add proxy feature, update readme

cmd/proxy.go

@@ -0,0 +1,86 @@
+package cmd
+
+import (
+	"fmt"
+	"io"
+	"log"
+	"net/http"
+	"strings"
+
+	md "github.com/JohannesKaufmann/html-to-markdown"
+	"github.com/elazarl/goproxy"
+	readability "github.com/go-shiori/go-readability"
+	"github.com/spf13/cobra"
+)
+
+type ProxyOptions struct {
+	port   int
+	output string
+}
+
+var proxyOpts *ProxyOptions
+
+func init() {
+	proxyOpts = &ProxyOptions{}
+
+	proxyCmd.Flags().IntVarP(&proxyOpts.port, "port", "p", 8080, "Port on which to start the proxy")
+	proxyCmd.Flags().StringVarP(&proxyOpts.output, "output", "o", "html", "response format [html, md]")
+
+	rootCmd.AddCommand(proxyCmd)
+}
+
+var proxyCmd = &cobra.Command{
+	Use:     "proxy",
+	Short:   "Start http proxy",
+	Example: "curl --insecure --location --proxy localhost:8080 https://www.eff.org/cyberspace-independence",
+	Args: func(cmd *cobra.Command, args []string) error {
+
+		// check provided output is in list
+		outputEnum := map[string]bool{
+			"html": true,
+			"md":   true,
+		}
+		if outputEnum[proxyOpts.output] != true {
+			return fmt.Errorf("invalid output specified: %s", proxyOpts.output)
+		}
+
+		return nil
+	},
+	Run: func(cmd *cobra.Command, args []string) {
+		proxy := goproxy.NewProxyHttpServer()
+		// proxy.Verbose = true
+
+		proxy.OnRequest().HandleConnect(goproxy.AlwaysMitm)
+
+		proxy.OnResponse().DoFunc(func(resp *http.Response, ctx *goproxy.ProxyCtx) *http.Response {
+
+			// extract HTML body
+			article, err := readability.FromReader(resp.Body, ctx.Req.URL)
+			if err != nil {
+				log.Fatal(err)
+			}
+
+			content := article.Content
+
+			if proxyOpts.output == "md" {
+				// convert content to markdown
+				content, err = md.NewConverter("", true, nil).ConvertString(content)
+				if err != nil {
+					log.Fatal(err)
+				}
+			}
+
+			stringReader := strings.NewReader(content)
+			resp.Body = io.NopCloser(stringReader)
+
+			log.Printf("Serving %s", ctx.Req.URL)
+
+			return resp
+		})
+
+		log.Printf("Proxy listening on port %d...", proxyOpts.port)
+		log.Printf("Usage: curl --insecure --location --proxy localhost:%d https://www.eff.org/cyberspace-independence", proxyOpts.port)
+
+		log.Fatal(http.ListenAndServe(fmt.Sprintf(":%d", proxyOpts.port), proxy))
+	},
+}