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 	switch (l->type) {
83 	case LINE_PRE_START:
84 	case LINE_PRE_END:
85 		if (hide_pre_context)
86 			l->flags = L_HIDDEN;
87 		break;
88 	case LINE_PRE_CONTENT:
89 		if (hide_pre_blocks)
90 			l->flags = L_HIDDEN;
91 		break;
92 	default:
93 		l->flags = 0;
94 		break;
95 	}
96 
97 	if (TAILQ_EMPTY(&p->head))
98 		TAILQ_INSERT_HEAD(&p->head, l, lines);
99 	else
100 		TAILQ_INSERT_TAIL(&p->head, l, lines);
101 
102 	return 1;
103 }
104 
105 static int
106 parse_text(struct parser *p, enum line_type t, const char *buf, size_t len)
107 {
108 	char *l;
109 
110 	if ((l = calloc(1, len+1)) == NULL)
111 		return 0;
112 	memcpy(l, buf, len);
113 	return emit_line(p, t, l, NULL);
114 }
115 
116 static int
117 parse_link(struct parser *p, enum line_type t, const char *buf, size_t len)
118 {
119 	char *l, *u;
120 	const char *url_start;
121 
122 	if (len <= 2)
123 		return emit_line(p, t, NULL, NULL);
124 	buf += 2;
125 	len -= 2;
126 
127 	while (len > 0 && isspace(buf[0])) {
128 		buf++;
129 		len--;
130 	}
131 
132 	if (len == 0)
133 		return emit_line(p, t, NULL, NULL);
134 
135 	url_start = buf;
136 	while (len > 0 && !isspace(buf[0])) {
137 		buf++;
138 		len--;
139 	}
140 
141 	if ((u = calloc(1, buf - url_start + 1)) == NULL)
142 		return 0;
143 	memcpy(u, url_start, buf - url_start);
144 
145 	if (len == 0)
146 		goto nolabel;
147 
148 	while (len > 0 && isspace(buf[0])) {
149 		buf++;
150 		len--;
151 	}
152 
153 	if (len == 0)
154 		goto nolabel;
155 
156 	if ((l = calloc(1, len + 1)) == NULL)
157 		return 0;
158 
159 	memcpy(l, buf, len);
160 	return emit_line(p, t, l, u);
161 
162 nolabel:
163 	if ((l = strdup(u)) == NULL)
164 		return 0;
165 	return emit_line(p, t, l, u);
166 }
167 
168 static int
169 parse_title(struct parser *p, enum line_type t, const char *buf, size_t len)
170 {
171 	char *l;
172 
173 	switch (t) {
174 	case LINE_TITLE_1:
175 		if (len <= 1)
176 			return emit_line(p, t, NULL, NULL);
177 		buf++;
178 		len--;
179 		break;
180 	case LINE_TITLE_2:
181 		if (len <= 2)
182 			return emit_line(p, t, NULL, NULL);
183 		buf += 2;
184 		len -= 2;
185 		break;
186 	case LINE_TITLE_3:
187 		if (len <= 3)
188 			return emit_line(p, t, NULL, NULL);
189 		buf += 3;
190 		len -= 3;
191 		break;
192 	default:
193 		/* unreachable */
194 		abort();
195 	}
196 
197 	while (len > 0 && isspace(buf[0])) {
198 		buf++;
199 		len--;
200 	}
201 
202 	if (len == 0)
203 		return emit_line(p, t, NULL, NULL);
204 
205 	if (t == LINE_TITLE_1 && *p->title == '\0')
206 		strncpy(p->title, buf, MIN(sizeof(p->title)-1, len));
207 
208 	if ((l = calloc(1, len+1)) == NULL)
209 		return 0;
210 	memcpy(l, buf, len);
211 	return emit_line(p, t, l, NULL);
212 }
213 
214 static int
215 parse_item(struct parser *p, enum line_type t, const char *buf, size_t len)
216 {
217 	char *l;
218 
219 	if (len == 1)
220 		return emit_line(p, t, NULL, NULL);
221 
222 	buf++;
223 	len--;
224 
225 	while (len > 0 && isspace(buf[0])) {
226 		buf++;
227 		len--;
228 	}
229 
230 	if (len == 0)
231 		return emit_line(p, t, NULL, NULL);
232 
233 	if ((l = calloc(1, len+1)) == NULL)
234 		return 0;
235 	memcpy(l, buf, len);
236 	return emit_line(p, t, l, NULL);
237 }
238 
239 static int
240 parse_quote(struct parser *p, enum line_type t, const char *buf, size_t len)
241 {
242 	char *l;
243 
244 	if (len == 1)
245 		return emit_line(p, t, NULL, NULL);
246 
247 	buf++;
248 	len--;
249 
250 	while (len > 0 && isspace(buf[0])) {
251 		buf++;
252 		len--;
253 	}
254 
255 	if (len == 0)
256 		return emit_line(p, t, NULL, NULL);
257 
258 	if ((l = calloc(1, len+1)) == NULL)
259 		return 0;
260 	memcpy(l, buf, len);
261 	return emit_line(p, t, l, NULL);
262 }
263 
264 static int
265 parse_pre_start(struct parser *p, enum line_type t, const char *buf, size_t len)
266 {
267 	char *l;
268 
269 	if (len <= 3)
270 		return emit_line(p, t, NULL, NULL);
271 
272 	buf += 3;
273 	len -= 3;
274 
275 	while (len > 0 && isspace(buf[0])) {
276 		buf++;
277 		len--;
278 	}
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 
286 	memcpy(l, buf, len);
287 	return emit_line(p, t, l, NULL);
288 }
289 
290 static int
291 parse_pre_cnt(struct parser *p, enum line_type t, const char *buf, size_t len)
292 {
293 	char *l;
294 
295 	if (len == 0)
296 		return emit_line(p, t, NULL, NULL);
297 
298 	if ((l = calloc(1, len+1)) == NULL)
299 		return 0;
300 	memcpy(l, buf, len);
301 	return emit_line(p, t, l, NULL);
302 }
303 
304 static int
305 parse_pre_end(struct parser *p, enum line_type t, const char *buf, size_t len)
306 {
307 	return emit_line(p, t, NULL, NULL);
308 }
309 
310 static inline enum line_type
311 detect_line_type(const char *buf, size_t len, int in_pre)
312 {
313 	if (len == 0)
314 		return LINE_TEXT;
315 
316 	if (in_pre) {
317 		if (len >= 3 &&
318 		    buf[0] == '`' && buf[1] == '`' && buf[2] == '`')
319 			return LINE_PRE_END;
320 		else
321 			return LINE_PRE_CONTENT;
322 	}
323 
324 	switch (*buf) {
325 	case '*': return LINE_ITEM;
326 	case '>': return LINE_QUOTE;
327 	case '=':
328 		if (len >= 1 && buf[1] == '>')
329 			return LINE_LINK;
330 		break;
331 	case '#':
332 		if (len == 1)
333 			return LINE_TEXT;
334 		if (buf[1] != '#')
335 			return LINE_TITLE_1;
336 		if (len == 2)
337 			return LINE_TEXT;
338 		if (buf[2] != '#')
339 			return LINE_TITLE_2;
340 		if (len == 3)
341 			return LINE_TEXT;
342 		return LINE_TITLE_3;
343 	case '`':
344 		if (len < 3)
345 			return LINE_TEXT;
346 		if (buf[0] == '`' && buf[1] == '`' && buf[2] == '`')
347 			return LINE_PRE_START;
348 		break;
349 	}
350 
351 	return LINE_TEXT;
352 }
353 
354 static int
355 gemtext_parse(struct parser *p, const char *buf, size_t size)
356 {
357 	return parser_foreach_line(p, buf, size, gemtext_foreach_line);
358 }
359 
360 static int
361 gemtext_foreach_line(struct parser *p, const char *line, size_t linelen)
362 {
363 	enum line_type t;
364 
365 	t = detect_line_type(line, linelen, p->flags);
366 	if (t == LINE_PRE_START)
367 		p->flags = 1;
368 	if (t == LINE_PRE_END)
369 		p->flags = 0;
370 	return parsers[t](p, t, line, linelen);
371 }
372 
373 static int
374 gemtext_free(struct parser *p)
375 {
376 	enum line_type	t;
377 
378 	/* flush the buffer */
379 	if (p->len != 0) {
380 		t = detect_line_type(p->buf, p->len, p->flags);
381 		if (!parsers[t](p, t, p->buf, p->len))
382 			return 0;
383 		if (p->flags && !emit_line(p, LINE_PRE_END, NULL, NULL))
384 			return 0;
385 	}
386 
387 	free(p->buf);
388 
389 	/*
390 	 * use the first level 2 or 3 header as page title if none
391 	 * found yet.
392 	 */
393 	if (*p->title == '\0')
394 		search_title(p, LINE_TITLE_2);
395 	if (*p->title == '\0')
396 		search_title(p, LINE_TITLE_3);
397 
398 	return 1;
399 }
400 
401 static void
402 search_title(struct parser *p, enum line_type level)
403 {
404 	struct line *l;
405 
406 	TAILQ_FOREACH(l, &p->head, lines) {
407 		if (l->type == level) {
408 			if (l->line == NULL)
409 				continue;
410 			strlcpy(p->title, l->line, sizeof(p->title));
411 			break;
412 		}
413 	}
414 }