execute template w queries

cmd/pinger/main.go

@@ -1,6 +1,10 @@
 package main
 
 import (
+	_ "embed"
+	"html/template"
+	"net/http"
+
 	"context"
 	"database/sql"
 	"flag"
@@ -73,8 +77,68 @@ func (s S) init(ctx context.Context) error {
 	return ctx.Err()
 }
 
-func (S) listen(ctx context.Context) error {
-	return ctx.Err()
+//go:embed index.html.tmpl
+var IndexTemplate string
+
+func (s S) listen(ctx context.Context) error {
+	t := template.New("template")
+	t.Funcs(map[string]any{
+		"query": func(q string) ([]map[string]any, error) {
+			rows, err := s.QueryContext(ctx, q)
+			if err != nil {
+				return nil, err
+			}
+			defer rows.Close()
+
+			columns, err := rows.Columns()
+			if err != nil {
+				return nil, err
+			}
+
+			results := []map[string]any{}
+			for rows.Next() {
+				var scanners []any
+				for range columns {
+					var a any
+					scanners = append(scanners, &a)
+				}
+				if err := rows.Scan(scanners...); err != nil {
+					return nil, err
+				}
+				result := map[string]any{}
+				for i, column := range columns {
+					result[column] = scanners[i]
+				}
+				results = append(results, result)
+			}
+
+			return results, rows.Err()
+		},
+	})
+	t, err := t.Parse(IndexTemplate)
+	if err != nil {
+		return err
+	}
+
+	server := &http.Server{
+		Addr: ":10000",
+		Handler: http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+			if err := t.Execute(w, map[string]any{
+				"DB": s.DB,
+			}); err != nil {
+				http.Error(w, err.Error(), http.StatusInternalServerError)
+			}
+		}),
+	}
+	go func() {
+		<-ctx.Done()
+		server.Close()
+	}()
+
+	if err := server.ListenAndServe(); err != nil && ctx.Err() == nil {
+		return err
+	}
+	return nil
 }
 
 func (s S) pingAndRecord(ctx context.Context) error {