// SPDX-FileCopyrightText: 2026 Filip Leonarski, Paul Scherrer Institute <filip.leonarski@psi.ch>
// SPDX-License-Identifier: GPL-3.0-only

#pragma once

#include <functional>
#include <QColor>
#include <QObject>
#include <QString>

class QChart;
class QWidget;

// The viewer's colour scheme: the light salmon one, or a dark indigo one. The View menu offers
// System, Light and Dark; System follows the desktop where Qt can read it (Qt 6.5+) and is light
// otherwise. A change applies at once: widgets that follow the palette repaint by themselves, and
// the ones that put colours into stylesheets, icons or charts listen to ThemeNotifier.
enum class ThemeChoice { System, Light, Dark };
ThemeChoice LoadThemeChoice();
void SetThemeChoice(ThemeChoice choice);   // stores the choice and applies it

// Sets the palette and starts following the desktop's scheme. Call once, after the Fusion style is
// set and before any window is made.
void InitTheme();
bool DarkTheme();

class ThemeNotifier : public QObject {
    Q_OBJECT
public:
    static ThemeNotifier *Instance();
signals:
    void changed();
};

// Sets the widget's stylesheet from `style`, now and again after every theme change.
void SetThemedStyleSheet(QWidget *widget, const std::function<QString()> &style);

// Colours that widgets put into their own stylesheets and drawings.
QColor AccentTextColor();   // headings and headline values: navy on light, light blue on dark
QColor IconInkColor();      // toolbar glyphs and flat toolbar-button text
QString SliderStyle();      // the coral/navy sliders of the toolbars
// The filled "hero" buttons and checked segments: navy on light, a lighter navy on dark, where the
// light one would sink into the indigo panels. Hover is a shade darker/lighter respectively.
QColor AccentFillColor();
QColor AccentFillHoverColor();
QString HeroButtonStyle();  // the filled push buttons (Analyze image / dataset, + Plot)
QColor GuideLineColor();    // chart hover cross-hairs and guide lines
// Chart series, one colour per run (index 0 is the primary line). Each is a light/dark pair of one
// hue, as the accents are: navy then amber first, a pair that stays apart for colour-blind readers too.
QColor PlotSeriesColor(int index);
QColor PlotMarkerColor();   // the "current image" marker: the coral of the sliders
QColor AlertTextColor();    // red text that must read on either background
QColor CautionTextColor();  // amber text, likewise

// Qt Charts do not follow the widget palette; this gives a chart the current scheme's colours. It
// recolours the series too, so call it before adding series that carry colours of their own.
void StyleChart(QChart *chart);
// Tints the grid lines with the slider groove's colour (salmon on light, indigo on dark) and mutes the
// dark theme's axis lines, where Qt's light grey competes with the data. Axes take the Qt theme's grid when they are
// added, so call it after the axes are in place.
void StyleChartAxes(QChart *chart);