1 files changed, 156 insertions, 0 deletions
diff --git a/cmd/gen-posix/http_hacks.go b/cmd/gen-posix/http_hacks.go
new file mode 100644
index 0000000..16b8a8d
--- /dev/null
+++ b/cmd/gen-posix/http_hacks.go
@@ -0,0 +1,156 @@
+package main
+
+import (
+	"bufio"
+	"bytes"
+	"errors"
+	"fmt"
+	"io"
+	"net/http"
+	"os"
+	"os/exec"
+	"strings"
+
+	"git.lukeshu.com/www/lib/httpcache"
+)
+
+func _checkURL(url string) (string, error) {
+	switch {
+	case strings.HasPrefix(url, "https://web.archive.org/"):
+		_, err := httpcache.Get(url, nil)
+		return url, err
+	case strings.HasPrefix(url, "https://www2.opengroup.org/ogsys/catalog/"):
+		_, err := httpcache.Get(url, nil)
+		if err == nil {
+			return url, nil
+		}
+		if !errors.Is(err, os.ErrNotExist) { // don't hide non-404 errors
+			return "", err
+		}
+		suffix := strings.TrimPrefix(url, "https://www2.opengroup.org/ogsys/catalog/")
+		url2 := "https://publications.opengroup.org/" + strings.ToLower(suffix)
+		_, err = httpcache.Get(url2, nil)
+		if err == nil {
+			return url2, nil
+		}
+		if !errors.Is(err, os.ErrNotExist) { // don't hide non-404 errors
+			return "", err
+		}
+		url3, err := _checkURL("https://web.archive.org/web/20170102/" + url)
+		if err == nil {
+			return url3, nil
+		}
+		return url+"#ERROR", nil
+	case url == "http://ieeexplore.ieee.org/servlet/opac?punumber=7394900":
+		return url+"#ERROR", nil
+	default:
+		_, err := httpcache.Get(url, nil)
+		if err != nil && errors.Is(err, os.ErrNotExist) {
+			return _checkURL("https://web.archive.org/web/20170102/" + url)
+		}
+		return url, err
+	}
+}
+
+func checkURL(url string) string {
+	url2, err := _checkURL(url)
+	if err != nil {
+		panic(fmt.Errorf("URL=%q: %v", url, err))
+	}
+	return url2
+}
+
+func nokogiriIgnoreFailure(htmlBytes []byte, expr string) string {
+	cmd := exec.Command("nokogiri", "-e", "puts "+expr)
+	cmd.Stderr = io.Discard
+	cmd.Stdin = bytes.NewReader(htmlBytes)
+	outBytes, _ := cmd.Output()
+	return strings.TrimSpace(string(outBytes))
+}
+
+func mockRedirect(url string) *http.Response {
+	resp, err := http.ReadResponse(bufio.NewReader(strings.NewReader(""+
+		"HTTP/1.1 302 Found\r\n"+
+		"Location: "+url+"\r\n"+
+		"\r\n")), nil)
+	if err != nil {
+		panic(err)
+	}
+	return resp
+}
+
+func mockForbidden() *http.Response {
+	resp, err := http.ReadResponse(bufio.NewReader(strings.NewReader(""+
+		"HTTP/1.1 403 Forbidden\r\n"+
+		"\r\n")), nil)
+	if err != nil {
+		panic(err)
+	}
+	return resp
+}
+
+func modifyResponse(url string, entry httpcache.CacheEntry, resp *http.Response) *http.Response {
+	switch {
+	case strings.HasPrefix(url, "https://web.archive.org/"):
+		htmlBytes, _ := io.ReadAll(resp.Body)
+		_ = resp.Body.Close()
+
+		// native Wayback Machine redirect
+		redirect := nokogiriIgnoreFailure(htmlBytes, `$_.css("p.impatient a").first["href"]`)
+		if strings.HasPrefix(redirect, "https://web.archive.org/web/") {
+			return mockRedirect(redirect)
+		}
+
+		// silly TOG SSO
+		if strings.Contains(url, "sso.opengroup.org") {
+			if bytes.Contains(htmlBytes, []byte("document.forms.postbinding.submit()")) {
+				redirect := nokogiriIgnoreFailure(htmlBytes, `$_.css("#postbinding").first["action"]`)
+				if redirect != "" {
+					return mockRedirect(redirect)
+				}
+			}
+			if bytes.Contains(htmlBytes, []byte("General Authorization Error")) {
+				return mockForbidden()
+			}
+		}
+
+		// We drained resp.Body, so re-create it.
+		resp, err := http.ReadResponse(bufio.NewReader(strings.NewReader(string(entry))), nil)
+		if err != nil {
+			panic(err)
+		}
+		return resp
+	default:
+		return resp
+	}
+}
+
+type mock404 struct {
+	Msg string
+}
+
+// Is implements the interface for [errors.Is].
+func (e *mock404) Is(target error) bool {
+	return target == os.ErrNotExist
+}
+
+// Error implements [error].
+func (e *mock404) Error() string {
+	return e.Msg
+}
+
+func checkRedirect(req *http.Request, via []*http.Request) error {
+	// net/http.defaultCheckRedirect
+	if len(via) >= 10 {
+		return errors.New("stopped after 10 redirects")
+	}
+
+	// detect redirects that should be 404s
+	oldURL := via[len(via)-1].URL
+	newURL := req.URL
+	if (newURL.Path == "/" || newURL.Path == "") && !(oldURL.Path == "/" || oldURL.Path == "") {
+		return &mock404{Msg: fmt.Sprintf("should have been a 404: %q redirected to %q", oldURL.String(), newURL.String())}
+	}
+
+	return nil
+}