Store permanent redirects

main.go

@@ -6,6 +6,7 @@ import (
 	"log"
 	"sort"
 	"time"
+	"bufio"
 	"errors"
 	"context"
 	"strings"
@@ -21,6 +22,7 @@ import (
 var (
 	hosts     tofu.KnownHosts
 	hostsfile *tofu.HostWriter
+	predirs   map[string]*url.URL
 )
 
 func xdgDataHome() string {
@@ -41,6 +43,75 @@ func init() {
 	if err != nil {
 		log.Fatal(err)
 	}
+
+	err = populatePRedirs()
+	if err != nil {
+		log.Fatal(err)
+	}
+}
+
+func populatePRedirs() error {
+	file, err := os.OpenFile(filepath.Join(xdgDataHome(), "konbata", "predirs"), os.O_RDONLY|os.O_CREATE, 0600)
+	if err != nil {
+		return err
+	}
+	defer file.Close()
+	scanner := bufio.NewScanner(file)
+	predirs = make(map[string]*url.URL)
+	for scanner.Scan() {
+		urls := strings.Split(scanner.Text(), " ")
+		if len(urls) != 2 {
+			continue
+		}
+		url0, err := url.Parse(urls[0])
+		if err != nil {
+			continue
+		}
+		if url0.Scheme != "gemini" {
+			continue
+		}
+		url1, err := url.Parse(urls[1])
+		if err != nil {
+			continue
+		}
+		if url1.Scheme != "gemini" {
+			continue
+		}
+		predirs[url0.String()] = url1
+	}
+	return nil
+}
+
+func savePRedirs() error {
+	file, err := os.OpenFile(filepath.Join(xdgDataHome(), "konbata", "predirs"), os.O_WRONLY|os.O_CREATE, 0600)
+	if err != nil {
+		return err
+	}
+	defer file.Close()
+	err = file.Truncate(0)
+	if err != nil {
+		return err
+	}
+	writer := bufio.NewWriter(file)
+	for url0, url1 := range predirs {
+		_, err = writer.WriteString(url0)
+		if err != nil {
+			return err
+		}
+		_, err = writer.WriteRune(' ')
+		if err != nil {
+			return err
+		}
+		_, err = writer.WriteString(url1.String())
+		if err != nil {
+			return err
+		}
+		_, err = writer.WriteRune('\n')
+		if err != nil {
+			return err
+		}
+	}
+	return writer.Flush()
 }
 
 func trustCertificate(hostname string, cert *x509.Certificate) error {
@@ -60,11 +131,36 @@ func trustCertificate(hostname string, cert *x509.Certificate) error {
 }
 
 func do(client gemini.Client, ctx context.Context, req *gemini.Request, via []*gemini.Request) (*gemini.Response, *gemini.Request, error) {
+	if target, exists := predirs[req.URL.String()]; exists {
+		via = append(via, req)
+		if len(via) > 5 {
+			return nil, req, errors.New("too many redirects")
+		}
+
+		redirect := *req
+		redirect.URL = target
+		return do(client, ctx, &redirect, via)
+	}
 	resp, err := client.Do(ctx, req)
 	if err != nil {
 		return resp, req, err
 	}
 
+	if resp.Status == gemini.StatusPermanentRedirect {
+		target, err := url.Parse(resp.Meta)
+		if err != nil {
+			return resp, req, err
+		}
+		if target.Scheme != "gemini" && target.Scheme != "" {
+			return resp, req, errors.New(fmt.Sprintf("tried to redirect to scheme %s", target.Scheme))
+		}
+		target = req.URL.ResolveReference(target)
+		predirs[req.URL.String()] = target
+		err = savePRedirs()
+		if err != nil {
+			return resp, req, err
+		}
+	}
 	if resp.Status.Class() == gemini.StatusRedirect {
 		via = append(via, req)
 		if len(via) > 5 {