1<?php
2/*
3 * Paste $v3.2 2025/09/07 https://github.com/boxlabss/PASTE
4 * demo: https://paste.boxlabs.uk/
5 *
6 * https://phpaste.sourceforge.io/
7 *
8 * This program is free software; you can redistribute it and/or
9 * modify it under the terms of the GNU General Public License
10 * as published by the Free Software Foundation; either version 3
11 * of the License, or (at your option) any later version.
12 * 
13 * This program is distributed in the hope that it will be useful,
14 * but WITHOUT ANY WARRANTY; without even the implied warranty of
15 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
16 * GNU General Public License in LICENCE for more details.
17 */
18declare(strict_types=1);
19
20require_once __DIR__ . '/includes/session.php';
21require_once __DIR__ . '/config.php';
22require_once __DIR__ . '/includes/functions.php';
23// Error handling
24paste_enable_themed_errors();
25
26// Highlighter bootstrap + language lists
27require_once __DIR__ . '/includes/hlbootstrap.php';
28require_once __DIR__ . '/includes/list_languages.php';
29
30ini_set('display_errors','0');
31ini_set('log_errors','1');
32date_default_timezone_set('UTC');
33
34// Load paste by ID, decrypting as needed. Returns ['title','content','code'] or null
35function load_paste(PDO $pdo, int $id): ?array {
36    try {
37        $st = $pdo->prepare("SELECT id,title,content,code,encrypt FROM pastes WHERE id=? LIMIT 1");
38        $st->execute([$id]);
39        $r = $st->fetch();
40        if (!$r) return null;
41
42        $title   = (string)$r['title'];
43        $content = (string)$r['content'];
44
45        if ((string)$r['encrypt'] === "1" && defined('SECRET')) {
46            $title   = decrypt($title,   hex2bin(SECRET))   ?? $title;
47            $content = decrypt($content, hex2bin(SECRET))   ?? $content;
48        }
49
50        // Stored content is HTML-escaped before encrypt; decode for diffing
51        $content = html_entity_decode($content, ENT_QUOTES|ENT_SUBSTITUTE, 'UTF-8');
52
53        return [
54            'title'   => $title,
55            'content' => $content,
56            'code'    => (string)($r['code'] ?? 'text'),
57        ];
58    } catch (Throwable $e) {
59        error_log("diff.php load_paste($id): ".$e->getMessage());
60        return null;
61    }
62}
63
64// Inline (word/char) diff > [leftHTML, rightHTML] with <span class="diff-inside-...">
65function inline_diff(string $a, string $b): array {
66    $split = static function(string $s): array {
67        preg_match_all('/\s+|[^\s]+/u', $s, $m);
68        return $m[0] ?: [$s];
69    };
70    $Aw = $split($a); $Bw = $split($b);
71    $useChar = (count($Aw) <= 4 || count($Bw) <= 4);
72    if ($useChar) {
73        $Aw = preg_split('//u', $a, -1, PREG_SPLIT_NO_EMPTY);
74        $Bw = preg_split('//u', $b, -1, PREG_SPLIT_NO_EMPTY);
75    }
76    $n=count($Aw); $m=count($Bw);
77    $L = array_fill(0,$n+1,array_fill(0,$m+1,0));
78    for($i=$n-1;$i>=0;$i--) for($j=$m-1;$j>=0;$j--) {
79        $L[$i][$j]=($Aw[$i]===$Bw[$j])?($L[$i+1][$j+1]+1):max($L[$i+1][$j],$L[$i][$j+1]);
80    }
81    $i=0;$j=0;$left='';$right='';
82    $esc = static fn($s)=>htmlspecialchars($s, ENT_QUOTES|ENT_SUBSTITUTE, 'UTF-8');
83    while($i<$n && $j<$m){
84        if($Aw[$i]===$Bw[$j]){ $left.=$esc($Aw[$i]); $right.=$esc($Bw[$j]); $i++; $j++; }
85        elseif($L[$i+1][$j] >= $L[$i][$j+1]){ $left.='<span class="diff-inside-del">'.$esc($Aw[$i]).'</span>'; $i++; }
86        else { $right.='<span class="diff-inside-add">'.$esc($Bw[$j]).'</span>'; $j++; }
87    }
88    while($i<$n){ $left.='<span class="diff-inside-del">'.$esc($Aw[$i]).'</span>'; $i++; }
89    while($j<$m){ $right.='<span class="diff-inside-add">'.$esc($Bw[$j]).'</span>'; $j++; }
90    return [$left,$right];
91}
92
93/**
94 * Index-based diff at line level > opcodes referencing original arrays.
95 * Opcodes:
96 *   - ['op'=>'eq','ai'=>i,'bi'=>j]
97 *   - ['op'=>'del','ai'=>i]
98 *   - ['op'=>'add','bi'=>j]
99 *
100 *   1) xdiff accelerator (parse unified diff) if available
101 *   2) Myers O((N+M)D) fallback in pure PHP
102 */
103function diff_lines_idx(array $A, array $B, ?callable $normalizer=null): array {
104    $An = $normalizer ? array_map($normalizer, $A) : $A;
105    $Bn = $normalizer ? array_map($normalizer, $B) : $B;
106
107    if (function_exists('xdiff_string_diff')) {
108        return _diff_idx_via_xdiff($An, $Bn);
109    }
110    return _diff_idx_via_myers($An, $Bn);
111}
112
113/* ---------- Fast path: use xdiff to compute unified diff, parse to opcodes ---------- */
114function _diff_idx_via_xdiff(array $A, array $B): array {
115    $N = count($A); $M = count($B);
116
117    // Join as text; ensure trailing newline to keep line counts exact
118    $left  = ($N ? implode("\n", $A) : '') . "\n";
119    $right = ($M ? implode("\n", $B) : '') . "\n";
120
121    // 0-context unified diff, non-minimal for speed
122    $ud = xdiff_string_diff($left, $right, 0, false);
123    if ($ud === false) {
124        // Fallback to trivial equality handling
125        $ops = [];
126        $eq = min($N, $M);
127        for ($i=0; $i<$eq; $i++) $ops[] = ['op'=>'eq','ai'=>$i,'bi'=>$i];
128        for ($i=$eq; $i<$N; $i++) $ops[] = ['op'=>'del','ai'=>$i];
129        for ($j=$eq; $j<$M; $j++) $ops[] = ['op'=>'add','bi'=>$j];
130        return $ops;
131    }
132    if ($ud === '') {
133        $ops = [];
134        for ($i=0; $i<$N && $i<$M; $i++) $ops[]=['op'=>'eq','ai'=>$i,'bi'=>$i];
135        for ($i=$M; $i<$N; $i++) $ops[]=['op'=>'del','ai'=>$i];
136        for ($j=$N; $j<$M; $j++) $ops[]=['op'=>'add','bi'=>$j];
137        return $ops;
138    }
139
140    $ops = [];
141    $ai = 0; $bi = 0;
142
143    $lines = preg_split("/\R/u", $ud);
144    foreach ($lines as $ln) {
145        if ($ln === '' && $ln !== '0') continue;
146
147        if (preg_match('/^@@\s+-([0-9]+)(?:,([0-9]+))?\s+\+([0-9]+)(?:,([0-9]+))?\s+@@/', $ln, $m)) {
148            $startA = max(0, (int)$m[1] - 1); // 0-based
149            $startB = max(0, (int)$m[3] - 1);
150            // Emit equal block before this hunk (between current cursors and hunk start)
151            $eq = min(max(0, $startA - $ai), max(0, $startB - $bi));
152            for ($k=0; $k<$eq; $k++) { $ops[] = ['op'=>'eq','ai'=>$ai,'bi'=>$bi]; $ai++; $bi++; }
153            continue;
154        }
155
156        $tag = $ln[0] ?? '';
157        if     ($tag === ' ') { $ops[] = ['op'=>'eq',  'ai'=>$ai,  'bi'=>$bi];  $ai++; $bi++; }
158        elseif ($tag === '-') { $ops[] = ['op'=>'del', 'ai'=>$ai];              $ai++;        }
159        elseif ($tag === '+') { $ops[] = ['op'=>'add',              'bi'=>$bi];         $bi++; }
160        else {
161            // headers '---', '+++', empty, etc > ignore
162        }
163    }
164
165    // Trailing equals after last hunk
166    $tailEq = min($N - $ai, $M - $bi);
167    for ($k=0; $k<$tailEq; $k++) { $ops[] = ['op'=>'eq','ai'=>$ai,'bi'=>$bi]; $ai++; $bi++; }
168    for (; $ai<$N; $ai++) $ops[] = ['op'=>'del','ai'=>$ai];
169    for (; $bi<$M; $bi++) $ops[] = ['op'=>'add','bi'=>$bi];
170
171    return $ops;
172}
173
174/* ---------- Fallback: Myers O((N+M)D) with path reconstruction ---------- */
175function _diff_idx_via_myers(array $A, array $B): array {
176    $N = count($A); $M = count($B);
177
178    if ($N === 0 && $M === 0) return [];
179    if ($N === 0) { $ops=[]; for($j=0;$j<$M;$j++) $ops[]=['op'=>'add','bi'=>$j]; return $ops; }
180    if ($M === 0) { $ops=[]; for($i=0;$i<$N;$i++) $ops[]=['op'=>'del','ai'=>$i]; return $ops; }
181
182    $max = $N + $M;
183    $off = $max;
184    $V = array_fill(0, 2 * $max + 1, 0);
185    $trace = [];
186
187    $Dend = 0;
188    for ($d = 0; $d <= $max; $d++) {
189        $trace[$d] = $V;
190
191        for ($k = -$d; $k <= $d; $k += 2) {
192            if ($k == -$d || ($k != $d && $V[$off + $k - 1] < $V[$off + $k + 1])) {
193                $x = $V[$off + $k + 1];       // down (insert B)
194            } else {
195                $x = $V[$off + $k - 1] + 1;   // right (delete A)
196            }
197            $y = $x - $k;
198
199            while ($x < $N && $y < $M && $A[$x] === $B[$y]) { $x++; $y++; }
200
201            $V[$off + $k] = $x;
202
203            if ($x >= $N && $y >= $M) {
204                $trace[$d] = $V;
205                $Dend = $d;
206                break 2;
207            }
208        }
209    }
210
211    $ops = [];
212    $x = $N; $y = $M;
213    for ($d = $Dend; $d > 0; $d--) {
214        $Vprev = $trace[$d-1];
215        $k  = $x - $y;
216
217        $down = ($k == -$d) || ($k != $d && $Vprev[$off + $k - 1] < $Vprev[$off + $k + 1]);
218        $kPrev   = $down ? $k + 1 : $k - 1;
219        $xStart  = $down ? $Vprev[$off + $kPrev] : $Vprev[$off + $kPrev] + 1;
220        $yStart  = $xStart - $kPrev;
221
222        while ($x > $xStart && $y > $yStart) { $x--; $y--; $ops[] = ['op'=>'eq','ai'=>$x,'bi'=>$y]; }
223
224        if ($down) {
225            $yStart--;
226            $ops[] = ['op'=>'add','bi'=>$yStart];
227        } else {
228            $xStart--;
229            $ops[] = ['op'=>'del','ai'=>$xStart];
230        }
231
232        $x = $xStart; $y = $yStart;
233    }
234
235    while ($x > 0 && $y > 0) { $x--; $y--; $ops[] = ['op'=>'eq','ai'=>$x,'bi'=>$y]; }
236    while ($x > 0) { $x--; $ops[] = ['op'=>'del','ai'=>$x]; }
237    while ($y > 0) { $y--; $ops[] = ['op'=>'add','bi'=>$y]; }
238
239    return array_reverse($ops);
240}
241
242// Build side-by-side & unified row arrays from ops (index-based).
243function build_tables_idx(array $ops, array $leftLines, array $rightLines): array {
244    $side=[]; $uni=[]; $li=1; $ri=1;
245    foreach ($ops as $op) {
246        if ($op['op']==='eq') {
247            $L=(string)($leftLines[$op['ai']] ?? '');
248            $R=(string)($rightLines[$op['bi']] ?? '');
249            $side[]=['lno'=>$li,'rno'=>$ri,'lclass'=>'ctx','rclass'=>'ctx','lhtml'=>$L,'rhtml'=>$R,'l_intra'=>false,'r_intra'=>false];
250            $uni[] =['lno'=>$li,'rno'=>$ri,'class'=>'ctx','html'=>$L,'intra'=>false];
251            $li++; $ri++;
252        } elseif ($op['op']==='del') {
253            $L=(string)($leftLines[$op['ai']] ?? '');
254            $side[]=['lno'=>$li,'rno'=>'','lclass'=>'del','rclass'=>'empty','lhtml'=>$L,'rhtml'=>'','l_intra'=>false,'r_intra'=>false];
255            $uni[] =['lno'=>$li,'rno'=>'','class'=>'del','html'=>$L,'intra'=>false];
256            $li++;
257        } else { // add
258            $R=(string)($rightLines[$op['bi']] ?? '');
259            $side[]=['lno'=>'','rno'=>$ri,'lclass'=>'empty','rclass'=>'add','lhtml'=>'','rhtml'=>$R,'l_intra'=>false,'r_intra'=>false];
260            $uni[] =['lno'=>'','rno'=>$ri,'class'=>'add','html'=>$R,'intra'=>false];
261            $ri++;
262        }
263    }
264    return [$side,$uni];
265}
266
267// Apply inline word/char diff across adjacent del/add in side-by-side rows.
268function apply_inline_sxs(array &$sideRows): void {
269    for ($i=0; $i<count($sideRows)-1; $i++) {
270        $a=$sideRows[$i]; $b=$sideRows[$i+1];
271        if ($a['lclass']==='del' && $b['rclass']==='add') {
272            [$L,$R] = inline_diff((string)$a['lhtml'], (string)$b['rhtml']);
273            $sideRows[$i]['lhtml']=$L; $sideRows[$i]['l_intra']=true;
274            $sideRows[$i+1]['rhtml']=$R; $sideRows[$i+1]['r_intra']=true;
275            $i++;
276        }
277    }
278}
279
280// Proper unified .diff (xdiff if present; else POSIX-ish fallback)
281function unified_diff_download(string $left, string $right, string $nameA='a', string $nameB='b', int $ctx=3): string {
282    if (function_exists('xdiff_string_diff')) {
283        // Use non-minimal for speed; we rewrite headers below
284        $ud = xdiff_string_diff($left, $right, $ctx, false);
285        if ($ud !== false) {
286            $ts = gmdate('Y-m-d H:i:s O');
287            $hdr = "--- {$nameA}\t{$ts}\n+++ {$nameB}\t{$ts}\n";
288            $ud = preg_replace('~^--- .*\R\+\+\+ .*\R~', $hdr, $ud, 1);
289            return $ud;
290        }
291    }
292
293    // Manual fallback
294    $aOrig = preg_split("/\R/u", $left);
295    $bOrig = preg_split("/\R/u", $right);
296    if ($aOrig === false) $aOrig = [$left];
297    if ($bOrig === false) $bOrig = [$right];
298
299    $ops = diff_lines_idx($aOrig, $bOrig, null);
300
301    $hunks = [];
302    $flush = static function (&$hunks, &$buf) {
303        if (empty($buf['lines'])) return;
304        $oldLen = max(0, $buf['oldLen']);
305        $newLen = max(0, $buf['newLen']);
306        $h = "@@ -{$buf['oldStart']}" . ($oldLen===1?'':",$oldLen")
307           . " +{$buf['newStart']}" . ($newLen===1?'':",$newLen") . " @@\n";
308        $h .= implode('', $buf['lines']);
309        $hunks[] = $h;
310        $buf = ['oldStart'=>0,'newStart'=>0,'oldLen'=>0,'newLen'=>0,'lines'=>[],'open'=>false];
311    };
312
313    $buf = ['oldStart'=>0,'newStart'=>0,'oldLen'=>0,'newLen'=>0,'lines'=>[],'open'=>false];
314    $ctxAhead = 0;
315    $ai=1; $bi=1;
316
317    $grab_context = static function($aOrig, $bOrig, $ai, $bi, $ctx) use (&$buf) {
318        $startA = max(1, $ai - $ctx);
319        $startB = max(1, $bi - $ctx);
320        $buf['oldStart'] = $startA;
321        $buf['newStart'] = $startB;
322        for ($k=0; $k<($ai-$startA); $k++) {
323            $buf['lines'][] = ' ' . rtrim((string)$aOrig[$startA-1+$k], "\r") . "\n";
324        }
325        $buf['oldLen'] += ($ai-$startA);
326        $buf['newLen'] += ($bi-$startB);
327    };
328
329    foreach ($ops as $op) {
330        if ($op['op'] === 'eq') {
331            if ($buf['open']) {
332                if ($ctxAhead < 3) {
333                    $line = rtrim((string)$aOrig[$op['ai']], "\r");
334                    $buf['lines'][] = ' ' . $line . "\n";
335                    $buf['oldLen']++; $buf['newLen']++; $ctxAhead++;
336                } else {
337                    $flush($hunks, $buf);
338                    $ctxAhead = 0;
339                }
340            }
341            $ai++; $bi++;
342        } elseif ($op['op'] === 'del') {
343            if (!$buf['open']) { $buf['open']=true; $ctxAhead=0; $grab_context($aOrig, $bOrig, $ai, $bi, 3); }
344            $line = rtrim((string)$aOrig[$op['ai']], "\r");
345            $buf['lines'][] = '-' . $line . "\n";
346            $buf['oldLen']++; $ai++;
347        } else { // add
348            if (!$buf['open']) { $buf['open']=true; $ctxAhead=0; $grab_context($aOrig, $bOrig, $ai, $bi, 3); }
349            $line = rtrim((string)$bOrig[$op['bi']], "\r");
350            $buf['lines'][] = '+' . $line . "\n";
351            $buf['newLen']++; $bi++;
352        }
353    }
354    if ($buf['open']) $flush($hunks, $buf);
355
356    $ts = gmdate('Y-m-d H:i:s O');
357    $out  = "--- {$nameA}\t{$ts}\n+++ {$nameB}\t{$ts}\n";
358    $out .= implode('', $hunks);
359    return $out;
360}
361
362// Render a single line with highlight.php if available (else plain-escaped).
363function hl_render_line(string $text, string $lang='text'): string {
364    global $highlighter;
365    static $hl = null;
366
367    $esc = static fn($s)=>htmlspecialchars($s, ENT_QUOTES|ENT_SUBSTITUTE, 'UTF-8');
368
369    if (($highlighter ?? 'geshi') === 'highlight') {
370        if ($hl === null) $hl = make_highlighter();
371        if ($hl) {
372            try {
373                if ($lang && !in_array(strtolower($lang), ['autodetect','text','plaintext'], true)) {
374                    $res = $hl->highlight($lang, $text);
375                    return '<span class="hljs">'.$res->value.'</span>';
376                }
377                $res = $hl->highlightAuto($text);
378                return '<span class="hljs">'.$res->value.'</span>';
379            } catch (Throwable $e) { /* fall through */ }
380        }
381    }
382    return $esc($text);
383}
384
385/* =========================================================
386 * Page inputs
387 * =======================================================*/
388
389$left  = '';
390$right = '';
391$leftLabel  = 'Old';
392$rightLabel = 'New';
393
394/* ---------- Minimal site/bootstrap so header/footer look right ---------- */
395$mod_rewrite = $mod_rewrite ?? '0';
396$baseurl     = $baseurl     ?? '/';
397$site_name   = $site_name   ?? '';
398$title       = 'Diff';
399$ges_style   = '';          // keep themes CSS-only
400$ads_1 = $ads_2 = $text_ads = ''; // optional ad slots
401
402try {
403    // site_info
404    $stmt = $pdo->query("SELECT * FROM site_info WHERE id='1'");
405    if ($stmt) {
406        $si = $stmt->fetch() ?: [];
407        $title     = trim($si['title'] ?? $title);
408        $des       = trim($si['des'] ?? '');
409        $baseurl   = rtrim(trim($si['baseurl'] ?? $baseurl), '/') . '/';
410        $keyword   = trim($si['keyword'] ?? '');
411        $site_name = trim($si['site_name'] ?? $site_name);
412        $email     = trim($si['email'] ?? '');
413        $twit      = trim($si['twit'] ?? '');
414        $face      = trim($si['face'] ?? '');
415        $gplus     = trim($si['gplus'] ?? '');
416        $ga        = trim($si['ga'] ?? '');
417        $additional_scripts = trim($si['additional_scripts'] ?? '');
418        if (isset($si['mod_rewrite']) && $si['mod_rewrite'] !== '') {
419            $mod_rewrite = (string)$si['mod_rewrite'];
420        }
421    }
422
423    // interface
424    $stmt = $pdo->query("SELECT * FROM interface WHERE id='1'");
425    if ($stmt) {
426        $iface = $stmt->fetch() ?: [];
427        $default_lang  = trim($iface['lang']  ?? 'en.php');
428        $default_theme = trim($iface['theme'] ?? 'default');
429        if (is_file(__DIR__ . "/langs/$default_lang")) {
430            require_once __DIR__ . "/langs/$default_lang";
431        }
432    } else {
433        $default_theme = $default_theme ?? 'default';
434    }
435
436    // permissions
437    $stmt = $pdo->query("SELECT * FROM site_permissions WHERE id='1'");
438    if ($stmt) {
439        $perm = $stmt->fetch() ?: [];
440        $disableguest = trim($perm['disableguest'] ?? 'off');
441        $siteprivate  = trim($perm['siteprivate']  ?? 'off');
442    }
443
444    // ads (optional)
445    $stmt = $pdo->query("SELECT * FROM ads WHERE id='1'");
446    if ($stmt) {
447        $ads  = $stmt->fetch() ?: [];
448        $text_ads = trim($ads['text_ads'] ?? '');
449        $ads_1    = trim($ads['ads_1'] ?? '');
450        $ads_2    = trim($ads['ads_2'] ?? '');
451    }
452} catch (Throwable $e) {
453    // keep sane defaults, but don't break the page
454    error_log('diff.php bootstrap: ' . $e->getMessage());
455    $default_theme = $default_theme ?? 'default';
456}
457
458/* ---------- Paste IDs from query (supports ?a & ?b) ---------- */
459$lid = isset($_GET['a']) ? (int)$_GET['a'] : (isset($_GET['left_id']) ? (int)$_GET['left_id'] : 0);
460$rid = isset($_GET['b']) ? (int)$_GET['b'] : (isset($_GET['right_id']) ? (int)$_GET['right_id'] : 0);
461
462if ($lid) { $p = load_paste($pdo, $lid); if ($p){ $left=$p['content'];  $leftLabel='Paste #'.$lid; } }
463if ($rid) { $p = load_paste($pdo, $rid); if ($p){ $right=$p['content']; $rightLabel='Paste #'.$rid; } }
464
465/* ---------- POST inputs (compare / download keeps buffers) ---------- */
466if ($_SERVER['REQUEST_METHOD']==='POST') {
467    $left       = (string)($_POST['left_text']  ?? $left);
468    $right      = (string)($_POST['right_text'] ?? $right);
469    $leftLabel  = trim((string)($_POST['left_label']  ?? $leftLabel))  ?: $leftLabel;
470    $rightLabel = trim((string)($_POST['right_label'] ?? $rightLabel)) ?: $rightLabel;
471}
472
473/* ---------- Language engine + maps ---------- */
474$engine = function_exists('paste_current_engine') ? paste_current_engine() : ($highlighter ?? 'geshi');
475
476if ($engine === 'highlight') {
477    $langs         = highlight_supported_languages();
478    $language_map  = highlight_language_map($langs);
479    $alias_map     = highlight_alias_map($langs);
480    $popular_langs = paste_popular_formats_highlight();
481} else {
482    $language_map  = geshi_language_map();
483    $alias_map     = geshi_alias_map($language_map);
484    $popular_langs = paste_popular_formats_geshi();
485}
486
487/* ---------- Picked languages ---------- */
488$lang_left  = strtolower((string)($_POST['left_lang']  ?? $_GET['left_lang']  ?? 'autodetect'));
489$lang_right = strtolower((string)($_POST['right_lang'] ?? $_GET['right_lang'] ?? 'autodetect'));
490$lang_left  = $alias_map[$lang_left]  ?? 'autodetect';
491$lang_right = $alias_map[$lang_right] ?? 'autodetect';
492
493$lang_left_label  = $language_map[$lang_left]  ?? ucfirst($lang_left);
494$lang_right_label = $language_map[$lang_right] ?? ucfirst($lang_right);
495
496/* ---------- highlight.php default style (no picker) ---------- */
497if (($highlighter ?? 'geshi') === 'highlight') {
498    $hl_style = $hl_style ?? 'hybrid.css'; // header.php reads this
499}
500
501/* ---------- View options ---------- */
502$view_mode = ($_GET['view'] ?? 'side') === 'unified' ? 'unified' : 'side';
503$wrap      = isset($_GET['wrap'])      ? (int)$_GET['wrap']      : 0;
504$lineno    = isset($_GET['lineno'])    ? (int)$_GET['lineno']    : 1;
505
506/* ---------- Ignore trailing whitespace (toggle via ?ignore_ws=1) ---------- */
507$ignore_ws = isset($_GET['ignore_ws']) ? (int)$_GET['ignore_ws'] : 0;
508$normalizer = $ignore_ws ? static fn($s) => rtrim($s, " \t") : null;
509
510/* ---------- Persisted split percentage ---------- */
511$split_pct = 50.0;
512if (isset($_POST['split_pct'])) {
513    $split_pct = (float)$_POST['split_pct'];
514} elseif (isset($_COOKIE['diffSplitPct'])) {
515    $split_pct = (float)$_COOKIE['diffSplitPct'];
516}
517$split_pct = max(20.0, min(80.0, (float)$split_pct));
518setcookie('diffSplitPct', (string)$split_pct, [
519    'expires'  => time() + 60*60*24*30,
520    'path'     => '/',
521    'secure'   => !empty($_SERVER['HTTPS']),
522    'httponly' => false,
523    'samesite' => 'Lax',
524]);
525
526/* ---------- Download unified diff ---------- */
527if (isset($_GET['download']) && $_GET['download'] === '1') {
528    $nameA = $leftLabel  ?: 'Old';
529    $nameB = $rightLabel ?: 'New';
530    $ud = unified_diff_download($left, $right, $nameA, $nameB, 3);
531    // Surface engine in headers for debug
532    header('X-Diff-Engine: '.(function_exists('xdiff_string_diff') ? 'xdiff' : 'myers'));
533    header('X-Diff-Ignore-WS: '.($ignore_ws ? '1':'0'));
534    header('Content-Type: text/x-diff; charset=utf-8');
535    header('Content-Disposition: attachment; filename="paste.diff"');
536    echo $ud;
537    exit;
538}
539
540/* ---------- Compute opcodes ---------- */
541$leftLines  = preg_split("/\R/u", $left);
542$rightLines = preg_split("/\R/u", $right);
543if ($leftLines === false)  $leftLines  = [$left];
544if ($rightLines === false) $rightLines = [$right];
545
546$ops = diff_lines_idx($leftLines, $rightLines, $normalizer);
547
548/* ---------- Build tables server-side ---------- */
549[$sideRows, $uniRows] = build_tables_idx($ops, $leftLines, $rightLines);
550
551/* ---------- Limit expensive inline diff pass for very large diffs ---------- */
552$perform_inline = true;
553$totalBytes = strlen($left) + strlen($right);
554if (count($sideRows) > 4000 || $totalBytes > 4*1024*1024) {
555    $perform_inline = false;
556}
557if ($perform_inline) {
558    apply_inline_sxs($sideRows);
559}
560
561/* ---------- Expose engine + toggle info to theme and headers ---------- */
562$engine_is_xdiff = function_exists('xdiff_string_diff');
563$engine_label    = $engine_is_xdiff ? 'xdiff' : 'myers';
564header('X-Diff-Engine: '.$engine_label);
565header('X-Diff-Ignore-WS: '.($ignore_ws ? '1':'0'));
566
567// Convenience strings the theme can show in the toolbar:
568$diff_engine_badge = '<span class="badge bg-secondary" title="Diff engine">'.$engine_label.'</span>';
569$ignore_ws_on      = (bool)$ignore_ws;
570
571// Build toggle URL for ignore_ws (preserve other query params)
572$qs = $_GET;
573$qs['ignore_ws'] = $ignore_ws ? 0 : 1;
574$ignore_ws_toggle_url = strtok($_SERVER['REQUEST_URI'], '?') . '?' . http_build_query($qs);
575
576/* ---------- Render theme ---------- */
577$themeDir = 'theme/' . htmlspecialchars($default_theme ?? 'default', ENT_QUOTES, 'UTF-8');
578
579// expose split pct to the view if needed by JS
580$GLOBALS['split_pct'] = $split_pct;
581
582// Also expose new goodies for the toolbar (the theme may choose to use them)
583$GLOBALS['diff_engine_badge']  = $diff_engine_badge;
584$GLOBALS['ignore_ws_on']       = $ignore_ws_on;
585$GLOBALS['ignore_ws_toggle']   = $ignore_ws_toggle_url;
586
587require_once $themeDir . '/header.php';
588require_once $themeDir . '/diff.php';
589require_once $themeDir . '/footer.php';