using System;

namespace MultiWheelC.TrajectoryPlanning.Mapping;

/// <summary>从只读规划地图生成简单的 RGBA 占据图字节数组。</summary>
internal static class PlanningMapImageRenderer
{
    /// <summary>
    /// 渲染规划地图为行主序 RGBA 像素。
    ///
    /// 参数：map 为只读规划快照；pixelsPerCell 为每个栅格的像素边长；width、height 返回图像像素尺寸。
    /// 返回：长度为 width × height × 4 的 RGBA 字节数组；不会修改地图。
    /// </summary>
    public static byte[] Render(PlanningGridMap map, int pixelsPerCell, out int width, out int height)
    {
        if (map == null) throw new ArgumentNullException(nameof(map));
        width = checked(map.Cols * pixelsPerCell);
        height = checked(map.Rows * pixelsPerCell);
        var rgba = new byte[checked(width * height * 4)];
        for (int row = 0; row < map.Rows; row++)
        for (int col = 0; col < map.Cols; col++)
        {
            bool occupied = map.IsOccupied(row, col);
            byte red = occupied ? (byte)220 : (byte)245;
            byte green = occupied ? (byte)45 : (byte)245;
            byte blue = occupied ? (byte)45 : (byte)245;
            int displayRow = map.Rows - 1 - row;
            for (int py = 0; py < pixelsPerCell; py++)
            for (int px = 0; px < pixelsPerCell; px++)
            {
                int index = ((displayRow * pixelsPerCell + py) * width + col * pixelsPerCell + px) * 4;
                rgba[index] = red; rgba[index + 1] = green; rgba[index + 2] = blue; rgba[index + 3] = 255;
            }
        }
        return rgba;
    }
}
