using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using Box2DX;
using Box2DX.Dynamics;
using Box2DX.Collision;
using Box2DX.Common;

public class ApplicationMain : MonoBehaviour
{
    public Material material;

    private World world;
    private Body body;
    private Body groundBody;

    private Vec2 translate(Vec2 p)
    {
        //return new Vec2(p.X * 3 + 100, p.Y * 3 + 100);
        return new Vec2(p.X, p.Y);
    }

    private void Awake()
    {
        material.SetPass(0);//设置该材质通道，0为默认值

        // if bodies reach the end of the world, but it will be slower.
        AABB worldAABB = new AABB();
        worldAABB.LowerBound.Set(-100.0f, -100.0f);
        worldAABB.UpperBound.Set(100.0f, 100.0f);

        // Define the gravity vector.
        Vec2 gravity = new Vec2(0.0f, -10.0f);

        // Do we want to let bodies sleep?
        bool doSleep = true;

        // Construct a world object, which will hold and simulate the rigid bodies.
        world = new World(worldAABB, gravity, doSleep);

        // Define the ground body.
        BodyDef groundBodyDef = new BodyDef();
        groundBodyDef.Position.Set(0.0f, -10.0f);

        // Call the body factory which creates the ground box shape.
        // The body is also added to the world.
        groundBody = world.CreateBody(groundBodyDef);

        // Define the ground box shape.
        PolygonDef groundShapeDef = new PolygonDef();

        // The extents are the half-widths of the box.
        groundShapeDef.SetAsBox(50.0f, 10.0f);

        // Add the ground shape to the ground body.
        groundBody.CreateShape(groundShapeDef);

        // Define the dynamic body. We set its position and call the body factory.
        BodyDef bodyDef = new BodyDef();
        bodyDef.Position.Set(0.0f, 80.0f);
        body = world.CreateBody(bodyDef);

        // Define another box shape for our dynamic body.
        PolygonDef shapeDef = new PolygonDef();
        shapeDef.SetAsBox(1.0f, 1.0f);

        // Set the box density to be non-zero, so it will be dynamic.
        shapeDef.Density = 1.0f;

        // Override the default friction.
        shapeDef.Friction = 0.3f;

        // Add the shape to the body.
        body.CreateShape(shapeDef);

        // Now tell the dynamic body to compute it's mass properties base
        // on its shape.
        body.SetMassFromShapes();

        // Prepare for simulation. Typically we use a time step of 1/60 of a
        // second (60Hz) and 10 iterations. This provides a high quality simulation
        // in most game scenarios.
    }

    private void Update()
    {
        float timeStep = 1.0f / 60.0f;
        int velocityIterations = 8;
        int positionIterations = 1;
        world.Step(timeStep, velocityIterations, positionIterations);
    }

    private void OnRenderObject()
    {
        //绘制正四边形，提供的坐标必须是顺时针或者逆时针
        Vec2 position = body.GetPosition();
        Draw(
            translate(new Vec2(position.X + 1, position.Y + 1))
            , translate(new Vec2(position.X + 1, position.Y - 1))
            , translate(new Vec2(position.X - 1, position.Y - 1))
            , translate(new Vec2(position.X - 1, position.Y + 1))
        );
        position = groundBody.GetPosition();
        Draw(
            translate(new Vec2(position.X + 50, position.Y + 10))
            , translate(new Vec2(position.X + 50, position.Y - 10))
            , translate(new Vec2(position.X - 50, position.Y - 10))
            , translate(new Vec2(position.X - 50, position.Y + 10))
        );
    }

    //绘制四边形,四个点坐标
    void Draw(Vec2 p1, Vec2 p2, Vec2 p3, Vec2 p4)
    {
        GL.PushMatrix();
        material.SetPass(0);//设置该材质通道，0为默认值

        GL.LoadOrtho();//设置绘制2d图像
        GL.Begin(GL.QUADS);//绘制类型为四边形

        GL.Vertex3(p1.X / Screen.width, p1.Y / Screen.height, 0);
        GL.Vertex3(p2.X / Screen.width, p2.Y / Screen.height, 0);
        GL.Vertex3(p3.X / Screen.width, p3.Y / Screen.height, 0);
        GL.Vertex3(p4.X / Screen.width, p4.Y / Screen.height, 0);

        GL.End();
        GL.PopMatrix();
    }

}