From f10d17d46e4ea80990416844b4314d564b3502dc Mon Sep 17 00:00:00 2001
From: QuietMisdreavus <victoria@quietmisdreavus.net>
Date: Fri, 31 Dec 2021 16:58:26 -0700
Subject: [PATCH] wip: half of the 'superscript' extension

---
 extensions/CMakeLists.txt    |   1 +
 extensions/core-extensions.c |   2 +
 extensions/superscript.c     | 141 +++++++++++++++++++++++++++++++++++
 extensions/superscript.h     |   9 +++
 test/spec.txt                |  44 +++++++++++
 5 files changed, 197 insertions(+)
 create mode 100644 extensions/superscript.c
 create mode 100644 extensions/superscript.h

diff --git a/extensions/CMakeLists.txt b/extensions/CMakeLists.txt
index 4977c98c3..d5d2284c0 100644
--- a/extensions/CMakeLists.txt
+++ b/extensions/CMakeLists.txt
@@ -11,6 +11,7 @@ set(LIBRARY_SOURCES
     ext_scanners.re
     ext_scanners.h
     tasklist.c
+    superscript.c
    )
 
 include_directories(
diff --git a/extensions/core-extensions.c b/extensions/core-extensions.c
index 131cdf402..1456116bf 100644
--- a/extensions/core-extensions.c
+++ b/extensions/core-extensions.c
@@ -7,6 +7,7 @@
 #include "tasklist.h"
 #include "registry.h"
 #include "plugin.h"
+#include "superscript.h"
 
 static int core_extensions_registration(cmark_plugin *plugin) {
   cmark_plugin_register_syntax_extension(plugin, create_table_extension());
@@ -15,6 +16,7 @@ static int core_extensions_registration(cmark_plugin *plugin) {
   cmark_plugin_register_syntax_extension(plugin, create_autolink_extension());
   cmark_plugin_register_syntax_extension(plugin, create_tagfilter_extension());
   cmark_plugin_register_syntax_extension(plugin, create_tasklist_extension());
+  cmark_plugin_register_syntax_extension(plugin, create_superscript_extension());
   return 1;
 }
 
diff --git a/extensions/superscript.c b/extensions/superscript.c
new file mode 100644
index 000000000..64112cb9d
--- /dev/null
+++ b/extensions/superscript.c
@@ -0,0 +1,141 @@
+#include "superscript.h"
+#include <inlines.h>
+#include <parser.h>
+#include <render.h>
+
+cmark_node_type CMARK_NODE_SUPERSCRIPT;
+
+static cmark_node *match(cmark_syntax_extension *self, cmark_parser *parser,
+                         cmark_node *parent, unsigned char character,
+                         cmark_inline_parser *inline_parser) {
+  cmark_node *res = NULL;
+  int startpos = cmark_inline_parser_get_offset(inline_parser) + 1;
+  int endpos = startpos;
+
+  if (character != '^')
+    return NULL;
+
+  // TODO: long-form parsing with parens
+  if (cmark_inline_parser_peek_at(inline_parser, endpos) == '(')
+    return NULL;
+
+  cmark_chunk *chunk = cmark_inline_parser_get_chunk(inline_parser);
+  bufsize_t len = chunk->len;
+
+  while (endpos < len && !cmark_isspace(cmark_inline_parser_peek_at(inline_parser, endpos)))
+    endpos++;
+
+  int nodelen = endpos - startpos;
+
+  // don't emit an empty node
+  if (nodelen == 0)
+    return NULL;
+
+  cmark_inline_parser_set_offset(inline_parser, startpos);
+
+  res = cmark_node_new_with_mem_and_ext(CMARK_NODE_SUPERSCRIPT, parser->mem, self);
+  res->as.literal = cmark_chunk_dup(chunk, startpos, nodelen);
+  res->start_line = cmark_inline_parser_get_line(inline_parser);
+  res->start_column = cmark_inline_parser_get_column(inline_parser);
+
+  cmark_inline_parser_set_offset(inline_parser, endpos);
+
+  res->end_line = cmark_inline_parser_get_line(inline_parser);
+  res->end_column = cmark_inline_parser_get_column(inline_parser);
+
+  const char *text = cmark_chunk_to_cstr(parser->mem, &res->as.literal);
+  cmark_node_set_string_content(res, text);
+
+  cmark_parse_inlines(parser, res, parser->refmap, parser->options);
+
+  return res;
+}
+
+static const char *get_type_string(cmark_syntax_extension *extension,
+                                   cmark_node *node) {
+  return node->type == CMARK_NODE_SUPERSCRIPT ? "superscript" : "<unknown>";
+}
+
+static int can_contain(cmark_syntax_extension *extension, cmark_node *node,
+                       cmark_node_type child_type) {
+  if (node->type != CMARK_NODE_SUPERSCRIPT)
+    return false;
+
+  return CMARK_NODE_TYPE_INLINE_P(child_type);
+}
+
+static void commonmark_render(cmark_syntax_extension *extension,
+                              cmark_renderer *renderer, cmark_node *node,
+                              cmark_event_type ev_type, int options) {
+  bool should_wrap = (cmark_strbuf_strchr(&node->content, ' ', 0) != -1);
+  bool entering = (ev_type == CMARK_EVENT_ENTER);
+  if (entering) {
+    if (should_wrap)
+      renderer->out(renderer, node, "^(", false, LITERAL);
+    else
+      renderer->out(renderer, node, "^", false, LITERAL);
+  } else if (!entering && should_wrap) {
+    renderer->out(renderer, node, ")", false, LITERAL);
+  }
+}
+
+static void latex_render(cmark_syntax_extension *extension,
+                         cmark_renderer *renderer, cmark_node *node,
+                         cmark_event_type ev_type, int options) {
+  bool entering = (ev_type == CMARK_EVENT_ENTER);
+  if (entering) {
+    renderer->out(renderer, node, "^{", false, LITERAL);
+  } else {
+    renderer->out(renderer, node, "}", false, LITERAL);
+  }
+}
+
+static void man_render(cmark_syntax_extension *extension,
+                       cmark_renderer *renderer, cmark_node *node,
+                       cmark_event_type ev_type, int options) {
+  // requires MOM
+  bool entering = (ev_type == CMARK_EVENT_ENTER);
+  if (entering) {
+    renderer->cr(renderer);
+    renderer->out(renderer, node, "\\*[SUP]", false, LITERAL);
+  } else {
+    renderer->out(renderer, node, "\\*[SUPX]", false, LITERAL);
+    renderer->cr(renderer);
+  }
+}
+
+static void html_render(cmark_syntax_extension *extension,
+                        cmark_html_renderer *renderer, cmark_node *node,
+                        cmark_event_type ev_type, int options) {
+  bool entering = (ev_type == CMARK_EVENT_ENTER);
+  if (entering) {
+    cmark_strbuf_puts(renderer->html, "<sup>");
+  } else {
+    cmark_strbuf_puts(renderer->html, "</sup>");
+  }
+}
+
+cmark_syntax_extension *create_superscript_extension(void) {
+  cmark_syntax_extension *ext = cmark_syntax_extension_new("superscript");
+  cmark_llist *special_chars = NULL;
+
+  cmark_syntax_extension_set_get_type_string_func(ext, get_type_string);
+  cmark_syntax_extension_set_can_contain_func(ext, can_contain);
+  cmark_syntax_extension_set_commonmark_render_func(ext, commonmark_render);
+  cmark_syntax_extension_set_plaintext_render_func(ext, commonmark_render);
+  cmark_syntax_extension_set_latex_render_func(ext, latex_render);
+  cmark_syntax_extension_set_man_render_func(ext, man_render);
+  cmark_syntax_extension_set_html_render_func(ext, html_render);
+  CMARK_NODE_SUPERSCRIPT = cmark_syntax_extension_add_node(1);
+
+  cmark_syntax_extension_set_match_inline_func(ext, match);
+//  cmark_syntax_extension_set_inline_from_delim_func(ext, insert);
+
+  cmark_mem *mem = cmark_get_default_mem_allocator();
+  special_chars = cmark_llist_append(mem, special_chars, (void *)'^');
+  cmark_syntax_extension_set_special_inline_chars(ext, special_chars);
+
+  cmark_syntax_extension_set_emphasis(ext, 1);
+
+  return ext;
+}
diff --git a/extensions/superscript.h b/extensions/superscript.h
new file mode 100644
index 000000000..465e1a2ab
--- /dev/null
+++ b/extensions/superscript.h
@@ -0,0 +1,9 @@
+#ifndef CMARK_GFM_SUPERSCRIPT_H
+#define CMARK_GFM_SUPERSCRIPT_H
+
+#include "cmark-gfm-core-extensions.h"
+
+extern cmark_node_type CMARK_NODE_SUPERSCRIPT;
+cmark_syntax_extension *create_superscript_extension(void);
+
+#endif /* CMARK_GFM_SUPERSCRIPT_H */
diff --git a/test/spec.txt b/test/spec.txt
index 582131d70..ce9bbed37 100644
--- a/test/spec.txt
+++ b/test/spec.txt
@@ -7734,6 +7734,50 @@ new paragraph~~.
 
 </div>
 
+<div class="extension">
+
+## Superscript (extension)
+
+GFM provides the `superscript` extension, which adds "superscript" spans.
+
+There are two ways to write superscripts. For simple uses, you can use a
+caret (`^`) to style the text between it and the next space (or the end of
+the line):
+
+```````````````````````````````` example superscript
+y = x^2 + 2
+
+Superscripting a whole ^word
+.
+<p>y = x<sup>2</sup> + 2</p>
+<p>Superscripting a whole <sup>word</sup></p>
+````````````````````````````````
+
+In addition, if you would like to raise more than one word, you can add
+parentheses around the text you would like to style in a superscript:
+
+```````````````````````````````` example superscript disabled
+I would like to ^(raise this whole phrase), please.
+.
+<p>I would like to <sup>raise this whole phrase</sup>, please.</p>
+````````````````````````````````
+
+Superscripts can be nested, by adding additional carets:
+
+```````````````````````````````` example superscript
+z = t^x^2
+.
+<p>z = t<sup>x<sup>2</sup></sup></p>
+````````````````````````````````
+
+```````````````````````````````` example superscript disabled
+For my next trick, I will ^(raise my text ^(twice)), at the same time!
+.
+<p>For my next trick, I will <sup>raise my text<sup>twice</sup></sup>, at the same time!</p>
+````````````````````````````````
+
+</div>
+
 ## Links
 
 A link contains [link text] (the visible text), a [link destination]