#ifndef OLLIE_GHOST_H
#define OLLIE_GHOST_H

#include <KTextEditor/InlineNoteProvider>
#include <KTextEditor/View>
#include <KTextEditor/Document>
#include <KTextEditor/Cursor>

#include <QTimer>
#include <QPainter>
#include <QFont>
#include <QFontMetricsF>
#include <QString>
#include <QStringList>
#include <QWidget>

class GhostOverlay;

/**
 * OllieGhostProvider renders AI code completions as translucent gray text
 * at the cursor position using KTextEditor's InlineNoteProvider API.
 *
 * The first line of a multi-line suggestion is rendered as an inline note
 * at end-of-line. Continuation lines are rendered via a floating overlay
 * widget positioned below the cursor line.
 *
 * Flow:
 *   1. Cursor moves or text changes → debounce timer starts (500ms)
 *   2. Timer fires → gather prefix/suffix, call 9P Complete asynchronously
 *   3. Result arrives → store suggestion lines, emit inlineNotesChanged
 *   4. paintInlineNote renders first line; GhostOverlay renders the rest
 *   5. Tab → accept (insert text), any other input → dismiss
 */
class OllieGhostProvider : public KTextEditor::InlineNoteProvider
{
    Q_OBJECT

public:
    explicit OllieGhostProvider(KTextEditor::View *view, class OllieKatePlugin *plugin, QObject *parent = nullptr);
    ~OllieGhostProvider() override;

    // InlineNoteProvider interface
    QList<int> inlineNotes(int line) const override;
    QSize inlineNoteSize(const KTextEditor::InlineNote &note) const override;
    void paintInlineNote(const KTextEditor::InlineNote &note, QPainter &painter, Qt::LayoutDirection direction) const override;

    /// Accept the current suggestion (insert into document). Returns true if accepted.
    bool accept();

    /// Dismiss the current suggestion without inserting.
    void dismiss();

    /// Cycle to next (+1) or previous (-1) suggestion.
    void cycle(int direction);

    /// Returns true if a suggestion is currently visible.
    bool hasSuggestion() const;

    /// Returns the view this provider is attached to.
    KTextEditor::View *view() const { return m_view; }

    /// Enable or disable ghost completions.
    void setEnabled(bool enabled);
    bool isEnabled() const { return m_enabled; }

public slots:
    void requestCompletion();

private slots:
    void onCursorPositionChanged();
    void onTextChanged();
    void onCompletionReply(const QString &result);

private:
    void clearSuggestion();
    void showSuggestionFromHistory();
    void showOverlay();
    void hideOverlay();
    QString gatherPrefix() const;
    QString gatherSuffix() const;

    KTextEditor::View *m_view;
    OllieKatePlugin *m_plugin;
    QTimer *m_debounce;
    GhostOverlay *m_overlay = nullptr;

    // Current suggestion state
    QStringList m_suggestionLines;  // suggestion split by newline
    int m_suggestionStartLine = -1; // document line where suggestion starts
    int m_suggestionStartCol = -1;  // column (end of line where cursor was)
    KTextEditor::Cursor m_triggerCursor; // cursor position when completion was triggered

    // Suggestion history for cycling
    QList<QStringList> m_history;   // all suggestions received at this cursor position
    int m_historyIndex = -1;        // current index into m_history

    bool m_enabled = true;     // ghost completions active
    bool m_requesting = false; // true while 9P call is in flight
};

/**
 * GhostOverlay is a transparent widget that paints continuation lines
 * of a multi-line ghost suggestion over the editor viewport.
 */
class GhostOverlay : public QWidget
{
    Q_OBJECT

public:
    explicit GhostOverlay(QWidget *parent = nullptr);
    void setLines(const QStringList &lines, const QFont &font);
    void clear();

protected:
    void paintEvent(QPaintEvent *event) override;

private:
    QStringList m_lines;
    QFont m_font;
};

#endif // OLLIE_GHOST_H