/*
 * qtmaildir - a Qt6 mail client for notmuch-indexed Maildirs
 * Copyright (C) 2026 Danilo M. <danix@danix.xyz>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 */

#pragma once

#include <QHash>
#include <QMainWindow>
#include <QThread>
#include <QUndoCommand>
#include <QUndoStack>

#include <functional>

#include "config.h"
#include "keymap.h"
#include "tagcolors.h"
#include "types.h"

class QAction;
class QLineEdit;
class QTableView;
class QLabel;
class QPushButton;
class QComboBox;
class QPlainTextEdit;
class QSplitter;

class ThreadListModel;
class MessageView;
class MailSync;
class NotmuchWorker;
class QueryCompleter;

class MainWindow : public QMainWindow
{
    Q_OBJECT
public:
    explicit MainWindow(const Config &config, QWidget *parent = nullptr);
    ~MainWindow() override;

    /// Every action name registerActions() installs. Derived from the actions
    /// themselves rather than hand-maintained, so it cannot drift from what is
    /// really registered.
    QStringList registeredActionNames() const;

    /// The cid: namespace prefix for the nth message of a thread.
    ///
    /// MainWindow is the only producer of this value in the application. It
    /// must never contain '!', which is the separator that keeps one message's
    /// cid: references from resolving to another's.
    static QString cidPrefixForIndex(int index);

    /// Path of the machine-written UI state file. Deliberately not
    /// Config::defaultPath(): the config is hand-edited and must never gain a
    /// base64 geometry blob, nor be rewritten on exit (QSettings does not
    /// preserve comments or key order).
    static QString uiStatePath();

protected:
    void closeEvent(QCloseEvent *event) override;

private slots:
    void runCurrentQuery();
    void onThreadsReady(const QVector<ThreadSummary> &threads, quint64 generation);
    void onQueryFinished(int total, quint64 generation);
    void onThreadSelected(const QModelIndex &current, const QModelIndex &previous);
    void onThreadLoaded(const QVector<MessageRef> &messages, quint64 generation);
    void onWorkerError(const QString &message);
    void onSyncFinished(bool success, int exitCode);
    void onAllTagsReady(const QStringList &tags);

private:
    void buildUi();

    /// Restores window geometry, splitter and thread-list header widths.
    /// A missing or rejected blob leaves the buildUi() defaults in place.
    void restoreUiState();
    void saveUiState() const;

    void registerActions();
    void buildMenus();
    void wireWorker();

    /// Asks the worker to re-enumerate the database tags for the completer.
    void requestAllTags();

    void showWarnings();
    void showShortcutReference();
    void showAbout();

    /// Creates a QAction, binds it to the sequence KeyMap holds for `name`,
    /// and registers it. `name` is the action name used in [keys].
    QAction *addAction(const QString &name, const QString &text,
                       const QString &description,
                       const std::function<void()> &handler);

    void tagSelected(const QStringList &add, const QStringList &remove,
                     const QString &description);

    /// Sends a tag change for a set of threads without touching the undo stack.
    /// Both tagSelected() and ThreadTagCommand route through this.
    void sendThreadTagChange(const QStringList &threadIds,
                             const QStringList &add,
                             const QStringList &remove,
                             const QString &description);

    /// Undoes the optimistic model update for a write the worker rejected.
    void revertPendingTagChange();

    friend class ThreadTagCommand;

    Config m_config;
    KeyMap m_keyMap;
    TagColors m_tagColors;

    QThread m_workerThread;
    NotmuchWorker *m_worker = nullptr;

    ThreadListModel *m_model = nullptr;
    MessageView *m_messageView = nullptr;
    MailSync *m_sync = nullptr;
    QUndoStack m_undoStack;

    QLineEdit *m_queryEdit = nullptr;
    QueryCompleter *m_queryCompleter = nullptr;
    QTableView *m_threadView = nullptr;
    QSplitter *m_splitter = nullptr;
    QComboBox *m_accountBox = nullptr;
    QPushButton *m_syncButton = nullptr;
    QLabel *m_statusLabel = nullptr;
    QPlainTextEdit *m_syncLog = nullptr;

    /// Action name (as used in [keys]) to the QAction implementing it. Owned
    /// by the window through the QObject parent, not by this hash.
    QHash<QString, QAction *> m_actions;

    /// One-line description per action, for the shortcut reference. Kept
    /// beside the actions so the dialog is generated, never hand-written in
    /// parallel with them.
    QHash<QString, QString> m_actionDescriptions;

    /// The tag list last received from the worker. Held here and not only in
    /// the completer so a mutation can ask whether it introduced a tag the
    /// completer does not yet offer, without a round trip.
    QStringList m_knownTags;

    quint64 m_generation = 0;
    QString m_lastQuery;
    QString m_currentThreadId;

    /// The optimistic update awaiting confirmation, kept so a worker error can
    /// put the model back. Only the most recent one: mutations are sent from
    /// the UI thread one user action at a time.
    TagChange m_pendingChange;
    QStringList m_pendingThreadIds;
};

/// Undo entry for a tag change over a set of threads.
///
/// Stores thread ids rather than message ids, so undo re-resolves them on the
/// worker and stays correct even if the selection has moved on.
class ThreadTagCommand : public QUndoCommand
{
public:
    ThreadTagCommand(MainWindow *window, const QStringList &threadIds,
                     const QStringList &add, const QStringList &remove,
                     const QString &description)
        : QUndoCommand(description), m_window(window), m_threadIds(threadIds),
          m_add(add), m_remove(remove), m_description(description) {}

    /// The stack calls redo() when the command is pushed. The change has
    /// already been sent by that point, so the first call is skipped.
    void redo() override
    {
        if (m_firstRedo) {
            m_firstRedo = false;
            return;
        }
        m_window->sendThreadTagChange(m_threadIds, m_add, m_remove,
                                      m_description);
    }

    void undo() override
    {
        // Inverted: what was added is removed and vice versa.
        m_window->sendThreadTagChange(m_threadIds, m_remove, m_add,
                                      QStringLiteral("Undo %1").arg(m_description));
    }

private:
    MainWindow *m_window;
    QStringList m_threadIds;
    QStringList m_add;
    QStringList m_remove;
    QString m_description;
    bool m_firstRedo = true;
};
