// • ▌ ▄ ·.  ▄▄▄·  ▄▄ • ▪   ▄▄· ▄▄▄▄·  ▄▄▄·  ▐▄▄▄  ▄▄▄ .
// ·██ ▐███▪▐█ ▀█ ▐█ ▀ ▪██ ▐█ ▌▪▐█ ▀█▪▐█ ▀█ •█▌ ▐█▐▌·
// ▐█ ▌▐▌▐█·▄█▀▀█ ▄█ ▀█▄▐█·██ ▄▄▐█▀▀█▄▄█▀▀█ ▐█▐ ▐▌▐▀▀▀
// ██ ██▌▐█▌▐█ ▪▐▌▐█▄▪▐█▐█▌▐███▌██▄▪▐█▐█ ▪▐▌██▐ █▌▐█▄▄▌
// ▀▀  █▪▀▀▀ ▀  ▀ ·▀▀▀▀ ▀▀▀·▀▀▀ ·▀▀▀▀  ▀  ▀ ▀▀  █▪ ▀▀▀
//      Magicbane Emulator Project © 2013 - 2022
//                www.magicbane.com

package engine.InterestManagement;

import engine.gameManager.ZoneManager;
import engine.math.Vector2f;
import engine.math.Vector3fImmutable;
import engine.objects.Zone;
import org.pmw.tinylog.Logger;

import java.util.HashMap;

import static java.lang.Math.PI;

public class Terrain {

    // Class variables

    public static final HashMap<Integer, short[][]> _heightmap_pixel_cache = new HashMap<>();
    public short[][] terrain_pixel_data;
    public Vector2f terrain_size = new Vector2f();
    public Vector2f cell_size = new Vector2f();
    public Vector2f cell_count = new Vector2f();
    public float terrain_scale;
    public float min_blend;
    public float max_blend;
    public int heightmap;
    Zone zone;

    public Terrain(Zone zone) {

        this.zone = zone;

        this.heightmap = this.zone.terrain_image;

        // Configure PLANAR zones to use the same
        // 16x16 pixel image that all other flat
        // terrains share.

        if (this.zone.terrain_type.equals("PLANAR"))
            this.heightmap = 1006300;

        // Load pixel data for this terrain from cache

        this.terrain_pixel_data = Terrain._heightmap_pixel_cache.get(heightmap);

        if (terrain_pixel_data == null)
            Logger.error("Pixel map empty for zone: " + this.zone.getObjectUUID() + ":" + this.zone.zoneName);

        // Configure terrain based on zone properties

        this.terrain_size.x = this.zone.major_radius * 2;
        this.terrain_size.y = this.zone.minor_radius * 2;

        this.cell_count.x = this.terrain_pixel_data.length - 1;
        this.cell_count.y = this.terrain_pixel_data[0].length - 1;

        this.cell_size.x = terrain_size.x / this.cell_count.x;
        this.cell_size.y = terrain_size.y / this.cell_count.y;

        this.max_blend = this.zone.max_blend / this.zone.major_radius;
        this.min_blend = this.zone.min_blend / this.zone.minor_radius;

        this.terrain_scale = this.zone.terrain_max_y / 255f;

    }

    public static Zone getNextZoneWithTerrain(Zone zone) {

        // Not all zones have a terrain.  Some are for display only
        // and heights returned are from the parent heightmap.  This
        // is controlled in the JSON via the has_terrain_gen field.

        Zone terrain_zone = zone;

        if (zone == null)
            return ZoneManager.seaFloor;

        if (zone.terrain != null)
            return zone;

        if (zone.equals(ZoneManager.seaFloor))
            return zone;

        while (terrain_zone.terrain == null)
            terrain_zone = terrain_zone.parent;

        return terrain_zone;
    }

    public static float getWorldHeight(Zone currentZone, Vector3fImmutable worldLoc) {

        Zone terrainZone;

        // Retrieve the next zone with a terrain defined.

        terrainZone = getNextZoneWithTerrain(currentZone);

        // Transform world loc into zone space coordinate system

        Vector2f terrainLoc = ZoneManager.worldToZoneSpace(worldLoc, terrainZone);

        // Interpolate height for this position in terrain

        float interpolatedChildHeight = terrainZone.terrain.getInterpolatedTerrainHeight(terrainLoc);
        interpolatedChildHeight += terrainZone.worldAltitude;

        return interpolatedChildHeight;
    }

    public static float getWorldHeight(Vector3fImmutable worldLoc) {

        Zone currentZone = ZoneManager.findSmallestZone(worldLoc);

        if (currentZone == null)
            return 0;

        return getWorldHeight(currentZone, worldLoc);

    }

    public Vector2f getTerrainCell(Vector2f terrainLoc) {

        Vector2f terrain_cell = new Vector2f(terrainLoc.x / this.cell_size.x, terrainLoc.y / this.cell_size.y);

        // Clamp values when standing directly on pole

        terrain_cell.x = Math.max(0, Math.min(this.cell_count.x - 1, terrain_cell.x));
        terrain_cell.y = Math.max(0, Math.min(this.cell_count.y - 1, terrain_cell.y));

        return terrain_cell;
    }

    public float getInterpolatedTerrainHeight(Vector2f terrainLoc) {

        try {
            float interpolatedHeight;

            Vector2f terrain_cell = getTerrainCell(terrainLoc);

            int pixel_x = (int) Math.floor(terrain_cell.x);
            int pixel_y = (int) Math.floor(terrain_cell.y);

            Vector2f pixel_offset = new Vector2f(terrain_cell.x % 1, terrain_cell.y % 1);

            //get 4 surrounding vertices from the pixel array.

            float topLeftHeight;
            float topRightHeight;
            float bottomLeftHeight;
            float bottomRightHeight;

            topLeftHeight = terrain_pixel_data[pixel_x][pixel_y];
            topRightHeight = terrain_pixel_data[pixel_x + 1][pixel_y];
            bottomLeftHeight = terrain_pixel_data[pixel_x][pixel_y + 1];
            bottomRightHeight = terrain_pixel_data[pixel_x + 1][pixel_y + 1];

            // Interpolate between the 4 vertices

            interpolatedHeight = topLeftHeight * (1 - pixel_offset.x) * (1 - pixel_offset.y);
            interpolatedHeight += topRightHeight * (1 - pixel_offset.y) * (pixel_offset.x);
            interpolatedHeight += (bottomLeftHeight * (1 - pixel_offset.x) * pixel_offset.y);
            interpolatedHeight += (bottomRightHeight * pixel_offset.y * pixel_offset.x);

            interpolatedHeight *= this.terrain_scale; // Scale height

            return interpolatedHeight;

        } catch (Exception e) {
            Logger.error(this.zone.zoneName + ":" + this.zone.getObjectUUID() + e);
            return 0;
        }
    }

    public float terrainBlend(Vector2f terrainLoc) {

        // Normalize terrain loc

        Vector2f normalizedLoc = new Vector2f(terrainLoc.x / this.terrain_size.x,
                terrainLoc.y / terrain_size.y);

        float minp = this.zone.min_blend / this.zone.major_radius;
        float maxp = this.zone.max_blend / this.zone.major_radius;

        float minpy = this.zone.min_blend / this.zone.minor_radius;
        float maxpy = this.zone.max_blend / this.zone.minor_radius;

        float xval;

        if (minp > 0.4f)
            xval = minp;
        else
            xval = Math.min(maxp, 0.4f);

        float yval;

        if (minpy > 0.4f)
            yval = minpy;
        else
            yval = Math.min(maxpy, 0.4f);

        float value;

        if (normalizedLoc.x <= 1 - xval || normalizedLoc.x <= normalizedLoc.y) {

            if (normalizedLoc.y < 1 - yval)
                return 1;

            value = (normalizedLoc.y - (1 - yval)) / yval;
        } else
            value = (normalizedLoc.x - (1 - xval)) / xval;

        value = (float) Math.atan((0.5f - value) * PI);

        return (value + 1) * 0.5f;
    }
}