import { ResizeObserver as ResizeObserverPolyfill } from '@juggle/resize-observer';
import { EventEmitter } from "./EventEmitter";

const ResizeObserver = window.ResizeObserver || ResizeObserverPolyfill;

interface WebGLCanvasOption {

    /**
     * Canvas element for outputting renderer images.
     * If a string is passed in:
     * Here will try `document.getElementById` and then `document.querySelector`
     * until a valid canvas element is found.
     */
    canvas?: HTMLCanvasElement | OffscreenCanvas | string;

    /**
     * Initialize with WebGL context.
     */
    context?: WebGLRenderingContext | WebGL2RenderingContext;

    /**
     * Parent node of canvas.
     */
    container?: HTMLElement | string;

    /**
     * Automatically adjust width and height to parent node width and height.
     */
    autoResize?: boolean;

    /**
     * Width of Canvas.
     * It will become invalid when autoResize is set.
     */
    width?: number;

    /**
     * Height of Canvas.
     * It will become invalid when autoResize is set.
     */
    height?: number;

    /**
     * Whether to use offline canvas.
     */
    isOffScreen?: boolean;

    /**
     * WebGL context attributes.
     */
    contextAttributes?: WebGLContextAttributes;
}

type WebGLCanvasEventMap = {

    /**
     * Emit When the canvas size changes.
     */
    "resize": void;
};

class WebGLCanvas extends EventEmitter<WebGLCanvasEventMap> {

    public readonly element: HTMLCanvasElement | OffscreenCanvas;

    public readonly context: WebGLRenderingContext | WebGL2RenderingContext;

    public readonly glVersion: 0 | 1 | 2;

    public readonly isOffScreen: boolean;

    public constructor(userOption?: WebGLCanvasOption) {

        super();

        const option: WebGLCanvasOption = userOption ?? {};

        let targetCanvas: HTMLCanvasElement | OffscreenCanvas | undefined = void 0;
        let targetContext: WebGLRenderingContext | WebGL2RenderingContext | undefined = void 0;
        let targetGLVersion: 0 | 1 | 2 = 0;
        let targetIsOffScreen: boolean = false;

        if (option.canvas instanceof HTMLCanvasElement || option.canvas instanceof OffscreenCanvas) {
            targetCanvas = option.canvas;
        }

        else if (typeof option.canvas === "string") {

            let findTarget: HTMLElement | null = null;

            findTarget = document.getElementById(option.canvas);

            if (findTarget instanceof HTMLCanvasElement) {
                targetCanvas = findTarget;
            }

            else {
                findTarget = document.querySelector(option.canvas);

                if (findTarget instanceof HTMLCanvasElement) {
                    targetCanvas = findTarget;
                }

                else {
                    console.warn(
                        `[ray-lab Renderer] Unable to search any valid canvas through "${option.canvas}". \r\n` +
                        "Created internal canvas instead..."
                    );
                }
            }
        }

        if (option.context) {

            if (targetCanvas && targetCanvas !== option.context.canvas) {
                console.warn(
                    "[ray-lab Renderer] The `canvas` element does not match the `context.canvas`: \r\n" + 
                    "The `canvas` option will be ignored. \r\n" +
                    "Please do not use `canvas` and `context` at the same time!"
                );
            }

            targetCanvas = option.context.canvas;
            targetContext = option.context;
        }

        if (targetCanvas) {

            if (targetCanvas instanceof HTMLCanvasElement) {

                if (option.isOffScreen) {

                    if (OffscreenCanvas) {
                        targetCanvas = targetCanvas.transferControlToOffscreen();
                        targetIsOffScreen = true;
                    }

                    else {
                        targetIsOffScreen = false;
                        console.warn(
                            "[ray-lab Renderer] The target environment does not support OffscreenCanvas \r\n" + 
                            "`isOffScreen` is ignored!"
                        );
                    }
                }

                else {
                    targetIsOffScreen = false;
                }
            }

            else if (targetCanvas instanceof OffscreenCanvas) {
                targetIsOffScreen = true;
            }
        }

        else {

            if (option.isOffScreen) {

                if (OffscreenCanvas) {
                    targetIsOffScreen = true;
                    targetCanvas = new OffscreenCanvas(option.width ?? 300, option.height ?? 150);
                }

                else {
                    targetIsOffScreen = false;
                    targetCanvas = document.createElement("canvas");
                    console.warn(
                        "[ray-lab Renderer] The target environment does not support OffscreenCanvas \r\n" + 
                        "`isOffScreen` is ignored!"
                    );
                }
            }

            else {
                targetIsOffScreen = false;
                targetCanvas = document.createElement("canvas");
            }
        }

        if (targetContext) {

            if (targetCanvas instanceof WebGL2RenderingContext) {
                targetGLVersion = 2;
            }

            else if (targetCanvas instanceof WebGLRenderingContext) {
                targetGLVersion = 1;
            }
        }

        else {
            let getContext: OffscreenRenderingContext | RenderingContext | null;

            getContext = targetCanvas.getContext("webgl2", option.contextAttributes);

            if (!getContext) {
                getContext = targetCanvas.getContext("webgl", option.contextAttributes);
            }
            
            if (WebGL2RenderingContext && (getContext instanceof WebGL2RenderingContext)) {
                targetContext = getContext;
                targetGLVersion = 2;
            }

            else if (getContext instanceof WebGLRenderingContext) {
                targetContext = getContext;
                targetGLVersion = 1;
            }

            else {
                throw new Error("[ray-lab Renderer] The target environment does not support WebGL :(");
            }
        }

        this.element = targetCanvas;
        this.context = targetContext;
        this.glVersion = targetGLVersion;
        this.isOffScreen = targetIsOffScreen;

        if (option.autoResize) {
            this.enableAutoResize(option.container);
        }

        else {
            this.resize(option.width, option.height);
        }
    }

    /**
     * Change the canvas size.
     * @param width - canvas width.
     * @param height - canvas height.
     */
    public resize(width?: number, height?: number) {

        let hasResized = false;

        if (width !== void 0) {
            this.element.width = width;
            hasResized = true;
        }

        if (height !== void 0) {
            this.element.height = height;
            hasResized = true;
        }

        if (hasResized) {
            this.emit("resize");
        }
    }

    private resizeObserver: ResizeObserver | undefined;

    /**
     * enable auto resize.
     * @param container - Parent node of canvas.
     */
    public enableAutoResize(container?: HTMLElement | string) {
        let targetcontainer: HTMLElement | null = null;

        if (container instanceof HTMLElement) {
            targetcontainer = container;
        }

        else if (typeof container === "string") {

            targetcontainer = document.getElementById(container);

            if (targetcontainer === null) {
                targetcontainer = document.querySelector(container);

                if (targetcontainer === null) {
                    console.warn(
                        `[ray-lab Renderer] Unable to search any valid container through "${container}".`
                    );
                }
            }
        }

        if (targetcontainer === null && this.element instanceof HTMLCanvasElement) {
            targetcontainer = this.element.parentElement;
        }

        if (targetcontainer === null) {
            console.warn(
                `[ray-lab Renderer] Unable to enable auto resize. \r\n` + 
                `Because a suitable container could not be found.`
            );
        }

        else {
            const resizeObserver = new ResizeObserver((entries) => {

                for (const entry of entries) {
                    if (entry.contentRect) {
                        this.resize(entry.contentRect.width, entry.contentRect.height);
                    }
                }
            });
    
            if (this.resizeObserver) {
                this.resizeObserver.disconnect();
            }
    
            this.resizeObserver = resizeObserver;

            if (this.element instanceof HTMLElement) {
                this.element.style.width = "100%";
                this.element.style.height = "100%";
                this.element.style.boxSizing = "border-box";
                this.element.style.display = "block";
            }
            
            resizeObserver.observe(targetcontainer);
            this.resize(targetcontainer.offsetWidth, targetcontainer.offsetHeight);
        }
    }

    /**
     * disable auto resize.
     */
    public disableAutoResize() {
        if (this.resizeObserver) {
            this.resizeObserver.disconnect();
        }

        this.resizeObserver = void 0;
    }
}

export { WebGLCanvas };
export type { WebGLCanvasOption };