collector: refactor metrics handler (#1773)

Signed-off-by: Jan-Otto Kröpke <mail@jkroepke.de>

pkg/collector/handler.go

@@ -0,0 +1,62 @@
+// Copyright 2024 The Prometheus Authors
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+//go:build windows
+
+package collector
+
+import (
+	"fmt"
+	"log/slog"
+	"time"
+
+	"github.com/prometheus/client_golang/prometheus"
+)
+
+// Interface guard.
+var _ prometheus.Collector = (*Handler)(nil)
+
+// Handler implements [prometheus.Collector] for a set of Windows Collection.
+type Handler struct {
+	maxScrapeDuration time.Duration
+	logger            *slog.Logger
+	collection        *Collection
+}
+
+// NewHandler returns a new Handler that implements a [prometheus.Collector] for the given metrics Collection.
+func (c *Collection) NewHandler(maxScrapeDuration time.Duration, logger *slog.Logger, collectors []string) (*Handler, error) {
+	collection := c
+
+	if len(collectors) != 0 {
+		var err error
+
+		collection, err = c.WithCollectors(collectors)
+		if err != nil {
+			return nil, fmt.Errorf("failed to create handler with collectors: %w", err)
+		}
+	}
+
+	return &Handler{
+		maxScrapeDuration: maxScrapeDuration,
+		collection:        collection,
+		logger:            logger,
+	}, nil
+}
+
+func (p *Handler) Describe(_ chan<- *prometheus.Desc) {}
+
+// Collect sends the collected metrics from each of the Collection to
+// prometheus.
+func (p *Handler) Collect(ch chan<- prometheus.Metric) {
+	p.collection.collectAll(ch, p.logger, p.maxScrapeDuration)
+}