feat(translate): translate a whole playlist

autotests/subtitleextractortest.cpp

@@ -0,0 +1,97 @@
+// SPDX-FileCopyrightText: 2026 Tri Vo Khac
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+#include "subtitleextractor.h"
+
+#include <QFile>
+#include <QProcess>
+#include <QStandardPaths>
+#include <QTemporaryDir>
+#include <QTest>
+
+using namespace Qt::Literals::StringLiterals;
+
+class SubtitleExtractorTest : public QObject
+{
+    Q_OBJECT
+
+private:
+    // Makes \a name in \a dir with a German audio track plus \a subtitleLanguages as
+    // SRT subtitle tracks, in that order.
+    static QString makeSample(const QTemporaryDir &dir, const QString &name, const QStringList &subtitleLanguages)
+    {
+        const QString ffmpeg = QStandardPaths::findExecutable(u"ffmpeg"_s);
+        const QString srt = dir.filePath(u"line.srt"_s);
+        QFile file(srt);
+        if (!file.open(QIODevice::WriteOnly) || file.write("1\n00:00:00,000 --> 00:00:01,000\nHello\n") < 0) {
+            return {};
+        }
+        file.close();
+
+        QStringList args{u"-v"_s, u"error"_s, u"-f"_s, u"lavfi"_s, u"-i"_s, u"sine=duration=1"_s};
+        for (qsizetype i = 0; i < subtitleLanguages.size(); ++i) {
+            args << u"-i"_s << srt;
+        }
+        args << u"-map"_s << u"0:a"_s << u"-metadata:s:a:0"_s << u"language=ger"_s;
+        for (qsizetype i = 0; i < subtitleLanguages.size(); ++i) {
+            args << u"-map"_s << u"%1:s"_s.arg(i + 1) << u"-metadata:s:s:%1"_s.arg(i) << u"language=%1"_s.arg(subtitleLanguages.at(i));
+        }
+        const QString path = dir.filePath(name);
+        args << u"-c:s"_s << u"srt"_s << path;
+        QProcess process;
+        process.start(ffmpeg, args);
+        if (!process.waitForFinished() || process.exitCode() != 0) {
+            qWarning() << process.readAllStandardError();
+            return {};
+        }
+        return path;
+    }
+
+private Q_SLOTS:
+    void initTestCase()
+    {
+        if (QStandardPaths::findExecutable(u"ffmpeg"_s).isEmpty()) {
+            QSKIP("ffmpeg is needed to make sample files");
+        }
+    }
+
+    void findTranslationSourcePrefersEnglish()
+    {
+        QTemporaryDir dir;
+        const QString path = makeSample(dir, u"episode.mkv"_s, {u"fre"_s, u"eng"_s});
+        QVERIFY(!path.isEmpty());
+        const Subtitles::SourceResult result = Subtitles::findTranslationSource(path);
+        QVERIFY2(result.error.isEmpty(), qPrintable(result.error));
+        // Stream 0 is the audio, 1 French, 2 English.
+        QCOMPARE(result.streamIndex, 2);
+
+        std::atomic_bool cancelled = false;
+        const Subtitles::ExtractResult cues = Subtitles::extractEmbedded(path, result.streamIndex, cancelled);
+        QCOMPARE(cues.cues.size(), 1);
+        QCOMPARE(cues.cues.first().text, u"Hello"_s);
+    }
+
+    void findTranslationSourceFallsBackToTheAudioLanguage()
+    {
+        QTemporaryDir dir;
+        const QString path = makeSample(dir, u"episode.mkv"_s, {u"fre"_s, u"ger"_s});
+        QVERIFY(!path.isEmpty());
+        QCOMPARE(Subtitles::findTranslationSource(path).streamIndex, 2);
+    }
+
+    void findTranslationSourceWithoutSubtitles()
+    {
+        QTemporaryDir dir;
+        const QString path = makeSample(dir, u"episode.mkv"_s, {});
+        QVERIFY(!path.isEmpty());
+        const Subtitles::SourceResult result = Subtitles::findTranslationSource(path);
+        QVERIFY(result.error.isEmpty());
+        QCOMPARE(result.streamIndex, -1);
+
+        QVERIFY(!Subtitles::findTranslationSource(dir.filePath(u"missing.mkv"_s)).error.isEmpty());
+    }
+};
+
+QTEST_GUILESS_MAIN(SubtitleExtractorTest)
+
+#include "subtitleextractortest.moc"