Simplify feed fetcher

- Add browser package to handle HTTP errors
- Reduce code duplication

reader/browser/browser.go

@@ -0,0 +1,55 @@
+// Copyright 2018 Frédéric Guillot. All rights reserved.
+// Use of this source code is governed by the Apache 2.0
+// license that can be found in the LICENSE file.
+
+package browser // import "miniflux.app/reader/browser"
+
+import (
+	"miniflux.app/errors"
+	"miniflux.app/http/client"
+)
+
+var (
+	errRequestFailed    = "Unable to open this link: %v"
+	errServerFailure    = "Unable to fetch this resource (Status Code = %d)"
+	errEncoding         = "Unable to normalize encoding: %q"
+	errEmptyFeed        = "This feed is empty"
+	errResourceNotFound = "Resource not found (404), this feed doesn't exists anymore, check the feed URL"
+	errNotAuthorized    = "You are not authorized to access this resource (invalid username/password)"
+)
+
+// Exec executes a HTTP request and handles errors.
+func Exec(request *client.Client) (*client.Response, *errors.LocalizedError) {
+	response, err := request.Get()
+	if err != nil {
+		if e, ok := err.(*errors.LocalizedError); ok {
+			return nil, e
+		}
+		return nil, errors.NewLocalizedError(errRequestFailed, err)
+	}
+
+	if response.IsNotFound() {
+		return nil, errors.NewLocalizedError(errResourceNotFound)
+	}
+
+	if response.IsNotAuthorized() {
+		return nil, errors.NewLocalizedError(errNotAuthorized)
+	}
+
+	if response.HasServerFailure() {
+		return nil, errors.NewLocalizedError(errServerFailure, response.StatusCode)
+	}
+
+	if response.StatusCode != 304 {
+		// Content-Length = -1 when no Content-Length header is sent.
+		if response.ContentLength == 0 {
+			return nil, errors.NewLocalizedError(errEmptyFeed)
+		}
+
+		if err := response.EnsureUnicodeBody(); err != nil {
+			return nil, errors.NewLocalizedError(errEncoding, err)
+		}
+	}
+
+	return response, nil
+}