ztrie(3)
========

NAME
----
ztrie - simple trie for tokenizable strings

SYNOPSIS
--------
----
//  This is a draft class, and may change without notice. It is disabled in
//  stable builds by default. If you use this in applications, please ask
//  for it to be pushed to stable state. Use --enable-drafts to enable.
#ifdef CZMQ_BUILD_DRAFT_API
// Callback function for ztrie_node to destroy node data.
typedef void (ztrie_destroy_data_fn) (
    void **data);

//  *** Draft method, for development use, may change without warning ***
//  Creates a new ztrie.
CZMQ_EXPORT ztrie_t *
    ztrie_new (char delimiter);

//  *** Draft method, for development use, may change without warning ***
//  Destroy the ztrie.
CZMQ_EXPORT void
    ztrie_destroy (ztrie_t **self_p);

//  *** Draft method, for development use, may change without warning ***
//  Inserts a new route into the tree and attaches the data. Returns -1     
//  if the route already exists, otherwise 0. This method takes ownership of
//  the provided data if a destroy_data_fn is provided.                     
CZMQ_EXPORT int
    ztrie_insert_route (ztrie_t *self, const char *path, void *data, ztrie_destroy_data_fn destroy_data_fn);

//  *** Draft method, for development use, may change without warning ***
//  Removes a route from the trie and destroys its data. Returns -1 if the
//  route does not exists, otherwise 0.                                   
//  the start of the list call zlist_first (). Advances the cursor.       
CZMQ_EXPORT int
    ztrie_remove_route (ztrie_t *self, const char *path);

//  *** Draft method, for development use, may change without warning ***
//  Returns true if the path matches a route in the tree, otherwise false.
CZMQ_EXPORT bool
    ztrie_matches (ztrie_t *self, const char *path);

//  *** Draft method, for development use, may change without warning ***
//  Returns the data of a matched route from last ztrie_matches. If the path
//  did not match, returns NULL. Do not delete the data as it's owned by    
//  ztrie.                                                                  
CZMQ_EXPORT void *
    ztrie_hit_data (ztrie_t *self);

//  *** Draft method, for development use, may change without warning ***
//  Returns the count of parameters that a matched route has.
CZMQ_EXPORT size_t
    ztrie_hit_parameter_count (ztrie_t *self);

//  *** Draft method, for development use, may change without warning ***
//  Returns the parameters of a matched route with named regexes from last   
//  ztrie_matches. If the path did not match or the route did not contain any
//  named regexes, returns NULL.                                             
CZMQ_EXPORT zhashx_t *
    ztrie_hit_parameters (ztrie_t *self);

//  *** Draft method, for development use, may change without warning ***
//  Returns the asterisk matched part of a route, if there has been no match
//  or no asterisk match, returns NULL.                                     
CZMQ_EXPORT const char *
    ztrie_hit_asterisk_match (ztrie_t *self);

//  *** Draft method, for development use, may change without warning ***
//  Print the trie
CZMQ_EXPORT void
    ztrie_print (ztrie_t *self);

//  *** Draft method, for development use, may change without warning ***
//  Self test of this class.
CZMQ_EXPORT void
    ztrie_test (bool verbose);

#endif // CZMQ_BUILD_DRAFT_API
----

DESCRIPTION
-----------

This is a variant of a trie or prefix tree where all the descendants of a
node have a common prefix of the string associated with that node. This
implementation is specialized for strings that can be tokenized by a delimiter
like a URL, URI or URN. Routes in the tree can be matched by regular expressions
and by using capturing groups parts of a matched route can be easily obtained.

Note that the performance for pure string based matching is okay but on short
strings zhash and zhashx are 3-4 times faster.

EXAMPLE
-------
.From ztrie_test method
----
//  Create a new trie for matching strings that can be tokenized by a slash
//  (e.g. URLs minus the protocol, address and port).
ztrie_t *self = ztrie_new ('/');
assert (self);

int ret = 0;

//  Let's start by inserting a couple of routes into the trie.
//  This one is for the route '/foo/bar' the slash at the beginning of the
//  route is important because everything before the first delimiter will be
//  discarded. A slash at the end of a route is optional though. The data
//  associated with this node is passed without destroy function which means
//  it must be destroyed by the caller.
int foo_bar_data = 10;
ret = ztrie_insert_route (self, "/foo/bar", &foo_bar_data, NULL);
assert (ret == 0);

//  Now suppose we like to match all routes with two tokens that start with
//  '/foo/' but aren't '/foo/bar'. This is possible by using regular
//  expressions which are enclosed in an opening and closing curly bracket.
//  Tokens that contain regular  expressions are always match after string
//  based tokens.
//  Note: There is no order in which regular expressions are sorted thus
//  if you enter multiple expressions for a route you will have to make
//  sure they don't have overlapping results. For example '/foo/{[^/]+}'
//  and '/foo/{\d+} having could turn out badly.
int foo_other_data = 100;
ret = ztrie_insert_route (self, "/foo/{[^/]+}", &foo_other_data, NULL);
assert (ret == 0);

//  Regular expression are only matched against tokens of the same level.
//  This allows us to append to are route with a regular expression as if
//  it were a string.
ret = ztrie_insert_route (self, "/foo/{[^/]+}/gulp", NULL, NULL);
assert (ret == 0);

//  Routes are identified by their endpoint, which is the last token of the route.
//  It is possible to insert routes for a node that already exists but isn't an
//  endpoint yet. The delimiter at the end of a route is optional and has no effect.
ret = ztrie_insert_route (self, "/foo/", NULL, NULL);
assert (ret == 0);

//  If you try to insert a route which already exists the method will return -1.
ret = ztrie_insert_route (self, "/foo", NULL, NULL);
assert (ret == -1);

//  It is not allowed to insert routes with empty tokens.
ret = ztrie_insert_route (self, "//foo", NULL, NULL);
assert (ret == -1);

//  Everything before the first delimiter is ignored so 'foo/bar/baz' is equivalent
//  to '/bar/baz'.
ret = ztrie_insert_route (self, "foo/bar/baz", NULL, NULL);
assert (ret == 0);
ret = ztrie_insert_route (self, "/bar/baz", NULL, NULL);
assert (ret == -1);

//  Of course you are allowed to remove routes, in case there is data associated with a
//  route and a destroy data function has been supplied that data will be destroyed.
ret = ztrie_remove_route (self, "/foo");
assert (ret == 0);

//  Removing a non existent route will  as well return -1.
ret = ztrie_remove_route (self, "/foo");
assert (ret == -1);

//  Removing a route with a regular expression must exactly match the entered one.
ret = ztrie_remove_route (self, "/foo/{[^/]+}");
assert (ret == 0);

//  Next we like to match a path by regular expressions and also extract matched
//  parts of a route. This can be done by naming the regular expression. The name of a
//  regular expression is entered at the beginning of the curly brackets and separated
//  by a colon from the regular expression. The first one in this examples is named
//  'name' and names the expression '[^/]'. If there is no capturing group defined in
//  the expression the whole matched string will be associated with this parameter. In
//  case you don't like the get the whole matched string use a capturing group, like
//  it has been done for the 'id' parameter. This is nice but you can even match as
//  many parameter for a token as you like. Therefore simply put the parameter names
//  separated by colons in front of the regular expression and make sure to add a
//  capturing group for each parameter. The first parameter will be associated with
//  the first capturing and so on.
char *data = (char *) malloc (80);
sprintf (data, "%s", "Hello World!");
ret = ztrie_insert_route (self, "/baz/{name:[^/]+}/{id:--(\\d+)}/{street:nr:(\\a+)(\\d+)}", data, NULL);
assert (ret == 0);

//  There is a lot you can do with regular expression but matching routes
//  of arbitrary length wont work. Therefore we make use of the asterisk
//  operator. Just place it at the end of your route, e.g. '/config/bar/*'.
ret = ztrie_insert_route (self, "/config/bar/*", NULL, NULL);
assert (ret == 0);

//  Appending to an asterisk as you would to with a regular expression
//  isn't valid.
ret = ztrie_insert_route (self, "/config/bar/*/bar", NULL, NULL);
assert (ret == -1);

//  The asterisk operator will only work as a leaf in the tree. If you
//  enter an asterisk in the middle of your route it will simply be
//  interpreted as a string.
ret = ztrie_insert_route (self, "/test/*/bar", NULL, NULL);
assert (ret == 0);

//  If a parent has an asterisk as child it is not allowed to have
//  other siblings.
ret = ztrie_insert_route (self, "/config/bar/foo/glup", NULL, NULL);
assert (ret != 0);

//  Test matches
bool hasMatch = false;

//  The route '/bar/foo' will fail to match as this route has never been inserted.
hasMatch = ztrie_matches (self, "/bar/foo");
assert (!hasMatch);

//  The route '/foo/bar' will match and we can obtain the data associated with it.
hasMatch = ztrie_matches (self, "/foo/bar");
assert (hasMatch);
int foo_bar_hit_data = *((int *) ztrie_hit_data (self));
assert (foo_bar_data == foo_bar_hit_data);

//  This route is part of another but is no endpoint itself thus the matches will fail.
hasMatch = ztrie_matches (self, "/baz/blub");
assert (!hasMatch);

//  This route will match our named regular expressions route. Thus we can extract data
//  from the route by their names.
hasMatch = ztrie_matches (self, "/baz/blub/--11/abc23");
assert (hasMatch);
char *match_data = (char *) ztrie_hit_data (self);
assert (streq ("Hello World!", match_data));
zhashx_t *parameters = ztrie_hit_parameters (self);
assert (zhashx_size (parameters) == 4);
assert (streq ("blub", (char *) zhashx_lookup (parameters, "name")));
assert (streq ("11", (char *) zhashx_lookup (parameters, "id")));
assert (streq ("abc", (char *) zhashx_lookup (parameters, "street")));
assert (streq ("23", (char *) zhashx_lookup (parameters, "nr")));
zhashx_destroy (&parameters);

//  This will match our asterisk route '/config/bar/*'. As the result we
//  can obtain the asterisk matched part of the route.
hasMatch = ztrie_matches (self, "/config/bar/foo/bar");
assert (hasMatch);
assert (streq (ztrie_hit_asterisk_match (self), "foo/bar"));

zstr_free (&data);
ztrie_destroy (&self);
----
