#include "translationservice.h"

#include "apikeystore.h"
#include "mediainfo.h"
#include "qtpotatosettings.h"
#include "translationpresets.h"
#include "translationstore.h"

#include <KLocalizedString>

#include <QCoroFuture>
#include <QCoroTimer>

#include <QCryptographicHash>
#include <QDir>
#include <QFileInfo>
#include <QHash>
#include <QLocale>
#include <QNetworkAccessManager>
#include <QPointer>
#include <QSaveFile>
#include <QStandardPaths>
#include <QFile>
#include <QSet>
#include <QtConcurrentRun>

#include <chrono>
#include <vector>

using namespace Qt::Literals::StringLiterals;
using namespace std::chrono_literals;

namespace
{
// Source lines before a batch that the model sees for context.
constexpr qsizetype ContextLines = 6;
constexpr int MaxAttempts = 3;
// Requests in flight at once. Batches only use source lines as context, so they don't
// depend on each other.
constexpr int ParallelRequests = 3;
// Bump when the prompt changes so old cached translations are not reused.
constexpr auto CacheVersion = "llm-v2";

QString cacheDir()
{
    return QStandardPaths::writableLocation(QStandardPaths::CacheLocation) + u"/translations"_s;
}

QList<GlossaryStore::Entry> glossaryEntriesFromVariants(const QVariantList &entries)
{
    QList<GlossaryStore::Entry> result;
    for (const QVariant &value : entries) {
        const QVariantMap map = value.toMap();
        result.append({map.value(u"source"_s).toString().trimmed(), map.value(u"target"_s).toString().trimmed(), map.value(u"episode"_s).toString()});
    }
    return result;
}

QVariantList glossaryEntriesToVariants(const QList<GlossaryStore::Entry> &entries)
{
    QVariantList result;
    for (const auto &entry : entries) {
        result.append(QVariantMap{{u"source"_s, entry.source}, {u"target"_s, entry.target}, {u"episode"_s, entry.episode}});
    }
    return result;
}
}

struct TranslationService::Job {
    std::atomic_bool cancelled = false;
    std::unique_ptr<LlmClient> client;
    QString mediaTitle;
    bool playlist = false;
    // In a playlist: the episode being translated (from 0) and how many there are.
    int episode = 0;
    int episodes = 0;
};

struct TranslationService::Batches {
    QStringList lines;
    QStringList translations;
    qsizetype batchSize = 0;
    qsizetype nextStart = 0;
    qsizetype doneLines = 0;
    QString error;
};

TranslationService::TranslationService(QObject *parent)
    : QObject(parent)
    , m_network(new QNetworkAccessManager(this))
{
}

TranslationService::~TranslationService()
{
    cancel();
}

bool TranslationService::isBusy() const
{
    return m_busy;
}

double TranslationService::progress() const
{
    return m_progress;
}

QString TranslationService::statusText() const
{
    return m_statusText;
}

QString TranslationService::errorText() const
{
    return m_errorText;
}

QStringList TranslationService::availableModels() const
{
    return m_availableModels;
}

QVariantList TranslationService::translationPresets() const
{
    QVariantList result;
    for (const auto &preset : TranslationPresets::all()) {
        result.append(QVariantMap{{u"id"_s, preset.id}, {u"name"_s, preset.name}, {u"description"_s, preset.description}, {u"guidance"_s, preset.guidance}});
    }
    return result;
}

bool TranslationService::isFetchingModels() const
{
    return m_fetchingModels;
}

QVariantList TranslationService::glossaryEntries() const
{
    return glossaryEntriesToVariants(m_glossary.entries);
}

QString TranslationService::glossaryDirectory() const
{
    return m_glossary.directory;
}

QString TranslationService::glossaryEpisode() const
{
    return m_glossaryEpisode;
}

QStringList TranslationService::glossaryEpisodes() const
{
    return GlossaryStore::sortedEpisodes(m_glossary.episodes);
}

QStringList TranslationService::sortedGlossaryEpisodes(const QStringList &episodes) const
{
    return GlossaryStore::sortedEpisodes(episodes);
}

QString TranslationService::glossaryError() const
{
    return m_glossaryError;
}

QUrl TranslationService::currentVideo() const
{
    return m_currentVideo;
}

void TranslationService::setCurrentVideo(const QUrl &url)
{
    if (url == m_currentVideo) {
        return;
    }
    m_currentVideo = url;
    forgetTranslation();
    // A playlist translation is meant to go on while the episodes play.
    if (m_job && !m_job->playlist) {
        cancel();
    }
    Q_EMIT currentVideoChanged();
}

void TranslationService::loadGlossary(const QUrl &videoUrl)
{
    const QString directory = videoUrl.isLocalFile() ? QFileInfo(videoUrl.toLocalFile()).absolutePath() : QString();
    m_glossaryEpisode = videoUrl.isLocalFile() ? QFileInfo(videoUrl.toLocalFile()).completeBaseName() : QString();
    m_glossary = directory.isEmpty() ? GlossaryStore::Glossary{} : GlossaryStore::load(directory);
    // A legacy glossary has no provenance for its old entries. Once it is
    // opened in an episode, keep it with that episode instead of presenting a
    // misleading shared bucket. Later episodes still reuse every term.
    if (!m_glossaryEpisode.isEmpty()) {
        m_glossary = GlossaryStore::assignUnassigned(m_glossary, m_glossaryEpisode);
    }
    if (!m_glossaryError.isEmpty()) {
        m_glossaryError.clear();
        Q_EMIT glossaryErrorChanged();
    }
    Q_EMIT glossaryChanged();
}

bool TranslationService::saveGlossary(const QVariantList &entries, const QStringList &episodes)
{
    GlossaryStore::Glossary candidate = m_glossary;
    candidate.entries = glossaryEntriesFromVariants(entries);
    candidate.episodes = episodes;
    if (!m_glossaryEpisode.isEmpty()) {
        candidate = GlossaryStore::assignUnassigned(candidate, m_glossaryEpisode);
    }
    const bool changed = GlossaryStore::serialize(candidate) != GlossaryStore::serialize(m_glossary);
    const GlossaryStore::Glossary previous = m_glossary;
    if (!candidate.directory.isEmpty()) {
        QString error;
        if (!GlossaryStore::save(candidate, &error)) {
            const QString message = error.isEmpty() ? i18n("Could not save the translation glossary.")
                                                     : i18n("Could not save the translation glossary: %1", error);
            if (m_glossaryError != message) {
                m_glossaryError = message;
                Q_EMIT glossaryErrorChanged();
            }
            return false;
        }
    }
    m_glossary = candidate;
    if (!m_glossaryError.isEmpty()) {
        m_glossaryError.clear();
        Q_EMIT glossaryErrorChanged();
    }
    Q_EMIT glossaryChanged();
    if (changed) {
        applyGlossaryEdits(previous, candidate);
    }
    return true;
}

void TranslationService::clearGlossary()
{
    saveGlossary({}, {});
}

QVariantMap TranslationService::importGlossaryFile(const QUrl &url, const QVariantList &entries, const QStringList &episodes)
{
    GlossaryStore::Glossary imported;
    QString error;
    if (!url.isLocalFile()) {
        return {{u"ok"_s, false}, {u"error"_s, i18n("Choose a local glossary file.")}};
    }
    if (!GlossaryStore::importFile(url.toLocalFile(), &imported, &error)) {
        return {{u"ok"_s, false}, {u"error"_s, i18n("Could not import glossary: %1", error)}};
    }
    const GlossaryStore::Glossary current{m_glossary.directory, glossaryEntriesFromVariants(entries), episodes};
    auto merged = GlossaryStore::mergeImported(current, imported);
    if (!m_glossaryEpisode.isEmpty()) {
        merged = GlossaryStore::assignUnassigned(merged, m_glossaryEpisode);
    }
    const qsizetype added = merged.entries.size() - current.entries.size();
    return {{u"ok"_s, true}, {u"entries"_s, glossaryEntriesToVariants(merged.entries)}, {u"episodes"_s, merged.episodes},
            {u"added"_s, added}, {u"skipped"_s, imported.entries.size() - added}};
}

QVariantMap TranslationService::exportGlossaryFile(const QUrl &url, const QVariantList &entries, const QStringList &episodes)
{
    if (!url.isLocalFile()) {
        return {{u"ok"_s, false}, {u"error"_s, i18n("Choose a local destination file.")}};
    }
    const GlossaryStore::Glossary draft{{}, glossaryEntriesFromVariants(entries), episodes};
    QString error;
    if (!GlossaryStore::exportFile(url.toLocalFile(), draft, &error)) {
        return {{u"ok"_s, false}, {u"error"_s, i18n("Could not export glossary: %1", error)}};
    }
    return {{u"ok"_s, true}};
}

void TranslationService::applyGlossaryEdits(const GlossaryStore::Glossary &previous, const GlossaryStore::Glossary &updated)
{
    if (m_lastTranslationPath.isEmpty() || !QFileInfo::exists(m_lastTranslationPath)) {
        return;
    }
    // A translation the user has edited since is theirs; leave it alone.
    const QString registryFile = TranslationStore::registryFile();
    TranslationStore::Registry registry = TranslationStore::load(registryFile);
    if (!TranslationStore::isOwned(registry, m_lastTranslationPath)) {
        return;
    }
    QFile file(m_lastTranslationPath);
    if (!file.open(QIODevice::ReadOnly)) {
        return;
    }
    QString text = QString::fromUtf8(file.readAll());
    file.close();

    QHash<QString, QString> oldTargets;
    for (const auto &entry : previous.entries) {
        oldTargets.insert(entry.source.trimmed(), entry.target.trimmed());
    }
    QList<QPair<QString, QString>> replacements;
    for (const auto &entry : updated.entries) {
        const QString source = entry.source.trimmed();
        const QString target = entry.target.trimmed();
        if (source.isEmpty() || target.isEmpty()) {
            continue;
        }
        const QString oldTarget = oldTargets.value(source);
        if (!oldTarget.isEmpty() && oldTarget != target) {
            replacements.append({oldTarget, target});
        } else if (oldTarget.isEmpty()) {
            replacements.append({source, target});
        }
    }
    QSet<QString> updatedSources;
    for (const auto &entry : updated.entries) {
        updatedSources.insert(entry.source.trimmed());
    }
    for (const auto &entry : previous.entries) {
        const QString source = entry.source.trimmed();
        const QString target = entry.target.trimmed();
        if (!source.isEmpty() && !target.isEmpty() && !updatedSources.contains(source)) {
            replacements.append({target, source});
        }
    }
    QStringList markers;
    for (qsizetype i = 0; i < replacements.size(); ++i) {
        const QString marker = u"\\uE000qtpotato-glossary-%1\\uE001"_s.arg(i);
        text.replace(replacements.at(i).first, marker);
        markers.append(marker);
    }
    for (qsizetype i = 0; i < markers.size(); ++i) {
        text.replace(markers.at(i), replacements.at(i).second);
    }

    const QByteArray data = text.toUtf8();
    QSaveFile output(m_lastTranslationPath);
    if (!output.open(QIODevice::WriteOnly) || output.write(data) < 0 || !output.commit()) {
        return;
    }
    // Still QtPotato's file, so a later translation may replace it.
    TranslationStore::recordRewrite(registry, m_lastTranslationPath, data);
    TranslationStore::save(registryFile, registry);
    Q_EMIT translated(QUrl::fromLocalFile(m_lastTranslationPath), true);
}

void TranslationService::translate(const QUrl &videoUrl, const QVariantMap &track, const QString &mediaTitle)
{
    cancel();
    m_job = std::make_shared<Job>();
    m_job->mediaTitle = mediaTitle;
    run(m_job, videoUrl, track);
}

void TranslationService::translatePlaylist(const QList<QUrl> &urls, const QVariantMap &currentTrack, const QString &currentTitle)
{
    cancel();
    // Start with the episode playing, then the ones after it, which are watched next.
    QList<QUrl> ordered;
    const qsizetype current = std::max<qsizetype>(0, urls.indexOf(m_currentVideo));
    for (qsizetype i = 0; i < urls.size(); ++i) {
        const QUrl &url = urls.at((current + i) % urls.size());
        if (!ordered.contains(url)) {
            ordered.append(url);
        }
    }
    m_job = std::make_shared<Job>();
    m_job->playlist = true;
    m_job->episodes = ordered.size();
    runPlaylist(m_job, ordered, currentTrack, currentTitle);
}

void TranslationService::cancel()
{
    if (!m_job) {
        return;
    }
    // The running coroutine keeps its own reference and stops at its next check.
    m_job->cancelled = true;
    if (m_job->client) {
        m_job->client->abort();
    }
    m_job.reset();
    setBusy(false);
    setStatusText({});
}

void TranslationService::fetchModels()
{
    if (!m_fetchingModels) {
        runFetchModels();
    }
}

void TranslationService::clearError()
{
    setErrorText({});
}

void TranslationService::forgetTranslation()
{
    m_lastTranslationPath.clear();
}

QCoro::Task<std::pair<LlmClient::Config, QString>> TranslationService::loadConfig()
{
    const auto settings = QtPotatoSettings::self();
    LlmClient::Config config{
        LlmClient::normalizedBaseUrl(settings->apiBaseUrl()),
        {},
        settings->model().trimmed(),
        settings->targetLanguage().trimmed(),
        settings->translationPreset().trimmed(),
        settings->customInstructions(),
        {},
    };

    if (!config.baseUrl.isValid() || config.baseUrl.scheme().isEmpty() || config.baseUrl.host().isEmpty()) {
        co_return std::pair{config, i18n("Set the API base URL in Settings first.")};
    }

    const ApiKeyStore::ReadResult key = co_await ApiKeyStore::readKey();
    if (!key.error.isEmpty()) {
        co_return std::pair{config, i18n("Could not read the API key from the wallet: %1", key.error)};
    }
    config.apiKey = key.key;
    co_return std::pair{config, QString()};
}

QCoro::Task<Subtitles::ExtractResult> TranslationService::loadCues(std::shared_ptr<Job> job, QUrl videoUrl, QVariantMap track)
{
    if (track.value(u"external"_s).toBool()) {
        const QString path = track.value(u"externalFilename"_s).toString();
        co_return co_await QtConcurrent::run([path] {
            QString error;
            QList<SubtitleCue> cues = Subtitles::parseFile(path, &error);
            return Subtitles::ExtractResult{cues, error};
        });
    }

    if (!videoUrl.isLocalFile()) {
        co_return Subtitles::ExtractResult{{}, i18n("Only subtitles of local files can be translated.")};
    }
    const int streamIndex = track.value(u"ffIndex"_s, -1).toInt();
    if (streamIndex < 0) {
        co_return Subtitles::ExtractResult{{}, i18n("mpv did not report where this subtitle track is stored.")};
    }

    const QString path = videoUrl.toLocalFile();
    co_return co_await QtConcurrent::run([path, streamIndex, job] {
        return Subtitles::extractEmbedded(path, streamIndex, job->cancelled);
    });
}

QCoro::Task<std::optional<LlmClient::Config>> TranslationService::startJob(std::shared_ptr<Job> job)
{
    setErrorText({});
    setProgress(0);
    setBusy(true);
    setStatusText(i18n("Reading subtitles…"));

    auto [config, configError] = co_await loadConfig();
    if (job->cancelled) {
        co_return std::nullopt;
    }
    if (configError.isEmpty() && config.model.isEmpty()) {
        configError = i18n("Choose a model in Settings first.");
    }
    if (!configError.isEmpty()) {
        fail(job, configError);
        co_return std::nullopt;
    }
    co_return config;
}

QCoro::Task<> TranslationService::run(std::shared_ptr<Job> job, QUrl videoUrl, QVariantMap track)
{
    const std::optional<LlmClient::Config> config = co_await startJob(job);
    if (!config) {
        co_return;
    }
    const Outcome outcome = co_await translateVideo(job, *config, videoUrl, track);
    if (job->cancelled) {
        co_return;
    }
    const QString error = outcome.error.isEmpty() ? publish(job, videoUrl, outcome) : outcome.error;
    if (!error.isEmpty()) {
        fail(job, error);
        co_return;
    }
    endJob(job);
}

QCoro::Task<> TranslationService::runPlaylist(std::shared_ptr<Job> job, QList<QUrl> urls, QVariantMap currentTrack, QString currentTitle)
{
    const std::optional<LlmClient::Config> config = co_await startJob(job);
    if (!config) {
        co_return;
    }

    int translatedCount = 0;
    int alreadyTranslatedCount = 0;
    QStringList problems;
    for (qsizetype i = 0; i < urls.size(); ++i) {
        const QUrl videoUrl = urls.at(i);
        const QString name = videoUrl.fileName();
        job->episode = int(i);
        setJobProgress(*job, 0);
        setJobStatus(*job, i18n("Reading subtitles…"));
        if (!savedTranslation(videoUrl).isEmpty()) {
            ++alreadyTranslatedCount;
            continue;
        }

        QVariantMap track = currentTrack;
        job->mediaTitle = currentTitle;
        if (videoUrl != m_currentVideo || currentTrack.isEmpty()) {
            if (!videoUrl.isLocalFile()) {
                problems.append(i18nc("@info %1 is a file name", "%1: only subtitles of local files can be translated", name));
                continue;
            }
            const QString path = videoUrl.toLocalFile();
            const Subtitles::SourceResult source = co_await QtConcurrent::run([path] {
                return Subtitles::findTranslationSource(path);
            });
            if (job->cancelled) {
                co_return;
            }
            if (!source.error.isEmpty() || source.streamIndex < 0) {
                problems.append(source.error.isEmpty() ? i18nc("@info %1 is a file name", "%1: no text subtitle", name)
                                                       : i18nc("@info %1 is a file name, %2 an error", "%1: %2", name, source.error));
                continue;
            }
            track = QVariantMap{{u"ffIndex"_s, source.streamIndex}};
            job->mediaTitle = MediaInfo::cleanTitle(name);
        }

        const Outcome outcome = co_await translateVideo(job, *config, videoUrl, track);
        if (job->cancelled) {
            co_return;
        }
        if (!outcome.error.isEmpty() && !outcome.skippable) {
            // Errors from the API or the disk would repeat for every episode.
            fail(job, i18nc("@info %1 is a file name, %2 an error", "Stopped translating the playlist at %1: %2", name, outcome.error));
            co_return;
        }
        const QString error = outcome.error.isEmpty() ? publish(job, videoUrl, outcome) : outcome.error;
        if (error.isEmpty()) {
            ++translatedCount;
        } else {
            problems.append(i18nc("@info %1 is a file name, %2 an error", "%1: %2", name, error));
        }
    }

    endJob(job);
    if (!problems.isEmpty()) {
        setErrorText(i18np("Translated %2 of %3 episodes. Skipped one:\n%4",
                           "Translated %2 of %3 episodes. Skipped %1:\n%4",
                           problems.size(),
                           translatedCount + alreadyTranslatedCount,
                           urls.size(),
                           problems.join(u'\n')));
    }
    Q_EMIT playlistTranslated(translatedCount, alreadyTranslatedCount, int(problems.size()));
}

QCoro::Task<TranslationService::Outcome> TranslationService::translateVideo(std::shared_ptr<Job> job, LlmClient::Config config, QUrl videoUrl, QVariantMap track)
{
    setJobProgress(*job, 0);
    setJobStatus(*job, i18n("Reading subtitles…"));
    Subtitles::ExtractResult source = co_await loadCues(job, videoUrl, track);
    if (job->cancelled) {
        co_return Outcome{};
    }
    if (!source.error.isEmpty()) {
        co_return Outcome::failed(source.error, true);
    }
    const QList<SubtitleCue> cues = Subtitles::mergeRepeated(source.cues);
    if (cues.isEmpty()) {
        co_return Outcome::failed(i18n("This subtitle track has no text to translate."), true);
    }

    // Episodes in one folder share a glossary. Streams have no folder, so they get none.
    const QString seriesDirectory = videoUrl.isLocalFile() ? QFileInfo(videoUrl.toLocalFile()).absolutePath() : QString();
    const bool useGlossary = !seriesDirectory.isEmpty();
    GlossaryStore::Glossary glossary = useGlossary ? GlossaryStore::load(seriesDirectory) : GlossaryStore::Glossary{};
    const QString episode = videoUrl.isLocalFile() ? QFileInfo(videoUrl.toLocalFile()).completeBaseName() : job->mediaTitle;
    // Returns an error message.
    const auto saveGlossaryGroups = [&]() -> QString {
        QString error;
        if (!GlossaryStore::save(glossary, &error)) {
            return i18n("Could not save the translation glossary: %1", error);
        }
        // Another episode of the playlist only updates the terms of the open series.
        if (!job->playlist || videoUrl == m_currentVideo) {
            m_glossary = glossary;
            m_glossaryEpisode = episode;
            Q_EMIT glossaryChanged();
        } else if (m_glossary.directory == glossary.directory) {
            m_glossary = glossary;
            Q_EMIT glossaryChanged();
        }
        return {};
    };
    if (useGlossary) {
        // New terms belong to the episode being translated. Migrate legacy or
        // imported entries without provenance to this first episode too. This
        // happens before the cache shortcut and never changes translation text.
        glossary = GlossaryStore::assignUnassigned(glossary, episode);
        if (const QString error = saveGlossaryGroups(); !error.isEmpty()) {
            co_return Outcome::failed(error);
        }
    }
    const QString sourceSrt = Subtitles::toSrt(cues);

    // Same subtitles, model, language, prompt settings and glossary give the same file, so it is translated once.
    const QString suffix = TranslationStore::languageSuffix(config.targetLanguage);
    const auto configKeyFor = [&](const GlossaryStore::Glossary &g) {
        QCryptographicHash hash(QCryptographicHash::Sha1);
        hash.addData(CacheVersion);
        hash.addData(config.model.toUtf8());
        hash.addData(config.targetLanguage.toUtf8());
        hash.addData(config.translationPreset.toUtf8());
        hash.addData(config.customInstructions.toUtf8());
        hash.addData(GlossaryStore::serialize(g).toUtf8());
        hash.addData(sourceSrt.toUtf8());
        return QString::fromLatin1(hash.result().toHex().left(12));
    };
    QString configKey = configKeyFor(glossary);
    QString outputPath = TranslationStore::cachePath(cacheDir(), videoUrl, configKey, suffix);

    if (QFileInfo::exists(outputPath)) {
        co_return Outcome::ready(outputPath, suffix, configKey, true);
    }

    if (useGlossary && QtPotatoSettings::self()->autoBuildGlossary()) {
        setJobStatus(*job, i18n("Building glossary…"));
        QStringList extractionLines;
        QHash<QString, bool> seen;
        for (const SubtitleCue &cue : cues) {
            if (!seen.contains(cue.text)) { seen.insert(cue.text, true); extractionLines.append(cue.text); }
        }
        constexpr qsizetype MaxGlossaryChars = 30000;
        // Long subtitles are sampled evenly so names from the whole episode are seen.
        qsizetype allChars = 0;
        for (const QString &line : std::as_const(extractionLines)) {
            allChars += line.size() + 1;
        }
        const qsizetype step = std::max<qsizetype>(1, (allChars + MaxGlossaryChars - 1) / MaxGlossaryChars);
        QStringList sampled;
        qsizetype total = 0;
        for (qsizetype i = 0; i < extractionLines.size(); i += step) {
            if (total + extractionLines.at(i).size() + 1 > MaxGlossaryChars) {
                break;
            }
            sampled.append(extractionLines.at(i));
            total += extractionLines.at(i).size() + 1;
        }
        job->client = std::make_unique<LlmClient>(m_network, config);
        const LlmClient::BatchResult extracted = co_await job->client->extractGlossary(sampled, job->mediaTitle);
        if (job->cancelled) {
            co_return Outcome{};
        }
        if (extracted.error.isEmpty()) {
            QList<GlossaryStore::Entry> additions;
            for (const QString &encoded : extracted.translations) {
                const qsizetype tab = encoded.indexOf(u'\t');
                if (tab > 0) additions.append({encoded.left(tab), encoded.mid(tab + 1)});
            }
            // Suggestions extracted while translating this episode belong to
            // this episode. Existing terms keep their original ownership.
            glossary = GlossaryStore::merge(glossary, additions, episode);
            if (const QString error = saveGlossaryGroups(); !error.isEmpty()) {
                co_return Outcome::failed(error);
            }
        } else {
            setJobStatus(*job, i18n("Glossary unavailable; translating without it."));
        }
        configKey = configKeyFor(glossary);
        outputPath = TranslationStore::cachePath(cacheDir(), videoUrl, configKey, suffix);
        if (QFileInfo::exists(outputPath)) {
            co_return Outcome::ready(outputPath, suffix, configKey, true);
        }
    }

    // Repeated lines (songs, catchphrases) are sent once.
    QStringList uniqueLines;
    QHash<QString, qsizetype> uniqueIndex;
    QList<qsizetype> cueToUnique;
    for (const SubtitleCue &cue : cues) {
        auto it = uniqueIndex.constFind(cue.text);
        if (it == uniqueIndex.cend()) {
            it = uniqueIndex.insert(cue.text, uniqueLines.size());
            uniqueLines.append(cue.text);
        }
        cueToUnique.append(*it);
    }

    QStringList glossaryLines;
    for (const auto &entry : std::as_const(glossary.entries)) {
        glossaryLines.append(entry.source + u" → "_s + entry.target);
    }
    config.glossaryText = glossaryLines.join(u'\n');

    job->client = std::make_unique<LlmClient>(m_network, config);
    auto batches = std::make_shared<Batches>();
    batches->lines = uniqueLines;
    batches->translations.resize(uniqueLines.size());
    batches->batchSize = QtPotatoSettings::self()->batchSize();
    setLinesStatus(*job, 0, uniqueLines.size());

    // Tasks start running as soon as they are created; awaiting them just waits for the end.
    std::vector<QCoro::Task<>> workers;
    for (int i = 0; i < ParallelRequests; ++i) {
        workers.push_back(translateBatches(job, batches));
    }
    for (QCoro::Task<> &worker : workers) {
        co_await std::move(worker);
    }
    if (job->cancelled) {
        co_return Outcome{};
    }
    if (!batches->error.isEmpty()) {
        co_return Outcome::failed(batches->error);
    }

    QList<SubtitleCue> output = cues;
    for (qsizetype i = 0; i < output.size(); ++i) {
        output[i].text = batches->translations.at(cueToUnique.at(i));
    }

    QDir().mkpath(QFileInfo(outputPath).absolutePath());
    QSaveFile file(outputPath);
    if (!file.open(QIODevice::WriteOnly) || file.write(Subtitles::toSrt(output).toUtf8()) < 0 || !file.commit()) {
        co_return Outcome::failed(i18n("Could not save the translation to %1: %2", outputPath, file.errorString()));
    }
    co_return Outcome::ready(outputPath, suffix, configKey, false);
}

QString TranslationService::publish(const std::shared_ptr<Job> &job, const QUrl &videoUrl, const Outcome &outcome)
{
    QFile file(outcome.cacheFile);
    if (!file.open(QIODevice::ReadOnly)) {
        return i18n("Could not read the translation from %1: %2", outcome.cacheFile, file.errorString());
    }
    // The cache keeps every version; the published copy is the one players load.
    const QString registryFile = TranslationStore::registryFile();
    TranslationStore::Registry registry = TranslationStore::load(registryFile);
    const TranslationStore::PublishResult published =
        TranslationStore::publish(registry, videoUrl, outcome.suffix, outcome.configKey, file.readAll(), outcome.cacheFile);
    TranslationStore::save(registryFile, registry);

    // Other episodes of a playlist load their translation when they are opened.
    if (!job->playlist || videoUrl == m_currentVideo) {
        m_lastTranslationPath = published.path;
        Q_EMIT translated(QUrl::fromLocalFile(published.path), outcome.fromCache);
    }
    return {};
}

void TranslationService::endJob(const std::shared_ptr<Job> &job)
{
    if (m_job != job) {
        return;
    }
    m_job.reset();
    setBusy(false);
    setStatusText({});
}

void TranslationService::setJobStatus(const Job &job, const QString &text)
{
    if (!job.playlist) {
        setStatusText(text);
        return;
    }
    setStatusText(i18nc("@info:status %1 and %2 are numbers, %3 is what is being done",
                        "Episode %1 of %2: %3",
                        job.episode + 1,
                        job.episodes,
                        text));
}

void TranslationService::setLinesStatus(const Job &job, qsizetype done, qsizetype total)
{
    // The line count would not fit after the episode number; the progress bar shows it.
    setJobStatus(job, job.playlist ? i18n("Translating…") : i18n("Translating… %1 of %2 lines", done, total));
}

void TranslationService::setJobProgress(const Job &job, double episodeProgress)
{
    setProgress(job.playlist ? (job.episode + episodeProgress) / job.episodes : episodeProgress);
}

QString TranslationService::savedTranslation(const QUrl &videoUrl) const
{
    const QString suffix = TranslationStore::languageSuffix(QtPotatoSettings::self()->targetLanguage().trimmed());
    return TranslationStore::savedTranslation(TranslationStore::load(TranslationStore::registryFile()), videoUrl, suffix);
}

QCoro::Task<LlmClient::BatchResult> TranslationService::translateLines(std::shared_ptr<Job> job, QStringList lines, QStringList context)
{
    LlmClient::BatchResult result;
    for (int attempt = 1; attempt <= MaxAttempts; ++attempt) {
        result = co_await job->client->translate(lines, context, job->mediaTitle);
        if (job->cancelled || result.error.isEmpty() || !result.retryable || attempt == MaxAttempts) {
            break;
        }
        co_await QCoro::sleepFor(2s * attempt);
        if (job->cancelled) {
            co_return result;
        }
    }
    if (job->cancelled || !result.error.isEmpty()) {
        co_return result;
    }

    QList<qsizetype> missing;
    for (qsizetype i = 0; i < result.translations.size(); ++i) {
        if (result.translations.at(i).isNull()) {
            missing.append(i);
        }
    }
    if (missing.isEmpty()) {
        co_return result;
    }
    if (lines.size() == 1) {
        co_return LlmClient::BatchResult{{}, i18n("The model did not translate this line: %1", lines.first()), false};
    }

    if (missing.size() == lines.size()) {
        // Nothing came back usable; smaller requests are easier for the model.
        const qsizetype half = lines.size() / 2;
        const LlmClient::BatchResult first = co_await translateLines(job, lines.first(half), context);
        if (job->cancelled || !first.error.isEmpty()) {
            co_return first;
        }
        QStringList secondContext = context + lines.first(half);
        secondContext = secondContext.mid(std::max<qsizetype>(0, secondContext.size() - ContextLines));
        const LlmClient::BatchResult second = co_await translateLines(job, lines.sliced(half), secondContext);
        if (job->cancelled || !second.error.isEmpty()) {
            co_return second;
        }
        co_return LlmClient::BatchResult{first.translations + second.translations, {}, false};
    }

    // Ask again only for the lines the model skipped.
    QStringList retryLines;
    for (const qsizetype i : missing) {
        retryLines.append(lines.at(i));
    }
    const LlmClient::BatchResult retry = co_await translateLines(job, retryLines, context);
    if (job->cancelled || !retry.error.isEmpty()) {
        co_return retry;
    }
    for (qsizetype i = 0; i < missing.size(); ++i) {
        result.translations[missing.at(i)] = retry.translations.at(i);
    }
    co_return result;
}

QCoro::Task<> TranslationService::translateBatches(std::shared_ptr<Job> job, std::shared_ptr<Batches> batches)
{
    // After an error, requests already sent may finish, but no new ones start.
    while (!job->cancelled && batches->error.isEmpty() && batches->nextStart < batches->lines.size()) {
        const qsizetype start = batches->nextStart;
        batches->nextStart += batches->batchSize;

        const qsizetype contextStart = std::max<qsizetype>(0, start - ContextLines);
        const LlmClient::BatchResult result =
            co_await translateLines(job, batches->lines.mid(start, batches->batchSize), batches->lines.mid(contextStart, start - contextStart));
        if (job->cancelled) {
            co_return;
        }
        if (!result.error.isEmpty()) {
            if (batches->error.isEmpty()) {
                batches->error = result.error;
            }
            co_return;
        }

        for (qsizetype i = 0; i < result.translations.size(); ++i) {
            batches->translations[start + i] = result.translations.at(i);
        }
        batches->doneLines += result.translations.size();
        setJobProgress(*job, double(batches->doneLines) / batches->lines.size());
        setLinesStatus(*job, batches->doneLines, batches->lines.size());
    }
}

QCoro::Task<> TranslationService::runFetchModels()
{
    QPointer<TranslationService> self(this);
    setFetchingModels(true);
    setErrorText({});

    const auto [config, configError] = co_await loadConfig();
    if (!self) {
        co_return;
    }
    if (!configError.isEmpty()) {
        setErrorText(configError);
        setFetchingModels(false);
        co_return;
    }

    LlmClient client(m_network, config);
    const LlmClient::ModelsResult result = co_await client.listModels();
    if (!self) {
        co_return;
    }
    if (!result.error.isEmpty()) {
        setErrorText(i18n("Could not list models: %1", result.error));
    } else if (result.models != m_availableModels) {
        m_availableModels = result.models;
        Q_EMIT availableModelsChanged();
    }
    setFetchingModels(false);
}

void TranslationService::fail(const std::shared_ptr<Job> &job, const QString &error)
{
    if (m_job != job) {
        return;
    }
    m_job.reset();
    setErrorText(error);
    setBusy(false);
    setStatusText({});
}

void TranslationService::setBusy(bool busy)
{
    if (busy != m_busy) {
        m_busy = busy;
        Q_EMIT busyChanged();
    }
}

void TranslationService::setProgress(double progress)
{
    if (progress != m_progress) {
        m_progress = progress;
        Q_EMIT progressChanged();
    }
}

void TranslationService::setStatusText(const QString &text)
{
    if (text != m_statusText) {
        m_statusText = text;
        Q_EMIT statusTextChanged();
    }
}

void TranslationService::setErrorText(const QString &text)
{
    if (text != m_errorText) {
        m_errorText = text;
        Q_EMIT errorTextChanged();
    }
}

void TranslationService::setFetchingModels(bool fetching)
{
    if (fetching != m_fetchingModels) {
        m_fetchingModels = fetching;
        Q_EMIT fetchingModelsChanged();
    }
}