feat: add proxy rotation functionality

internal/proxyrotator/proxyrotator.go

@@ -0,0 +1,60 @@
+// SPDX-FileCopyrightText: Copyright The Miniflux Authors. All rights reserved.
+// SPDX-License-Identifier: Apache-2.0
+
+package proxyrotator // import "miniflux.app/v2/internal/proxyrotator"
+
+import (
+	"net/url"
+	"sync"
+)
+
+var ProxyRotatorInstance *ProxyRotator
+
+// ProxyRotator manages a list of proxies and rotates through them.
+type ProxyRotator struct {
+	proxies      []*url.URL
+	currentIndex int
+	mutex        sync.Mutex
+}
+
+// NewProxyRotator creates a new ProxyRotator with the given proxy URLs.
+func NewProxyRotator(proxyURLs []string) (*ProxyRotator, error) {
+	parsedProxies := make([]*url.URL, 0, len(proxyURLs))
+
+	for _, p := range proxyURLs {
+		proxyURL, err := url.Parse(p)
+		if err != nil {
+			return nil, err
+		}
+		parsedProxies = append(parsedProxies, proxyURL)
+	}
+
+	return &ProxyRotator{
+		proxies:      parsedProxies,
+		currentIndex: 0,
+		mutex:        sync.Mutex{},
+	}, nil
+}
+
+// GetNextProxy returns the next proxy in the rotation.
+func (pr *ProxyRotator) GetNextProxy() *url.URL {
+	pr.mutex.Lock()
+	defer pr.mutex.Unlock()
+
+	if len(pr.proxies) == 0 {
+		return nil
+	}
+
+	proxy := pr.proxies[pr.currentIndex]
+	pr.currentIndex = (pr.currentIndex + 1) % len(pr.proxies)
+
+	return proxy
+}
+
+// HasProxies checks if there are any proxies available in the rotator.
+func (pr *ProxyRotator) HasProxies() bool {
+	pr.mutex.Lock()
+	defer pr.mutex.Unlock()
+
+	return len(pr.proxies) > 0
+}