feat: translate subtitles with an OpenAI-compatible LLM

src/translate/translationservice.h

@@ -0,0 +1,91 @@
+#pragma once
+
+#include "llmclient.h"
+#include "subtitleextractor.h"
+
+#include <QCoroTask>
+
+#include <QObject>
+#include <QStringList>
+#include <QUrl>
+#include <QVariantMap>
+#include <QtQml/qqmlregistration.h>
+
+#include <atomic>
+#include <memory>
+
+class QNetworkAccessManager;
+
+// Translates a whole subtitle track with an LLM, batch by batch, and caches the result
+// as an .srt file that mpv can load as the secondary subtitle.
+class TranslationService : public QObject
+{
+    Q_OBJECT
+    QML_ELEMENT
+
+    Q_PROPERTY(bool busy READ isBusy NOTIFY busyChanged)
+    Q_PROPERTY(double progress READ progress NOTIFY progressChanged)
+    Q_PROPERTY(QString statusText READ statusText NOTIFY statusTextChanged)
+    Q_PROPERTY(QString errorText READ errorText NOTIFY errorTextChanged)
+    Q_PROPERTY(QStringList availableModels READ availableModels NOTIFY availableModelsChanged)
+    Q_PROPERTY(bool fetchingModels READ isFetchingModels NOTIFY fetchingModelsChanged)
+
+public:
+    explicit TranslationService(QObject *parent = nullptr);
+    ~TranslationService() override;
+
+    bool isBusy() const;
+    double progress() const;
+    QString statusText() const;
+    QString errorText() const;
+    QStringList availableModels() const;
+    bool isFetchingModels() const;
+
+    // \a track is an entry of MpvItem::subtitleTracks.
+    Q_INVOKABLE void translate(const QUrl &videoUrl, const QVariantMap &track, const QString &mediaTitle);
+    Q_INVOKABLE void cancel();
+    // Asks the API configured in the settings for its models.
+    Q_INVOKABLE void fetchModels();
+    Q_INVOKABLE void clearError();
+
+Q_SIGNALS:
+    void busyChanged();
+    void progressChanged();
+    void statusTextChanged();
+    void errorTextChanged();
+    void availableModelsChanged();
+    void fetchingModelsChanged();
+    void translated(const QUrl &subtitleUrl, bool fromCache);
+
+private:
+    struct Job;
+    struct Batches;
+
+    QCoro::Task<> run(QUrl videoUrl, QVariantMap track);
+    QCoro::Task<> runFetchModels();
+    // Translates \a lines, retrying failures and asking again for lines the model skipped.
+    QCoro::Task<LlmClient::BatchResult> translateLines(std::shared_ptr<Job> job, QStringList lines, QStringList context);
+    // Takes batches from \a batches until none are left; several run side by side.
+    QCoro::Task<> translateBatches(std::shared_ptr<Job> job, std::shared_ptr<Batches> batches);
+    QCoro::Task<Subtitles::ExtractResult> loadCues(std::shared_ptr<Job> job, QUrl videoUrl, QVariantMap track);
+
+    // Reads the settings and the API key. The second value is an error message when
+    // something is missing.
+    QCoro::Task<std::pair<LlmClient::Config, QString>> loadConfig();
+    void fail(const std::shared_ptr<Job> &job, const QString &error);
+
+    void setBusy(bool busy);
+    void setProgress(double progress);
+    void setStatusText(const QString &text);
+    void setErrorText(const QString &text);
+    void setFetchingModels(bool fetching);
+
+    QNetworkAccessManager *m_network;
+    std::shared_ptr<Job> m_job;
+    bool m_busy = false;
+    double m_progress = 0.0;
+    QString m_statusText;
+    QString m_errorText;
+    QStringList m_availableModels;
+    bool m_fetchingModels = false;
+};