import { createIndexBuffer, createVertexArray, createVertexBuffer, GLProgram, IndexBuffer, VertexArray, VertexBuffer } from "./glWrapper";
import {OBJ} from "webgl-obj-loader";
import { assertBoolean } from "./util";

type VertexType = "position" | "normal" | "textureUV";

type Vertexes = {[key in VertexType]:VertexBuffer};

export class Model{
    vertexes : Vertexes;
    ibo :IndexBuffer;
    vao :VertexArray;
    constructor(gl:WebGL2RenderingContext,vertex:Vertexes,index :IndexBuffer){
        this.vertexes = vertex;
        this.vao = createVertexArray(gl);
        this.ibo = index;
    }
    ready(gl:WebGL2RenderingContext,p : GLProgram){
        const VertexLayouts = {
            "position":{
                count:3,
                type:gl.FLOAT,
                normalize:false,
                stride:0,
                offset:0
            },
            "normal":{
                count:3,
                type:gl.FLOAT,
                normalize:false,
                stride:0,
                offset:0
            },
            "textureUV":{
                count:2,
                type:gl.FLOAT,
                normalize:false,
                stride:0,
                offset:0
            }
        }
        this.vao.bind(gl);
        for(const [name,buf] of Object.entries(this.vertexes)){
            const loc = p.getAttribLocation(gl,name);
            assertBoolean(loc >= 0,"there is no",name,"attribute");
            this.vao.addBuffer(gl,buf,loc,VertexLayouts[name]);
        }
        this.ibo.bind(gl);
        this.vao.unbind(gl);
    }
    draw(gl:WebGL2RenderingContext){
        this.vao.bind(gl);
        gl.drawElements(gl.TRIANGLES,this.ibo.count,gl.UNSIGNED_SHORT,0);
        this.vao.unbind(gl);
    }
    static async loadFromOBJ(gl:WebGL2RenderingContext,src:RequestInfo,init?:RequestInit){
        const response = await fetch(src,init);
        const text = await response.text();
        const mesh = new OBJ.Mesh(text);
        const position = createVertexBuffer(gl,mesh.vertices);
        const normal = createVertexBuffer(gl,mesh.vertexNormals);
        const texture = createVertexBuffer(gl,mesh.textures);
        const index = createIndexBuffer(gl,mesh.indices);
        return new Model(gl,{
            position: position,
            normal: normal,
            textureUV: texture
        }, index);
    }
}