening on %s...\n", addr)
 	log.Fatal(http.ListenAndServe(addr, nil))