/*
 * ***** BEGIN GPL LICENSE BLOCK *****
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 *
 * 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.
 *
 * The Original Code is Copyright (C) 2009 Blender Foundation.
 * All rights reserved.
 *
 * ***** END GPL LICENSE BLOCK *****
 */

/** \file blender/editors/interface/interface_eyedropper_depth.c
 *  \ingroup edinterface
 *
 * This file defines an eyedropper for picking 3D depth value (primary use is depth-of-field).
 *
 * Defines:
 * - #UI_OT_eyedropper_depth
 */

#include "MEM_guardedalloc.h"

#include "DNA_space_types.h"
#include "DNA_screen_types.h"
#include "DNA_object_types.h"
#include "DNA_view3d_types.h"

#include "BLI_string.h"
#include "BLI_math_vector.h"

#include "BKE_context.h"
#include "BKE_main.h"
#include "BKE_screen.h"
#include "BKE_unit.h"

#include "DEG_depsgraph.h"

#include "RNA_access.h"

#include "UI_interface.h"

#include "WM_api.h"
#include "WM_types.h"

#include "ED_screen.h"
#include "ED_space_api.h"
#include "ED_view3d.h"

#include "interface_intern.h"
#include "interface_eyedropper_intern.h"

/**
 * \note #DepthDropper is only internal name to avoid confusion with other kinds of eye-droppers.
 */
typedef struct DepthDropper {
	PointerRNA ptr;
	PropertyRNA *prop;

	float init_depth; /* for resetting on cancel */

	bool  accum_start; /* has mouse been presed */
	float accum_depth;
	int   accum_tot;

	ARegionType *art;
	void *draw_handle_pixel;
	char name[200];
} DepthDropper;


static void depthdropper_draw_cb(const struct bContext *C, ARegion *ar, void *arg)
{
	DepthDropper *ddr = arg;
	eyedropper_draw_cursor_text(C, ar, ddr->name);
}


static int depthdropper_init(bContext *C, wmOperator *op)
{
	DepthDropper *ddr;
	int index_dummy;

	SpaceType *st;
	ARegionType *art;

	st = BKE_spacetype_from_id(SPACE_VIEW3D);
	art = BKE_regiontype_from_id(st, RGN_TYPE_WINDOW);

	op->customdata = ddr = MEM_callocN(sizeof(DepthDropper), "DepthDropper");

	UI_context_active_but_prop_get(C, &ddr->ptr, &ddr->prop, &index_dummy);

	/* fallback to the active camera's dof */
	if (ddr->prop == NULL) {
		RegionView3D *rv3d = CTX_wm_region_view3d(C);
		if (rv3d && rv3d->persp == RV3D_CAMOB) {
			View3D *v3d = CTX_wm_view3d(C);
			if (v3d->camera && v3d->camera->data && !ID_IS_LINKED(v3d->camera->data)) {
				RNA_id_pointer_create(v3d->camera->data, &ddr->ptr);
				ddr->prop = RNA_struct_find_property(&ddr->ptr, "dof_distance");
			}
		}
	}

	if ((ddr->ptr.data == NULL) ||
	    (ddr->prop == NULL) ||
	    (RNA_property_editable(&ddr->ptr, ddr->prop) == false) ||
	    (RNA_property_type(ddr->prop) != PROP_FLOAT))
	{
		return false;
	}

	ddr->art = art;
	ddr->draw_handle_pixel = ED_region_draw_cb_activate(art, depthdropper_draw_cb, ddr, REGION_DRAW_POST_PIXEL);
	ddr->init_depth = RNA_property_float_get(&ddr->ptr, ddr->prop);

	return true;
}

static void depthdropper_exit(bContext *C, wmOperator *op)
{
	WM_cursor_modal_restore(CTX_wm_window(C));

	if (op->customdata) {
		DepthDropper *ddr = (DepthDropper *)op->customdata;

		if (ddr->art) {
			ED_region_draw_cb_exit(ddr->art, ddr->draw_handle_pixel);
		}

		MEM_freeN(op->customdata);

		op->customdata = NULL;
	}
}

/* *** depthdropper id helper functions *** */
/**
 * \brief get the ID from the screen.
 *
 */
static void depthdropper_depth_sample_pt(bContext *C, DepthDropper *ddr, int mx, int my, float *r_depth)
{
	/* we could use some clever */
	bScreen *screen = CTX_wm_screen(C);
	ScrArea *sa = BKE_screen_find_area_xy(screen, SPACE_TYPE_ANY, mx, my);
	Scene *scene = CTX_data_scene(C);

	UnitSettings *unit = &scene->unit;
	const bool do_split = (unit->flag & USER_UNIT_OPT_SPLIT) != 0;

	ScrArea *area_prev = CTX_wm_area(C);
	ARegion *ar_prev = CTX_wm_region(C);

	ddr->name[0] = '\0';

	if (sa) {
		if (sa->spacetype == SPACE_VIEW3D) {
			ARegion *ar = BKE_area_find_region_xy(sa, RGN_TYPE_WINDOW, mx, my);
			if (ar) {
				struct Depsgraph *depsgraph = CTX_data_depsgraph(C);
				View3D *v3d = sa->spacedata.first;
				RegionView3D *rv3d = ar->regiondata;
				/* weak, we could pass in some reference point */
				const float *view_co = v3d->camera ? v3d->camera->obmat[3] : rv3d->viewinv[3];
				const int mval[2] = {
				    mx - ar->winrct.xmin,
				    my - ar->winrct.ymin};
				float co[3];

				CTX_wm_area_set(C, sa);
				CTX_wm_region_set(C, ar);

				/* grr, always draw else we leave stale text */
				ED_region_tag_redraw(ar);

				view3d_operator_needs_opengl(C);

				if (ED_view3d_autodist(depsgraph, ar, v3d, mval, co, true, NULL)) {
					const float mval_center_fl[2] = {
					    (float)ar->winx / 2,
					    (float)ar->winy / 2};
					float co_align[3];

					/* quick way to get view-center aligned point */
					ED_view3d_win_to_3d(v3d, ar, co, mval_center_fl, co_align);

					*r_depth = len_v3v3(view_co, co_align);

					bUnit_AsString(ddr->name, sizeof(ddr->name),
					               (double)*r_depth,
					               4, unit->system, B_UNIT_LENGTH, do_split, false);
				}
				else {
					BLI_strncpy(ddr->name, "Nothing under cursor", sizeof(ddr->name));
				}
			}
		}
	}

	CTX_wm_area_set(C, area_prev);
	CTX_wm_region_set(C, ar_prev);
}

/* sets the sample depth RGB, maintaining A */
static void depthdropper_depth_set(bContext *C, DepthDropper *ddr, const float depth)
{
	RNA_property_float_set(&ddr->ptr, ddr->prop, depth);
	RNA_property_update(C, &ddr->ptr, ddr->prop);
}

/* set sample from accumulated values */
static void depthdropper_depth_set_accum(bContext *C, DepthDropper *ddr)
{
	float depth = ddr->accum_depth;
	if (ddr->accum_tot) {
		depth /= (float)ddr->accum_tot;
	}
	depthdropper_depth_set(C, ddr, depth);
}

/* single point sample & set */
static void depthdropper_depth_sample(bContext *C, DepthDropper *ddr, int mx, int my)
{
	float depth = -1.0f;
	if (depth != -1.0f) {
		depthdropper_depth_sample_pt(C, ddr, mx, my, &depth);
		depthdropper_depth_set(C, ddr, depth);
	}
}

static void depthdropper_depth_sample_accum(bContext *C, DepthDropper *ddr, int mx, int my)
{
	float depth = -1.0f;
	depthdropper_depth_sample_pt(C, ddr, mx, my, &depth);
	if (depth != -1.0f) {
		ddr->accum_depth += depth;
		ddr->accum_tot++;
	}
}

static void depthdropper_cancel(bContext *C, wmOperator *op)
{
	DepthDropper *ddr = op->customdata;
	depthdropper_depth_set(C, ddr, ddr->init_depth);
	depthdropper_exit(C, op);
}

/* main modal status check */
static int depthdropper_modal(bContext *C, wmOperator *op, const wmEvent *event)
{
	DepthDropper *ddr = (DepthDropper *)op->customdata;

	/* handle modal keymap */
	if (event->type == EVT_MODAL_MAP) {
		switch (event->val) {
			case EYE_MODAL_CANCEL:
				depthdropper_cancel(C, op);
				return OPERATOR_CANCELLED;
			case EYE_MODAL_SAMPLE_CONFIRM:
				if (ddr->accum_tot == 0) {
					depthdropper_depth_sample(C, ddr, event->x, event->y);
				}
				else {
					depthdropper_depth_set_accum(C, ddr);
				}
				depthdropper_exit(C, op);
				return OPERATOR_FINISHED;
			case EYE_MODAL_SAMPLE_BEGIN:
				/* enable accum and make first sample */
				ddr->accum_start = true;
				depthdropper_depth_sample_accum(C, ddr, event->x, event->y);
				break;
			case EYE_MODAL_SAMPLE_RESET:
				ddr->accum_tot = 0;
				ddr->accum_depth = 0.0f;
				depthdropper_depth_sample_accum(C, ddr, event->x, event->y);
				depthdropper_depth_set_accum(C, ddr);
				break;
		}
	}
	else if (event->type == MOUSEMOVE) {
		if (ddr->accum_start) {
			/* button is pressed so keep sampling */
			depthdropper_depth_sample_accum(C, ddr, event->x, event->y);
			depthdropper_depth_set_accum(C, ddr);
		}
	}

	return OPERATOR_RUNNING_MODAL;
}

/* Modal Operator init */
static int depthdropper_invoke(bContext *C, wmOperator *op, const wmEvent *UNUSED(event))
{
	/* init */
	if (depthdropper_init(C, op)) {
		WM_cursor_modal_set(CTX_wm_window(C), BC_EYEDROPPER_CURSOR);

		/* add temp handler */
		WM_event_add_modal_handler(C, op);

		return OPERATOR_RUNNING_MODAL;
	}
	else {
		depthdropper_exit(C, op);
		return OPERATOR_CANCELLED;
	}
}

/* Repeat operator */
static int depthdropper_exec(bContext *C, wmOperator *op)
{
	/* init */
	if (depthdropper_init(C, op)) {
		/* cleanup */
		depthdropper_exit(C, op);

		return OPERATOR_FINISHED;
	}
	else {
		return OPERATOR_CANCELLED;
	}
}

static bool depthdropper_poll(bContext *C)
{
	PointerRNA ptr;
	PropertyRNA *prop;
	int index_dummy;
	uiBut *but;

	/* check if there's an active button taking depth value */
	if ((CTX_wm_window(C) != NULL) &&
	    (but = UI_context_active_but_prop_get(C, &ptr, &prop, &index_dummy)) &&
	    (but->type == UI_BTYPE_NUM) &&
	    (prop != NULL))
	{
		if ((RNA_property_type(prop) == PROP_FLOAT) &&
		    (RNA_property_subtype(prop) & PROP_UNIT_LENGTH) &&
		    (RNA_property_array_check(prop) == false))
		{
			return 1;
		}
	}
	else {
		RegionView3D *rv3d = CTX_wm_region_view3d(C);
		if (rv3d && rv3d->persp == RV3D_CAMOB) {
			View3D *v3d = CTX_wm_view3d(C);
			if (v3d->camera && v3d->camera->data && !ID_IS_LINKED(v3d->camera->data)) {
				return 1;
			}
		}
	}

	return 0;
}

void UI_OT_eyedropper_depth(wmOperatorType *ot)
{
	/* identifiers */
	ot->name = "Eyedropper Depth";
	ot->idname = "UI_OT_eyedropper_depth";
	ot->description = "Sample depth from the 3D view";

	/* api callbacks */
	ot->invoke = depthdropper_invoke;
	ot->modal = depthdropper_modal;
	ot->cancel = depthdropper_cancel;
	ot->exec = depthdropper_exec;
	ot->poll = depthdropper_poll;

	/* flags */
	ot->flag = OPTYPE_BLOCKING | OPTYPE_INTERNAL;

	/* properties */
}