[evolution] I#353 - [Prefer Plain] Generate plain text from text/html, if not available

[Milan Crha <mcrha src gnome org>]

commit bf38f23d01739e4e8a485a01245f1e9a7edd4701
Author: Milan Crha <mcrha redhat com>
Date:   Fri Sep 11 08:38:44 2020 +0200

    I#353 - [Prefer Plain] Generate plain text from text/html, if not available
    
    Closes https://gitlab.gnome.org/GNOME/evolution/-/issues/353

 src/mail/e-http-request.c                          |  15 +-
 .../prefer-plain/e-mail-parser-prefer-plain.c      | 197 +++++++++++++++++++--
 src/web-extensions/e-web-extension.c               |   7 +-
 3 files changed, 197 insertions(+), 22 deletions(-)
---
diff --git a/src/mail/e-http-request.c b/src/mail/e-http-request.c
index d8690b7545..bd5f8d44e4 100644
--- a/src/mail/e-http-request.c
+++ b/src/mail/e-http-request.c
@@ -188,6 +188,7 @@ e_http_request_process_sync (EContentRequest *request,
        gchar *mail_uri = NULL;
        GInputStream *stream;
        gboolean force_load_images = FALSE;
+       gboolean disable_remote_content = FALSE;
        EImageLoadingPolicy image_policy;
        gchar *uri_md5;
        EShell *shell;
@@ -341,9 +342,17 @@ e_http_request_process_sync (EContentRequest *request,
        if (!e_shell_get_online (shell))
                goto cleanup;
 
-       settings = e_util_ref_settings ("org.gnome.evolution.mail");
-       image_policy = g_settings_get_enum (settings, "image-loading-policy");
-       g_object_unref (settings);
+       if (WEBKIT_IS_WEB_VIEW (requester))
+               disable_remote_content = g_strcmp0 (webkit_web_view_get_uri (WEBKIT_WEB_VIEW (requester)), 
"evo://disable-remote-content") == 0;
+
+       if (disable_remote_content) {
+               force_load_images = FALSE;
+               image_policy = E_IMAGE_LOADING_POLICY_NEVER;
+       } else {
+               settings = e_util_ref_settings ("org.gnome.evolution.mail");
+               image_policy = g_settings_get_enum (settings, "image-loading-policy");
+               g_object_unref (settings);
+       }
 
        /* Item not found in cache, but image loading policy allows us to fetch
         * it from the interwebs */
diff --git a/src/modules/prefer-plain/e-mail-parser-prefer-plain.c 
b/src/modules/prefer-plain/e-mail-parser-prefer-plain.c
index af84ef9af6..823b4240a1 100644
--- a/src/modules/prefer-plain/e-mail-parser-prefer-plain.c
+++ b/src/modules/prefer-plain/e-mail-parser-prefer-plain.c
@@ -18,8 +18,6 @@
 #include <gtk/gtk.h>
 #include <glib/gi18n.h>
 
-#include "e-mail-parser-prefer-plain.h"
-
 #include <em-format/e-mail-extension-registry.h>
 #include <em-format/e-mail-parser-extension.h>
 #include <em-format/e-mail-part.h>
@@ -28,14 +26,11 @@
 #include <libebackend/libebackend.h>
 #include <e-util/e-util.h>
 
-#define d(x)
+#include "e-mail-parser-prefer-plain.h"
 
 typedef struct _EMailParserPreferPlain EMailParserPreferPlain;
 typedef struct _EMailParserPreferPlainClass EMailParserPreferPlainClass;
 
-typedef EExtension EMailParserPreferPlainLoader;
-typedef EExtensionClass EMailParserPreferPlainLoaderClass;
-
 struct _EMailParserPreferPlain {
        EMailParserExtension parent;
 
@@ -57,10 +52,7 @@ enum {
        ONLY_PLAIN
 };
 
-G_DEFINE_DYNAMIC_TYPE (
-       EMailParserPreferPlain,
-       e_mail_parser_prefer_plain,
-       E_TYPE_MAIL_PARSER_EXTENSION)
+G_DEFINE_DYNAMIC_TYPE (EMailParserPreferPlain, e_mail_parser_prefer_plain, E_TYPE_MAIL_PARSER_EXTENSION)
 
 static const gchar *parser_mime_types[] = {
        "multipart/alternative",
@@ -196,6 +188,150 @@ hide_parts (GQueue *work_queue)
        }
 }
 
+static gchar *
+mail_parser_prefer_plain_dup_part_text (CamelMimePart *mime_part,
+                                       GCancellable *cancellable)
+{
+       CamelDataWrapper *data_wrapper;
+       CamelMedium *medium;
+       CamelStream *stream;
+       GByteArray *array;
+       gchar *content;
+
+       if (!mime_part)
+               return NULL;
+
+       array = g_byte_array_new ();
+       medium = CAMEL_MEDIUM (mime_part);
+
+       /* Stream takes ownership of the byte array. */
+       stream = camel_stream_mem_new_with_byte_array (array);
+       data_wrapper = camel_medium_get_content (medium);
+       camel_data_wrapper_decode_to_stream_sync (
+               data_wrapper, stream, NULL, NULL);
+
+       content = g_strndup ((gchar *) array->data, array->len);
+
+       g_object_unref (stream);
+
+       return content;
+}
+
+typedef struct _AsyncContext {
+       gchar *text_input;
+       gchar *text_output;
+       GCancellable *cancellable;
+       EFlag *flag;
+       WebKitWebView *web_view;
+} AsyncContext;
+
+static void
+mail_parser_prefer_plain_convert_jsc_call_done_cb (GObject *source,
+                                                  GAsyncResult *result,
+                                                  gpointer user_data)
+{
+       WebKitJavascriptResult *js_result;
+       AsyncContext *async_context = user_data;
+       GError *error = NULL;
+
+       g_return_if_fail (async_context != NULL);
+
+       js_result = webkit_web_view_run_javascript_finish (WEBKIT_WEB_VIEW (source), result, &error);
+
+       if (error) {
+               if (!g_error_matches (error, G_IO_ERROR, G_IO_ERROR_CANCELLED) &&
+                   (!g_error_matches (error, WEBKIT_JAVASCRIPT_ERROR, WEBKIT_JAVASCRIPT_ERROR_SCRIPT_FAILED) 
||
+                    /* WebKit can return empty error message, thus ignore those. */
+                    (error->message && *(error->message))))
+                       g_warning ("%s: JSC call failed: %s:%d: %s", G_STRFUNC, g_quark_to_string 
(error->domain), error->code, error->message);
+               g_clear_error (&error);
+       }
+
+       if (js_result) {
+               JSCException *exception;
+               JSCValue *value;
+
+               value = webkit_javascript_result_get_js_value (js_result);
+               exception = jsc_context_get_exception (jsc_value_get_context (value));
+
+               if (exception) {
+                       g_warning ("%s: JSC call failed: %s", G_STRFUNC, jsc_exception_get_message 
(exception));
+                       jsc_context_clear_exception (jsc_value_get_context (value));
+               } else if (jsc_value_is_string (value)) {
+                       async_context->text_output = jsc_value_to_string (value);
+               }
+
+               webkit_javascript_result_unref (js_result);
+       }
+
+       g_clear_object (&async_context->web_view);
+
+       e_flag_set (async_context->flag);
+}
+
+static gboolean
+mail_parser_prefer_plain_convert_text (gpointer user_data)
+{
+       AsyncContext *async_context = user_data;
+       gchar *script;
+
+       g_return_val_if_fail (async_context != NULL, FALSE);
+
+       async_context->web_view = g_object_ref_sink (e_web_view_new ());
+
+       e_web_view_load_uri (E_WEB_VIEW (async_context->web_view), "evo://disable-remote-content");
+
+       script = e_web_view_jsc_printf_script (
+               "var elem;\n"
+               "elem = document.createElement('X-EVO-CONVERT');\n"
+               "elem.innerHTML = %s;\n"
+               "EvoConvert.ToPlainText(elem, -1);",
+               async_context->text_input);
+
+       webkit_web_view_run_javascript (async_context->web_view, script, async_context->cancellable,
+               mail_parser_prefer_plain_convert_jsc_call_done_cb, async_context);
+
+       g_free (script);
+
+       return FALSE;
+}
+
+static gchar *
+mail_parser_prefer_plain_convert_content_sync (CamelMimePart *mime_part,
+                                              GCancellable *cancellable)
+{
+       AsyncContext async_context;
+       gchar *res = NULL;
+
+       memset (&async_context, 0, sizeof (AsyncContext));
+
+       async_context.text_input = mail_parser_prefer_plain_dup_part_text (mime_part, cancellable);
+
+       if (!async_context.text_input || g_cancellable_is_cancelled (cancellable)) {
+               g_free (async_context.text_input);
+               return NULL;
+       }
+
+       async_context.flag = e_flag_new ();
+       async_context.cancellable = cancellable;
+
+       /* Run it in the main/GUI thread */
+       g_timeout_add (1, mail_parser_prefer_plain_convert_text, &async_context);
+
+       e_flag_wait (async_context.flag);
+       e_flag_free (async_context.flag);
+
+       if (async_context.text_output) {
+               res = async_context.text_output;
+               async_context.text_output = NULL;
+       }
+
+       g_free (async_context.text_input);
+       g_free (async_context.text_output);
+
+       return res;
+}
+
 static gboolean
 empe_prefer_plain_parse (EMailParserExtension *extension,
                          EMailParser *parser,
@@ -250,12 +386,40 @@ empe_prefer_plain_parse (EMailParserExtension *extension,
                if (emp_pp->mode != ONLY_PLAIN)
                        return FALSE;
 
-               /* Enforcing text/plain but got only HTML part, so add it
-                * as attachment to not show empty message preview, which
-                * is confusing. */
-               make_part_attachment (
-                       parser, part, part_id, TRUE,
-                       cancellable, out_mail_parts);
+               if (!e_mail_part_is_attachment (part)) {
+                       gchar *content;
+
+                       partidlen = part_id->len;
+
+                       g_string_truncate (part_id, partidlen);
+                       g_string_append_printf (part_id, ".alternative-prefer-plain.%d.converted", -1);
+
+                       content = mail_parser_prefer_plain_convert_content_sync (part, cancellable);
+
+                       if (content) {
+                               EMailPart *mail_part;
+                               CamelMimePart *text_part;
+
+                               text_part = camel_mime_part_new ();
+                               camel_mime_part_set_content (text_part, content, strlen (content), 
"application/vnd.evolution.plaintext");
+                               mail_part = e_mail_part_new (text_part, part_id->str);
+                               e_mail_part_set_mime_type (mail_part, "application/vnd.evolution.plaintext");
+                               g_free (content);
+
+                               g_queue_push_tail (out_mail_parts, mail_part);
+                       }
+
+                       g_string_truncate (part_id, partidlen);
+               }
+
+               if (emp_pp->show_suppressed || e_mail_part_is_attachment (part)) {
+                       /* Enforcing text/plain but got only HTML part, so add it
+                        * as attachment to not show empty message preview, which
+                        * is confusing. */
+                       make_part_attachment (
+                               parser, part, part_id, TRUE,
+                               cancellable, out_mail_parts);
+               }
 
                return TRUE;
        }
@@ -565,4 +729,3 @@ e_mail_parser_prefer_plain_type_register (GTypeModule *type_module)
 {
        e_mail_parser_prefer_plain_register_type (type_module);
 }
-
diff --git a/src/web-extensions/e-web-extension.c b/src/web-extensions/e-web-extension.c
index 979818a67c..deea1bdaa7 100644
--- a/src/web-extensions/e-web-extension.c
+++ b/src/web-extensions/e-web-extension.c
@@ -104,11 +104,14 @@ web_page_send_request_cb (WebKitWebPage *web_page,
        request_uri = webkit_uri_request_get_uri (request);
        page_uri = webkit_web_page_get_uri (web_page);
 
+       if (!request_uri)
+               return FALSE;
+
        /* Always load the main resource. */
        if (g_strcmp0 (request_uri, page_uri) == 0 ||
            /* Do not influence real pages, like those with eds OAuth sign-in */
-           g_str_has_prefix (page_uri, "http:") ||
-           g_str_has_prefix (page_uri, "https:"))
+           (page_uri && (g_str_has_prefix (page_uri, "http:") ||
+                         g_str_has_prefix (page_uri, "https:"))))
                return FALSE;
 
        if (g_str_has_prefix (request_uri, "http:") ||