Add In-Reply-To and References headers to the outgoing message.

@@ -17,6 +17,150 @@
 
 #include "mail.h"
 
+#define DATEBUFSIZE 128
+
+static char *
+concat (const char *s1, const char *s2)
+{
+  int len = (s1 ? strlen (s1) : 0) + (s2 ? strlen (s2) : 0) + 2;
+  char *s = malloc (len);
+  if (s)
+    {
+      char *p = s;
+      
+      if (s1)
+	{
+	  strcpy (p, s1);
+	  p += strlen (s1);
+	  *p++ = ' ';
+	}
+      if (s2)
+	strcpy (p, s2);
+    }
+  return s;
+}
+
+void
+make_in_reply_to (compose_env_t *env, message_t msg)
+{
+  char *value, *s1 = NULL, *s2 = NULL;
+  header_t hdr;
+
+  if (message_get_header (msg, &hdr))
+    return;
+  
+  if (header_aget_value (hdr, MU_HEADER_DATE, &value))
+    {
+      envelope_t envelope = NULL;
+      value = malloc (DATEBUFSIZE);
+      if (value)
+	{
+	  message_get_envelope (msg, &envelope);
+	  envelope_date (envelope, value, DATEBUFSIZE, NULL);
+	}
+    }
+
+  if (value)
+    asprintf (&s1, "Your message of %s", value);
+  
+  if (header_aget_value (hdr, MU_HEADER_MESSAGE_ID, &value) == 0)
+    {
+      asprintf (&s2, "\n\t%s", value);
+      free (value);
+    }
+
+  if (s1 || s2)
+    {
+      value = concat (s1, s2);
+      free (s1);
+      free (s2);
+      compose_header_set (env, MU_HEADER_IN_REPLY_TO, value,
+			  COMPOSE_REPLACE);
+      free (value);
+    }      
+}
+
+int
+strip_message_id (char *msgid, char **val)
+{
+  address_t addr;
+  char *p = strchr (msgid, '<');
+  if (!p)
+    p = msgid;
+  if (address_create (&addr, p) == 0)
+    {
+      size_t count = 0;
+      char *p;
+      
+      address_get_count (addr, &count);
+      if (count != 1)
+	{
+	  address_destroy (&addr);
+	  return 1;
+	}
+      if (address_aget_email (addr, 1, &p))
+	return -1;
+      address_destroy (&addr);
+      *val = malloc (strlen (p) + 3);
+      if (!*val)
+	{
+	  free (p);
+	  return -1;
+	}
+      sprintf (*val, "<%s>", p);
+      free (p);
+      return 0;
+    }
+  return 1;
+}
+
+int
+get_msgid_header (header_t hdr, const char *name, char **val)
+{
+  char *p;
+  int status = header_aget_value (hdr, name, &p);
+  if (status)
+    return status;
+  status = strip_message_id (p, val);
+  free (p);
+  return status;
+}
+
+/* rfc2822:
+   
+   The "References:" field will contain the contents of the parent's
+   "References:" field (if any) followed by the contents of the parent's
+   "Message-ID:" field (if any).  If the parent message does not contain
+   a "References:" field but does have an "In-Reply-To:" field
+   containing a single message identifier, then the "References:" field
+   will contain the contents of the parent's "In-Reply-To:" field
+   followed by the contents of the parent's "Message-ID:" field (if
+   any).  If the parent has none of the "References:", "In-Reply-To:",
+   or "Message-ID:" fields, then the new message will have no
+   References:" field. */
+
+void
+make_references (compose_env_t *env, message_t msg)
+{
+  char *ref = NULL, *msgid = NULL;
+  header_t hdr;
+
+  if (message_get_header (msg, &hdr))
+    return;
+
+  get_msgid_header (hdr, MU_HEADER_MESSAGE_ID, &msgid);
+  if (get_msgid_header (hdr, MU_HEADER_REFERENCES, &ref))
+    get_msgid_header (hdr, MU_HEADER_IN_REPLY_TO, &ref);
+
+  if (ref || msgid)
+    {
+      char *s = concat (ref, msgid);
+      free (ref);
+      free (msgid);
+      compose_header_set (env, MU_HEADER_REFERENCES, s, COMPOSE_REPLACE);
+    }
+}
+  
 /*
  * r[eply] [msglist] -- GNU extension
  * r[espond] [msglist] -- GNU extension
@@ -39,7 +183,7 @@ mail_reply (int argc, char **argv)
 
       compose_init (&env);
 
-      if (util_get_message (mbox, cursor, &msg, 1))
+      if (util_get_message (mbox, cursor, &msg, MSG_NODELETED))
 	return 1;
 
       message_get_header (msg, &hdr);
@@ -99,6 +243,8 @@ mail_reply (int argc, char **argv)
       fprintf (ofile, "Subject: %s\n\n",
 	       compose_header_get (&env, MU_HEADER_SUBJECT, ""));
 
+      make_in_reply_to (&env, msg);
+      make_references (&env, msg);
       status = mail_send0 (&env, 0);
       compose_destroy (&env);
       return status;