0615451d856749db2e4febb4995ff8aee72a8f25
angie
  Wed Jan 7 12:04:18 2015 -0800
Adding cartJson lib module (to be used by hgAi).  It parses JSON commands andreturns information in JSON to support moving more UI actions into Javascript.
The lib supports basic queries and actions like getting a list of the groups,
tracks and tables (incl. hubs & CTs) and changing the clade/genome/db.  Apps/CGIs
can extend it to handle new commands by registering handler functions.

diff --git src/hg/inc/cartJson.h src/hg/inc/cartJson.h
new file mode 100644
index 0000000..80bcf57
--- /dev/null
+++ src/hg/inc/cartJson.h
@@ -0,0 +1,58 @@
+/* cartJson - parse and execute JSON commands to update cart and/or return cart data as JSON. */
+
+#ifndef CARTJSON_H
+#define CARTJSON_H
+
+#include "cart.h"
+#include "hash.h"
+#include "jsonWrite.h"
+
+#define CARTJSON_COMMAND "cjCmd"
+
+struct cartJson
+    // Use the cart to perform commands dispatched from handlerHash; print results with jsonWrite.
+    {
+    struct cart *cart;
+    struct hash *handlerHash;
+    struct jsonWrite *jw;
+    };
+
+struct cartJson *cartJsonNew(struct cart *cart);
+/* Allocate and return a cartJson object with default handlers. */
+
+typedef void CartJsonHandler(struct cartJson *cj, struct hash *paramHash);
+/* Implementation of some command; paramHash associates parameter names with
+ * jsonElement values. */
+
+char *cartJsonOptionalParam(struct hash *paramHash, char *name);
+/* Convenience function for a CartJsonHandler function: Look up name in paramHash.
+ * Return the string contained in its jsonElement value, or NULL if not found. */
+
+char *cartJsonRequiredParam(struct hash *paramHash, char *name, struct jsonWrite *jw,
+                            char *context);
+/* Convenience function for a CartJsonHandler function: Look up name in paramHash.
+ * If found, return the string contained in its jsonElement value.
+ * If not, write an error message (using context) and return NULL. */
+
+void cartJsonRegisterHandler(struct cartJson *cj, char *command, CartJsonHandler *handler);
+/* Associate handler with command; when javascript sends command, handler will be executed. */
+
+void cartJsonExecute(struct cartJson *cj);
+/* Get commands from cgi, print Content-type, execute commands, print results as JSON. */
+
+void cartJsonFree(struct cartJson **pCj);
+/* Close **pCj's contents and nullify *pCj. */
+
+void cartJsonChangeDb(struct cartJson *cj, struct hash *paramHash);
+/* Change db to new value, update cart and print JSON of new position & gene suggest track. */
+
+void cartJsonChangeOrg(struct cartJson *cj, struct hash *paramHash);
+/* Change org to new value, update cart and print JSON of new db menu, new position etc. */
+
+void cartJsonChangeClade(struct cartJson *cj, struct hash *paramHash);
+/* Change clade to new value, update cart, and print JSON of new org & db menus, new position etc */
+
+void cartJsonGetGroupsTracksTables(struct cartJson *cj, struct hash *paramHash);
+/* Print info necessary for group/track/table menus. */
+
+#endif /* CARTJSON_H */