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Date:: Thu May 13 19:19:10 2021 UTC
Message:: heuristic to obtain the page title if not h1 found
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1 /*
2  * Copyright (c) 2021 Omar Polo <op@omarpolo.com>
3  *
4  * Permission to use, copy, modify, and distribute this software for any
5  * purpose with or without fee is hereby granted, provided that the above
6  * copyright notice and this permission notice appear in all copies.
7  *
8  * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
9  * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
10  * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
11  * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
12  * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
13  * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
14  * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
15  */
16 
17 /*
18  * A streaming gemtext parser.
19  *
20  * TODO:
21  *  - handle NULs
22  *  - UTF8
23  */
24 
25 #include "telescope.h"
26 
27 #include <ctype.h>
28 #include <string.h>
29 #include <stdlib.h>
30 
31 static int	gemtext_parse(struct parser*, const char*, size_t);
32 static int	gemtext_foreach_line(struct parser*, const char*, size_t);
33 static int	gemtext_free(struct parser*);
34 
35 static int	parse_text(struct parser*, enum line_type, const char*, size_t);
36 static int	parse_link(struct parser*, enum line_type, const char*, size_t);
37 static int	parse_title(struct parser*, enum line_type, const char*, size_t);
38 static int	parse_item(struct parser*, enum line_type, const char*, size_t);
39 static int	parse_quote(struct parser*, enum line_type, const char*, size_t);
40 static int	parse_pre_start(struct parser*, enum line_type, const char*, size_t);
41 static int	parse_pre_cnt(struct parser*, enum line_type, const char*, size_t);
42 static int	parse_pre_end(struct parser*, enum line_type, const char*, size_t);
43 static void	search_title(struct parser*, enum line_type);
44 
45 typedef int (parselinefn)(struct parser*, enum line_type, const char*, size_t);
46 
47 static parselinefn *parsers[] = {
48 	parse_text,		/* LINE_TEXT */
49 	parse_link,		/* LINE_LINK */
50 	parse_title,		/* LINE_TITLE_1 */
51 	parse_title,		/* LINE_TITLE_2 */
52 	parse_title,		/* LINE_TITLE_3 */
53 	parse_item,		/* LINE_ITEM */
54 	parse_quote,		/* LINE_QUOTE */
55 	parse_pre_start,	/* LINE_PRE_START */
56 	parse_pre_cnt,		/* LINE_PRE_CONTENT */
57 	parse_pre_end,		/* LINE_PRE_END */
58 };
59 
60 void
61 gemtext_initparser(struct parser *p)
62 {
63 	memset(p, 0, sizeof(*p));
64 
65 	p->name = "text/gemini";
66 	p->parse = &gemtext_parse;
67 	p->free  = &gemtext_free;
68 }
69 
70 static inline int
71 emit_line(struct parser *p, enum line_type type, char *line, char *alt)
72 {
73 	struct line *l;
74 
75 	if ((l = calloc(1, sizeof(*l))) == NULL)
76 		return 0;
77 
78 	l->type = type;
79 	l->line = line;
80 	l->alt = alt;
81 
82 	if (TAILQ_EMPTY(&p->head))
83 		TAILQ_INSERT_HEAD(&p->head, l, lines);
84 	else
85 		TAILQ_INSERT_TAIL(&p->head, l, lines);
86 
87 	return 1;
88 }
89 
90 static int
91 parse_text(struct parser *p, enum line_type t, const char *buf, size_t len)
92 {
93 	char *l;
94 
95 	if ((l = calloc(1, len+1)) == NULL)
96 		return 0;
97 	memcpy(l, buf, len);
98 	return emit_line(p, t, l, NULL);
99 }
100 
101 static int
102 parse_link(struct parser *p, enum line_type t, const char *buf, size_t len)
103 {
104 	char *l, *u;
105 	const char *url_start;
106 
107 	if (len <= 2)
108 		return emit_line(p, t, NULL, NULL);
109 	buf += 2;
110 	len -= 2;
111 
112 	while (len > 0 && isspace(buf[0])) {
113 		buf++;
114 		len--;
115 	}
116 
117 	if (len == 0)
118 		return emit_line(p, t, NULL, NULL);
119 
120 	url_start = buf;
121 	while (len > 0 && !isspace(buf[0])) {
122 		buf++;
123 		len--;
124 	}
125 
126 	if ((u = calloc(1, buf - url_start + 1)) == NULL)
127 		return 0;
128 	memcpy(u, url_start, buf - url_start);
129 
130 	if (len == 0)
131 		goto nolabel;
132 
133 	while (len > 0 && isspace(buf[0])) {
134 		buf++;
135 		len--;
136 	}
137 
138 	if (len == 0)
139 		goto nolabel;
140 
141 	if ((l = calloc(1, len + 1)) == NULL)
142 		return 0;
143 
144 	memcpy(l, buf, len);
145 	return emit_line(p, t, l, u);
146 
147 nolabel:
148 	if ((l = strdup(u)) == NULL)
149 		return 0;
150 	return emit_line(p, t, l, u);
151 }
152 
153 static int
154 parse_title(struct parser *p, enum line_type t, const char *buf, size_t len)
155 {
156 	char *l;
157 
158 	switch (t) {
159 	case LINE_TITLE_1:
160 		if (len <= 1)
161 			return emit_line(p, t, NULL, NULL);
162 		buf++;
163 		len--;
164 		break;
165 	case LINE_TITLE_2:
166 		if (len <= 2)
167 			return emit_line(p, t, NULL, NULL);
168 		buf += 2;
169 		len -= 2;
170 		break;
171 	case LINE_TITLE_3:
172 		if (len <= 3)
173 			return emit_line(p, t, NULL, NULL);
174 		buf += 3;
175 		len -= 3;
176 		break;
177 	default:
178 		/* unreachable */
179 		abort();
180 	}
181 
182 	while (len > 0 && isspace(buf[0])) {
183 		buf++;
184 		len--;
185 	}
186 
187 	if (len == 0)
188 		return emit_line(p, t, NULL, NULL);
189 
190 	if (t == LINE_TITLE_1 && *p->title == '\0')
191 		strncpy(p->title, buf, MIN(sizeof(p->title)-1, len));
192 
193 	if ((l = calloc(1, len+1)) == NULL)
194 		return 0;
195 	memcpy(l, buf, len);
196 	return emit_line(p, t, l, NULL);
197 }
198 
199 static int
200 parse_item(struct parser *p, enum line_type t, const char *buf, size_t len)
201 {
202 	char *l;
203 
204 	if (len == 1)
205 		return emit_line(p, t, NULL, NULL);
206 
207 	buf++;
208 	len--;
209 
210 	while (len > 0 && isspace(buf[0])) {
211 		buf++;
212 		len--;
213 	}
214 
215 	if (len == 0)
216 		return emit_line(p, t, NULL, NULL);
217 
218 	if ((l = calloc(1, len+1)) == NULL)
219 		return 0;
220 	memcpy(l, buf, len);
221 	return emit_line(p, t, l, NULL);
222 }
223 
224 static int
225 parse_quote(struct parser *p, enum line_type t, const char *buf, size_t len)
226 {
227 	char *l;
228 
229 	if (len == 1)
230 		return emit_line(p, t, NULL, NULL);
231 
232 	buf++;
233 	len--;
234 
235 	while (len > 0 && isspace(buf[0])) {
236 		buf++;
237 		len--;
238 	}
239 
240 	if (len == 0)
241 		return emit_line(p, t, NULL, NULL);
242 
243 	if ((l = calloc(1, len+1)) == NULL)
244 		return 0;
245 	memcpy(l, buf, len);
246 	return emit_line(p, t, l, NULL);
247 }
248 
249 static int
250 parse_pre_start(struct parser *p, enum line_type t, const char *buf, size_t len)
251 {
252 	char *l;
253 
254 	if (len <= 3)
255 		return emit_line(p, t, NULL, NULL);
256 
257 	buf += 3;
258 	len -= 3;
259 
260 	while (len > 0 && isspace(buf[0])) {
261 		buf++;
262 		len--;
263 	}
264 
265 	if (len == 0)
266 		return emit_line(p, t, NULL, NULL);
267 
268 	if ((l = calloc(1, len+1)) == NULL)
269 		return 0;
270 
271 	memcpy(l, buf, len);
272 	return emit_line(p, t, l, NULL);
273 }
274 
275 static int
276 parse_pre_cnt(struct parser *p, enum line_type t, const char *buf, size_t len)
277 {
278 	char *l;
279 
280 	if (len == 0)
281 		return emit_line(p, t, NULL, NULL);
282 
283 	if ((l = calloc(1, len+1)) == NULL)
284 		return 0;
285 	memcpy(l, buf, len);
286 	return emit_line(p, t, l, NULL);
287 }
288 
289 static int
290 parse_pre_end(struct parser *p, enum line_type t, const char *buf, size_t len)
291 {
292 	return emit_line(p, t, NULL, NULL);
293 }
294 
295 static inline enum line_type
296 detect_line_type(const char *buf, size_t len, int in_pre)
297 {
298 	if (len == 0)
299 		return LINE_TEXT;
300 
301 	if (in_pre) {
302 		if (len >= 3 &&
303 		    buf[0] == '`' && buf[1] == '`' && buf[2] == '`')
304 			return LINE_PRE_END;
305 		else
306 			return LINE_PRE_CONTENT;
307 	}
308 
309 	switch (*buf) {
310 	case '*': return LINE_ITEM;
311 	case '>': return LINE_QUOTE;
312 	case '=':
313 		if (len >= 1 && buf[1] == '>')
314 			return LINE_LINK;
315 		break;
316 	case '#':
317 		if (len == 1)
318 			return LINE_TEXT;
319 		if (buf[1] != '#')
320 			return LINE_TITLE_1;
321 		if (len == 2)
322 			return LINE_TEXT;
323 		if (buf[2] != '#')
324 			return LINE_TITLE_2;
325 		if (len == 3)
326 			return LINE_TEXT;
327 		return LINE_TITLE_3;
328 	case '`':
329 		if (len < 3)
330 			return LINE_TEXT;
331 		if (buf[0] == '`' && buf[1] == '`' && buf[2] == '`')
332 			return LINE_PRE_START;
333 		break;
334 	}
335 
336 	return LINE_TEXT;
337 }
338 
339 static int
340 gemtext_parse(struct parser *p, const char *buf, size_t size)
341 {
342 	return parser_foreach_line(p, buf, size, gemtext_foreach_line);
343 }
344 
345 static int
346 gemtext_foreach_line(struct parser *p, const char *line, size_t linelen)
347 {
348 	enum line_type t;
349 
350 	t = detect_line_type(line, linelen, p->flags);
351 	if (t == LINE_PRE_START)
352 		p->flags = 1;
353 	if (t == LINE_PRE_END)
354 		p->flags = 0;
355 	return parsers[t](p, t, line, linelen);
356 }
357 
358 static int
359 gemtext_free(struct parser *p)
360 {
361 	enum line_type	t;
362 
363 	/* flush the buffer */
364 	if (p->len != 0) {
365 		t = detect_line_type(p->buf, p->len, p->flags);
366 		if (!parsers[t](p, t, p->buf, p->len))
367 			return 0;
368 		if (p->flags && !emit_line(p, LINE_PRE_END, NULL, NULL))
369 			return 0;
370 	}
371 
372 	free(p->buf);
373 
374 	/*
375 	 * use the first level 2 or 3 header as page title if none
376 	 * found yet.
377 	 */
378 	if (*p->title == '\0')
379 		search_title(p, LINE_TITLE_2);
380 	if (*p->title == '\0')
381 		search_title(p, LINE_TITLE_3);
382 
383 	return 1;
384 }
385 
386 static void
387 search_title(struct parser *p, enum line_type level)
388 {
389 	struct line *l;
390 
391 	TAILQ_FOREACH(l, &p->head, lines) {
392 		if (l->type == level) {
393 			if (l->line == NULL)
394 				continue;
395 			strlcpy(p->title, l->line, sizeof(p->title));
396 		}
397 	}
398 }