/* SPDX-License-Identifier: MIT */
/*
 * konrmdraw.c
 *
 * Copyright (c) 2026 KonAki
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in all
 * copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 */

#include "konrmdraw.h"

#define SHADOW_COLOR 0x80000000u

/*** helpers ***/

static int floorDiv(int a, int b)
{
	int q = a / b;

	return (a % b != 0 && (a < 0) != (b < 0)) ? q - 1 : q;
}

int kon_rmTileSize(const kon_rmSheets_t *sheets)
{
	int sheet, columns, rows;

	if (!sheets) return 0;
	for (sheet = 0; sheet < KON_RM_SHEETS; sheet++) {
		const kon_image *image = sheets->image[sheet];

		if (image && kon_rmSheetSize(sheet, &columns, &rows) && image->width >= columns) return image->width / columns * 2;
	}
	return 0;
}

static void drawTile(kon_framebuffer_t *fb, const kon_rmSheets_t *sheets, int tileId, int frame, int x, int y)
{
	kon_rmQuad_t quads[4];
	int n = kon_rmTileQuads(tileId, frame, quads), i;

	for (i = 0; i < n; i++) {
		const kon_image *image = sheets->image[quads[i].sheet];
		int columns, rows, half;
		kon_rect_t src;

		if (!image || !kon_rmSheetSize(quads[i].sheet, &columns, &rows)) continue;
		half = image->width / columns;
		if (half < 1) continue;
		src.x = quads[i].sx * half;
		src.y = quads[i].sy * half;
		src.w = quads[i].w * half;
		src.h = quads[i].h * half;
		kon_drawImageRegion(fb, x + quads[i].dx * half, y + quads[i].dy * half, image, src);
	}
}

static void drawShadow(kon_framebuffer_t *fb, int size, int bits, int x, int y)
{
	int i, half = size / 2;

	for (i = 0; i < 4; i++) {
		if (bits & (1 << i)) kon_fillRectangle(fb, x + (i % 2) * half, y + (i / 2) * half, half, half, SHADOW_COLOR);
	}
}

/*** drawing ***/

void kon_rmDrawTiles(kon_framebuffer_t *fb, const kon_rmMap_t *map, const kon_rmTileset_t *tileset, const kon_rmSheets_t *sheets, int frame, int cameraX, int cameraY, int pass)
{
	int size, firstColumn, lastColumn, firstRow, lastRow, cx, cy;

	if (!fb || !map || !sheets || map->width < 1 || map->height < 1) return;
	size = kon_rmTileSize(sheets);
	if (size < 2) return;

	firstColumn = floorDiv(cameraX, size);
	lastColumn = floorDiv(cameraX + fb->width - 1, size);
	firstRow = floorDiv(cameraY, size);
	lastRow = floorDiv(cameraY + fb->height - 1, size);

	for (cy = firstRow; cy <= lastRow; cy++) {
		for (cx = firstColumn; cx <= lastColumn; cx++) {
			int mx = kon_rmRoundX(map, cx), my = kon_rmRoundY(map, cy);
			int x = cx * size - cameraX, y = cy * size - cameraY;
			int tiles[4], layer;

			if (mx < 0 || my < 0 || mx >= map->width || my >= map->height) continue;
			for (layer = 0; layer < 4; layer++) tiles[layer] = kon_rmTile(map, layer, mx, my);

			if (pass == 0) {
				for (layer = 0; layer < 4; layer++) {
					if (layer == 2) drawShadow(fb, size, kon_rmTile(map, 4, mx, my), x, y);
					if (tiles[layer] > 0 && !kon_rmTileIsHigher(kon_rmFlags(tileset, tiles[layer]))) drawTile(fb, sheets, tiles[layer], frame, x, y);
				}
			} else {
				for (layer = 0; layer < 4; layer++) {
					if (tiles[layer] > 0 && kon_rmTileIsHigher(kon_rmFlags(tileset, tiles[layer]))) drawTile(fb, sheets, tiles[layer], frame, x, y);
				}
			}
		}
	}
}