Add experimental support for chat markers

Support chat marker (XEP-0333) stanzas when the "--chat-marker" switch
is provided on the command line. A chat marker is prefixed by 'M':

~~~
M:groupchat:test@conference.example.com/msantos:me@example.com/162315501161646113068402:
~~~

The idea is to allow scripts to react based on whether a message has
been read, for example, escalating via other channels.

src/xmppipe.c

@@ -64,6 +64,7 @@ void xmppipe_ping(xmppipe_state_t *);
 enum {
     OPT_NO_TLS_VERIFY = 1,
     OPT_CHAT,
+    OPT_CHAT_MARKER,
 };
 
 static const char * const xmppipe_states[] = {
@@ -88,6 +89,7 @@ static const struct option long_options[] =
     {"buffer-size",        required_argument,  NULL, 'b'},
     {"flow-control",       required_argument,  NULL, 'c'},
     {"chat",               no_argument,        NULL, OPT_CHAT},
+    {"chat-marker",        no_argument,        NULL, OPT_CHAT_MARKER},
     {"discard",            no_argument,        NULL, 'd'},
     {"discard-to-stdout",  no_argument,        NULL, 'D'},
     {"ignore-eof",         no_argument,        NULL, 'e'},
@@ -255,6 +257,10 @@ main(int argc, char **argv)
                 state->opt &= ~XMPPIPE_OPT_GROUPCHAT;
                 break;
 
+            case OPT_CHAT_MARKER:
+                state->opt |= XMPPIPE_OPT_CHAT_MARKER;
+                break;
+
             case 'h':
             default:
                 usage(state);
@@ -1033,7 +1039,6 @@ handle_presence_error(xmpp_conn_t * const conn, xmpp_stanza_t * const stanza,
             text ? text : "no description");
 }
 
-
     int
 handle_message(xmpp_conn_t * const conn, xmpp_stanza_t * const stanza,
         void * const userdata)
@@ -1045,12 +1050,15 @@ handle_message(xmpp_conn_t * const conn, xmpp_stanza_t * const stanza,
     const char *type = NULL;
     const char *from = NULL;
     const char *to = NULL;
+    const char *ns;
 
     char *etype = NULL;
     char *efrom = NULL;
     char *eto = NULL;
     char *emessage = NULL;
 
+    char *symbol = "m";
+
     if (xmpp_stanza_get_child_by_name(stanza, "delay"))
         return 1;
 
@@ -1070,38 +1078,49 @@ handle_message(xmpp_conn_t * const conn, xmpp_stanza_t * const stanza,
     if (XMPPIPE_STREQ(type, "groupchat") && XMPPIPE_STREQ(from, state->mucjid))
         return 1;
 
+    child = xmpp_stanza_get_child_by_name(stanza, "displayed");
+    if (child != NULL) {
+        ns = xmpp_stanza_get_ns(child);
+        if (XMPPIPE_STREQ(ns, "urn:xmpp:chat-markers:0")) {
+          if (!(state->opt & XMPPIPE_OPT_CHAT_MARKER))
+            return 1;
+
+          symbol = "M";
+        }
+    }
+
     child = xmpp_stanza_get_child_by_name(stanza, "body");
-    if (child == NULL)
-        return 1;
 
-    message = xmpp_stanza_get_text(child);
-    if (message == NULL)
-        return 1;
+    if (child != NULL) {
+        message = xmpp_stanza_get_text(child);
+        if (message != NULL) {
+          if (state->encode) {
+            size_t len = strlen(message);
+            unsigned char *buf = NULL;
+            size_t n = 0;
 
-    if (state->encode) {
-        size_t len = strlen(message);
-        unsigned char *buf = NULL;
-        size_t n = 0;
+            xmpp_base64_decode_bin(state->ctx, message, len, &buf, &n);
 
-        xmpp_base64_decode_bin(state->ctx, message, len, &buf, &n);
+            if (buf == NULL) {
+                /* Not a base64 message */
+                return 1;
+            }
 
-        if (buf == NULL) {
-            /* Not a base64 message */
-            return 1;
+            emessage = xmppipe_nfmt_encode((char *)buf, n);
+            xmpp_free(state->ctx, buf);
+          }
+          else {
+            emessage = xmppipe_fmt_encode(message);
+          }
         }
-
-        emessage = xmppipe_nfmt_encode((char *)buf,n);
-        xmpp_free(state->ctx, buf);
-    }
-    else {
-        emessage = xmppipe_fmt_encode(message);
     }
 
     etype = xmppipe_fmt_encode(type);
     efrom = xmppipe_fmt_encode(from);
     eto = xmppipe_fmt_encode(to);
 
-    (void)printf("m:%s:%s:%s:%s\n", etype, efrom, eto, emessage);
+    (void)printf("%s:%s:%s:%s:%s\n", symbol, etype, efrom, eto,
+        emessage == NULL ? "" : emessage);
 
     state->interval = 0;
 

src/xmppipe.h

@@ -23,7 +23,7 @@
 
 #include <strophe.h>
 
-#define XMPPIPE_VERSION "0.11.0"
+#define XMPPIPE_VERSION "0.12.0"
 #define XMPPIPE_RESOURCE "xmppipe"
 
 #define XMPPIPE_STREQ(a,b)      (strcmp((a),(b)) == 0)
@@ -53,6 +53,7 @@ enum {
     XMPPIPE_OPT_EOF = 1 << 2,               /* Keep running on stdin EOF */
     XMPPIPE_OPT_SIGPIPE = 1 << 3,           /* Exit if no occupants in MUC */
     XMPPIPE_OPT_GROUPCHAT = 1 << 4,         /* Use groupchat */
+    XMPPIPE_OPT_CHAT_MARKER = 1 << 5,       /* Display chat markers */
 };
 
 enum {