path: root/src/commonmark.c

#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <assert.h>
#include <ctype.h>

#include "config.h"
#include "cmark.h"
#include "node.h"
#include "buffer.h"
#include "utf8.h"
#include "scanners.h"
#include "render.h"

#define safe_strlen(s) cmark_strbuf_safe_strlen(s)
#define OUT(s, wrap, escaping) renderer->out(renderer, s, wrap, escaping)
#define LIT(s) renderer->out(renderer, s, false, LITERAL)
#define CR() renderer->cr(renderer)
#define BLANKLINE() renderer->blankline(renderer)

// Functions to convert cmark_nodes to commonmark strings.

static inline void outc(cmark_renderer *renderer, cmark_escaping escape,
                        int32_t c, unsigned char nextc) {
  bool needs_escaping = false;
  char encoded[20];

  needs_escaping =
      escape != LITERAL &&
      ((escape == NORMAL &&
        (c == '*' || c == '_' || c == '[' || c == ']' || c == '#' || c == '<' ||
         c == '>' || c == '\\' || c == '`' || c == '!' ||
         (c == '&' && isalpha(nextc)) || (c == '!' && nextc == '[') ||
         (renderer->begin_content && (c == '-' || c == '+' || c == '=')) ||
         ((c == '.' || c == ')') &&
          isdigit(renderer->buffer->ptr[renderer->buffer->size - 1])))) ||
       (escape == URL && (c == '`' || c == '<' || c == '>' || isspace(c) ||
                          c == '\\' || c == ')' || c == '(')) ||
       (escape == TITLE &&
        (c == '`' || c == '<' || c == '>' || c == '"' || c == '\\')));

  if (needs_escaping) {
    if (isspace(c)) {
      // use percent encoding for spaces
      sprintf(encoded, "%%%2x", c);
      cmark_strbuf_puts(renderer->buffer, encoded);
      renderer->column += 3;
    } else {
      cmark_render_ascii(renderer, "\\");
      cmark_render_code_point(renderer, c);
    }
  } else {
    cmark_render_code_point(renderer, c);
  }
}

static int longest_backtick_sequence(const char *code) {
  int longest = 0;
  int current = 0;
  size_t i = 0;
  size_t code_len = safe_strlen(code);
  while (i <= code_len) {
    if (code[i] == '`') {
      current++;
    } else {
      if (current > longest) {
        longest = current;
      }
      current = 0;
    }
    i++;
  }
  return longest;
}

static int shortest_unused_backtick_sequence(const char *code) {
  int32_t used = 1;
  int current = 0;
  size_t i = 0;
  size_t code_len = safe_strlen(code);
  while (i <= code_len) {
    if (code[i] == '`') {
      current++;
    } else {
      if (current) {
        used |= (1 << current);
      }
      current = 0;
    }
    i++;
  }
  // return number of first bit that is 0:
  i = 0;
  while (used & 1) {
    used = used >> 1;
    i++;
  }
  return (int)i;
}

static bool is_autolink(cmark_node *node) {
  cmark_chunk *title;
  cmark_chunk *url;
  cmark_node *link_text;
  char *realurl;
  int realurllen;

  if (node->type != CMARK_NODE_LINK) {
    return false;
  }

  url = &node->as.link.url;
  if (url->len == 0 || scan_scheme(url, 0) == 0) {
    return false;
  }

  title = &node->as.link.title;
  // if it has a title, we can't treat it as an autolink:
  if (title->len > 0) {
    return false;
  }

  link_text = node->first_child;
  cmark_consolidate_text_nodes(link_text);
  realurl = (char *)url->data;
  realurllen = url->len;
  if (strncmp(realurl, "mailto:", 7) == 0) {
    realurl += 7;
    realurllen -= 7;
  }
  return (realurllen == link_text->as.literal.len &&
          strncmp(realurl, (char *)link_text->as.literal.data,
                  link_text->as.literal.len) == 0);
}

// if node is a block node, returns node.
// otherwise returns first block-level node that is an ancestor of node.
static cmark_node *get_containing_block(cmark_node *node) {
  while (node && (node->type < CMARK_NODE_FIRST_BLOCK ||
                  node->type > CMARK_NODE_LAST_BLOCK)) {
    node = node->parent;
  }
  return node;
}

static int S_render_node(cmark_renderer *renderer, cmark_node *node,
                         cmark_event_type ev_type, int options) {
  cmark_node *tmp;
  int list_number;
  cmark_delim_type list_delim;
  int numticks;
  int i;
  bool entering = (ev_type == CMARK_EVENT_ENTER);
  const char *info, *code, *title;
  size_t info_len, code_len;
  char listmarker[20];
  char *emph_delim;
  bufsize_t marker_width;

  // Don't adjust tight list status til we've started the list.
  // Otherwise we loose the blank line between a paragraph and
  // a following list.
  if (!(node->type == CMARK_NODE_ITEM && node->prev == NULL && entering)) {
    tmp = get_containing_block(node);
    renderer->in_tight_list_item =
        (tmp->type == CMARK_NODE_ITEM &&
         cmark_node_get_list_tight(tmp->parent)) ||
        (tmp && tmp->parent && tmp->parent->type == CMARK_NODE_ITEM &&
         cmark_node_get_list_tight(tmp->parent->parent));
  }

  switch (node->type) {
  case CMARK_NODE_DOCUMENT:
    break;

  case CMARK_NODE_BLOCK_QUOTE:
    if (entering) {
      LIT("> ");
      renderer->begin_content = true;
      cmark_strbuf_puts(renderer->prefix, "> ");
    } else {
      cmark_strbuf_truncate(renderer->prefix, renderer->prefix->size - 2);
      BLANKLINE();
    }
    break;

  case CMARK_NODE_LIST:
    if (!entering && node->next && (node->next->type == CMARK_NODE_CODE_BLOCK ||
                                    node->next->type == CMARK_NODE_LIST)) {
      // this ensures 2 blank lines after list,
      // if before code block or list:
      LIT("\n");
    }
    break;

  case CMARK_NODE_ITEM:
    if (cmark_node_get_list_type(node->parent) == CMARK_BULLET_LIST) {
      marker_width = 2;
    } else {
      list_number = cmark_node_get_list_start(node->parent);
      list_delim = cmark_node_get_list_delim(node->parent);
      tmp = node;
      while (tmp->prev) {
        tmp = tmp->prev;
        list_number += 1;
      }
      // we ensure a width of at least 4 so
      // we get nice transition from single digits
      // to double
      sprintf(listmarker, "%d%s%s", list_number,
              list_delim == CMARK_PAREN_DELIM ? ")" : ".",
              list_number < 10 ? "  " : " ");
      marker_width = safe_strlen(listmarker);
    }
    if (entering) {
      if (cmark_node_get_list_type(node->parent) == CMARK_BULLET_LIST) {
        LIT("* ");
        renderer->begin_content = true;
        cmark_strbuf_puts(renderer->prefix, "  ");
      } else {
        LIT(listmarker);
        renderer->begin_content = true;
        for (i = marker_width; i--;) {
          cmark_strbuf_putc(renderer->prefix, ' ');
        }
      }
    } else {
      cmark_strbuf_truncate(renderer->prefix,
                            renderer->prefix->size - marker_width);
      CR();
    }
    break;

  case CMARK_NODE_HEADING:
    if (entering) {
      for (i = cmark_node_get_heading_level(node); i > 0; i--) {
        LIT("#");
      }
      LIT(" ");
      renderer->begin_content = true;
      renderer->no_wrap = true;
    } else {
      renderer->no_wrap = false;
      BLANKLINE();
    }
    break;

  case CMARK_NODE_CODE_BLOCK:
    BLANKLINE();
    info = cmark_node_get_fence_info(node);
    info_len = safe_strlen(info);
    code = cmark_node_get_literal(node);
    code_len = safe_strlen(code);
    // use indented form if no info, and code doesn't
    // begin or end with a blank line, and code isn't
    // first thing in a list item
    if (info_len == 0 &&
        (code_len > 2 && !isspace(code[0]) &&
         !(isspace(code[code_len - 1]) && isspace(code[code_len - 2]))) &&
        !(node->prev == NULL && node->parent &&
          node->parent->type == CMARK_NODE_ITEM)) {
      LIT("    ");
      cmark_strbuf_puts(renderer->prefix, "    ");
      OUT(cmark_node_get_literal(node), false, LITERAL);
      cmark_strbuf_truncate(renderer->prefix, renderer->prefix->size - 4);
    } else {
      numticks = longest_backtick_sequence(code) + 1;
      if (numticks < 3) {
        numticks = 3;
      }
      for (i = 0; i < numticks; i++) {
        LIT("`");
      }
      LIT(" ");
      OUT(info, false, LITERAL);
      CR();
      OUT(cmark_node_get_literal(node), false, LITERAL);
      CR();
      for (i = 0; i < numticks; i++) {
        LIT("`");
      }
    }
    BLANKLINE();
    break;

  case CMARK_NODE_HTML_BLOCK:
    BLANKLINE();
    OUT(cmark_node_get_literal(node), false, LITERAL);
    BLANKLINE();
    break;

  case CMARK_NODE_CUSTOM_BLOCK:
    BLANKLINE();
    OUT(entering ? cmark_node_get_on_enter(node) : cmark_node_get_on_exit(node),
        false, LITERAL);
    BLANKLINE();
    break;

  case CMARK_NODE_THEMATIC_BREAK:
    BLANKLINE();
    LIT("-----");
    BLANKLINE();
    break;

  case CMARK_NODE_PARAGRAPH:
    if (!entering) {
      BLANKLINE();
    }
    break;

  case CMARK_NODE_TEXT:
    OUT(cmark_node_get_literal(node), true, NORMAL);
    break;

  case CMARK_NODE_LINEBREAK:
    if (!(CMARK_OPT_HARDBREAKS & options)) {
      LIT("\\");
    }
    CR();
    break;

  case CMARK_NODE_SOFTBREAK:
    if (renderer->width == 0 && !(CMARK_OPT_HARDBREAKS & options)) {
      CR();
    } else {
      OUT(" ", true, LITERAL);
    }
    break;

  case CMARK_NODE_CODE:
    code = cmark_node_get_literal(node);
    code_len = safe_strlen(code);
    numticks = shortest_unused_backtick_sequence(code);
    for (i = 0; i < numticks; i++) {
      LIT("`");
    }
    if (code_len == 0 || code[0] == '`') {
      LIT(" ");
    }
    OUT(cmark_node_get_literal(node), true, LITERAL);
    if (code_len == 0 || code[code_len - 1] == '`') {
      LIT(" ");
    }
    for (i = 0; i < numticks; i++) {
      LIT("`");
    }
    break;

  case CMARK_NODE_HTML_INLINE:
    OUT(cmark_node_get_literal(node), false, LITERAL);
    break;

  case CMARK_NODE_CUSTOM_INLINE:
    OUT(entering ? cmark_node_get_on_enter(node) : cmark_node_get_on_exit(node),
        false, LITERAL);
    break;

  case CMARK_NODE_STRONG:
    if (entering) {
      LIT("**");
    } else {
      LIT("**");
    }
    break;

  case CMARK_NODE_EMPH:
    // If we have EMPH(EMPH(x)), we need to use *_x_*
    // because **x** is STRONG(x):
    if (node->parent && node->parent->type == CMARK_NODE_EMPH &&
        node->next == NULL && node->prev == NULL) {
      emph_delim = "_";
    } else {
      emph_delim = "*";
    }
    if (entering) {
      LIT(emph_delim);
    } else {
      LIT(emph_delim);
    }
    break;

  case CMARK_NODE_LINK:
    if (is_autolink(node)) {
      if (entering) {
        LIT("<");
        if (strncmp(cmark_node_get_url(node), "mailto:", 7) == 0) {
          LIT((const char *)cmark_node_get_url(node) + 7);
        } else {
          LIT((const char *)cmark_node_get_url(node));
        }
        LIT(">");
        // return signal to skip contents of node...
        return 0;
      }
    } else {
      if (entering) {
        LIT("[");
      } else {
        LIT("](");
        OUT(cmark_node_get_url(node), false, URL);
        title = cmark_node_get_title(node);
        if (safe_strlen(title) > 0) {
          LIT(" \"");
          OUT(title, false, TITLE);
          LIT("\"");
        }
        LIT(")");
      }
    }
    break;

  case CMARK_NODE_IMAGE:
    if (entering) {
      LIT("![");
    } else {
      LIT("](");
      OUT(cmark_node_get_url(node), false, URL);
      title = cmark_node_get_title(node);
      if (safe_strlen(title) > 0) {
        OUT(" \"", true, LITERAL);
        OUT(title, false, TITLE);
        LIT("\"");
      }
      LIT(")");
    }
    break;

  default:
    assert(false);
    break;
  }

  return 1;
}

char *cmark_render_commonmark(cmark_node *root, int options, int width) {
  if (options & CMARK_OPT_HARDBREAKS) {
    // disable breaking on width, since it has
    // a different meaning with OPT_HARDBREAKS
    width = 0;
  }
  return cmark_render(root, options, width, outc, S_render_node);
}