/**
 * Copyright (c) 2018-2020 mol* contributors, licensed under MIT, See LICENSE file for more info.
 *
 * @author Alexander Rose <alexander.rose@weirdbyte.de>
 * @author David Sehnal <david.sehnal@gmail.com>
 */

import { BehaviorSubject, Subscription } from 'rxjs';
import { now } from '../mol-util/now';
import { Vec3 } from '../mol-math/linear-algebra'
import InputObserver, { ModifiersKeys, ButtonsType } from '../mol-util/input/input-observer'
import Renderer, { RendererStats, RendererParams } from '../mol-gl/renderer'
import { GraphicsRenderObject } from '../mol-gl/render-object'
import { TrackballControls, TrackballControlsParams } from './controls/trackball'
import { Viewport } from './camera/util'
import { createContext, WebGLContext, getGLContext } from '../mol-gl/webgl/context';
import { Representation } from '../mol-repr/representation';
import Scene from '../mol-gl/scene';
import { GraphicsRenderVariant } from '../mol-gl/webgl/render-item';
import { PickingId } from '../mol-geo/geometry/picking';
import { MarkerAction } from '../mol-util/marker-action';
import { Loci, EmptyLoci, isEmptyLoci } from '../mol-model/loci';
import { Camera } from './camera';
import { ParamDefinition as PD } from '../mol-util/param-definition';
import { BoundingSphereHelper, DebugHelperParams } from './helper/bounding-sphere-helper';
import { SetUtils } from '../mol-util/set';
import { Canvas3dInteractionHelper } from './helper/interaction-events';
import { PostprocessingParams, PostprocessingPass } from './passes/postprocessing';
import { MultiSampleParams, MultiSamplePass } from './passes/multi-sample';
import { PixelData } from '../mol-util/image';
import { readTexture } from '../mol-gl/compute/util';
import { DrawPass } from './passes/draw';
import { PickPass } from './passes/pick';
import { Task } from '../mol-task';
import { ImagePass, ImageProps } from './passes/image';
import { Sphere3D } from '../mol-math/geometry';
import { isDebugMode } from '../mol-util/debug';

export const Canvas3DParams = {
    cameraMode: PD.Select('perspective', [['perspective', 'Perspective'], ['orthographic', 'Orthographic']]),
    cameraFog: PD.Numeric(50, { min: 0, max: 100, step: 1 }),
    cameraClipFar: PD.Boolean(true),
    cameraResetDurationMs: PD.Numeric(250, { min: 0, max: 1000, step: 1 }, { description: 'The time it takes to reset the camera.' }),
    transparentBackground: PD.Boolean(false),

    multiSample: PD.Group(MultiSampleParams),
    postprocessing: PD.Group(PostprocessingParams),
    renderer: PD.Group(RendererParams),
    trackball: PD.Group(TrackballControlsParams),
    debug: PD.Group(DebugHelperParams)
}
export const DefaultCanvas3DParams = PD.getDefaultValues(Canvas3DParams);
export type Canvas3DProps = PD.Values<typeof Canvas3DParams>

export { Canvas3D }

interface Canvas3D {
    readonly webgl: WebGLContext,

    add(repr: Representation.Any): void
    remove(repr: Representation.Any): void
    /**
     * This function must be called if animate() is not set up so that add/remove actions take place.
     */
    commit(isSynchronous?: boolean): void
    update(repr?: Representation.Any, keepBoundingSphere?: boolean): void
    clear(): void

    requestDraw(force?: boolean): void
    animate(): void
    identify(x: number, y: number): PickingId | undefined
    mark(loci: Representation.Loci, action: MarkerAction): void
    getLoci(pickingId: PickingId): Representation.Loci

    readonly didDraw: BehaviorSubject<now.Timestamp>
    readonly reprCount: BehaviorSubject<number>

    handleResize(): void
    /** Focuses camera on scene's bounding sphere, centered and zoomed. */
    requestCameraReset(durationMs?: number): void
    readonly camera: Camera
    readonly boundingSphere: Readonly<Sphere3D>
    downloadScreenshot(): void
    getPixelData(variant: GraphicsRenderVariant): PixelData
    setProps(props: Partial<Canvas3DProps>): void
    getImagePass(): ImagePass

    /** Returns a copy of the current Canvas3D instance props */
    readonly props: Readonly<Canvas3DProps>
    readonly input: InputObserver
    readonly stats: RendererStats
    readonly interaction: Canvas3dInteractionHelper['events']

    dispose(): void
}

const requestAnimationFrame = typeof window !== 'undefined' ? window.requestAnimationFrame : (f: (time: number) => void) => setImmediate(()=>f(Date.now()))
const DefaultRunTask = (task: Task<unknown>) => task.run()

namespace Canvas3D {
    export interface HoverEvent { current: Representation.Loci, buttons: ButtonsType, button: ButtonsType.Flag, modifiers: ModifiersKeys }
    export interface ClickEvent { current: Representation.Loci, buttons: ButtonsType, button: ButtonsType.Flag, modifiers: ModifiersKeys }

    export function fromCanvas(canvas: HTMLCanvasElement, props: Partial<Canvas3DProps> = {}, runTask = DefaultRunTask) {
        const gl = getGLContext(canvas, {
            alpha: true,
            antialias: true,
            depth: true,
            preserveDrawingBuffer: true,
            premultipliedAlpha: false,
        })
        if (gl === null) throw new Error('Could not create a WebGL rendering context')
        const input = InputObserver.fromElement(canvas)
        const webgl = createContext(gl)

        if (isDebugMode) {
            const loseContextExt = gl.getExtension('WEBGL_lose_context')
            if (loseContextExt) {
                canvas.addEventListener('mousedown', e => {
                    if (webgl.isContextLost) return
                    if (!e.shiftKey || !e.ctrlKey || !e.altKey) return

                    console.log('lose context')
                    loseContextExt.loseContext()

                    setTimeout(() => {
                        if (!webgl.isContextLost) return
                        console.log('restore context')
                        loseContextExt.restoreContext()
                    }, 1000)
                }, false)
            }
        }

        // https://www.khronos.org/webgl/wiki/HandlingContextLost

        canvas.addEventListener('webglcontextlost', e => {
            webgl.setContextLost()
            e.preventDefault()
            if (isDebugMode) console.log('context lost')
        }, false)

        canvas.addEventListener('webglcontextrestored', () => {
            if (!webgl.isContextLost) return
            webgl.handleContextRestored()
            if (isDebugMode) console.log('context restored')
        }, false)

        return Canvas3D.create(webgl, input, props, runTask)
    }

    export function create(webgl: WebGLContext, input: InputObserver, props: Partial<Canvas3DProps> = {}, runTask = DefaultRunTask): Canvas3D {
        const p = { ...DefaultCanvas3DParams, ...props }

        const reprRenderObjects = new Map<Representation.Any, Set<GraphicsRenderObject>>()
        const reprUpdatedSubscriptions = new Map<Representation.Any, Subscription>()
        const reprCount = new BehaviorSubject(0)

        const startTime = now()
        const didDraw = new BehaviorSubject<now.Timestamp>(0 as now.Timestamp)

        const { gl, contextRestored } = webgl

        let width = gl.drawingBufferWidth
        let height = gl.drawingBufferHeight

        const scene = Scene.create(webgl)

        const camera = new Camera({
            position: Vec3.create(0, 0, 100),
            mode: p.cameraMode,
            fog: p.cameraFog,
            clipFar: p.cameraClipFar
        })

        const controls = TrackballControls.create(input, camera, p.trackball)
        const renderer = Renderer.create(webgl, p.renderer)
        const debugHelper = new BoundingSphereHelper(webgl, scene, p.debug);
        const interactionHelper = new Canvas3dInteractionHelper(identify, getLoci, input);

        const drawPass = new DrawPass(webgl, renderer, scene, camera, debugHelper)
        const pickPass = new PickPass(webgl, renderer, scene, camera, 0.5)
        const postprocessing = new PostprocessingPass(webgl, camera, drawPass, p.postprocessing)
        const multiSample = new MultiSamplePass(webgl, camera, drawPass, postprocessing, p.multiSample)

        const contextRestoredSub = contextRestored.subscribe(() => {
            pickPass.pickDirty = true
            draw(true)
        })

        let drawPending = false
        let cameraResetRequested = false
        let nextCameraResetDuration: number | undefined = void 0

        function getLoci(pickingId: PickingId) {
            let loci: Loci = EmptyLoci
            let repr: Representation.Any = Representation.Empty
            reprRenderObjects.forEach((_, _repr) => {
                const _loci = _repr.getLoci(pickingId)
                if (!isEmptyLoci(_loci)) {
                    if (!isEmptyLoci(loci)) {
                        console.warn('found another loci, this should not happen')
                    }
                    loci = _loci
                    repr = _repr
                }
            })
            return { loci, repr }
        }

        function mark(reprLoci: Representation.Loci, action: MarkerAction) {
            const { repr, loci } = reprLoci
            let changed = false
            if (repr) {
                changed = repr.mark(loci, action)
            } else {
                reprRenderObjects.forEach((_, _repr) => { changed = _repr.mark(loci, action) || changed })
            }
            if (changed) {
                scene.update(void 0, true)
                const prevPickDirty = pickPass.pickDirty
                draw(true)
                pickPass.pickDirty = prevPickDirty // marking does not change picking buffers
            }
        }

        function render(force: boolean) {
            if (webgl.isContextLost) return false

            let didRender = false
            controls.update(currentTime)
            Viewport.set(camera.viewport, 0, 0, width, height)
            const cameraChanged = camera.update()
            multiSample.update(force || cameraChanged, currentTime)

            if (force || cameraChanged || multiSample.enabled) {
                renderer.setViewport(0, 0, width, height)
                if (multiSample.enabled) {
                    multiSample.render(true, p.transparentBackground)
                } else {
                    drawPass.render(!postprocessing.enabled, p.transparentBackground)
                    if (postprocessing.enabled) postprocessing.render(true)
                }
                pickPass.pickDirty = true
                didRender = true
            }

            return didRender;
        }

        let forceNextDraw = false;
        let currentTime = 0;

        function draw(force?: boolean) {
            if (render(!!force || forceNextDraw)) {
                didDraw.next(now() - startTime as now.Timestamp)
            }
            forceNextDraw = false;
            drawPending = false
        }

        function requestDraw(force?: boolean) {
            if (drawPending) return
            drawPending = true
            forceNextDraw = !!force;
        }

        function animate() {
            currentTime = now();
            commit();
            camera.transition.tick(currentTime);

            draw(false);
            if (!camera.transition.inTransition && !webgl.isContextLost) {
                interactionHelper.tick(currentTime);
            }
            requestAnimationFrame(animate)
        }

        function identify(x: number, y: number): PickingId | undefined {
            return webgl.isContextLost ? undefined : pickPass.identify(x, y)
        }

        function commit(isSynchronous: boolean = false) {
            const allCommited = commitScene(isSynchronous);
            // Only reset the camera after the full scene has been commited.
            if (allCommited) resolveCameraReset();
        }

        function resolveCameraReset() {
            if (!cameraResetRequested) return;
            const { center, radius } = scene.boundingSphere;
            const duration = nextCameraResetDuration === undefined ? p.cameraResetDurationMs : nextCameraResetDuration
            camera.focus(center, radius, radius, duration);
            nextCameraResetDuration = void 0;
            cameraResetRequested = false;
        }

        const sceneCommitTimeoutMs = 250;
        function commitScene(isSynchronous: boolean) {
            if (!scene.needsCommit) return true;

            if (!scene.commit(isSynchronous ? void 0 : sceneCommitTimeoutMs)) return false;

            if (debugHelper.isEnabled) debugHelper.update();
            reprCount.next(reprRenderObjects.size);
            return true;
        }

        function add(repr: Representation.Any) {
            registerAutoUpdate(repr);

            const oldRO = reprRenderObjects.get(repr)
            const newRO = new Set<GraphicsRenderObject>()
            repr.renderObjects.forEach(o => newRO.add(o))

            if (oldRO) {
                if (!SetUtils.areEqual(newRO, oldRO)) {
                    newRO.forEach(o => { if (!oldRO.has(o)) scene.add(o) })
                    oldRO.forEach(o => { if (!newRO.has(o)) scene.remove(o) })
                }
            } else {
                repr.renderObjects.forEach(o => scene.add(o))
            }
            reprRenderObjects.set(repr, newRO)

            scene.update(repr.renderObjects, false)
        }

        function remove(repr: Representation.Any) {
            unregisterAutoUpdate(repr);

            const renderObjects = reprRenderObjects.get(repr)
            if (renderObjects) {
                renderObjects.forEach(o => scene.remove(o))
                reprRenderObjects.delete(repr)
                scene.update(repr.renderObjects, false, true)
            }
        }

        function registerAutoUpdate(repr: Representation.Any) {
            if (reprUpdatedSubscriptions.has(repr)) return;

            reprUpdatedSubscriptions.set(repr, repr.updated.subscribe(_ => {
                if (!repr.state.syncManually) add(repr);
            }))
        }

        function unregisterAutoUpdate(repr: Representation.Any) {
            const updatedSubscription = reprUpdatedSubscriptions.get(repr);
            if (updatedSubscription) {
                updatedSubscription.unsubscribe();
                reprUpdatedSubscriptions.delete(repr);
            }
        }

        handleResize()

        return {
            webgl,

            add,
            remove,
            commit,
            update: (repr, keepSphere) => {
                if (repr) {
                    if (!reprRenderObjects.has(repr)) return;
                    scene.update(repr.renderObjects, !!keepSphere);
                } else {
                    scene.update(void 0, !!keepSphere)
                }
            },
            clear: () => {
                reprUpdatedSubscriptions.forEach(v => v.unsubscribe())
                reprUpdatedSubscriptions.clear()
                reprRenderObjects.clear()
                scene.clear()
                debugHelper.clear()
                requestDraw(true)
                reprCount.next(reprRenderObjects.size)
            },

            // draw,
            requestDraw,
            animate,
            identify,
            mark,
            getLoci,

            handleResize,
            requestCameraReset: (durationMs) => {
                nextCameraResetDuration = durationMs;
                cameraResetRequested = true;
            },
            camera,
            boundingSphere: scene.boundingSphere,
            downloadScreenshot: () => {
                // TODO
            },
            getPixelData: (variant: GraphicsRenderVariant) => {
                switch (variant) {
                    case 'color': return webgl.getDrawingBufferPixelData()
                    case 'pickObject': return pickPass.objectPickTarget.getPixelData()
                    case 'pickInstance': return pickPass.instancePickTarget.getPixelData()
                    case 'pickGroup': return pickPass.groupPickTarget.getPixelData()
                    case 'depth': return readTexture(webgl, drawPass.depthTexture) as PixelData
                }
            },
            didDraw,
            reprCount,
            setProps: (props: Partial<Canvas3DProps>) => {
                if (props.cameraMode !== undefined && props.cameraMode !== camera.state.mode) {
                    camera.setState({ mode: props.cameraMode })
                }
                if (props.cameraFog !== undefined && props.cameraFog !== camera.state.fog) {
                    camera.setState({ fog: props.cameraFog })
                }
                if (props.cameraClipFar !== undefined && props.cameraClipFar !== camera.state.clipFar) {
                    camera.setState({ clipFar: props.cameraClipFar })
                }
                if (props.cameraResetDurationMs !== undefined) p.cameraResetDurationMs = props.cameraResetDurationMs
                if (props.transparentBackground !== undefined) p.transparentBackground = props.transparentBackground

                if (props.postprocessing) postprocessing.setProps(props.postprocessing)
                if (props.multiSample) multiSample.setProps(props.multiSample)
                if (props.renderer) renderer.setProps(props.renderer)
                if (props.trackball) controls.setProps(props.trackball)
                if (props.debug) debugHelper.setProps(props.debug)
                requestDraw(true)
            },
            getImagePass: (props: Partial<ImageProps> = {}) => {
                return new ImagePass(webgl, renderer, scene, camera, debugHelper, props)
            },

            get props() {
                return {
                    cameraMode: camera.state.mode,
                    cameraFog: camera.state.fog,
                    cameraClipFar: camera.state.clipFar,
                    cameraResetDurationMs: p.cameraResetDurationMs,
                    transparentBackground: p.transparentBackground,

                    postprocessing: { ...postprocessing.props },
                    multiSample: { ...multiSample.props },
                    renderer: { ...renderer.props },
                    trackball: { ...controls.props },
                    debug: { ...debugHelper.props }
                }
            },
            get input() {
                return input
            },
            get stats() {
                return renderer.stats
            },
            get interaction() {
                return interactionHelper.events
            },
            dispose: () => {
                contextRestoredSub.unsubscribe()

                scene.clear()
                debugHelper.clear()
                input.dispose()
                controls.dispose()
                renderer.dispose()
                interactionHelper.dispose()
            }
        }

        function handleResize() {
            width = gl.drawingBufferWidth
            height = gl.drawingBufferHeight

            renderer.setViewport(0, 0, width, height)
            Viewport.set(camera.viewport, 0, 0, width, height)
            Viewport.set(controls.viewport, 0, 0, width, height)

            drawPass.setSize(width, height)
            pickPass.setSize(width, height)
            postprocessing.setSize(width, height)
            multiSample.setSize(width, height)

            requestDraw(true)
        }
    }
}