1/*
2 * Copyright (c) 2010  Aurelien Jacobs <aurel@gnuage.org>
3 * Copyright (c) 2017  Clément Bœsch <u@pkh.me>
4 *
5 * This file is part of FFmpeg.
6 *
7 * FFmpeg is free software; you can redistribute it and/or
8 * modify it under the terms of the GNU Lesser General Public
9 * License as published by the Free Software Foundation; either
10 * version 2.1 of the License, or (at your option) any later version.
11 *
12 * FFmpeg is distributed in the hope that it will be useful,
13 * but WITHOUT ANY WARRANTY; without even the implied warranty of
14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
15 * Lesser General Public License for more details.
16 *
17 * You should have received a copy of the GNU Lesser General Public
18 * License along with FFmpeg; if not, write to the Free Software
19 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
20 */
21
22#include "libavutil/avassert.h"
23#include "libavutil/avstring.h"
24#include "libavutil/common.h"
25#include "libavutil/parseutils.h"
26#include "htmlsubtitles.h"
27#include <ctype.h>
28
29static int html_color_parse(void *log_ctx, const char *str)
30{
31    uint8_t rgba[4];
32    int nb_sharps = 0;
33    while (str[nb_sharps] == '#')
34        nb_sharps++;
35    str += FFMAX(0, nb_sharps - 1);
36    if (av_parse_color(rgba, str, strcspn(str, "\" >"), log_ctx) < 0)
37        return -1;
38    return rgba[0] | rgba[1] << 8 | rgba[2] << 16;
39}
40
41static void rstrip_spaces_buf(AVBPrint *buf)
42{
43    if (av_bprint_is_complete(buf))
44        while (buf->len > 0 && buf->str[buf->len - 1] == ' ')
45            buf->str[--buf->len] = 0;
46}
47
48/*
49 * Fast code for scanning text enclosed in braces. Functionally
50 * equivalent to this sscanf call:
51 *
52 * sscanf(in, "{\\an%*1u}%n", &len) >= 0 && len > 0
53 */
54static int scanbraces(const char* in) {
55    if (strncmp(in, "{\\an", 4) != 0) {
56        return 0;
57    }
58    if (!av_isdigit(in[4])) {
59        return 0;
60    }
61    if (in[5] != '}') {
62        return 0;
63    }
64    return 1;
65}
66
67/* skip all {\xxx} substrings except for {\an%d}
68   and all microdvd like styles such as {Y:xxx} */
69static void handle_open_brace(AVBPrint *dst, const char **inp, int *an, int *closing_brace_missing)
70{
71    const char *in = *inp;
72
73    *an += scanbraces(in);
74
75    if (!*closing_brace_missing) {
76        if (   (*an != 1 && in[1] == '\\')
77            || (in[1] && strchr("CcFfoPSsYy", in[1]) && in[2] == ':')) {
78            char *bracep = strchr(in+2, '}');
79            if (bracep) {
80                *inp = bracep;
81                return;
82            } else
83                *closing_brace_missing = 1;
84        }
85    }
86
87    av_bprint_chars(dst, *in, 1);
88}
89
90struct font_tag {
91    char face[128];
92    int size;
93    uint32_t color;
94};
95
96/*
97 * Fast code for scanning the rest of a tag. Functionally equivalent to
98 * this sscanf call:
99 *
100 * sscanf(in, "%127[^<>]>%n", buffer, lenp) == 2
101 */
102static int scantag(const char* in, char* buffer, int* lenp) {
103    int len;
104
105    for (len = 0; len < 128; len++) {
106        const char c = *in++;
107        switch (c) {
108        case '\0':
109            return 0;
110        case '<':
111            return 0;
112        case '>':
113            buffer[len] = '\0';
114            *lenp = len+1;
115            return 1;
116        default:
117            break;
118        }
119        buffer[len] = c;
120    }
121    return 0;
122}
123
124/*
125 * The general politic of the convert is to mask unsupported tags or formatting
126 * errors (but still alert the user/subtitles writer with an error/warning)
127 * without dropping any actual text content for the final user.
128 */
129int ff_htmlmarkup_to_ass(void *log_ctx, AVBPrint *dst, const char *in)
130{
131    char *param, buffer[128];
132    int len, tag_close, sptr = 0, line_start = 1, an = 0, end = 0;
133    int closing_brace_missing = 0;
134    int i, likely_a_tag;
135
136    /*
137     * state stack is only present for fonts since they are the only tags where
138     * the state is not binary. Here is a typical use case:
139     *
140     *   <font color="red" size=10>
141     *     red 10
142     *     <font size=50> RED AND BIG </font>
143     *     red 10 again
144     *   </font>
145     *
146     * On the other hand, using the state system for all the tags should be
147     * avoided because it breaks wrongly nested tags such as:
148     *
149     *   <b> foo <i> bar </b> bla </i>
150     *
151     * We don't want to break here; instead, we will treat all these tags as
152     * binary state markers. Basically, "<b>" will activate bold, and "</b>"
153     * will deactivate it, whatever the current state.
154     *
155     * This will also prevents cases where we have a random closing tag
156     * remaining after the opening one was dropped. Yes, this happens and we
157     * still don't want to print a "</b>" at the end of the dialog event.
158     */
159    struct font_tag stack[16];
160
161    memset(&stack[0], 0, sizeof(stack[0]));
162
163    for (; !end && *in; in++) {
164        switch (*in) {
165        case '\r':
166            break;
167        case '\n':
168            if (line_start) {
169                end = 1;
170                break;
171            }
172            rstrip_spaces_buf(dst);
173            av_bprintf(dst, "\\N");
174            line_start = 1;
175            break;
176        case ' ':
177            if (!line_start)
178                av_bprint_chars(dst, *in, 1);
179            break;
180        case '{':
181            handle_open_brace(dst, &in, &an, &closing_brace_missing);
182            break;
183        case '<':
184            /*
185             * "<<" are likely latin guillemets in ASCII or some kind of random
186             * style effect; see sub/badsyntax.srt in the FATE samples
187             * directory for real test cases.
188             */
189
190            likely_a_tag = 1;
191            for (i = 0; in[1] == '<'; i++) {
192                av_bprint_chars(dst, '<', 1);
193                likely_a_tag = 0;
194                in++;
195            }
196
197            tag_close = in[1] == '/';
198            if (tag_close)
199                likely_a_tag = 1;
200
201            av_assert0(in[0] == '<');
202
203            len = 0;
204
205            if (scantag(in+tag_close+1, buffer, &len) && len > 0) {
206                const int skip = len + tag_close;
207                const char *tagname = buffer;
208                while (*tagname == ' ') {
209                    likely_a_tag = 0;
210                    tagname++;
211                }
212                if ((param = strchr(tagname, ' ')))
213                    *param++ = 0;
214
215                /* Check if this is likely a tag */
216#define LIKELY_A_TAG_CHAR(x) (((x) >= '0' && (x) <= '9') || \
217                              ((x) >= 'a' && (x) <= 'z') || \
218                              ((x) >= 'A' && (x) <= 'Z') || \
219                               (x) == '_' || (x) == '/')
220                for (i = 0; tagname[i]; i++) {
221                    if (!LIKELY_A_TAG_CHAR(tagname[i])) {
222                        likely_a_tag = 0;
223                        break;
224                    }
225                }
226
227                if (!av_strcasecmp(tagname, "font")) {
228                    if (tag_close && sptr > 0) {
229                        struct font_tag *cur_tag  = &stack[sptr--];
230                        struct font_tag *last_tag = &stack[sptr];
231
232                        if (cur_tag->size) {
233                            if (!last_tag->size)
234                                av_bprintf(dst, "{\\fs}");
235                            else if (last_tag->size != cur_tag->size)
236                                av_bprintf(dst, "{\\fs%d}", last_tag->size);
237                        }
238
239                        if (cur_tag->color & 0xff000000) {
240                            if (!(last_tag->color & 0xff000000))
241                                av_bprintf(dst, "{\\c}");
242                            else if (last_tag->color != cur_tag->color)
243                                av_bprintf(dst, "{\\c&H%"PRIX32"&}", last_tag->color & 0xffffff);
244                        }
245
246                        if (cur_tag->face[0]) {
247                            if (!last_tag->face[0])
248                                av_bprintf(dst, "{\\fn}");
249                            else if (strcmp(last_tag->face, cur_tag->face))
250                                av_bprintf(dst, "{\\fn%s}", last_tag->face);
251                        }
252                    } else if (!tag_close && sptr < FF_ARRAY_ELEMS(stack) - 1) {
253                        struct font_tag *new_tag = &stack[sptr + 1];
254
255                        *new_tag = stack[sptr++];
256
257                        while (param) {
258                            if (!av_strncasecmp(param, "size=", 5)) {
259                                param += 5 + (param[5] == '"');
260                                if (sscanf(param, "%u", &new_tag->size) == 1)
261                                    av_bprintf(dst, "{\\fs%u}", new_tag->size);
262                            } else if (!av_strncasecmp(param, "color=", 6)) {
263                                int color;
264                                param += 6 + (param[6] == '"');
265                                color = html_color_parse(log_ctx, param);
266                                if (color >= 0) {
267                                    new_tag->color = 0xff000000 | color;
268                                    av_bprintf(dst, "{\\c&H%"PRIX32"&}", new_tag->color & 0xffffff);
269                                }
270                            } else if (!av_strncasecmp(param, "face=", 5)) {
271                                param += 5 + (param[5] == '"');
272                                len = strcspn(param,
273                                              param[-1] == '"' ? "\"" :" ");
274                                av_strlcpy(new_tag->face, param,
275                                           FFMIN(sizeof(new_tag->face), len+1));
276                                param += len;
277                                av_bprintf(dst, "{\\fn%s}", new_tag->face);
278                            }
279                            if ((param = strchr(param, ' ')))
280                                param++;
281                        }
282                    }
283                    in += skip;
284                } else if (tagname[0] && !tagname[1] && strchr("bisu", av_tolower(tagname[0]))) {
285                    av_bprintf(dst, "{\\%c%d}", (char)av_tolower(tagname[0]), !tag_close);
286                    in += skip;
287                } else if (!av_strncasecmp(tagname, "br", 2) &&
288                           (!tagname[2] || (tagname[2] == '/' && !tagname[3]))) {
289                    av_bprintf(dst, "\\N");
290                    in += skip;
291                } else if (likely_a_tag) {
292                    if (!tag_close) // warn only once
293                        av_log(log_ctx, AV_LOG_WARNING, "Unrecognized tag %s\n", tagname);
294                    in += skip;
295                } else {
296                    av_bprint_chars(dst, '<', 1);
297                }
298            } else {
299                av_bprint_chars(dst, *in, 1);
300            }
301            break;
302        default:
303            av_bprint_chars(dst, *in, 1);
304            break;
305        }
306        if (*in != ' ' && *in != '\r' && *in != '\n')
307            line_start = 0;
308    }
309
310    if (!av_bprint_is_complete(dst))
311        return AVERROR(ENOMEM);
312
313    while (dst->len >= 2 && !strncmp(&dst->str[dst->len - 2], "\\N", 2))
314        dst->len -= 2;
315    dst->str[dst->len] = 0;
316    rstrip_spaces_buf(dst);
317
318    return 0;
319}
320