From 280703edd8e27fdd971604a85a04a91938ba608c Mon Sep 17 00:00:00 2001
From: blank X <theblankx@protonmail.com>
Date: Tue, 10 Aug 2021 16:07:09 +0700
Subject: [PATCH] Store permanent errors

---
 main.go | 99 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 99 insertions(+)

diff --git a/main.go b/main.go
index 8417416..bb26ebf 100644
--- a/main.go
+++ b/main.go
@@ -9,6 +9,7 @@ import (
 	"bufio"
 	"errors"
 	"context"
+	"strconv"
 	"strings"
 	"net/url"
 	"crypto/x509"
@@ -23,6 +24,7 @@ var (
 	hosts     tofu.KnownHosts
 	hostsfile *tofu.HostWriter
 	predirs   map[string]*url.URL
+	perrors   map[string]PError
 )
 
 func xdgDataHome() string {
@@ -48,6 +50,11 @@ func init() {
 	if err != nil {
 		log.Fatal(err)
 	}
+
+	err = populatePErrors()
+	if err != nil {
+		log.Fatal(err)
+	}
 }
 
 func populatePRedirs() error {
@@ -114,6 +121,80 @@ func savePRedirs() error {
 	return writer.Flush()
 }
 
+func populatePErrors() error {
+	file, err := os.OpenFile(filepath.Join(xdgDataHome(), "konbata", "perrors"), os.O_RDONLY|os.O_CREATE, 0600)
+	if err != nil {
+		return err
+	}
+	defer file.Close()
+	scanner := bufio.NewScanner(file)
+	perrors = make(map[string]PError)
+	unescaper := strings.NewReplacer("\\n", "\n", "\\\\", "\\")
+	for scanner.Scan() {
+		values := strings.SplitN(scanner.Text(), " ", 3)
+		if len(values) != 3 {
+			continue
+		}
+		url, err := url.Parse(values[0])
+		if err != nil {
+			continue
+		}
+		if url.Scheme != "gemini" {
+			continue
+		}
+		code, err := strconv.Atoi(values[1])
+		if err != nil {
+			continue
+		}
+		perrors[url.String()] = PError{
+			code: gemini.Status(code),
+			message: unescaper.Replace(values[2]),
+		}
+	}
+	return nil
+}
+
+func savePErrors() error {
+	file, err := os.OpenFile(filepath.Join(xdgDataHome(), "konbata", "perrors"), 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)
+	escaper := strings.NewReplacer("\\", "\\\\", "\n", "\\n")
+	for url, perror := range perrors {
+		_, err = writer.WriteString(url)
+		if err != nil {
+			return err
+		}
+		_, err = writer.WriteRune(' ')
+		if err != nil {
+			return err
+		}
+		_, err = writer.WriteString(strconv.Itoa(int(perror.code)))
+		if err != nil {
+			return err
+		}
+		_, err = writer.WriteRune(' ')
+		if err != nil {
+			return err
+		}
+		_, err = escaper.WriteString(writer, perror.message)
+		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 {
 	host := tofu.NewHost(hostname, cert.Raw)
 	knownHost, ok := hosts.Lookup(hostname)
@@ -141,6 +222,9 @@ func do(client gemini.Client, ctx context.Context, req *gemini.Request, via []*g
 		redirect.URL = target
 		return do(client, ctx, &redirect, via)
 	}
+	if perror, exists := perrors[req.URL.String()]; exists {
+		return nil, req, errors.New(fmt.Sprintf("%d %s", perror.code, perror.message))
+	}
 	resp, err := client.Do(ctx, req)
 	if err != nil {
 		return resp, req, err
@@ -161,6 +245,16 @@ func do(client gemini.Client, ctx context.Context, req *gemini.Request, via []*g
 			return resp, req, err
 		}
 	}
+	if resp.Status.Class() == gemini.StatusPermanentFailure {
+		perrors[req.URL.String()] = PError{
+			code: resp.Status,
+			message: resp.Meta,
+		}
+		err = savePErrors()
+		if err != nil {
+			return resp, req, err
+		}
+	}
 	if resp.Status.Class() == gemini.StatusRedirect {
 		via = append(via, req)
 		if len(via) > 5 {
@@ -304,6 +398,11 @@ func (a ByTime) Swap(i, j int) {
 	a[i], a[j] = a[j], a[i]
 }
 
+type PError struct {
+	code    gemini.Status
+	message string
+}
+
 type AtomWriter struct {
 	Title string
 	Items []FeedItem