import { Nullable } from "../../types";
import { Observable } from "../../Misc/observable";
import { IDisposable, Scene } from "../../scene";
import { WebXRExperienceHelper } from "./webXRExperienceHelper";
import { WebXRState, WebXRRenderTarget } from './webXRTypes';
/**
 * Button which can be used to enter a different mode of XR
 */
export class WebXREnterExitUIButton {
    /**
     * Creates a WebXREnterExitUIButton
     * @param element button element
     * @param sessionMode XR initialization session mode
     * @param referenceSpaceType the type of reference space to be used
     */
    constructor(
        /** button element */
        public element: HTMLElement,
        /** XR initialization options for the button */
        public sessionMode: XRSessionMode,
        /** Reference space type */
        public referenceSpaceType: XRReferenceSpaceType
    ) { }
    /**
     * Overwritable function which can be used to update the button's visuals when the state changes
     * @param activeButton the current active button in the UI
     */
    update(activeButton: Nullable<WebXREnterExitUIButton>) {
    }
}

/**
 * Options to create the webXR UI
 */
export class WebXREnterExitUIOptions {
    /**
     * Context to enter xr with
     */
    renderTarget?: Nullable<WebXRRenderTarget>;

    /**
     * User provided buttons to enable/disable WebXR. The system will provide default if not set
     */
    customButtons?: Array<WebXREnterExitUIButton>;
}
/**
 * UI to allow the user to enter/exit XR mode
 */
export class WebXREnterExitUI implements IDisposable {
    private _overlay: HTMLDivElement;
    private _buttons: Array<WebXREnterExitUIButton> = [];
    private _activeButton: Nullable<WebXREnterExitUIButton> = null;
    /**
     * Fired every time the active button is changed.
     *
     * When xr is entered via a button that launches xr that button will be the callback parameter
     *
     * When exiting xr the callback parameter will be null)
     */
    public activeButtonChangedObservable = new Observable<Nullable<WebXREnterExitUIButton>>();
    /**
     * Creates UI to allow the user to enter/exit XR mode
     * @param scene the scene to add the ui to
     * @param helper the xr experience helper to enter/exit xr with
     * @param options options to configure the UI
     * @returns the created ui
     */
    public static CreateAsync(scene: Scene, helper: WebXRExperienceHelper, options: WebXREnterExitUIOptions): Promise<WebXREnterExitUI> {
        var ui = new WebXREnterExitUI(scene, options);
        var supportedPromises = ui._buttons.map((btn) => {
            return helper.sessionManager.supportsSessionAsync(btn.sessionMode);
        });
        helper.onStateChangedObservable.add((state) => {
            if (state == WebXRState.NOT_IN_XR) {
                ui._updateButtons(null);
            }
        });
        return Promise.all(supportedPromises).then((results) => {
            results.forEach((supported, i) => {
                if (supported) {
                    ui._overlay.appendChild(ui._buttons[i].element);
                    ui._buttons[i].element.onclick = async() => {
                        if (helper.state == WebXRState.IN_XR) {
                            ui._updateButtons(null);
                            await helper.exitXRAsync();
                            return;
                        } else if (helper.state == WebXRState.NOT_IN_XR) {
                            ui._updateButtons(ui._buttons[i]);
                            if (options.renderTarget) {
                                await helper.enterXRAsync(ui._buttons[i].sessionMode, ui._buttons[i].referenceSpaceType, options.renderTarget);
                            }
                        }
                    };
                }
            });
            return ui;
        });
    }

    private constructor(private scene: Scene, options: WebXREnterExitUIOptions) {
        this._overlay = document.createElement("div");
        this._overlay.style.cssText = "z-index:11;position: absolute; right: 20px;bottom: 50px;";

        if (options.customButtons) {
            this._buttons = options.customButtons;
        } else {
            var hmdBtn = document.createElement("button");
            hmdBtn.style.cssText = "color: #868686; border-color: #868686; border-style: solid; margin-left: 10px; height: 50px; width: 80px; background-color: rgba(51,51,51,0.7); background-repeat:no-repeat; background-position: center; outline: none;";
            hmdBtn.innerText = "HMD";
            this._buttons.push(new WebXREnterExitUIButton(hmdBtn, "immersive-vr", "local-floor"));
            this._buttons[this._buttons.length - 1].update = function(activeButton: WebXREnterExitUIButton) {
                this.element.style.display = (activeButton === null || activeButton === this) ? "" : "none";
                this.element.innerText = activeButton === this ? "EXIT" : "HMD";
            };
            this._updateButtons(null);
        }

        var renderCanvas = scene.getEngine().getRenderingCanvas();
        if (renderCanvas && renderCanvas.parentNode) {
            renderCanvas.parentNode.appendChild(this._overlay);
            scene.onDisposeObservable.addOnce(() => {
                this.dispose();
            });
        }
    }

    private _updateButtons(activeButton: Nullable<WebXREnterExitUIButton>) {
        this._activeButton = activeButton;
        this._buttons.forEach((b) => {
            b.update(this._activeButton);
        });
        this.activeButtonChangedObservable.notifyObservers(this._activeButton);
    }

    /**
     * Disposes of the object
     */
    dispose() {
        var renderCanvas = this.scene.getEngine().getRenderingCanvas();
        if (renderCanvas && renderCanvas.parentNode && renderCanvas.parentNode.contains(this._overlay)) {
            renderCanvas.parentNode.removeChild(this._overlay);
        }
        this.activeButtonChangedObservable.clear();
    }
}