Dump reasonable turtle of schema to http

library/api.pl

@@ -61,12 +61,15 @@
 % JSON manipulation
 :- use_module(library(json_ld)).
 
+% File processing - especially for turtle
+:- use_module(library(file_utils), [checkpoint_to_turtle/3]).
+
+%%%%%%%%%%%%% API Paths %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+
 %% Set base location
 % We may want to allow this as a setting...
 http:location(root, '/', []).
 
-%%%%%%%%%%%%% API Paths %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
-
 :- http_handler(root(.), connect_handler(Method),
                 [method(Method),
                  methods([get,post])]). 
@@ -583,17 +586,22 @@
  * try_dump_schema(DB_URI, Request) is det. 
  * 
  * This should write out to the current stream in the appropriate format.
+ *
+ * This is structured in such a way that  
  */ 
 try_dump_schema(DB_URI, Request) :-
     with_mutex(
         DB_URI, 
         (
             try_get_param('terminus:encoding', Request, Encoding),
             (   Encoding = 'terminus:turtle'
-            ->  true
-            ;   Encoding = 'terminus:json_ld'
-            ->  true
-            ;   true
+            ->  current_output(Out),
+                checkpoint_to_turtle(DB_URI, schema, TTL_File),
+                read_file_to_string(TTL_File, String, []),
+                format('Content-type: application/turtle~n~n~s', [String])
+            ;   format(atom(MSG), 'Unimplemented encoding ~s', [Encoding]),
+                % Give a better error code etc. This is silly.
+                throw(http_reply(method_not_allowed('try_dump_schema', MSG)))
             )
         )
     ).

library/file_utils.pl

@@ -31,7 +31,9 @@
               make_checkpoint_directory/3,
               ttl_to_hdt/2,
               ntriples_to_hdt/2,
-              cleanup_edinburgh_escapes/1
+              cleanup_edinburgh_escapes/1,
+              last_checkpoint_file/3,
+              checkpoint_to_turtle/3
           ]).
 
 :- use_module(utils).
@@ -491,25 +493,54 @@
     ;   true),
     close(Out).
 
+/* 
+ * last_checkpoint_file(Collection,File) is det. 
+ * 
+ * Give the file location of the last checkpoint for 
+ * transformation (to turtle json-ld etc). 
+ */ 
+last_checkpoint_file(C,G,File) :-
+    current_checkpoint_directory(C,G,CPD),
+    interpolate([CPD,'/1-ckp.hdt'],File).
 
 /** 
- * hdt_to_turtle(+FileIn,+FileOut) is det.
+ * checkpoint_to_turtle(+C,+G,-Output_File) is det.
  * 
  * Create a hdt file from ttl using the rdf2hdt tool.
  */
-/*
-This does not generate a reasonable header at all. 
-We can probably do better by dumping to ntriples and then piping through rapper/raptor. 
- 
-hdt_to_turtle(FileIn,FileOut) :-
-    process_create(path(hdt2rdf), ['-f','turtle',FileIn,FileOut],
-                   [ stdout(pipe(Out)),
+checkpoint_to_turtle(Collection,Graph,Output_File) :-
+
+    last_checkpoint_file(Collection,Graph,FileIn), 
+    user:file_search_path(terminus_home, Dir),
+    get_time(T),floor(T,N),
+    interpolate([Dir,'/tmp/',N,'.ntriples'],NTriples_File),
+    process_create(path(hdt2rdf), ['-f','ntriples',FileIn,NTriples_File],
+                   [ stdout(pipe(NT_Out)),
                      process(PID)
                    ]),
     process_wait(PID,Status),
     (   Status=killed(Signal)
     ->  interpolate(["hdt2rdf killed with signal ",Signal], M),
         throw(error(M))
     ;   true),
+    close(NT_Out),
+
+    get_collection_prefix_list(Collection,List),
+    prefix_list_to_rapper_args(List,Prefix_Args),
+    append([['-i','ntriples','-o','turtle'],Prefix_Args,[NTriples_File]], Args),
+
+    interpolate([Dir,'/tmp/',N,'.ttl'],Output_File),
+    open(Output_File, write, Out),
+
+    process_create(path(rapper), Args,
+                   [ stderr(null),
+                     stdout(stream(Out)),
+                     process(Rapper_PID)
+                   ]),
+    process_wait(Rapper_PID,Rapper_Status),
+    (   Rapper_Status=killed(Rapper_Signal)
+    ->  interpolate(["hdt2rdf killed with signal ",Rapper_Signal], M),
+        throw(error(M))
+    ;   true),
+
     close(Out).
-*/

library/prefixes.pl

@@ -7,7 +7,8 @@
               get_collection_prefixes/2,
               get_collection_prefix_list/2,
               global_prefix_expand/2,
-              literal_expand/2
+              literal_expand/2,
+              prefix_list_to_rapper_args/2
           ]).
 
 /** <module> Prefixes
@@ -172,11 +173,20 @@
           List).
 
 /* 
- * get_collection_prefixes_list(Collection:atom,Prefixes:dict) is det.
+ * get_collection_prefix_list(Collection:atom,Prefixes:dict) is det.
  * 
  * return a list of pairs of prefixes.
  */
 get_collection_prefix_list(Collection,List) :-
     get_collection_prefix_pairs(Collection,Pairs),
     maplist([A-B,A=B]>>(true), Pairs, List).
 
+/* 
+ * prefix_list_to_rapper_args(Collection:atom,Prefixes:dict) is det.
+ * 
+ * return a list of arguments for rapper.
+ */
+prefix_list_to_rapper_args([],[]).
+prefix_list_to_rapper_args([P=U|Rest],['-f',Arg|Arg_Rest]) :-
+    interpolate(['xmlns:',P,'="',U,'"'],Arg),
+    prefix_list_to_rapper_args(Rest,Arg_Rest).

library/triplestore.pl

@@ -11,7 +11,6 @@
               commit/2,
               rollback/2,
               check_graph_exists/2,
-              last_plane_number/2,
               graph_checkpoint/3,
               current_checkpoint_directory/3,
               last_checkpoint_number/2,
@@ -341,11 +340,11 @@
     ).
 
 /** 
- * collapse_planes(+Collection_Id,+Graph_Id:graph_identifier) is det.
+ * checkpoint(+Collection_Id,+Graph_Id:graph_identifier) is det.
  * 
  * Create a new graph checkpoint from our current dynamic triple state
  */
-collapse_planes(Collection_Id,Graph_Id) :-
+checkpoint(Collection_Id,Graph_Id) :-
     make_checkpoint_directory(Collection_Id,Graph_Id, _),
     with_output_graph(
         graph(Collection_Id,Graph_Id,ckp,ttl),