Add a translation assistant to the panel

Each field's original sits beside the field to write, and a translation that fell behind shows what the original said when it was translated and what it says now, word by word. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
2026-10-01 10:53:31 +02:00
parent 76d022053b
commit 6fc600e6a1
16 changed files with 837 additions and 61 deletions
--- a/app/Support/TextDiff.php
+++ b/app/Support/TextDiff.php
@@ -0,0 +1,99 @@
+<?php
+
+declare(strict_types=1);
+
+namespace App\Support;
+
+/**
+ * What changed between two versions of a text, word by word, as HTML with
+ * `<del>` and `<ins>` — enough to show a translator which sentence of the
+ * original to look at again.
+ */
+final class TextDiff
+{
+    /**
+     * Above this many words on either side the comparison is skipped: it is
+     * quadratic, and a text that long changed is better reread whole.
+     */
+    protected const MAX_WORDS = 1500;
+
+    public static function html(?string $old, ?string $new): ?string
+    {
+        $a = self::words($old);
+        $b = self::words($new);
+
+        if (count($a) > self::MAX_WORDS || count($b) > self::MAX_WORDS) {
+            return null;
+        }
+
+        // Longest common subsequence, then walked back into runs.
+        $m = count($a);
+        $n = count($b);
+        $lcs = array_fill(0, $m + 1, array_fill(0, $n + 1, 0));
+
+        for ($i = $m - 1; $i >= 0; $i--) {
+            for ($j = $n - 1; $j >= 0; $j--) {
+                $lcs[$i][$j] = $a[$i] === $b[$j] ? $lcs[$i + 1][$j + 1] + 1 : max($lcs[$i + 1][$j], $lcs[$i][$j + 1]);
+            }
+        }
+
+        $out = [];
+        $i = $j = 0;
+
+        while ($i < $m || $j < $n) {
+            if ($i < $m && $j < $n && $a[$i] === $b[$j]) {
+                $out[] = ['=', $a[$i]];
+                $i++;
+                $j++;
+            } elseif ($i < $m && ($j === $n || $lcs[$i + 1][$j] >= $lcs[$i][$j + 1])) {
+                // What went comes before what replaced it.
+                $out[] = ['-', $a[$i]];
+                $i++;
+            } else {
+                $out[] = ['+', $b[$j]];
+                $j++;
+            }
+        }
+
+        $html = '';
+        $run = null;
+        $buffer = [];
+
+        $flush = function () use (&$html, &$run, &$buffer): void {
+            if ($buffer === []) {
+                return;
+            }
+
+            $text = e(implode(' ', $buffer));
+            $html .= match ($run) {
+                '+' => "<ins>{$text}</ins> ",
+                '-' => "<del>{$text}</del> ",
+                default => "{$text} ",
+            };
+            $buffer = [];
+        };
+
+        foreach ($out as [$op, $word]) {
+            if ($op !== $run) {
+                $flush();
+                $run = $op;
+            }
+
+            $buffer[] = $word;
+        }
+
+        $flush();
+
+        return trim($html);
+    }
+
+    /**
+     * @return array<int, string>
+     */
+    protected static function words(?string $text): array
+    {
+        $plain = trim((string) preg_replace('/\s+/u', ' ', html_entity_decode(strip_tags(str_replace(['</p>', '<br>', '<br/>', '<br />'], ' ', (string) $text)))));
+
+        return $plain === '' ? [] : explode(' ', $plain);
+    }
+}