import {
    AbstractMesh,
    DualShockPad,
    Engine,
    FreeCamera,
    FreeCameraGamepadInput,
    Gamepad as b_Gamepad,
    Mesh,
    Quaternion,
    Scene,
    Vector3,
    WebXRDefaultExperience,
    WebXRSessionManager,
} from '@babylonjs/core/Legacy/legacy';

if ((navigator as any).oscpu?.startsWith('Linux')) {
    // ^ oscpu is undefined on chrome on Android, at least...

    DualShockPad.prototype.update = function () {
        b_Gamepad.prototype.update.call(this);
        (window as any).G = this;

        (this as any)._rightStickAxisX = 3;
        (this as any)._rightStickAxisY = 4;

        this.buttonCross = this.browserGamepad.buttons[0].value;
        this.buttonCircle = this.browserGamepad.buttons[1].value;
        this.buttonTriangle = this.browserGamepad.buttons[2].value;
        this.buttonSquare = this.browserGamepad.buttons[3].value;

        this.buttonL1 = this.browserGamepad.buttons[4].value;
        this.buttonR1 = this.browserGamepad.buttons[5].value;
        this.leftTrigger = this.browserGamepad.buttons[6].value;
        this.rightTrigger = this.browserGamepad.buttons[7].value;
        this.buttonShare = this.browserGamepad.buttons[8].value;
        this.buttonOptions = this.browserGamepad.buttons[9].value;

        this.buttonLeftStick = this.browserGamepad.buttons[11].value;
        this.buttonRightStick = this.browserGamepad.buttons[12].value;

        this.dPadUp = this.browserGamepad.axes[7].value < 0 ? 1 : 0;
        this.dPadDown = this.browserGamepad.axes[7].value > 0 ? 1 : 0;
        this.dPadLeft = this.browserGamepad.axes[6].value < 0 ? 1 : 0;
        this.dPadRight = this.browserGamepad.axes[6].value > 0 ? 1 : 0;
    };
}

export type Interactivity = {
    floorMeshes: () => Mesh[],
    touchableMeshes: () => Mesh[],
};

export type EngineOptions = {
    initialPos: Vector3,
    initialRotation: Vector3,
    canvas: HTMLCanvasElement | null,
};

export type ButtonState = { [button: number]: boolean };

export class GamepadState {
    buttons: ButtonState = {};

    constructor (
        public gp: Gamepad, // NB. browser's Gamepad class, not Babylon's Gamepad class.
    ) {}

    latch(button: number): boolean {
        let result = false;
        const b = this.gp.buttons[button];
        if (b) {
            if (b.pressed) {
                if (!this.isDown(button)) result = true;
                this.buttons[button] = true;
            } else {
                this.buttons[button] = false;
            }
        }
        return result;
    }

    isDown(button: number): boolean {
        return this.buttons[button] ?? false;
    }
}

export class RunningEngine {
    camera!: FreeCamera;
    xrSessionManager: WebXRSessionManager | null = null;
    gamepadInput!: FreeCameraGamepadInput;

    leanBase: { position: Vector3 } | null = null;
    recenterBase: { rotation: Quaternion } | null = null;

    padStates: Map<Gamepad, GamepadState> = new Map();

    static async start(
        interactivity: Interactivity,
        options0: Partial<EngineOptions> = {},
    ): Promise<RunningEngine> {
        const options = Object.assign({
            initialPos: new Vector3(0, 1.6, 0),
            initialRotation: new Vector3(0, 0, 0).scaleInPlace(2 * Math.PI),
            canvas: document.getElementById("renderCanvas") as HTMLCanvasElement,
        }, options0);
        const engine = new Engine(options.canvas, true);
        const scene = new Scene(engine);
        const xr = await scene.createDefaultXRExperienceAsync({});
        return new RunningEngine(options, engine, interactivity, scene, xr);
    }

    private constructor (
        public options: EngineOptions,
        public engine: Engine,
        public interactivity: Interactivity,
        public scene: Scene,
        public xr: WebXRDefaultExperience,
    ) {
        this.xrSessionManager = this.xr.baseExperience?.sessionManager ?? null;

        if (this.xrSessionManager) {
            this.camera = this.xr.baseExperience.camera;
        } else {
            this.camera = new FreeCamera("camera",
                                         this.options.initialPos,
                                         this.scene);
            this.camera.rotation = this.options.initialRotation;
            this.camera.minZ = 0.1;
            this.camera.inertia = 0.75;
            this.camera.speed = 0.5;
            this.camera.attachControl(true);
        }

        this.gamepadInput = new FreeCameraGamepadInput();
        this.gamepadInput.gamepadMoveSensibility = 320;
        this.gamepadInput.gamepadAngularSensibility = 100;
        this.camera.inputs.add(this.gamepadInput);
        this.gamepadInput.attachControl();

        this.scene.gravity = new Vector3(0, -9.81 / 90, 0);
        this.scene.collisionsEnabled = true;

        this.camera.checkCollisions = true;
        this.camera.applyGravity = false;
        (this.camera as any)._needMoveForGravity = true;
        this.camera.ellipsoid = new Vector3(0.25, this.options.initialPos.y / 2, 0.25);

        if (this.options.canvas) {
            const canvas = this.options.canvas;
            if (this.xrSessionManager) {
                canvas.onclick = () => this.xrEnable();
            } else {
                canvas.onclick = () => canvas.requestPointerLock?.();
            }
        }

        this.engine.runRenderLoop(() => {
            Array.from(navigator.getGamepads()).forEach(gp => {
                if (gp !== null) this.checkGamepadInput(gp);
            });
            this.scene.render();
        });

        window.addEventListener("resize", () => this.engine.resize());
    }

    padStateFor(gp: Gamepad): GamepadState {
        const state = this.padStates.get(gp);
        if (state) return state;
        const newState = new GamepadState(gp);
        this.padStates.set(gp, newState);
        return newState;
    }

    checkGamepadInput(gp: Gamepad) {
        const state = this.padStateFor(gp);

        if (state.latch(2)) location.reload();
        if (state.latch(5)) this.turn180();

        if (this.xrSessionManager) {
            this.updateLean(gp);
            if (state.latch(0)) this.xrTeleport();
            if (state.latch(1)) this.xrTouch();
            if (state.latch(3)) this.xrEnable();

            if (state.latch(4)) {
                this.recenterBase = {
                    rotation: this.xr.baseExperience.camera.rotationQuaternion.clone(),
                };
            }
            if (state.isDown(4) && this.recenterBase) {
                this.xr.baseExperience.camera.rotationQuaternion.copyFrom(
                    this.recenterBase.rotation);
            }
        }
    }

    updateLean(gp: Gamepad) {
        const pos = new Vector3((gp.axes[0]), (-gp.axes[1]), (-gp.axes[3]));
        if (pos.length() > 0.0625) {
            if (this.leanBase === null) {
                this.leanBase = { position: this.xr.baseExperience.camera.position };
            }
            this.xr.baseExperience.camera.position =
                pos.applyRotationQuaternion(this.xr.baseExperience.camera.absoluteRotation)
                    .scale(0.25)
                    .add(this.leanBase.position);
        } else {
            if (this.leanBase !== null) {
                this.xr.baseExperience.camera.position = this.leanBase.position;
            }
            this.leanBase = null;
        }
    }

    turn180() {
        const r = this.xrSessionManager
            ? this.xr.baseExperience.camera.rotationQuaternion.toEulerAngles()
            : this.camera.rotation;
        r.y += Math.PI;
        r.y %= 2 * Math.PI;
        if (this.xrSessionManager) {
            this.xr.baseExperience.camera.rotationQuaternion.copyFrom(r.toQuaternion());
        }
    }

    xrTouch() {
        const ray = this.xr.baseExperience.camera.getForwardRay();
        const meshes = this.interactivity.touchableMeshes();
        const hit = this.scene.pickWithRay(ray, m => meshes.indexOf(m as any) !== -1);

        if (hit === null) return;
        if (meshes.indexOf(hit.pickedMesh as any) === -1) return;

        this.camera.onCollide?.(hit.pickedMesh!);
    }

    xrTeleport() {
        if (!this.xrSessionManager) return;

        const ray = this.xr.baseExperience.camera.getForwardRay();
        const meshes = this.interactivity.floorMeshes();
        const hit = this.scene.pickWithRay(ray, m => meshes.indexOf(m as any) !== -1);

        if (hit === null) return;
        if (meshes.indexOf(hit.pickedMesh as any) === -1) return;
        if (hit.pickedPoint === null) return;

        const pos = hit.pickedPoint.add(new Vector3(0, 1.6, 0));
        this.xr.baseExperience.camera.position = pos;
        this.xr.baseExperience.camera.rotation = Vector3.Zero();
        if (this.leanBase !== null) this.leanBase.position = pos;
    }

    xrEnable() {
        if (!this.xrSessionManager) return;
        this.xr.baseExperience.enterXRAsync('immersive-vr', 'local').then(() => {
            this.xr.baseExperience.camera.position = this.options.initialPos;
            this.xr.baseExperience.camera.rotation = this.options.initialRotation;
            this.xr.baseExperience.sessionManager.session.onselect = () => this.xrTeleport();
        });
    }
}