1 files changed, 100 insertions, 0 deletions
diff --git a/src/libdisfluid/disfluid-activity-object.h b/src/libdisfluid/disfluid-activity-object.h
new file mode 100644
index 0000000..d079f89
--- /dev/null
+++ b/src/libdisfluid/disfluid-activity-object.h
@@ -0,0 +1,100 @@
+#ifndef DISFLUID_ACTIVITY_OBJECT_INCLUDED
+# define DISFLUID_ACTIVITY_OBJECT_INCLUDED
+
+# include <config.h>
+# include "string-desc.h"
+# include <jansson.h>
+
+MAYBE_UNUSED static int
+activity_object_context_prefix (json_t * object,
+				string_desc_t * context_prefix);
+
+# include "disfluid-append-only-file.h"
+# include "safe-alloc.h"
+
+static bool
+activity_object_is_as (json_t * value, bool with_hash)
+{
+  static const char *as = "https://www.w3.org/ns/activitystreams#";
+  const size_t as_len_h = strlen (as);
+  const size_t as_len_s = as_len_h - 1;
+  size_t as_len = as_len_s;
+  if (with_hash)
+    {
+      as_len = as_len_h;
+    }
+  return (json_is_string (value)
+	  && json_string_length (value) == as_len
+	  && strncmp (json_string_value (value), as, as_len) == 0);
+}
+
+static int
+activity_object_context_prefix (json_t * object,
+				string_desc_t * context_prefix)
+{
+  context_prefix->_nbytes = 0;
+  context_prefix->_data = NULL;
+  if (!json_is_object (object))
+    {
+      return -1;
+    }
+  json_t *context = json_object_get (object, "@context");
+  if (activity_object_is_as (context, false))
+    {
+      /* This is the only context. */
+      context_prefix->_nbytes = 0;
+      context_prefix->_data = NULL;
+      return 0;
+    }
+  else if (json_is_object (context))
+    {
+      json_t *vocab = json_object_get (context, "@vocab");
+      if (activity_object_is_as (vocab, true))
+	{
+	  /* Also not prefixed. */
+	  context_prefix->_nbytes = 0;
+	  context_prefix->_data = NULL;
+	  return 0;
+	}
+      /* Maybe it is a value of the context object. */
+      const char *key;
+      json_t *value;
+      context_prefix->_nbytes = 0;
+      context_prefix->_data = NULL;
+      json_object_foreach (context, key, value)
+      {
+	if (key[0] != '@' && activity_object_is_as (value, true))
+	  {
+	    FREE (context_prefix->_data);
+	    context_prefix->_nbytes = strlen (key) + 1;	/* for the final : */
+	    if (ALLOC_N (context_prefix->_data, context_prefix->_nbytes) < 0)
+	      {
+		return -2;
+	      }
+	    memcpy (context_prefix->_data, key, context_prefix->_nbytes - 1);
+	    context_prefix->_data[context_prefix->_nbytes - 1] = ':';
+	  }
+      }
+      if (context_prefix->_data != NULL)
+	{
+	  return 0;
+	}
+    }
+  else if (json_is_array (context))
+    {
+      size_t n = json_array_size (context);
+      for (size_t i = 0; i < n; i++)
+	{
+	  json_t *value = json_array_get (context, i);
+	  if (activity_object_is_as (value, false))
+	    {
+	      context_prefix->_nbytes = 0;
+	      context_prefix->_data = NULL;
+	      return 0;
+	    }
+	}
+    }
+  return -1;
+}
+
+#endif /* not DISFLUID_ACTIVITY_OBJECT_INCLUDED */