html_smartypants.c

/*
 * Copyright (c) 2015, Vicent Marti
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */

#include "buffer.h"
#include "html.h"

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

#if defined(_WIN32)
#define snprintf	_snprintf
#endif

struct smartypants_data {
	int in_squote;
	int in_dquote;
};

static size_t smartypants_cb__ltag(struct buf *ob, struct smartypants_data *smrt, uint8_t previous_char, const uint8_t *text, size_t size);
static size_t smartypants_cb__dquote(struct buf *ob, struct smartypants_data *smrt, uint8_t previous_char, const uint8_t *text, size_t size);
static size_t smartypants_cb__amp(struct buf *ob, struct smartypants_data *smrt, uint8_t previous_char, const uint8_t *text, size_t size);
static size_t smartypants_cb__period(struct buf *ob, struct smartypants_data *smrt, uint8_t previous_char, const uint8_t *text, size_t size);
static size_t smartypants_cb__number(struct buf *ob, struct smartypants_data *smrt, uint8_t previous_char, const uint8_t *text, size_t size);
static size_t smartypants_cb__dash(struct buf *ob, struct smartypants_data *smrt, uint8_t previous_char, const uint8_t *text, size_t size);
static size_t smartypants_cb__parens(struct buf *ob, struct smartypants_data *smrt, uint8_t previous_char, const uint8_t *text, size_t size);
static size_t smartypants_cb__squote(struct buf *ob, struct smartypants_data *smrt, uint8_t previous_char, const uint8_t *text, size_t size);
static size_t smartypants_cb__backtick(struct buf *ob, struct smartypants_data *smrt, uint8_t previous_char, const uint8_t *text, size_t size);
static size_t smartypants_cb__escape(struct buf *ob, struct smartypants_data *smrt, uint8_t previous_char, const uint8_t *text, size_t size);

static size_t (*smartypants_cb_ptrs[])
	(struct buf *, struct smartypants_data *, uint8_t, const uint8_t *, size_t) =
{
	NULL,					/* 0 */
	smartypants_cb__dash,	/* 1 */
	smartypants_cb__parens,	/* 2 */
	smartypants_cb__squote, /* 3 */
	smartypants_cb__dquote, /* 4 */
	smartypants_cb__amp,	/* 5 */
	smartypants_cb__period,	/* 6 */
	smartypants_cb__number,	/* 7 */
	smartypants_cb__ltag,	/* 8 */
	smartypants_cb__backtick, /* 9 */
	smartypants_cb__escape, /* 10 */
};

static const uint8_t smartypants_cb_chars[] = {
	0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
	0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
	0, 0, 4, 0, 0, 0, 5, 3, 2, 0, 0, 0, 0, 1, 6, 0,
	0, 7, 0, 7, 0, 0, 0, 0, 0, 0, 0, 0, 8, 0, 0, 0,
	0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
	0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 10, 0, 0, 0,
	9, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
	0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
	0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
	0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
	0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
	0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
	0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
	0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
	0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
	0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
};

static inline int
word_boundary(uint8_t c)
{
	return c == 0 || isspace(c) || ispunct(c);
}

static inline int
fraction_boundary(uint8_t c)
{
	return c == 0 || isspace(c) || (c != '/' && ispunct(c));
}

// If 'text' begins with any kind of single quote (e.g. "'" or "&apos;" etc.),
// returns the length of the sequence of characters that makes up the single-
// quote.  Otherwise, returns zero.
static size_t
squote_len(const uint8_t *text, size_t size)
{
	static char* single_quote_list[] = { "'", "&#39;", "&#x27;", "&apos;", NULL };
	char** p;

	for (p = single_quote_list; *p; ++p) {
		size_t len = strlen(*p);
		if (size >= len && memcmp(text, *p, len) == 0) {
			return len;
		}
	}

	return 0;
}

// Converts " or ' at very beginning or end of a word to left or right quote
static int
smartypants_quotes(struct buf *ob, uint8_t previous_char, uint8_t next_char, uint8_t quote, int *is_open)
{
	char ent[8];

	if (*is_open && !word_boundary(next_char))
		return 0;

	if (!(*is_open) && !word_boundary(previous_char))
		return 0;

	snprintf(ent, sizeof(ent), "&%c%cquo;", (*is_open) ? 'r' : 'l', quote);
	*is_open = !(*is_open);
	bufputs(ob, ent);
	return 1;
}

// Converts ' to left or right single quote; but the initial ' might be in
// different forms, e.g. &apos; or &#39; or &#x27;.
// 'squote_text' points to the original single quote, and 'squote_size' is its length.
// 'text' points at the last character of the single-quote, e.g. ' or ;
static size_t
smartypants_squote(struct buf *ob, struct smartypants_data *smrt, uint8_t previous_char, const uint8_t *text, size_t size,
				   const uint8_t *squote_text, size_t squote_size)
{
	if (size >= 2) {
		uint8_t t1 = tolower(text[1]);
		int next_squote_len = squote_len(text+1, size-1);

		// convert '' to &ldquo; or &rdquo;
		if (next_squote_len > 0) {
			uint8_t next_char = (size > 1+next_squote_len) ? text[1+next_squote_len] : 0;
			if (smartypants_quotes(ob, previous_char, next_char, 'd', &smrt->in_dquote))
				return next_squote_len;
		}

		if (smartypants_quotes(ob, previous_char, size > 0 ? text[1] : 0, 's', &smrt->in_squote))
			return 0;

		// trailing single quotes: students', tryin'
		if (word_boundary(t1)) {
			BUFPUTSL(ob, "&rsquo;");
			return 0;
		}

		// Tom's, isn't, I'm, I'd
		if ((t1 == 's' || t1 == 't' || t1 == 'm' || t1 == 'd') &&
			(size == 3 || word_boundary(text[2]))) {
			BUFPUTSL(ob, "&rsquo;");
			return 0;
		}

		// you're, you'll, you've
		if (size >= 3) {
			uint8_t t2 = tolower(text[2]);

			if (((t1 == 'r' && t2 == 'e') ||
				(t1 == 'l' && t2 == 'l') ||
				(t1 == 'v' && t2 == 'e')) &&
				(size == 4 || word_boundary(text[3]))) {
				BUFPUTSL(ob, "&rsquo;");
				return 0;
			}
		}
	}

	bufput(ob, squote_text, squote_size);
	return 0;
}

// Converts ' to left or right single quote.
static size_t
smartypants_cb__squote(struct buf *ob, struct smartypants_data *smrt, uint8_t previous_char, const uint8_t *text, size_t size)
{
	return smartypants_squote(ob, smrt, previous_char, text, size, text, 1);
}

// Converts (c), (r), (tm)
static size_t
smartypants_cb__parens(struct buf *ob, struct smartypants_data *smrt, uint8_t previous_char, const uint8_t *text, size_t size)
{
	if (size >= 3) {
		uint8_t t1 = tolower(text[1]);
		uint8_t t2 = tolower(text[2]);

		if (t1 == 'c' && t2 == ')') {
			BUFPUTSL(ob, "&copy;");
			return 2;
		}

		if (t1 == 'r' && t2 == ')') {
			BUFPUTSL(ob, "&reg;");
			return 2;
		}

		if (size >= 4 && t1 == 't' && t2 == 'm' && text[3] == ')') {
			BUFPUTSL(ob, "&trade;");
			return 3;
		}
	}

	bufputc(ob, text[0]);
	return 0;
}

// Converts "--" to em-dash, etc.
static size_t
smartypants_cb__dash(struct buf *ob, struct smartypants_data *smrt, uint8_t previous_char, const uint8_t *text, size_t size)
{
	if (size >= 3 && text[1] == '-' && text[2] == '-') {
		BUFPUTSL(ob, "&mdash;");
		return 2;
	}

	if (size >= 2 && text[1] == '-') {
		BUFPUTSL(ob, "&ndash;");
		return 1;
	}

	bufputc(ob, text[0]);
	return 0;
}

// Converts &quot; etc.
static size_t
smartypants_cb__amp(struct buf *ob, struct smartypants_data *smrt, uint8_t previous_char, const uint8_t *text, size_t size)
{
	if (size >= 6 && memcmp(text, "&quot;", 6) == 0) {
		if (smartypants_quotes(ob, previous_char, size >= 7 ? text[6] : 0, 'd', &smrt->in_dquote))
			return 5;
	}

	int len = squote_len(text, size);
	if (len > 0) {
		return (len-1) + smartypants_squote(ob, smrt, previous_char, text+(len-1), size-(len-1), text, len);
	}

	if (size >= 4 && memcmp(text, "&#0;", 4) == 0)
		return 3;

	bufputc(ob, '&');
	return 0;
}

// Converts "..." to ellipsis
static size_t
smartypants_cb__period(struct buf *ob, struct smartypants_data *smrt, uint8_t previous_char, const uint8_t *text, size_t size)
{
	if (size >= 3 && text[1] == '.' && text[2] == '.') {
		BUFPUTSL(ob, "&hellip;");
		return 2;
	}

	if (size >= 5 && text[1] == ' ' && text[2] == '.' && text[3] == ' ' && text[4] == '.') {
		BUFPUTSL(ob, "&hellip;");
		return 4;
	}

	bufputc(ob, text[0]);
	return 0;
}

// Converts `` to opening double quote
static size_t
smartypants_cb__backtick(struct buf *ob, struct smartypants_data *smrt, uint8_t previous_char, const uint8_t *text, size_t size)
{
	if (size >= 2 && text[1] == '`') {
		if (smartypants_quotes(ob, previous_char, size >= 3 ? text[2] : 0, 'd', &smrt->in_dquote))
			return 1;
	}

	bufputc(ob, text[0]);
	return 0;
}

// Converts 1/2, 1/4, 3/4
static size_t
smartypants_cb__number(struct buf *ob, struct smartypants_data *smrt, uint8_t previous_char, const uint8_t *text, size_t size)
{
	if (fraction_boundary(previous_char) && size >= 3) {
		if (text[0] == '1' && text[1] == '/' && text[2] == '2') {
			if (size == 3 || fraction_boundary(text[3])) {
				BUFPUTSL(ob, "&frac12;");
				return 2;
			}
		}

		if (text[0] == '1' && text[1] == '/' && text[2] == '4') {
			if (size == 3 || fraction_boundary(text[3]) ||
				(size >= 5 && tolower(text[3]) == 't' && tolower(text[4]) == 'h')) {
				BUFPUTSL(ob, "&frac14;");
				return 2;
			}
		}

		if (text[0] == '3' && text[1] == '/' && text[2] == '4') {
			if (size == 3 || fraction_boundary(text[3]) ||
				(size >= 6 && tolower(text[3]) == 't' && tolower(text[4]) == 'h' && tolower(text[5]) == 's')) {
				BUFPUTSL(ob, "&frac34;");
				return 2;
			}
		}
	}

	bufputc(ob, text[0]);
	return 0;
}

// Converts " to left or right double quote
static size_t
smartypants_cb__dquote(struct buf *ob, struct smartypants_data *smrt, uint8_t previous_char, const uint8_t *text, size_t size)
{
	if (!smartypants_quotes(ob, previous_char, size > 0 ? text[1] : 0, 'd', &smrt->in_dquote))
		BUFPUTSL(ob, "&quot;");

	return 0;
}

static size_t
smartypants_cb__ltag(struct buf *ob, struct smartypants_data *smrt, uint8_t previous_char, const uint8_t *text, size_t size)
{
	static const char *skip_tags[] = {
	  "pre", "code", "var", "samp", "kbd", "math", "script", "style"
	};
	static const size_t skip_tags_count = 8;

	size_t next_to_closing_a = 0;
	size_t tag, i = 0;

	while (i < size && text[i] != '>')
		i++;

	for (tag = 0; tag < skip_tags_count; ++tag) {
		if (sdhtml_is_tag(text, size, skip_tags[tag]) == HTML_TAG_OPEN)
			break;
	}

	if (tag < skip_tags_count) {
		for (;;) {
			while (i < size && text[i] != '<')
				i++;

			if (i == size)
				break;

			if (sdhtml_is_tag(text + i, size - i, skip_tags[tag]) == HTML_TAG_CLOSE)
				break;

			i++;
		}

		while (i < size && text[i] != '>')
			i++;
	}

	if (sdhtml_is_tag(text, size, "a") == HTML_TAG_CLOSE) {
		while (i < size && text[i] != '>')
			i++;

		next_to_closing_a = 1;
	}

	bufput(ob, text, i + 1);

	// Pretty tricky: since people may refer to something or someone
	// with a link but use the possessive form right after it, we need
	// to check whether a single quote is next to a closing "</a"> tag.
	if (next_to_closing_a && strncmp("&#39;", text+(i+1), 5) == 0) {
		bufput(ob, "&rsquo;", 7);
		i += 5;
	}

	return i;
}

static size_t
smartypants_cb__escape(struct buf *ob, struct smartypants_data *smrt, uint8_t previous_char, const uint8_t *text, size_t size)
{
	if (size < 2)
		return 0;

	switch (text[1]) {
	case '\\':
	case '"':
	case '\'':
	case '.':
	case '-':
	case '`':
		bufputc(ob, text[1]);
		return 1;

	default:
		bufputc(ob, '\\');
		return 0;
	}
}

#if 0
static struct {
    uint8_t c0;
    const uint8_t *pattern;
    const uint8_t *entity;
    int skip;
} smartypants_subs[] = {
    { '\'', "'s>",      "&rsquo;",  0 },
    { '\'', "'t>",      "&rsquo;",  0 },
    { '\'', "'re>",     "&rsquo;",  0 },
    { '\'', "'ll>",     "&rsquo;",  0 },
    { '\'', "'ve>",     "&rsquo;",  0 },
    { '\'', "'m>",      "&rsquo;",  0 },
    { '\'', "'d>",      "&rsquo;",  0 },
    { '-',  "--",       "&mdash;",  1 },
    { '-',  "<->",      "&ndash;",  0 },
    { '.',  "...",      "&hellip;", 2 },
    { '.',  ". . .",    "&hellip;", 4 },
    { '(',  "(c)",      "&copy;",   2 },
    { '(',  "(r)",      "&reg;",    2 },
    { '(',  "(tm)",     "&trade;",  3 },
    { '3',  "<3/4>",    "&frac34;", 2 },
    { '3',  "<3/4ths>", "&frac34;", 2 },
    { '1',  "<1/2>",    "&frac12;", 2 },
    { '1',  "<1/4>",    "&frac14;", 2 },
    { '1',  "<1/4th>",  "&frac14;", 2 },
    { '&',  "&#0;",      0,       3 },
};
#endif

void
sdhtml_smartypants(struct buf *ob, const uint8_t *text, size_t size)
{
	size_t i;
	struct smartypants_data smrt = {0, 0};

	if (!text)
		return;

	bufgrow(ob, size);

	for (i = 0; i < size; ++i) {
		size_t org;
		uint8_t action = 0;

		org = i;
		while (i < size && (action = smartypants_cb_chars[text[i]]) == 0)
			i++;

		if (i > org)
			bufput(ob, text + org, i - org);

		if (i < size) {
			i += smartypants_cb_ptrs[(int)action]
				(ob, &smrt, i ? text[i - 1] : 0, text + i, size - i);
		}
	}
}