blogc: generate table of contents tree

this commit allows users to use the `{{ TOCTREE }}` variable in their
templates, to get automatically generated table of contents for entries.
The variable is binded to each entry, so it can be used in any block
that runs in entry context, like `{% block entry %}`.

There's a small performance penalty for this, because the table of
contents is rendered for any entry, despite being used or not, and not
generated on-demand.

still missing documentation. tests are good enough.

1 files changed, 33 insertions, 3 deletions

diff --git a/src/blogc/source-parser.c b/src/blogc/source-parser.c
index 18cf95a..13df9e3 100644
--- a/src/blogc/source-parser.c
+++ b/src/blogc/source-parser.c
@@ -1,6 +1,6 @@
 /*
  * blogc: A blog compiler.
- * Copyright (C) 2014-2019 Rafael G. Martins <rafael@rafaelmartins.eng.br>
+ * Copyright (C) 2014-2020 Rafael G. Martins <rafael@rafaelmartins.eng.br>
  *
  * This program can be distributed under the terms of the BSD License.
  * See the file LICENSE.
@@ -11,6 +11,7 @@
 
 #include "content-parser.h"
 #include "source-parser.h"
+#include "toctree.h"
 #include "../common/error.h"
 #include "../common/utils.h"
 
@@ -27,7 +28,8 @@ typedef enum {
 
 
 bc_trie_t*
-blogc_source_parse(const char *src, size_t src_len, bc_error_t **err)
+blogc_source_parse(const char *src, size_t src_len, int toctree_maxdepth,
+    bc_error_t **err)
 {
     if (err == NULL || *err != NULL)
         return NULL;
@@ -153,8 +155,11 @@ blogc_source_parse(const char *src, size_t src_len, bc_error_t **err)
                     bc_trie_insert(rv, "RAW_CONTENT", tmp);
                     char *first_header = NULL;
                     char *description = NULL;
+                    char *endl = NULL;
+                    bc_slist_t *headers = NULL;
+                    bool read_headers = (NULL == bc_trie_lookup(rv, "TOCTREE"));
                     content = blogc_content_parse(tmp, &end_excerpt,
-                        &first_header, &description);
+                        &first_header, &description, &endl, read_headers ? &headers : NULL);
                     if (first_header != NULL) {
                         // do not override source-provided first_header.
                         if (NULL == bc_trie_lookup(rv, "FIRST_HEADER")) {
@@ -177,6 +182,31 @@ blogc_source_parse(const char *src, size_t src_len, bc_error_t **err)
                             free(description);
                         }
                     }
+                    if (headers != NULL) {
+                        // we already validated that the user do not defined TOCTREE
+                        // manually in source file.
+                        const char *maxdepth = bc_trie_lookup(rv, "TOCTREE_MAXDEPTH");
+                        if (maxdepth != NULL) {
+                            char *endptr;
+                            toctree_maxdepth = strtol(maxdepth, &endptr, 10);
+                            if (*maxdepth != '\0' && *endptr != '\0') {
+                                *err = bc_error_parser(BLOGC_ERROR_SOURCE_PARSER, src, src_len,
+                                    current,
+                                    "Invalid value for 'TOCTREE_MAXDEPTH' variable: %s.",
+                                    maxdepth);
+                                blogc_toctree_free(headers);
+                                free(endl);
+                                free(content);
+                                break;
+                            }
+                        }
+                        char *toctree = blogc_toctree_render(headers, toctree_maxdepth, endl);
+                        blogc_toctree_free(headers);
+                        if (toctree != NULL) {
+                            bc_trie_insert(rv, "TOCTREE", toctree);
+                        }
+                    }
+                    free(endl);
                     bc_trie_insert(rv, "CONTENT", content);
                     bc_trie_insert(rv, "EXCERPT", end_excerpt == 0 ?
                         bc_strdup(content) : bc_strndup(content, end_excerpt));