/*
 * m2gtkshim.c - small C support library for the m2-GTK4 Modula-2 bindings.
 *
 * GNU Modula-2 cannot register GObject subclasses (no class_init /
 * vfunc overrides), which blocks widgets and paintables that need a
 * custom snapshot.  This shim provides two such types whose snapshot
 * vfuncs hand a Cairo context to a Modula-2 callback, so the drawing
 * itself reuses the existing Cairo binding:
 *
 *   M2GtkWidget  - a GtkWidget subclass; the M2 callback is
 *                  void draw(GtkWidget *w, cairo_t *cr,
 *                            int width, int height, gpointer user);
 *   M2Paintable  - a GdkPaintable implementation; the M2 callback is
 *                  void draw(cairo_t *cr, int width, int height,
 *                            gpointer user);
 *
 * The M2 callback addresses and user data are supplied at construction;
 * an optional destroy notify frees the user data.
 */

#include <gtk/gtk.h>

/* ------------------------------------------------------------------ */
/* M2GtkWidget                                                         */
/* ------------------------------------------------------------------ */

typedef void (*M2WidgetDrawFunc) (GtkWidget *widget, cairo_t *cr,
                                  int width, int height, gpointer user_data);

typedef struct _M2GtkWidget M2GtkWidget;
typedef struct _M2GtkWidgetClass M2GtkWidgetClass;

struct _M2GtkWidget
{
  GtkWidget parent_instance;
  M2WidgetDrawFunc draw;
  gpointer user_data;
  GDestroyNotify destroy;
};

struct _M2GtkWidgetClass
{
  GtkWidgetClass parent_class;
};

G_DEFINE_TYPE (M2GtkWidget, m2_gtk_widget, GTK_TYPE_WIDGET)

static void
m2_gtk_widget_snapshot (GtkWidget *widget, GtkSnapshot *snapshot)
{
  M2GtkWidget *self = (M2GtkWidget *) widget;
  int width = gtk_widget_get_width (widget);
  int height = gtk_widget_get_height (widget);

  if (self->draw == NULL || width <= 0 || height <= 0)
    return;

  graphene_rect_t bounds = GRAPHENE_RECT_INIT (0.f, 0.f, width, height);
  cairo_t *cr = gtk_snapshot_append_cairo (snapshot, &bounds);
  self->draw (widget, cr, width, height, self->user_data);
  cairo_destroy (cr);
}

static void
m2_gtk_widget_finalize (GObject *object)
{
  M2GtkWidget *self = (M2GtkWidget *) object;

  if (self->destroy != NULL)
    self->destroy (self->user_data);

  G_OBJECT_CLASS (m2_gtk_widget_parent_class)->finalize (object);
}

static void
m2_gtk_widget_class_init (M2GtkWidgetClass *klass)
{
  GObjectClass *object_class = G_OBJECT_CLASS (klass);
  GtkWidgetClass *widget_class = GTK_WIDGET_CLASS (klass);

  object_class->finalize = m2_gtk_widget_finalize;
  widget_class->snapshot = m2_gtk_widget_snapshot;
}

static void
m2_gtk_widget_init (M2GtkWidget *self)
{
  self->draw = NULL;
  self->user_data = NULL;
  self->destroy = NULL;
}

GtkWidget *
m2_gtk_widget_new (M2WidgetDrawFunc draw, gpointer user_data,
                   GDestroyNotify destroy)
{
  M2GtkWidget *self = g_object_new (m2_gtk_widget_get_type (), NULL);

  self->draw = draw;
  self->user_data = user_data;
  self->destroy = destroy;
  return GTK_WIDGET (self);
}

/* ------------------------------------------------------------------ */
/* M2Paintable (implements GdkPaintable)                               */
/* ------------------------------------------------------------------ */

typedef void (*M2PaintableDrawFunc) (cairo_t *cr, int width, int height,
                                     gpointer user_data);

typedef struct _M2Paintable M2Paintable;
typedef struct _M2PaintableClass M2PaintableClass;

struct _M2Paintable
{
  GObject parent_instance;
  M2PaintableDrawFunc draw;
  gpointer user_data;
  GDestroyNotify destroy;
  int width;
  int height;
};

struct _M2PaintableClass
{
  GObjectClass parent_class;
};

static void
m2_paintable_snapshot (GdkPaintable *paintable, GtkSnapshot *snapshot,
                       double width, double height)
{
  M2Paintable *self = (M2Paintable *) paintable;
  graphene_rect_t bounds = GRAPHENE_RECT_INIT (0.f, 0.f, (float) width,
                                               (float) height);
  cairo_t *cr = gtk_snapshot_append_cairo (snapshot, &bounds);

  if (self->draw != NULL)
    self->draw (cr, (int) width, (int) height, self->user_data);

  cairo_destroy (cr);
}

static int
m2_paintable_get_intrinsic_width (GdkPaintable *paintable)
{
  return ((M2Paintable *) paintable)->width;
}

static int
m2_paintable_get_intrinsic_height (GdkPaintable *paintable)
{
  return ((M2Paintable *) paintable)->height;
}

static double
m2_paintable_get_intrinsic_aspect_ratio (GdkPaintable *paintable)
{
  M2Paintable *self = (M2Paintable *) paintable;

  return self->height > 0 ? (double) self->width / (double) self->height : 0.0;
}

static void
m2_paintable_paintable_init (GdkPaintableInterface *iface)
{
  iface->snapshot = m2_paintable_snapshot;
  iface->get_intrinsic_width = m2_paintable_get_intrinsic_width;
  iface->get_intrinsic_height = m2_paintable_get_intrinsic_height;
  iface->get_intrinsic_aspect_ratio = m2_paintable_get_intrinsic_aspect_ratio;
}

G_DEFINE_TYPE_WITH_CODE (M2Paintable, m2_paintable, G_TYPE_OBJECT,
                         G_IMPLEMENT_INTERFACE (GDK_TYPE_PAINTABLE,
                                                m2_paintable_paintable_init))

static void
m2_paintable_finalize (GObject *object)
{
  M2Paintable *self = (M2Paintable *) object;

  if (self->destroy != NULL)
    self->destroy (self->user_data);

  G_OBJECT_CLASS (m2_paintable_parent_class)->finalize (object);
}

static void
m2_paintable_class_init (M2PaintableClass *klass)
{
  G_OBJECT_CLASS (klass)->finalize = m2_paintable_finalize;
}

static void
m2_paintable_init (M2Paintable *self)
{
  self->draw = NULL;
  self->user_data = NULL;
  self->destroy = NULL;
  self->width = 0;
  self->height = 0;
}

GdkPaintable *
m2_paintable_new (M2PaintableDrawFunc draw, int width, int height,
                  gpointer user_data, GDestroyNotify destroy)
{
  M2Paintable *self = g_object_new (m2_paintable_get_type (), NULL);

  self->draw = draw;
  self->width = width;
  self->height = height;
  self->user_data = user_data;
  self->destroy = destroy;
  return GDK_PAINTABLE (self);
}

/* ------------------------------------------------------------------ */
/* M2ListModel (implements GListModel)                                 */
/* ------------------------------------------------------------------ */

typedef guint    (*M2ListModelGetNItemsFunc) (gpointer user_data);
typedef gpointer (*M2ListModelGetItemFunc)   (guint position,
                                              gpointer user_data);

typedef struct _M2ListModel M2ListModel;
typedef struct _M2ListModelClass M2ListModelClass;

struct _M2ListModel
{
  GObject parent_instance;
  M2ListModelGetNItemsFunc get_n_items;
  M2ListModelGetItemFunc get_item;
  gpointer user_data;
  GDestroyNotify destroy;
  GType item_type;
};

struct _M2ListModelClass
{
  GObjectClass parent_class;
};

static guint
m2_list_model_get_n_items (GListModel *list)
{
  M2ListModel *self = (M2ListModel *) list;

  return self->get_n_items != NULL ? self->get_n_items (self->user_data) : 0;
}

static GType
m2_list_model_get_item_type (GListModel *list)
{
  return ((M2ListModel *) list)->item_type;
}

static gpointer
m2_list_model_get_item (GListModel *list, guint position)
{
  M2ListModel *self = (M2ListModel *) list;

  return self->get_item != NULL ? self->get_item (position, self->user_data)
                                : NULL;
}

static void
m2_list_model_list_init (GListModelInterface *iface)
{
  iface->get_n_items = m2_list_model_get_n_items;
  iface->get_item_type = m2_list_model_get_item_type;
  iface->get_item = m2_list_model_get_item;
}

G_DEFINE_TYPE_WITH_CODE (M2ListModel, m2_list_model, G_TYPE_OBJECT,
                         G_IMPLEMENT_INTERFACE (G_TYPE_LIST_MODEL,
                                                m2_list_model_list_init))

static void
m2_list_model_finalize (GObject *object)
{
  M2ListModel *self = (M2ListModel *) object;

  if (self->destroy != NULL)
    self->destroy (self->user_data);

  G_OBJECT_CLASS (m2_list_model_parent_class)->finalize (object);
}

static void
m2_list_model_class_init (M2ListModelClass *klass)
{
  G_OBJECT_CLASS (klass)->finalize = m2_list_model_finalize;
}

static void
m2_list_model_init (M2ListModel *self)
{
  self->get_n_items = NULL;
  self->get_item = NULL;
  self->user_data = NULL;
  self->destroy = NULL;
  self->item_type = G_TYPE_OBJECT;
}

GListModel *
m2_list_model_new (M2ListModelGetNItemsFunc get_n_items,
                   M2ListModelGetItemFunc get_item, GType item_type,
                   gpointer user_data, GDestroyNotify destroy)
{
  M2ListModel *self = g_object_new (m2_list_model_get_type (), NULL);

  self->get_n_items = get_n_items;
  self->get_item = get_item;
  self->item_type = item_type;
  self->user_data = user_data;
  self->destroy = destroy;
  return G_LIST_MODEL (self);
}

void
m2_list_model_items_changed (GListModel *model, guint position,
                             guint removed, guint added)
{
  g_list_model_items_changed (model, position, removed, added);
}

/* ------------------------------------------------------------------ */
/* M2LayoutManager (subclass of GtkLayoutManager)                      */
/* ------------------------------------------------------------------ */

typedef void (*M2LayoutMeasureFunc) (GtkWidget *widget, int orientation,
                                     int for_size, int *minimum, int *natural,
                                     gpointer user_data);
typedef void (*M2LayoutAllocateFunc) (GtkWidget *widget, int width, int height,
                                      int baseline, gpointer user_data);

typedef struct _M2LayoutManager M2LayoutManager;
typedef struct _M2LayoutManagerClass M2LayoutManagerClass;

struct _M2LayoutManager
{
  GtkLayoutManager parent_instance;
  M2LayoutMeasureFunc measure;
  M2LayoutAllocateFunc allocate;
  gpointer user_data;
  GDestroyNotify destroy;
};

struct _M2LayoutManagerClass
{
  GtkLayoutManagerClass parent_class;
};

static void
m2_layout_manager_measure (GtkLayoutManager *manager, GtkWidget *widget,
                           GtkOrientation orientation, int for_size,
                           int *minimum, int *natural, int *minimum_baseline,
                           int *natural_baseline)
{
  M2LayoutManager *self = (M2LayoutManager *) manager;

  *minimum = 0;
  *natural = 0;
  if (self->measure != NULL)
    self->measure (widget, (int) orientation, for_size, minimum, natural,
                   self->user_data);
  *minimum_baseline = -1;
  *natural_baseline = -1;
}

static void
m2_layout_manager_allocate (GtkLayoutManager *manager, GtkWidget *widget,
                            int width, int height, int baseline)
{
  M2LayoutManager *self = (M2LayoutManager *) manager;

  if (self->allocate != NULL)
    self->allocate (widget, width, height, baseline, self->user_data);
}

G_DEFINE_TYPE (M2LayoutManager, m2_layout_manager, GTK_TYPE_LAYOUT_MANAGER)

static void
m2_layout_manager_finalize (GObject *object)
{
  M2LayoutManager *self = (M2LayoutManager *) object;

  if (self->destroy != NULL)
    self->destroy (self->user_data);

  G_OBJECT_CLASS (m2_layout_manager_parent_class)->finalize (object);
}

static void
m2_layout_manager_class_init (M2LayoutManagerClass *klass)
{
  GObjectClass *object_class = G_OBJECT_CLASS (klass);
  GtkLayoutManagerClass *manager_class = GTK_LAYOUT_MANAGER_CLASS (klass);

  object_class->finalize = m2_layout_manager_finalize;
  manager_class->measure = m2_layout_manager_measure;
  manager_class->allocate = m2_layout_manager_allocate;
}

static void
m2_layout_manager_init (M2LayoutManager *self)
{
  self->measure = NULL;
  self->allocate = NULL;
  self->user_data = NULL;
  self->destroy = NULL;
}

GtkLayoutManager *
m2_layout_manager_new (M2LayoutMeasureFunc measure, M2LayoutAllocateFunc allocate,
                       gpointer user_data, GDestroyNotify destroy)
{
  M2LayoutManager *self = g_object_new (m2_layout_manager_get_type (), NULL);

  self->measure = measure;
  self->allocate = allocate;
  self->user_data = user_data;
  self->destroy = destroy;
  return GTK_LAYOUT_MANAGER (self);
}

/* Position a child at (x, y) with the given size (helper for allocate). */
void
m2_layout_allocate_child (GtkWidget *child, int x, int y, int width, int height)
{
  graphene_point_t point = GRAPHENE_POINT_INIT (x, y);
  GskTransform *transform = gsk_transform_translate (NULL, &point);

  gtk_widget_allocate (child, width, height, -1, transform);
  gsk_transform_unref (transform);
}

/* ------------------------------------------------------------------ */
/* M2SnapshotPaintable (GdkPaintable using GtkSnapshot)                */
/* ------------------------------------------------------------------ */

typedef void (*M2SnapshotDrawFunc) (GtkSnapshot *snapshot, int width,
                                    int height, gpointer user_data);

typedef struct _M2SnapshotPaintable M2SnapshotPaintable;
typedef struct _M2SnapshotPaintableClass M2SnapshotPaintableClass;

struct _M2SnapshotPaintable
{
  GObject parent_instance;
  M2SnapshotDrawFunc draw;
  gpointer user_data;
  GDestroyNotify destroy;
  int width;
  int height;
};

struct _M2SnapshotPaintableClass
{
  GObjectClass parent_class;
};

static void
m2_snapshot_paintable_snapshot (GdkPaintable *paintable, GtkSnapshot *snapshot,
                                double width, double height)
{
  M2SnapshotPaintable *self = (M2SnapshotPaintable *) paintable;

  if (self->draw != NULL)
    self->draw (snapshot, (int) width, (int) height, self->user_data);
}

static int
m2_snapshot_paintable_get_intrinsic_width (GdkPaintable *paintable)
{
  return ((M2SnapshotPaintable *) paintable)->width;
}

static int
m2_snapshot_paintable_get_intrinsic_height (GdkPaintable *paintable)
{
  return ((M2SnapshotPaintable *) paintable)->height;
}

static double
m2_snapshot_paintable_get_intrinsic_aspect_ratio (GdkPaintable *paintable)
{
  M2SnapshotPaintable *self = (M2SnapshotPaintable *) paintable;

  return self->height > 0 ? (double) self->width / (double) self->height : 0.0;
}

static void
m2_snapshot_paintable_paintable_init (GdkPaintableInterface *iface)
{
  iface->snapshot = m2_snapshot_paintable_snapshot;
  iface->get_intrinsic_width = m2_snapshot_paintable_get_intrinsic_width;
  iface->get_intrinsic_height = m2_snapshot_paintable_get_intrinsic_height;
  iface->get_intrinsic_aspect_ratio = m2_snapshot_paintable_get_intrinsic_aspect_ratio;
}

G_DEFINE_TYPE_WITH_CODE (M2SnapshotPaintable, m2_snapshot_paintable,
                         G_TYPE_OBJECT,
                         G_IMPLEMENT_INTERFACE (GDK_TYPE_PAINTABLE,
                                                m2_snapshot_paintable_paintable_init))

static void
m2_snapshot_paintable_finalize (GObject *object)
{
  M2SnapshotPaintable *self = (M2SnapshotPaintable *) object;

  if (self->destroy != NULL)
    self->destroy (self->user_data);

  G_OBJECT_CLASS (m2_snapshot_paintable_parent_class)->finalize (object);
}

static void
m2_snapshot_paintable_class_init (M2SnapshotPaintableClass *klass)
{
  G_OBJECT_CLASS (klass)->finalize = m2_snapshot_paintable_finalize;
}

static void
m2_snapshot_paintable_init (M2SnapshotPaintable *self)
{
  self->draw = NULL;
  self->user_data = NULL;
  self->destroy = NULL;
  self->width = 0;
  self->height = 0;
}

GdkPaintable *
m2_snapshot_paintable_new (M2SnapshotDrawFunc draw, int width, int height,
                           gpointer user_data, GDestroyNotify destroy)
{
  M2SnapshotPaintable *self = g_object_new (m2_snapshot_paintable_get_type (),
                                            NULL);

  self->draw = draw;
  self->width = width;
  self->height = height;
  self->user_data = user_data;
  self->destroy = destroy;
  return GDK_PAINTABLE (self);
}